manual for geotechnical - abu dhabi

MANUAL FOR GEOTECHNICAL

INVESTIGATION AND GEOTECHNICAL

DESIGN

PART 2: GROUND INVESTIGATION AND

GEOTECHNICAL DESIGN

DOCUMENT NO: TR-509

SECOND EDITION

JUNE-2021

2

DOCUMENT AMENDMENT PAGE

EDITION

NO.

REVISION

NO.

DATE PAGE NO. AMENDMENTS NOTES

01 00 DEC

2016

02 01 JUNE

2021

TR-509-2:

TABLE-2

(PAGE-20)

Addition as below:

In addition to boreholes, the excavated trial pits

shall be utilized to collect bulk samples from

subgrade. CBR and other field/laboratory tests shall

be carried out on samples collected at/below

subgrade instead of zone planned to be excavated

for pavement construction.

02 01 JUNE

2021

TR-509-2:

TABLE-2

(PAGE-21)

Modify as below:

Low rise buildings (e.g. toll plaza or road

maintenance depot), shades or other landscaping

structures.

One exploratory hole at building/structure location

02 01 JUNE

2021

TR-509-2:

TABLE-2

(PAGE-22)

Notes added as below:

The provided spacing in table-2 are between two

similar type of exploratory holes and should be

finalized in conjunction with the depth

requirements provided in Table-3.

02 01 JUNE

2021

TR-509-2:

TABLE-3

(PAGE-25)

Modify as below:

Low rise buildings (e.g. toll plaza or road

maintenance depot), shades or other landscaping

structures.

02 01 JUNE

2021

TR-509-2:

TABLE-3

(PAGE-26)


It is designer responsibility to ensure that required

criteria of investigation shall be fulfilled during the

design stage. In-case, investigation results may

require further additional number of boreholes

and/or few boreholes may require to extend up to

greater depth, efforts shall be made to execute it

during design stage. However, if due to time or

other constrains the additional/extended boreholes

cannot be executed during design stage along with

main investigation, then particular additional scope

can be added to verification stage investigation

(construction stage). Approval and agreement with

authority reviewer shall be required in this regard

and design Consultant shall undertake full

responsibility of the design, errors and associated

risks due to non-compliance to the investigation

requirements at design stage (if any).

02 01 JUNE

2021

TR-509-2:

TABLE-11

(PAGE-43)

Addition as below:

Water Soluble Salts in Soil: BS 1377: Part 3: 1990

(Amd. 9028-96), and Earth Manual Des.8: A.

3

Shall be tested at 0.5m interval for soil above

groundwater table and few samples from soil

below groundwater table.

02 01 JUNE

2021

TR-509-2:

TABLE-13

(PAGE-47)

Addition as below:

Total Dissolved Solids (TDS): BS 1377 : Part 3 : 1990:

Cl: 8. A

Adequate frequency below groundwater table.

02 01 JUNE

2021

TR-509-2:

TABLE-14

(PAGE-49)


Where, in-situ/laboratory tests not performed to

determine modulus of elasticity (Em). For non-

cohesive soil a criteria of Em = 1N and for rock

stratum a criteria of (Em=J x Mr x UCS) shall be

adopted.

02 01 JUNE

2021

TR-509-2:

8.1 (PAGE-

85)

Modified as below:

The recommended analysis is a total stress analysis

in which the seismic demand (represented by the

earthquake induced stresses) is compared to the

seismic capacity (undrained cyclic shear strength of

the soil, which is also called liquefaction

resistance). The seismic demand will be denoted as

CSR (cyclic stress ratio), whereas seismic capacity

will be denoted as CRR (cyclic resistance ratio).

The safety factor (SF), computed as a ratio between

CRR and CSR, should not be less than 1.25.

Evaluation of settlements in dry sands due to

seismic densification can be carried out using

guidance available in Kramer (154). In order to

conduct proper assessment of liquefaction

potential, investigations of soil characteristics are

required in terms of in situ Standard Penetration

Tests (SPT) or Cone Penetration Tests (CPT). It is to

be noted that CPT data is preferred for assessing

potential for liquefaction and seismic densification

of loose granular strata during an earthquake

event.

If soils are found to be susceptible to liquefaction

and the ensuing effects are deemed capable of

affecting the load bearing capacity or the stability

of the foundations/roads/pavement, measures,

such as ground improvement and/or pile

foundation (structures) shall be taken to ensure

stability.

The liquefaction hazard may be neglected when

one of the following conditions is fulfilled:

i) Sands have a clay content greater than

20% with plasticity index (PI) larger than

10.

ii) Sands have a silt content greater than

35% and at the same time the SPT

normalized blow count value (N1(60)) is

larger than 20.

4

iii) Sands are clean, with SPT normalized

blow count value (N1(60)) larger than 30.

02 01 JUNE

2021

TR-509-2:

TABLE-26

(PAGE-90)

Modified as below:

Methods described in Tomlinson(2) (2001)(102),

Bowles (1996)(159) and Hong Kong Geoguide 1

(1994)(160).

Methods described in Tomlinson(3) (2008) (161). AASHTO LRFD (2017) or Latest Edition/Interim(4) Notes added as below:

(2) For Spread footings minimum safety factor of 3.0 shall be adopted to calculate net allowable bearing capacity and total tolerable settlement shall not exceed 25mm.

(3) Pile allowable compression capacities based on ASD method shall be calculated by using minimum factor of safety (2.5 for skin friction and 3.0 for end bearing). Tension capacities shall not exceed 70% of allowable compression load.

(4) Pile strength design shall comply with LRFD bridge design specifications and guidelines set forth in ADQCC roads structures design manual TR-516.

(5) In order to calculate the compression capacity for piles socket in rock, end bearing shall be ignored.

02 01 JUNE

2021

TR-509-2:

TABLE-26

(PAGE-91)

Modified as below:

Strength, trafficability, requirement of capping,

settlement/collapses due to low CBR/loose layer

underneath or weak subgrade, and/or presence

of unsuitable/soluble material below subgrade.

02 01 JUNE

2021

TR-509-2:

8.5 (PAGE-

92)

New Section (Ground Improvement & Treatment of Voids/Cavities) added: The geotechnical risks and hazards shall be identified in details by performing geophysical/geotechnical investigation at design and verification stage. In case investigation findings indicates “unfavourable” conditions susceptible to liquefaction and/or settlement of roads/pavement/infrastructures/structures/utilities etc. Ground improvement (such as soil replacement, reinforcement with geosynthetics, vibro-compaction or vibro-flotation, vibro replacement (stone columns), dynamic compaction/replacement, CMC columns (controlled modulus columns/rigid inclusions), Rapid Impact Compaction (RIC), High Energy Impact Compaction (HEIC), soil mixing or other applicable techniques) shall be performed prior to construction over it. The conventional ground improvement techniques listed above are for general guidelines and should be finalize at site by Ground Improvement Specialist in function of the soil type (gradation and density) and the site trials results, in order to efficiently satisfy the performance criteria.

5

An indicative plan showing the location of the proposed improvement techniques shall be prepared based on the findings of the existing and complementary subsurface investigation data at the project design stage. The following performance requirements shall be followed as guideline (post improvement);

02 01 JUNE

2021

TR-509-2:

8.5.1

(PAGE-92)

New sub section added as below:

Minimum Criteria for Roads/Pavement:

i) Total settlement (immediate and long-

term) shall not exceed 25mm at 100%

design load and shall not be considered less

than 40 kN/m2 (considering vehicle load of

HL-93).

ii) The safety factor against liquefaction shall

not be less than 1.25.

iii) The in-situ CBR of improved ground shall

not be less than CBR value adopted in

design and in general shall not be less than

10% at 5mm penetration for any condition.

02 01 JUNE

2021

TR-509-2:

8.5.2

(PAGE-93)


Minimum Criteria for Structures/Infrastructures/Utilities Foundation:

i) Total settlement (immediate and long-

term) shall not exceed 25mm (footings)

and 50mm (Raft) at 100% of design load.

ii) The safety factor against liquefaction shall


iii) The post-improvement vertical and lateral

settlements induced by earthquake loading

shall be limited to a maximum of 20 mm at

the top of the ground.

iv) Angular distortion (differential settlement)

of points 5m apart shall be less than 1:500.

v) A minimum equivalent Young’s Elastic

Modulus for the treated ground of 30MPa.

vi) SPT: Minimum N value of 30 along the

improved depth of granular material.

vii) CPT: Minimum cone tip resistance value of

10 MPa along the improved depth of

granular material.

viii) Minimum relative density of 70%.

ix) An effective angle of shear resistance not

less than 35° for the medium dense to

dense sand (granular material).

The parameters of each locality must be checked for

the material type, mineralogy, size, and for the

deposit thickness before the final decision to be

made on the improvement method, level of energy

used, and spacing of improvement points.

Moreover, the thickness of the soil cover, which is

important in determining the improvement method,

can be checked through the pre-CPT/SPT testing

with close spacing. It shall be noted that vibrations

6

induced by heavy machinery shall be limited, while

working next to existing structures or utilities that

are sensitive to vibrations.

The efficiency of the final adopted improvement

method for the project, final thickness/depth of the

improvement ground and verification of set

performance criteria shall be checked by performing

post ground improvement in- situ tests (SPT, CPT,

Plate load test (PLT), Zone Load test, CBR etc.).

The suitability of the soil material shall be

determined by performing standard laboratory tests

(such as gradation, plasticity index (P.I), proctor, CBR,

organic content, water soluble salts (WSS), total

dissolved salts (TDS), sulphate, chloride, pH and/or

other.) by testing collected soil samples as per the

standard requirements provided under TR-542

(part-1 & 2).

02 01 JUNE

2021

TR-509-2:

8.5.3

(PAGE-93

& 94)


Voids/Cavities Treatment: The risk of voids/cavities

and highly fractured zones within right of way (ROW)

and underneath the foundation

(structures/infrastructure/utilities) shall be

investigated (geophysical/geotechnical) at design

stage to determine vertical/lateral extent and shall

be verified at verification stage by executing probing

holes (grid spacing 10m x 10m) with the depth of

each probe reaching a minimum penetration of

10.0m below the last cavity encountered, and

cavities filled with low mobility grout.

All encountered open cavities/voids/highly

fractured zones shall be grouted prior to

construction over it. Grouting design and

specifications shall be developed by considering the

nature of material/ vertical and lateral extent and

shall be design/performed by a company specialized

in such works.

In addition, the subgrade layer (road/pavement)

shall be reinforced with geogrid layers in order to

cater for any potential of cavities collapse, leading to

excessive settlement in future. The type and

strength of geogrid shall be finalized in consultation

with geogrid designer/supplier based on

effectiveness for the problem in hand and

performance warranties.

02 01 JUNE

2021

TR-509-2:

8.6 (PAGE-

94)

New section (Criteria to design retaining

walls/foundation subjected to overturning loads)

added as below:

External stability of retaining walls design and

foundation subjected to overturning loads (such as

shade foundations) shall fulfil the serviceability

criteria by following the minimum factor of safety

i.e. FoS = 2.0 (overturning), FoS = 1.5 (sliding) and

7

FoS = 3.0 (Bearing Capacity). The global stability shall


For strength limit state the stability checks shall be

in compliance with the guideline of AASHTO LRFD

and set forth in ADQCC roads structures design

manual TR-516. In general, the larger dimension

from design of SLS & ULS shall be consider.

02 01 JUNE

2021

TR-509-2:

8.7 (PAGE-

94 & 95)

New section (Slope Stability analysis) added as

below:

Slope Stability analysis shall be carried out to

evaluate the stability of earth and rock-fill,

embankments, excavated slopes, and natural slopes

in soil and rock. The stability of slope depends upon

certain factors and shall be considered in the

analysis (analytical or empirical methods).

i) Uncertainty in the accuracy with which the

slope stability analysis represents the

actual mechanism of failure.

ii) Uncertainty in the accuracy with which the

input parameters (shear strength,

groundwater conditions, slope geometry,

etc.).

iii) The likelihood and duration of exposure to

various types of external loading.

Stability analyses must be formulated with great

care. Since the available shearing resistance of the

soil depends on pore water drainage conditions,

those conditions must be considered carefully in the

selection of shear strength and pore pressure

conditions for the analysis. A minimum surcharge

load of 20 kPa shall be consider.

Accordingly, in static condition, the slope design

shall satisfy minimum safety factor criteria of 1.5

(permanent) and 1.3 (temporary) and 1.1 for seismic

case. Erosion protection measures shall be provided

as appropriate to design requirements in compliance

with ADQCC standards and specifications.

For stability analysis in rock slopes, following modes

of failure shall be considered as applicable.

i) Planar failure

ii) Polygonal failure

iii) Wedge failure

iv) Toppling failure

Stereographic and kinematic analysis shall be

performed as appropriate and applicable to project

specific requirements.

02 01 JUNE

2021

TR-509-2:

9.2.1

(PAGE-96)

Modified as below:

i) Boreholes, trial pits, cone penetration tests

(CPT)

02 01 JUNE

2021

TR-509-2:

9.3 (PAGE-

100 & 101)

Modified and new addition as below:

For new works the subgrade/foundation requires

assessment and shall be carried out as per the

criteria provided in table-2 & 3 of this manual.

8

In case soil investigation indicates that subgrade is

suspected to liquefaction and/or

excessive/differential settlement more than

tolerable limits, due to unsuitable material/weak

ground condition and/or presence of water soluble

content/pure salt layer underneath and/or other

risks and geo-hazards, that may affect the stability of

roads/pavement and/or foundation of

structures/infrastructure/utilities, than ground

improvement measures shall be taken into account,

to mitigate the effect of both liquefaction and

settlement, prior to construction over it. Subgrade

shall be reinforced with geogrid layers and the

requirements shall be determined at design stage.

The type and strength of geogrid shall be finalized in

consultation with geogrid designer/supplier based

on the effectiveness for the problem in hand and

performance warranties. For ground improvement,

requirements and criteria provided in section 8.5 of

TR-509-2 shall be followed.

The suitability of the material shall be evaluated

based on the criteria provided in ADQCC TR-542 (1

& 2). The sum of the organic matters’ content and

the soluble salt content as a total shall not exceed

2% in both natural soil and imported backfill.

Similarly, mitigation due to shallow groundwater

table (such as capillary break, subsurface drainage

etc.) shall also be adopted at design stage. For the

provision of capillary break layer (wrapped in

geotextile), the criteria of design groundwater table

of minimum1.5m below formation level (TR-514-2,

Standard DWG C-5) shall be followed.

02 01 JUNE

2021

TR-509-2:

CITED

REFERENCES

(PAGE-

161)

Modified as below;

Tomlinson, M. J. Pile design and construction

practice. 5th edition. s.l. : Taylor Francis, 2008.

02 01 JUNE

2021

TR-509-2:

APPENDIX A

(PAGE-120

TO 124)

New figures added as below (information only):

Figure A6: Reported Loose Soil Thickness-Abu

Dhabi

Figure A7: Reported Sabkha Deposit -Abu Dhabi

Figure A8: Reported Halite Deposit-Abu Dhabi

Figure A9: Reported Voids/Cavities-Abu Dhabi

Figure A10: Reported Geohazard Risk-Abu Dhabi

Document No: TR-509

Second Edition

June - 2021

Department of Municipal Affairs and Transport

PO Box 20

Abu Dhabi, United Arab Emirates

© Copyright 2016, by the Department of Municipal Affairs and Transport. All Rights Reserved. This

document, or parts there of, may not be reproduced in any form without written permission of the

publisher.

GEOTECHNICAL INVESTIGATION

PART-2: GROUND INVESTIGATION AND GEOTECHNICAL DESIGN

Page i TOC Second Edition June-2021

TABLE OF CONTENTS

List of Figures ............................................................................................................................... v

List of Tables ................................................................................................................................. v

Glossary ...................................................................................................................................... vii

Abbreviations and Acronyms ...................................................................................................... x

Nomenclature and Symbols ....................................................................................................... xii

1 INTRODUCTION ..................................................................................................................... 1

1.1 Overview ........................................................................................................................... 1

1.2 Purpose and scope ........................................................................................................... 1

1.3 Application of this manual ................................................................................................. 1

1.4 Content and format ........................................................................................................... 2

2 ABU DHABI GEOLOGY AND GEOTECHNICAL HAZARDS .................................................. 3

2.1 Overview ........................................................................................................................... 3

2.2 Geology of the Region ...................................................................................................... 3

2.2.1 Introduction ................................................................................................................ 3

2.2.2 Solid geology ............................................................................................................. 3

2.2.3 Superficial geology .................................................................................................... 5

2.3 Characteristics of Abu Dhabi strata ................................................................................... 7

2.3.1 Introduction ................................................................................................................ 7

2.3.2 Aeolian sands ............................................................................................................ 7

2.3.3 Sabkha ...................................................................................................................... 8

2.3.4 Lagoonal muds .......................................................................................................... 8

2.3.5 Fluvial sands/gravels ................................................................................................. 9

2.3.6 Bedrocks.................................................................................................................... 9

3 PRELIMINARY SOURCES STUDY ....................................................................................... 13

3.1 Overview ......................................................................................................................... 13

3.2 Scope of preliminary sources study ................................................................................ 13

4 GROUND INVESTIGATION PLANNING ............................................................................... 14

4.1 Overview ......................................................................................................................... 14

4.2 Introduction ..................................................................................................................... 14

4.3 Ground investigations proposals ..................................................................................... 16

4.3.1 Phasing of ground investigation ............................................................................... 16

4.3.2 Guidelines for overall coverage of exploratory holes spacings and depths ............... 17

4.4 Soils and rocks sampling and testing to obtain engineering parameters for use in

geotechnical design ................................................................................................................... 27



Page ii TOC Second Edition June-2021

4.4.1 General .................................................................................................................... 27

4.4.2 Difficulties in parameter determination ..................................................................... 31

4.5 Guidelines for engineering parameters typically required ................................................ 36

4.6 Laboratory tests for determining soils, groundwater and rock properties and engineering

parameters ................................................................................................................................ 42

4.6.1 Soils and groundwater ............................................................................................. 42

4.6.2 Rock ........................................................................................................................ 49

5 GROUND INVESTIGATION PROCUREMENT ...................................................................... 52

5.1 Overview ......................................................................................................................... 52

5.2 Procurement of a ground investigation company ............................................................ 52

5.2.1 Quality of ground investigation personnel ................................................................ 53

5.2.2 Laboratory quality .................................................................................................... 54

5.3 Specification and bill of quantities ................................................................................... 55

5.4 Specification of ground investigation of contaminated land ............................................. 55

5.5 Ground investigation company performance ................................................................... 58

6 IN SITU TESTING AND ITS INTERPRETATION................................................................... 59

6.1 Overview ......................................................................................................................... 59

6.2 Standard penetration testing ........................................................................................... 59

6.2.1 Introduction .............................................................................................................. 59

6.2.2 Influence of different practices and equipment on SPT results ................................. 59

6.2.3 Corrections applied to SPT results ........................................................................... 61

6.2.4 Engineering parameters and direct design methods ................................................ 63

6.3 Cone penetration testing ................................................................................................. 65

6.3.1 Introduction .............................................................................................................. 65

6.3.2 Test methods ........................................................................................................... 66

6.3.3 Factors that can affect CPT results .......................................................................... 66

6.3.4 Presentation of results ............................................................................................. 67

6.3.5 Soils characteristics, engineering parameters, direct design methods and other

applications ............................................................................................................................ 69

6.4 In situ density tests ......................................................................................................... 72

6.5 Geophysical surveys ....................................................................................................... 72

6.5.1 Introduction .............................................................................................................. 72

6.5.2 Planning .................................................................................................................. 73

6.5.3 Procurement of geophysical survey work ................................................................. 78

7 GROUND INVESTIGATION REPORTING ............................................................................ 81

7.1 Description of soils and rocks, borehole and trial pit records ........................................... 81



Page iii TOC Second Edition June-2021

7.2 Laboratory test reporting ................................................................................................. 81

7.3 Electronic transfer of geotechnical data .......................................................................... 81

8 GEOTECHNICAL DESIGN .................................................................................................... 82

8.1 Seismic loading ............................................................................................................... 82

8.2 Interpretative ground model ............................................................................................ 86

8.3 Selection of geotechnical design parameters .................................................................. 87

8.4 Geotechnical design ....................................................................................................... 89

8.5 Ground improvement & treatment of voids/cavities ......................................................... 92

8.5.1 Minimum criteria for Roads/Pavement: .................................................................... 92

8.5.2 Minimum criteria for Structures/Infrastructures/Utilities Foundation .......................... 93

8.5.3 Voids/Cavities Treatment ......................................................................................... 93

8.6 Criteria to design retaining walls/foundation subjected to overturning loads .................... 94

8.7 Slope Stability analysis ................................................................................................... 94

9 GEOTECHNICAL ASPECTS OF ROAD PAVEMENTS ........................................................ 96

9.1 Overview ......................................................................................................................... 96

9.2 Pavement investigation and assessment ........................................................................ 96

9.2.1 Introduction .............................................................................................................. 96

9.2.2 Visual condition survey ............................................................................................ 96

9.2.3 Trial pits through the pavement layer ....................................................................... 97

9.2.4 Asphalt cores ........................................................................................................... 97

9.2.5 Dynamic cone penetrometer (DCP) ......................................................................... 98

9.2.6 Ground penetrating radar (GPR) .............................................................................. 99

9.2.7 Laboratory testing .................................................................................................. 100

9.2.8 Testing pavement “strength” .................................................................................. 100

9.3 Subgrade investigation and assessment ....................................................................... 100

Cited References ....................................................................................................................... 102

Other References ...................................................................................................................... 112

Appendix A: Geological map, litho-stratigraphical section, tectonic setting maps and

geohazard risk maps ................................................................................................................ 114

Appendix B: Abu Dhabi soils and rock strata typical geotechnical hazards and risks ....... 125

Appendix C: Preliminary sources study.................................................................................. 129

Appendix D: Example template evaluation sheets for ground investigation companies .... 136

Appendix E: Template bill of quantities for ground investigation ......................................... 146

NOTE: APPENDICES ARE AVAILABLE IN THE PDF COPIES ................................................ 146

Appendix F: SPT corrections spreadsheet template .............................................................. 169

Appendix G: Cone penetration testing .................................................................................... 171



Page iv TOC Second Edition June-2021

Appendix H: Borehole geophysical techniques ..................................................................... 174

Appendix I: Example exploratory hole record ........................................................................ 178


Appendix J: Example reporting forms for soils and rock laboratory tests ........................... 181


Appendix K: Example geological profiles ............................................................................... 305


Appendix L: International Standards - Limit state geotechnical design ............................... 307



Page v TOC Second Edition June-2021

LIST OF FIGURES

Figure 1: Cone penetrometer components ............................................................................... 66

Figure 2: Refraction methodology (from Wightman et al (2003)(116)) .................................... 75

Figure 3: Example of moderately conservative and worst credible values and parameters . 89

Figure 4: Example dynamic cone penetration test ................................................................... 99

Figure A1: Geological Map of the United Arab Emirates (Huntington Geology & Geophysics

Ltd, 1979(1)) ............................................................................................................................... 115

Figure A2: Abu Dhabi litho-stratigraphy (Alsharhan (2008)(2)) ............................................. 116

Figure A3: Tectonic setting of the Arabian plate (Aldama et al (138)) .......................................... 117

Figure A4: Maximum considered earthquake ground motion for the United Arab Emirates of 0.2s (Ss)

spectral response acceleration (5% of critical damping), Site class B (Abu Dhabi Guide to the Use

of International Building Codes, (149)) ........................................................................................ 118

Figure A5: Maximum considered earthquake ground motion for the United Arab Emirates of 1.0s (S1)

spectral response acceleration (5% of critical damping), Site class B (Abu Dhabi Guide to the Use

of International Building Codes (149)) ......................................................................................... 119

Figure A6: Reported Loose Soil Thickness-Abu Dhabi ................................................................ 120

Figure A7: Reported Sabkha Deposit - Abu Dhabi ...................................................................... 121

Figure A8: Reported Halite Deposit- Abu Dhabi .......................................................................... 122

Figure A9: Reported Voids/Cavities- Abu Dhabi .......................................................................... 123

Figure A10: Reported Geohazard Risk- Abu Dhabi ..................................................................... 124

LIST OF TABLES

Table 1: Abu Dhabi main soils and bedrock strata units ........................................................... 7

Table 2: Guidelines for overall exploratory holes spacings for detailed design .................... 19

Table 3: Guidelines for exploratory holes depths .................................................................... 23

Table 4: Soils properties/engineering parameters, symbols and units ................................... 28

Table 5: Rock properties/engineering parameters, symbols and units .................................. 30

Table 6: Quality classification for soil samples ........................................................................ 32

Table 7: Sampling techniques for Abu Dhabi soils .................................................................. 32

Table 8: Guidelines on the minimum number of samples to be tested for particular soils

laboratory tests ........................................................................................................................... 34

Table 9: Guidelines on the minimum number of samples to be tested for particular rock

laboratory tests ........................................................................................................................... 35

Table 10: Engineering parameters commonly required for design and to be considered in

planning a ground investigation ................................................................................................ 37

Table 11: Soil properties and engineering parameters commonly determined from laboratory

tests for Abu Dhabi road projects.............................................................................................. 43

Table 12: Soil properties and engineering parameters occasionally determined from

laboratory tests for Abu Dhabi road projects ........................................................................... 45

Table 13: Groundwater properties commonly determined from laboratory tests for Abu Dhabi

road projects ............................................................................................................................... 48

Table 14: Rock properties and engineering parameters commonly determined from




Page vi TOC Second Edition June-2021

Table 15: Rock properties and engineering parameters occasionally determined from


Table 16: Site categorisation in relation to the ground investigation of landfills and

contaminated land (after UK Site Investigation Steering Group (1993)(93)) ........................... 57

Table 17: Correction factors in sands for rod length ............................................................... 61

Table 18: Correction factors CN for vertical effective stress (σv’) owing to overburden of the

soils ............................................................................................................................................. 62

Table 19: Engineering parameters commonly derived from SPT results ............................... 64

Table 20: Soil characteristics and engineering parameters commonly derived from CPT

results .......................................................................................................................................... 70

Table 21: Tests commonly undertaken for Abu Dhabi road projects for determining the in situ

density of soils ............................................................................................................................ 72

Table 22: Summary of geophysical survey techniques and their application ........................ 74

Table 23: Summary of uses and limitations of frequently used seismic methods ................. 76

Table 24: Summary of seismic hazard studies results for Abu Dhabi at various return periods.

..................................................................................................................................................... 83

Table 25: Seismic design parameters for Site Class B for use in seismic design according to

IBC (Abu Dhabi Guide to the Use of International Building Codes (149)) ............................... 84

Table 26: International Standards and references commonly used for geotechnical design 90

Table 27: Abu Dhabi design guidelines for use in geotechnical design in Abu Dhabi road

projects ........................................................................................................................................ 92

Table B1: Abu Dhabi typical geotechnical hazards and risks ............................................... 126

Table C1: General information required for a preliminary sources study ............................ 130

Table C2: Sources of information for a preliminary sources study ...................................... 132

Table C3: Notes on site reconnaissance ................................................................................. 134

Table D1: Example template technical evaluation sheet for Ground Investigation Companies

................................................................................................................................................... 137

Table D2: Example template health and safety questionnaire ............................................... 144

Table F1: SPT corrections spreadsheet template ................................................................... 170

Table G1: Summary of typical checks and recalibrations to be made for CPT .................... 172

Table G2: Check list for information required for CPT to check data quality ....................... 173

Table H1: Tools and methods for subsurface investigations ................................................ 175

Table H2: Geophysical methods and techniques for logging boreholes .............................. 176

Table H3: Borehole logs and their applications and limitations ............................................ 177

Table L1: International Standards – Limit state geotechnical design ................................... 308



Page vii GLOSSARY Second Edition June-2021

GLOSSARY

Borehole: A general term for a small diameter hole sunk in the ground, usually vertically but

occasionally may be horizontal or inclined, to recover samples of soil and rock strata and

groundwater and to carry out tests to establish the properties of the strata.

Characteristic value parameters: Soil parameters which are defined as being a cautious estimate

of the value affecting the occurrence of the limit. This is analogous to moderately conservative

parameters.

Cone penetration test: The cone penetration test, often referred to as CPT, is an in situ test to

determine the geotechnical engineering properties of soils and to delineate soil stratigraphy. The test

method consists of pushing an instrumented cone, with the tip facing down, into the ground at a

controlled rate.

Earthwork: Work of excavating or raising of ground. Exploratory holes: A general term for boreholes, sunk by various means including cable percussion and rotary coring and rotary open holing, trial pits and trial trenches. Geophysical Survey Company: A specialist contractor who carry out geophysical survey work. Geotechnical design: The use of scientific principles, technical information and thought in the definition of the ground engineering aspects a structure, earthwork or system to perform pre-specified functions with the maximum economy and efficiency. Geotechnical engineering: The application of sciences of soils and rock mechanics and engineering geology in building, civil engineering construction and the protection of the environment. Geotechnical hazard: Unfavourable ground and or groundwater conditions that may pose a risk to

construction or of adverse performance of completed works.

Geotechnical practitioner: A person specialising in geotechnical engineering or engineering

geology.

Geotechnical risk: The risk posed to construction or to appropriate function of completed works by the ground or groundwater conditions at a site. Geotechnical risk register: A live and continuously updated table or spreadsheet that provides an up to date register of the project geotechnical risks. The register usually contains a description of the risk, an assessment of its likelihood and consequences, proposed mitigation measures and owners. Ground investigation: The process by which geological, geotechnical and other relevant information is obtained for a project. Ground Investigation Company: A company that specialises in the likes of borehole drilling, soils and rock in situ and laboratory testing. Ground Investigation Factual Report: The report that presents the results of a ground investigation. The report will normally include the records of borehole and trial pits, soils and rock in situ and laboratory testing.

http://en.wikipedia.org/wiki/Geotechnical_engineering

http://en.wikipedia.org/wiki/Soil_mechanics

http://en.wikipedia.org/wiki/Stratigraphy



Page viii GLOSSARY Second Edition June-2021

Ground model: A conceptual model based on the geology and morphology of the site, and used to speculate on likely ground and groundwater conditions and their variability. Groundwater: Water that is present under the earth’s surface. Groundwater that is situated below the surface of the land, irrespective of its source and transient status. Saturated soils having high groundwater elevations within the foundations and landscaped areas of road pavements require special under drain removal systems. Likelihood: The probability of a risk occurring.

Liquefaction: The process by which typically saturated unconsolidated sediments are transformed into a substance that acts like a liquid. Moderately conservative parameters: Engineering parameters which are the geotechnical practitioner’s conservative best estimate. Overseeing Organisation: The governmental or other body with overall responsibility for the

project.

Piezocone test: A cone penetration test where pore pressure measurement is also made.

Pile load capacity: The load that a pile can carry without failing, usually defined in terms of ultimate

capacity and capacity such that restricts movement within serviceability limits.

Porewater pressure: The pressure of groundwater held within a soil or rock, in gaps between the

particles (pores).

Preliminary sources study: An examination of all existing information concerning a site, such as

geological maps, previous borehole records, historic maps, aerial photograph, satellite imagery, to

assess ground conditions and previous land use.

Risk: The chance of something happening that will have an impact upon project objectives. Risk

components are the probability or likelihood of failing to achieve a particular outcome, and the

consequences and impacts of failing to achieve that outcome.

Road earthworks: A general term for any embankment, cutting that may be encountered in the

transportation system.

Road structures: A general term for any bridge, culvert, catch basin, drop inlet, retaining wall,

cribbing, manhole, endwall, building, sewer, service pipe, underdrain, foundation drain and similar

features, that may be encountered in the transportation system.

Seismic hazard: Unfavourable condition resulting from earthquake activity that may pose a risk to

construction or have an adverse affect on the performance of completed works.

Seismic loading: The application of an earthquake-generated load to a structure.

Standard penetration test: The standard penetration test, often referred to as SPT, is an in situ

dynamic penetration test designed to provide information on the geotechnical engineering properties

of a soil. Procedures for the test are described in British Standard BS EN ISO 22476-3: 2005 and

ASTM D1586-08a.

http://en.wikipedia.org/wiki/Sediment

http://en.wikipedia.org/wiki/Groundwater

http://en.wikipedia.org/wiki/Soil

http://en.wikipedia.org/wiki/Rock_(geology)

http://en.wikipedia.org/wiki/Earthquake

http://en.wikipedia.org/wiki/Structure

http://en.wikipedia.org/wiki/Geotechnical_engineering

http://en.wikipedia.org/wiki/Soil_mechanics

http://en.wikipedia.org/wiki/British_Standard

http://en.wikipedia.org/wiki/ASTM



Page ix GLOSSARY Second Edition June-2021

Trial pit: A general term for an excavation usually by machine, occasionally by small tools and hand-

dig to inspect and record the soil and rock strata conditions, any groundwater entry and to recover

strata samples.

Trial trench pit: A general term for an elongated excavation usually by machine to inspect and

record the soil and rock strata conditions, any groundwater entry and to recover strata samples.

Worst credible parameters: Engineering parameters which are the worst that the geotechnical

practitioner realistically believes might occur.



Page x ABBREVIATIONS Second Edition June-2021

ABBREVIATIONS AND ACRONYMS

AASHTO American Association of State Highway and Transportation Officials

A2LA American Association for Laboratory Accreditation

AGS Association of Geotechnical and Geoenvironmental Specialists

AS Aeolian sand

ASTM American Society for Testing and Materials

BDA British Drilling Association

BP Before present

BRE Building Research Establishment

BS British Standard

CAD Computer aided drafting

CD Consolidated drained (triaxial test)

CIRIA Construction Industry Research and Information Association

CNIA Critical National Infrastructure Authority

CPT Cone penetration test

CPTU Cone penetration test with porewater pressure measurement

CU+PWP Consolidated undrained with porewater pressure measurement (triaxial test)

CV Curriculum vitae

DMRB Design Manual for Roads and Bridges (UK)

DPC Dynamic cone penetrometer

EHS Environment, health and safety

FGS Fluvial sand/gravel

GPR Ground penetrating Radar

H Horizontal

H&S Health and safety

IBC International Building Codes

ISSMFE International Society for Soil Mechanics and Foundation Engineering

ISRM International Society for Rock Mechanics

L Lagoonal mud

LRDF Load and resistance design factor

MASW Multichannel analysis of surface waves (related to geophysical survey)

NDT Non-destructive testing

OO Overseeing Organisation

PGA Peak ground acceleration

PPE Personal protection equipment

R Rock

S Sabkha

SASW Spectral analysis of surface waves (related to geophysical survey)



Page xi ABBREVIATIONS Second Edition June-2021

SPT Standard penetration test

TRL Transport Research Laboratory

UAE United Arab Emirates

UBC Uniform Building Code

UK United Kingdom

UKAS United Kingdom Accreditation Service

US United States of America

UU Unconsolidated undrained (triaxial test)

V Vertical



Page xii ABBREVIATIONS Second Edition June-2021

NOMENCLATURE AND SYMBOLS

Symbol Units Property/engineering parameters

c’ kPa (kN/m2)* Drained cohesion intercept

cr kPa (kN/m2)* Remoulded shear strength

cr’ kPa (kN/m2)* Drained residual cohesion intercept

c’crit kPa (kN/m2)* Critical state cohesion intercept (usually zero)

CN - Correction factor related to SPT rod length

cu kPa (kN/m2)* Undrained shear strength

cv m2/yr Coefficient of consolidation (one dimensional)

CaCO3 % Carbonate content (total)

CBR % California Bearing Ratio

Cl %, mg/l Chloride (total, water soluble)

Dr - Relative density

Ip % Plasticity index (PI)

E MPa Young’s modulus of elasticity

E’ MPa (MN/m2)* Young’s modulus of elasticity (drained)

Eh mV Redox potential

E’0.01 & Es

MPa (MN/m2)* Young’s modulus of elasticity (small strain)

Eu MPa (MN/m2)* Young’s modulus of elasticity (undrained)

Er - Energy ratio of SPT hammer

fs MPa Sleeve friction- cone penetration test

G MPa (MN/m2)* Shear modulus

Gmax MPa (MN/m2)* Very low strain shear modulus

Gs MPa Shear modulus (small strain/initial modulus)

γ Mg/m3 Bulk density/Mass density

I - Point load index, axial (Ia), diametral (ld), lump (Il)

ID - Density index

j - Mass factor j

k m/s Coefficient of permeability, horizontal (kh), vertical (kv) as appropriate

Ko - Coefficient of earth pressure at rest



Page xiii ABBREVIATIONS Second Edition June-2021


ks kN/m3 Modulus of subgrade reaction

LL % Liquid limit (wI)

m - Rock material constant

mv m2/MN Coefficient of volume compressibility (one dimensional)

n % Porosity

N - Standard Penetration Test (SPT) blow count (uncorrected)

N60 - SPT blow count corrected to a standard energy ratio of 60% of the theoretical free-fall hammer energy (and rod length where appropriate)

(N1)60 - SPT blow count corrected to a standard energy ratio of 60% of the theoretical free-fall hammer energy (and rod length where appropriate) and the effective overburden pressure

OCR - Overconsolidation ratio

PI % Plasticity index

PL % Plastic limit (wp)

PSD - Particle size distribution

qc MPa Cone resistance - cone penetration test

RMR - Rock mass rating

rs Ohms.m Apparent resistivity

s - Rock material constant

SO4 %, mg/l Sulphate (total, water soluble)

u kN/m2 Porewater pressure

UCS MPa Uniaxial compressive strength

ν - Poisson’s ratio

ν’ - Drained Poisson’s ratio

νu - Undrained Poisson’s ratio

w % Moisture content

wI % Liquid limit (LL)

wp % Plastic limit (PL)

γd Mg/m3 Dry density

γdmax Mg/m3 Maximum dry density

γdmin Mg/m3 Minimum dry density

λ - Correction factor related to SPT rod length

ρs Mg/m3 Particle density



Page xiv ABBREVIATIONS Second Edition June-2021


σh kPa (kN/m2)* In situ horizontal stress

σv kPa (kN/m2)* In situ vertical stress

’ degrees Peak drained (effective stress) angle of shear resistance

’crit degrees Critical state drained (effective stress) angle of shear resistance

r’ degrees Residual drained (effective stress) angle of shear resistance

Notes:

* Units in brackets also commonly used.



Page 1 01-INTRODUCTION Second Edition June-2021

1 INTRODUCTION

1.1 Overview In 2010, the Abu Dhabi Department of Transport commenced with the “Unifying and Standardizing

of Road Engineering Practices” Project. The objective of the project was to enhance the

management, planning, design, construction, maintenance and operation of all roads and related

infrastructures in the Emirate and ensure a safe and uniform operational and structural capacity

throughout the road network.

To achieve this objective a set of standards, specifications, guidelines and manuals were developed

in consultation with all relevant authorities in the Abu Dhabi Emirate including the Department of

Municipal Affairs (DMA) and Urban Planning Council (UPC). In future, all authorities or agencies

involved in roads and road infrastructures in the Emirate shall exercise their functions and

responsibilities in accordance with these documents. The purpose, scope and applicability of each

document are clearly indicated in each document.

It is recognized that there are already published documents with similar objectives and contents

prepared by other authorities. Such related publications are mentioned in each new document and

are being superseded by the publication of the new document, except in cases where previously

published documents are recognized and referenced in the new document.

1.2 Purpose and scope The Manual for Geotechnical Investigation and Geotechnical Design comprises two parts as follows:

Part 1: Management of Geotechnical Risk. Part 1 of the Manual sets out the role of geotechnical

practitioners in managing the quality of geotechnical investigations, ground interpretation and also

in geotechnical design and geotechnical construction. Part 1 of the Manual also sets out the

procedure of Geotechnical Certification, which provides a clear and consistent framework for the

management of the geotechnical risk in a project throughout its lifetime. The format of the reports

and documents to be prepared and submitted to the Overseeing Organisation (OO) under

Geotechnical Certification as a project progresses is presented. The documents to be submitted may

include reports covering preliminary sources study, the planning of ground investigation works, the

interpretation of geotechnical investigations, geotechnical design and geotechnical construction.

Part 2: Ground Investigation and Geotechnical Design. Part 2 of the Manual provides guidance on

Abu Dhabi soils and bedrock strata and the geotechnical hazards that they can present. It also

provides guidance on undertaking preliminary sources studies, the planning and procurement of

ground investigations and on in situ and laboratory testing and geotechnical design.

1.3 Application of this manual The Geotechnical Certification procedure set out in the Part 1 of the Manual: Managing Geotechnical

Risk is mandatory for all Abu Dhabi Department of Transport – Main Roads Projects. Other

authorities may adopt the procedure as they require.

Where a third party development is proposed immediately adjacent to, under or over a road for which

Abu Dhabi Department of Transport is responsible then Abu Dhabi Department of Transport

acceptance of the scheme aspects impacting on the road will be required. In such cases the third



Page 2 01-INTRODUCTION Second Edition June-2021

party developer shall follow the Geotechnical Certification procedure to ensure that there is

appropriate quality management of the geotechnical risks that could impact on the road.

Part 2 of the Manual: Ground Investigation and Geotechnical Design provides guidance for the

geotechnical practitioner engaged on Abu Dhabi road projects.

1.4 Content and format The general content and layout of the Manual for Geotechnical Investigation and Geotechnical

Design is as follows:

Manual Part 1: Managing Geotechnical Risk

Chapter 1 provides an introduction to the Manual for Geotechnical Investigation and

Geotechnical Design. Chapter 2 describes the need for geotechnical practitioners in projects and

their general role. Chapter 2 also presents a categorisation of geotechnical practitioners relative

to their education, professional qualifications and industry experience to provide for the

appointment of appropriate staff to project roles and thereby promote quality of geotechnical

work. Chapters 3 to Chapter 7 inclusive set out the four Key Stages of the geotechnical

certification process to be followed to manage geotechnical risk on projects. The documents

required to be prepared and submitted under each Key Stage are described. Chapter 8 describes

the preparation of a geotechnical risk register and the undertaking of geotechnical risk analysis.

Manual Part 2: Ground Investigation and Geotechnical Design

Chapter 1 provides an introduction to the Manual for Geotechnical Investigation and

Geotechnical Design, which is common with Part 1 Chapter 1. Chapter 2 provides a description

of the geology of the Region, the characteristics of Abu Dhabi strata and the geotechnical

hazards and risks that are typical of Abu Dhabi Emirate. Chapter 3 describes the general scope

of the preliminary sources study that should be undertaken in the early stages of a project.

Chapter 4 provides guidance on the planning of ground investigation and Chapter 5 presents

advice on the procurement of a Ground Investigation Company. Chapter 6 describes in situ

testing best practice for standard penetration testing (SPT), cone penetration testing (CPT),

density and geophysical surveys, which are commonly undertaken in Abu Dhabi. Chapter 7

covers laboratory testing reporting and electronic transfer of geotechnical data. Chapter 8

provides guidance on standards to be used in geotechnical design and Chapter 9 presents

guidance on the geotechnical aspects of road pavements.



Page 3 02-ABU DHABI GEOLOGY AND GEOTECHNICAL HAZARDS Second Edition June-2021

2 ABU DHABI GEOLOGY AND GEOTECHNICAL

HAZARDS

2.1 Overview This chapter provides a description of the geology of the Region, the characteristics of Abu Dhabi

strata and the typical geotechnical hazards that may be encountered in Abu Dhabi Emirate.

2.2 Geology of the Region

2.2.1 Introduction The geology of Abu Dhabi is characterised by a classic carbonate-evaporite complex influenced by

the deposition of marine sediments associated with numerous sea level changes. Abu Dhabi is

relatively low lying with the exception of the mountainous area adjacent to Al Ain which marks the

boundary of the emirate with neighbouring Oman. The surface geology is dominated by aeolian sand

dunes reaching heights of 150m inland in the region of Liwa and with coastal areas dominated by

sabkha/evaporite deposits which extend more than 80km southwards into desert areas. A copy of

the Geological Map of the United Arab Emirates (Huntington Geology & Geophysics Ltd (1979) (1))

is included as Figure A1 in Appendix A and the litho-stratigraphy of Abu Dhabi (Alsharhan (2008)

(2)) is included as Figure A2 in Appendix A. It is to be noted an updated geological map of UAE is

currently in preparation with the British Geological Survey.

2.2.2 Solid geology Few rocks older than about 100 million years (Ma) crop out within the territory of Abu Dhabi. For

completeness, however, all the major solid geology formations from Cambrian to Recent are

described, as these may be encountered in some deeper investigations.

2.2.2.1 Palaeozoic (540 Ma to 250 Ma) Throughout the Palaeozoic, Arabia was located south of the equator forming part of the mega-

continent Gondwana. The oldest rocks in Abu Dhabi that can be seen at the surface occur around

the various salt diapirs such as Jebel Dhanna in the west of the emirate and the offshore diapiric

islands (which includes Zirku island, Sir Bani Yas and Das Island). These older rocks, comprising

shales, dolomites, siltstones and volcanics (Alsharhan (2008) (2)) have been brought to the surface

as a by-product of the process of diapirism. Diapirism describes the effect of buoyant salt deposits

(in this case, salts of the Hormuz Formation) rising through the overlying rocks and bringing

fragments of buried rock upwards to the surface. The salt of the Hormuz Formation was deposited

some 540 Ma during the Cambrian-Precambrian period , by evaporation from a shallow sea. As

sediments were laid down over the Hormuz Salt, the salt, which is less dense than the overlying

rocks, and is incompressible, has risen to the surface, flowing through fractures and faults in the

rock.

Following the Hercynian Orogeny in the early Carboniferous, fine to medium grained cross bedded

quartzose sandstones of the Uanayzah Formation (previously termed the Pre Khuff Formation)

overlain by siltstone, mudstone and minor claystones were laid down under fluvial conditions. As the

climate warmed, a carbonate-evaporite environment developed and in the Mid-Late Permian the

Khuff Formation was laid down in a shallow marine environment. These deposits comprise a

complex sequence of bioclastic dolomite, limestone and anhydrite.




2.2.2.2 Mesozoic (250 Ma to 65 Ma) During the Upper Permian-Late Triassic the Arabian Shield was uplifted to the west and conditions

became more arid (Alsharhan (2008) (2)). During the Lower Triassic a near shore shallow marine

environment dominated, leading to the deposition of the Sudair Formation. The Sudair Formation

comprises an interbedded sequence of terrigeneous mudstones and dolomites. By the Mid-Triassic

the Jilh (Gulailah) Formation was deposited under sabkha conditions comprising anhydrite, dolomite

and mudstone with minor wackestone, packstone and grainstone. By the Late Triassic the Minjur

Formation was deposited in a fluvio-deltaic environment comprising quartz sandstone, mudstones

and thin coal seams progressing upwards into shale, sandstone and dolomitic limestone.

Marine conditions continued throughout the Lower to Upper Jurassic, depositing the Marrat

Formation and Hamlah Formation, a sequence of wackestone, lime mudstone (limestone with less

than 10% grains in a mud-supported sediment) and quartzose sandstone; and the Izhara and Araej

Formations, an interbedded sequence of argillaceous mudstones, packstones and grainstones. The

formations of the Sila Group of the upper Jurassic are typically found in onshore areas of Abu Dhabi,

identified during drilling of wells. The formations of the Sila Group comprise: Tuwaiq Mountain

Formation, Dukhan Formation, Diyab Formation, Arab Formation, Qatar Formation, Hith Formation

and Asab Formation. The sedimentary rocks were deposited in a changing, gradually shallowing

marine environment, depositing mudstones, packstone, grainstone and calcareous shales.

A rapid sea level rise in the area occurred during the Lower Cretaceous with the deposition of the

Habshan, Lekhwar, Kharaib and Shuaiba Formations; a sequence of lime mudstone, wackestone,

dolomite and dolomitic limestone. The Wasia Group of the Mid-Cretaceous is bounded above and

below by unconformities, comprising shale, mudstone, packstone, wackestone, grainstone and

limestone. The formations of the Wasia Group comprise: Nahr Umr Formation, Mauddud Formation,

Shilaif Formation and Mishrif Formation. The shales and marls of the Laffan Formation (Upper

Cretaceous) rest unconformably on the underlying Wasia Group. The overlying Halul Formation and

Fiqa Formation comprise interbedded calcareous shale, mudstone and limestone. The Simsima

Formation deposited over most of Abu Dhabi consists of packstone, wackestone and dolomitic

limestone with corals.

2.2.2.3 Palaeogene – Neogene (65 Ma to 2 Ma) The Palaeogene rocks across Abu Dhabi comprise: the Umm Er Radhuma Formation, the Rus

Formation and the Dammam Formation consisting of shales, packstone, wackestone and limestone.

Uplift and erosion occurred during the late Eocene-early Oligocene followed by marine transgression

leading to the deposition of the Oligocene Asmari Formation comprising dolomitic limestone with thin

interbeds of marls and calcareous mudstone (Alsharhan (2008) (2)). The Oligocene Asmari

Formation is overlain by the Gachsaran (Lower Fars) Formation comprising anhydrite, dolomite and

limestone and interbedded anhydrite, shales, marls and limestones

The sedimentary rocks of the Miocene were deposited during a period coinciding with a major fall in

sea level. The majority of the Miocene deposits are combined into a single geological Group, the

Fars Group, and this has been divided into Lower Fars, sometimes termed the Gacharan Formation

(about 20 Ma to 18 Ma, and the overlying Upper Fars. These units comprise a sequence of marls

and mudstones, sandstone (calcarenite), limestone and evaporates (typically gypsum and anhydrite)

dipping gently to the south. A particular unit of the Upper Fars is the Barzaman unit that contains a

sequence of conglomerate deposits. The underlying Shuwaihat Formation (part of the Upper Fars)




crops out in western Abu Dhabi comprising evaporite deposits replaced upwards by dune sand which

are exposed on Shuwaihat Island and Jebel Dhanna and south of Sila (Glennie, 2007). The

Baynunah Formation unconformably overlies the Shuwaihat Formation comprising fluvial sands and

gravels with abundant fossils including crocodiles, hippopotamus and turtles. The Baynunah

Formation forms small mesas found in the western region of Abu Dhabi.

2.2.3 Superficial geology The Quaternary Period was marked by cycles of cooling and warming associated with ice ages and

inter-glacial periods in northern and southern climes and causing rises and falls in global sea levels,

influencing the climate and leading to the deposition of the superficial deposits seen across Abu

Dhabi. With the exception of small exposures of the underlying bedrock, Abu Dhabi is covered by

superficial deposits laid down during the Quaternary period. The Quaternary deposits predominantly

comprise:

• aeolian sands deposited during periods of lower sea levels, most notably during the last ice

age (20,000 years BP (before present)) when sea levels dropped 120m to 130m below

present levels;

• sabkha and fluvial deposits laid down during periods of marine transgression.

2.2.3.1 Aeolian sand The surface of the interior of Abu Dhabi is dominated by aeolian dune sands occasionally interrupted

by interdune areas occupied by sabkha and gravel plains. The aeolian sands exhibit several

morphologies stretching from the coast, south to the Rub-al-Khali with the border of Saudi Arabia

and Oman. Mega dunes dominate the area around Liwa reaching up to 150m above interdune

sabkha areas. Smaller dunes occur in the south overlying alluvial fans that flank the Oman mountains

(Glennie (2007) (3)).

The aeolian sands vary in composition. Inland the sands consist predominately of siliclastic grains

(quartz, feldspar and lithic grains). Near the coast the sands consist mostly of calcium carbonate

derived from fragments of calcareous shells and corals. Carbonate dunes are known locally as

‘miliolite’ and can be seen along the Abu Dhabi – Al Ain Road and the Hameem Road. Miliolite are

often white in colour due to the carbonate content, further inland the dunes change from white to red

due to the a decrease in carbonate content and increase in quantities of iron oxide.

2.2.3.2 Sabkha Sabkha are extensive salt flats underlain by sand, silt and clay that are often encrusted with salt

(halite). Sabkhas occur along the coast (coastal sabkha) and inland (inland sabkha) across the

surface of Abu Dhabi. The two main factors which control the formation of the sabkha are the depth

to water table and the effects of wind deflation.

Coastal sabkha

Coastal sabkha dominates the coastline from Abu Dhabi Island westwards to the Qatar Peninsula,

covering much of the islands south west and northeast of Abu Dhabi Island and extending up to

15km inland (Glennie (2001)(4))

Coastal sabkha are extremely flat and are formed when the water table, which is saline, due to the

proximity of the sea, occurs at shallow depths within the capillary zone. The saline water evaporates




from the surface which then becomes saturated with halite to form a crust. Beneath the crust calcium

sulphate (CaSO4) becomes concentrated forming a mush of gypsum crystals. As ground

temperatures rise, water of crystallisation is driven from the gypsum crystals to form anhydrite. Active

coastal sabkhas also feature a mat of thin black algae. Most of the time the surface is dry and cracked

however, during spring tides and during storm events sea water inundates the mats causing the

algae to regenerate into a slimy, rubbery surface. With time the mat once again becomes dry and a

halite crust forms. Algae mats are seen extensively along the coastline of Abu Dhabi south of

Musaffah.

Inland sabkha

Inland sabkha have no direct hydrological connection with the sea and derive moisture from rare

rainfall and a shallow water table within the capillary zone. Inland sabkhas tend to occur in areas

dominated by sand dunes; the best examples of inland sabkha are found in the interdunal areas

between the large sand dunes of Liwa in the west of the emirate and are often found on the landward

margins of the coastal sabkha. As with coastal sabkha, inland sabkha develop halite crusts

concentrated by evaporation of groundwater, which contains dissolved salts from the surrounding

rocks and soils. Algae mats are not well developed on inland sabkha but are present in rare locations.

The Sabkha Matti is the most famous inland sabkha occupying the western extremities of Abu Dhabi.

The Sabkha Matti is recorded to extend up to 150km inland from the coast and is up to 60km wide

(Glennie (2007)(3)).

2.2.3.3 Lagoonal Muds Recent processes along the coast have resulted in the deposition some deposits (typically carbonate

muds) nearshore, and in some cases these have been buried by recent reclamation. These deposits

– sometimes referred to as lagoonal muds - are thought to have been deposited in shallow lagoons

(Butler (1970) (5)) and in the region of Yas Island are typically up to 3m in thickness. Due to limited

availability of investigation data along the coastline, their lateral and vertical extent elsewhere is

undefined.

2.2.3.4 Duricrusts Duricrusts are typically formed from cementation of sediments by precipitation of iron oxides or other

minerals contained in percolating groundwater. Precipitation of these minerals is often initiated by

the evaporation of the percolating fluids under the intense desert heat. They occur as a hardened

surface layer that can range from a few centimetres to several metres thick, sometimes with a

leached, cavernous, porous or friable zone underneath (Fookes (1978)(6)).

2.2.3.5 Fluvial Sediments Fluvial sediments are rarely found at the surface in Abu Dhabi as they are often covered by aeolian

sands. Fluvial sediments are most commonly found flanking the foothills of the Hajar Mountains in

the eastern part of the Emirate and can be found further west in the Al Ain region near Jebel Hafeet.

Fluvial gravels have also been exposed on the western side of the Sabkha Matti, comprising pebbles

of limestone and volcanics (Glennie (2007) (3)).

The fluvial sands and gravels are formed from outwash fans at the base of the eastern Hajar

mountains and may extend outwards from the base of the mountains for distances of up to 70 km.




The source rocks of these deposits tend to be the Asmari, Dammam and Rus formation limestones

and marls that are present on the eastern flanks of the Hajar range combined with gabbros and other

igneous rocks that form the central parts of the mountains.

Away from the mountain areas, flat, wide or ribbon-like areas of dry dusty silt are often present at

the ground surface. These represent the silty deposits of flood lagoons that periodically form in the

low lying desert and coastal areas.

2.3 Characteristics of Abu Dhabi strata

2.3.1 Introduction This Section provides a description of the engineering characteristics and the typical uses and issues

relating to the main soils and bedrock strata units encountered in Abu Dhabi Emirate, as listed in

Table 1 below. Guidance of the typical geotechnical hazards and risks in Abu Dhabi Emirate

associated with these main strata units are summarised in Table B1 in Appendix B. The geotechnical

practitioner will need to identify all project specific geotechnical hazards for a scheme and prepare

a geotechnical risk register in order to provide for active management of the geotechnical risks during

the lifetime of a project.

Table 1: Abu Dhabi main soils and bedrock strata units

Abu Dhabi main strata units

Soils - aeolian sands

- sabkha

- fluvial deposits (sands/gravels)

Bedrock strata - recent evaporates

- conglomerate

- sandstone and siltstone

- mudstone and gypsum

- calcarenites

- limestone

2.3.2 Aeolian sands The aeolian sands vary in composition between siliclastic deposits inland and calcium carbonate

deposits derived from fragments of shells near the coast. The aeolian sands are fine to medium

grained and contain sub-rounded to well rounded particles of quartz, carbonate and evaporite

minerals. The deposits are generally clay and silt free and have moderate to good permeability. The

consistency of the materials varies from loose to very dense. Many of the larger sand dunes comprise

an upper layer of loose, mobile, single sized sand grains overlying a core of denser single sized sand

that has been cemented by pressure solution and re-cementation of the carbonate and evaporite

particles.

In the region aeolian sands are typically used as general earthworks and structural backfill.

Depending on source area and history after deposition, the sands can have a high salt content




(sodium chloride) and this should be checked before using the materials close to concrete

foundations or as fine aggregate in concrete mixes.

Owing to the uniform grading of the deposits, there have been issues related to poor compaction of

aeolian sands where standard compaction procedures have been used to place the material in

engineering works. It is often necessary to flood the deposits with water and use a heavy vibratory

roller in order to achieve the required compaction. Sometimes, however, the moisture content versus

maximum dry density curve for these deposits is very flat, allowing them to be compacted in a

completely dry state (known as dry compaction) to achieve reasonable levels of compaction.

2.3.3 Sabkha Sabkha comprises fine, poor to well graded sands or silts that have been inundated by hypersaline

groundwater.

The coastal sabkhas are highly variable materials both horizontally and vertically. Much of the

horizontal variation can be considered to be related to the position of the material relative to the

shoreline. In the vertical dimension, the coastal sabkha comprises a series of layers having a range

of textures and varying degrees of cementation depending on the quantities and state of the calcium

carbonates and calcium sulphates present.

Inland sabkhas are typically variable in the horizontal direction only, owing to the relatively constant

level of groundwater table beneath the existing surface.

Owing to their mode of deposition sabkha typically contains high concentrations of chloride and

sulphates giving rise to aggressive environments for buried concrete and steel. This together with

their fine grading usually makes them unsuitable as structural fill.

Extensive sabkha deposits are found across the emirate of Abu Dhabi and due to the variability the

deposits they are typically either excavated and replaced or left in place and treated. Ground

improvement methods typically used on sabkha deposits include pre-loading and surcharging,

dynamic compaction and stone columns, the method employed being dependant upon the type and

thickness of sabkha present.

Historically in the region, existing unpaved tracks followed sabkha flats as they provided a hard

surface to travel along in comparison with the surrounding soft desert sand. During periods of heavy

rain, however, the roads often became impassable, as the surface crust of the sabkha would lose its

strength when saturated, causing vehicles to sink into the underlying crystal mush.

Gypsum and anhydrite, which are typically abundant in sabkha deposits, can undergo alternate

hydration and dehydration under hot and humid conditions. If placed beneath a foundation or road

pavement, swelling or shrinkage can occur as a result of the volume changes associated with the

hydration or dehydration processes.

Significant variability in the compressibility (ranging from high to low compressibility) characteristics

of sabkha sediments can be expected, that can result in large differential settlements.

2.3.4 Lagoonal muds The lagoonal muds, such as are encountered near Yas Island, are typically silty carbonate sands

and sandy silts. They are commonly very soft with very high moisture contents and commence at




near zero datum and are up to approximately 3m in thickness. Due to their low strength they can

cause bearing capacity and trafficability problems for construction traffic and make a poor foundation

for roads and other civil engineering structures.

2.3.5 Fluvial sands/gravels The fluvial sediments typically comprise dense to very dense silty gravel of limestone, gabbro and/or

igneous or volcanic rocks. The deposits are typically poorly graded and sub-rounded to rounded and

can range from cobble/coarse gravel size down to sand and silt size. Particle size is typically related

to the spatial location within an alluvial fan deposit. Deposits further from the mountain source areas

tend to be finer grained.

Over time, many layers of different sized gravels may be deposited in the same area and become

mixed with wind blown sands, silts and salts, so that different elevations can contain different sized

deposits. When excavated, these materials (locally termed Gatch) characteristically comprise

clayey, silty and gravelly sands or sandy gravels. The fines (clay and silt size particles) are typically

of the order of 20% to 30% and of low to medium plasticity.

Gatch materials are easily excavated and have been used extensively for desert road construction

in the region, as the cementing properties of the salts gives good resistance to wind erosion. When

compacted to a dense state, Gatch can remain stable for many years. If inundated with fresh water

chemical changes can, however, occur resulting in softening and swelling, erosion and/or

dissolution. Gatch materials with a high fines and soluble salt content can make them unsuitable for

use as structural fill. The more uniform deposits of fluvial sand and gravel can, however, make good

aggregate for concrete, provided they are clear of contamination by salts or sulphates.

2.3.6 Bedrocks The rock strata encountered in shallow ground investigations across most of the Abu Dhabi region

are typically of the Miocene Upper Fars (including Baynounah, Shuweihat and Barzaman) and Lower

Fars (sometimes called the Gachsaran) Formations and mainly comprise calcarenite, mudstone and

gypsum with deposits of conglomerate in the Barzamam Formation. In the east of the Emirate, older

deposits of the Asmari, Dammam and Simsima Formations consisting of mudstones, lime-

mudstones and limestones are present. The Muthaymima Formation, situated between the Simsima

and Dammam Formations contains a sequence of conglomerates. The typical characteristics of the

most commonly encountered rocks are summarised below.

2.3.6.1 Recent evaporites Recent evaporites such as halite, anhydrite and gypsum are common near the surface in many parts

of Abu Dhabi, particularly along the coast and in the inland sabkha regions. The deposits tend to be

chemically unstable, subject to volume change and dissolution, and contain very high sulphates and

chlorides that make them unsuitable for use as construction fills.

2.3.6.2 Conglomerate Conglomerates encountered in the Abu Dhabi region typically belong to the Barzaman Unit of the

Upper Fars Formation and comprise fluvial sediments representing cemented outwash fans

containing sub-rounded gravels and cobbles of gabbroic rocks. Given their origin, the coarser

conglomerates are typically encountered within 30 km or so of the base of the Hajar Mountains and

as they progress westwards become intercalated with layers of dolomite marls, claystones and

siltstones. The conglomerates generally comprise larger clasts of fine to medium sub-rounded to




rounded gravels within a matrix of fine silt sized materials. The matrix varies in colour from brownish

to reddish. The matrix materials are often washed out when coring and standard penetration tests

(SPTs) show refusal with little or no penetration.

In the eastern part of the Abu Dhabi Emirate, a thick sequence of conglomerates from the upper part

of the Muthaymimah Formation may be encountered. These comprise cemented sub-rounded to

rounded limestone of pebble to boulder size.

Conglomerates can be useful sources of structural fill for earthworks and depending on grain size

and degree of cementation may also be suitable as aggregate for concrete if suitably processed.

2.3.6.3 Sandstone and siltstone In the western part of Abu Dhabi, sandstones and siltstones of the Gachsaran and Baynounah

Formations may be encountered. These are typically weakly cemented and often referred to as the

Miocene Clastics.

The sandstones are generally fine to medium grained and are often interbeddded with siltstones and

intercalations of marly mudstones. The unconfined compressive strength (UCS) values for these

strata typically range between 2.5MPa and 10MPa.

The materials can usually be excavated easily by mechanical excavators and when excavated can

make for good general fill materials for use in embankments or building platforms. They can,

however, contain high concentrations of sulphates and chlorides that create an aggressive chemical

environment for concrete. In extreme cases high gypsum contents can make the strata susceptible

to collapse due to dissolution of the gypsum particles.

Excavated rock slopes tend to be prone to failure and deterioration unless properly designed and

protected. Rock slope stability is governed by the spacing, orientation and condition of the

discontinuities within the rock mass and excavations in these materials must be designed

accordingly, based on geological mapping and rock mass characterisation.

In temporary cuts, these deposits can often stand near vertical in the short term, but may suffer brittle

collapse if cut too steep or left unsupported for long periods.

2.3.6.4 Mudstone and gypsum Mudstones intercalated with gypsum (evaporites) are seen generally in all parts of the Emirate. In

the eastern part of the Emirate, they occur in the Asmari and Lower Fars Formations and are

sometimes interbedded with friable marls. Towards the western region, marly dolomites and

anhydrites dominate.

Structurally these deposits are horizontally bedded and show gentle and simple folding. The UCS

values of gypsum are typically in the range of 10MPa to 15MPa and that of mudstone are typically

in the range of 2MPa to 3MPa.

Where the mudstone and gypsum deposits are interlayered, particularly in the Upper Fars units,

cavities are known to occur as a result of dissolution of the gypsum where groundwater flow tends

to concentrate at the mudstone/gypsum interface.

Gypsum is a sulphate based evaporite that is susceptible to dissolution and is generally not

recommended for use in earthworks unless it is permanently saturated in saline water or can be




protected from contact with fresh water. Excavation of thick gypsum deposits, due to the strength

and massive nature of the deposits, typically requires heavy ripping or cutting machinery.

The mudstones are generally easily excavated by mechanical means but have a tendency to

disintegrate. The high fines content can make them difficult to compact in earthworks and they can

contain high sulphates as a result of thin intercalations of gypsum.

If exposed in excavations, permanent cut slopes in gypsum and mudstone will suffer from surface

erosion and may require application of a surface protection such as shotcrete. Excavations can also

suffer from shallow landslides over time as a result of stress release leading to increases in moisture

content in the mudstone and consequent loss of strength.

2.3.6.5 Calcarenite Calcarenites are weakly cemented calcareous sandstones typically occurring within the Upper Fars

Formation. They are usually creamy in colour and have a high concentration of carbonate minerals.

The strata may also be classified as Calcisiltite (silt sized) and Calcilutite (clay sized) rocks, based

on grain size. The deposits are generally very weak to weak with UCS values of between 1MPa and

1.5MPa. Calcernites can typically be excavated easily by mechanical excavators and when

excavated makes for good general fill for use in embankments or building platforms. They can,

however, contain high concentrations of sulphates and chlorides that create an aggressive chemical

environment for concrete.

Rock slopes in the coarser grained deposits tend to be reasonably resistant to erosion. The finer

grained deposits, however, can suffer from erosion and may need surface protection for permanent

cuttings. Rock slope stability is governed by the weak strength of the rock material and also by the

spacing, orientation and condition of the discontinuities within the rock mass. Excavations in these

materials must be designed accordingly, based on geological mapping and rock mass

characterisation.

In temporary cuts, these deposits can often stand near vertical in the short term, but may suffer brittle

collapse if cut too steep or left unsupported for long periods.

2.3.6.6 Limestone Many limestone units are present in the region but are only exposed at ground surface in the eastern

parts of the Abu Dhabi emirate, near Al Ain and the Hajar mountains. Limestones predominate in

the Asmari, Dammam and Simsima Formations. The limestones vary in composition from weak

marly limestones to strong reef limestones. UCS values for the limestones show a wide range from

5MPa to 100MPa.

Excavatability depends on the material strength and spacing of bedding and joint planes. Stronger,

massive units may require blasting but the weaker more fractured rock masses can be excavated

by heavy to moderate ripping machines.

Rock slope stability is governed by the spacing, orientation and condition of the discontinuities within

the rock mass and excavations in these materials must be designed accordingly based on geological

mapping and rock mass characterisation.




Stronger limestone units from the Dammam and Simsima Units can make good road or concrete

aggregate. Other deposits can make for good general fill but may require crushing to obtain suitable

particle sizes. The deposits are typically not prone to high sulphates or chlorides.



Page 13 03-PRELIMINARY SOURCES STUDY Second Edition June-2021

3 PRELIMINARY SOURCES STUDY

3.1 Overview The preliminary sources study is an important part of the geotechnical studies for any Abu Dhabi

roads project. This chapter provides guidance for carrying out a preliminary sources study and

associated site reconnaissance. It also provides details on the sorts of information that are typically

available and should be considered for review.

3.2 Scope of preliminary sources study It is essential to carry out a preliminary sources study at an early stage in any geotechnical

investigation. The primary objectives of the preliminary sources study are to evaluate the ground and

groundwater conditions based on existing information and to assess the scope of any further

investigations that are required. This should cover both engineering and environmental assessment

aspects of a scheme. A list of the sorts of information that may be routinely required for a preliminary

sources study is given in Table C1 in Appendix C. The precise information to be gathered should,

however, be project specific with the scope of the preliminary sources study being determined by

the project geotechnical practitioner.

A significant amount of information about a site may already be available in existing records. A list of the most important sources of information is given in Table C2 in Appendix C. As part of the preliminary sources study a reconnaissance of the site and where possible also the

area immediately surrounding it, should be made. Table C3 in Appendix C provides a summary of

the procedure for site reconnaissance and the main points to be routinely considered. The precise

extent of the reconnaissance required at any site should, however, be established by the

geotechnical practitioner taking account of the particular circumstances of the site and scheme. The

geotechnical practitioner should extend or modify the standard procedure to reflect the site and

scheme needs.

Road and railway cuttings and the likes of quarries in the locality of a site can provide useful

information on soil and rock types and their stability characteristics. Similarly the likes of

embankments, buildings or other structures with a history of settlement can provide useful evidence

of unstable or compressible soils. Surface (geomorphological) features on a site can also provide

evidence of the ground conditions that exist, for example ground collapse depressions might be

indicative of underground cavities.

Further information on carrying out preliminary sources studies can be found in

BS5930:1999+A2:2010 (7), AASHTO Manual on Subsurface Investigations (1988) (8) and in Section

1 of ICE (1998) -The Value of Geotechnics in Construction (9).



Page 14 04-GROUND INVESTIGATION PLANNING Second Edition June-2021

4 GROUND INVESTIGATION PLANNING

4.1 Overview This chapter provides guidance on the phasing of ground investigations, and guidelines for

exploratory holes spacings and depths. It also provides advice on soils and rock sampling, guidance

on engineering parameters typically required for geotechnical design and on soils and rock

laboratory testing to obtain those engineering parameters.

4.2 Introduction The composition and the extent of the geotechnical investigations for a scheme should reflect the

anticipated type and design of the proposed construction. Consequently the geotechnical practitioner

should seek all pertinent information for a scheme from the designer at the early stages of

geotechnical investigation planning and design. For guidance, the sorts of details that should be

obtained are given below:

• Road earthworks: locations, layout, dimensions, geometry and elevations of the sections at

grade, in cutting and on embankment.

• Road structures: locations of bridges and their approaches, tunnels and their approaches,

retaining walls, gantry signage and buildings (for example toll booths, low rise office buildings

or maintenance depots). Information on the structures layout, type of construction

anticipated together with design load and performance criteria.

• Borrow pit requirements and re-use of earthworks materials.

The precise details to be obtained will be project specific and must be established by the

geotechnical practitioner.

With such information the geotechnical practitioner can optimise the design of the geotechnical

investigations and thereby provide overall value for money.

The geotechnical investigations should provide sufficient data on the ground and groundwater

conditions to facilitate a full description of the essential ground properties and a reliable assessment

of the soil and rock parameters to be used in design calculations.

The typical aspects to be considered by the geotechnical practitioner when scoping a ground

investigation are as follows:

The ground

i) the suitability of the site with respect to the proposed construction and the level of

acceptable risks;

ii) the deformation of the ground caused by the structure or earthworks or resulting from

construction works and its behaviour over time;

iii) the safety with respect to limit states, for example settlement, subsidence, ground heave,

uplift, slippage of soil and rock masses;




iv) the loads transmitted to the structure from the ground, for example lateral pressures on

piles, and the extent to which they depend on its design and construction;

v) the foundation methods, for example ground improvement, whether it is possible to

excavate, drivability of piles, drainage;

vi) the sequence of foundation works;

vii) the effects of the structure;

viii) any additional structural measures required, for example support of excavations,

anchorage, sleeving of bored piles, removal of obstructions;

ix) the effects of construction on the surroundings;

x) the type and extent of contamination on, and in the vicinity of the site including the

effectiveness of any existing measures installed to contain or remediate contamination.

Use of excavated materials for construction

i) suitability of the intended use;

ii) the extent of the deposits;

iii) whether it is possible to extract and process the materials, and whether and how suitable

material can be separated and disposed of;

iv) the prospective methods to improve soil and rock;

v) the workability of the soil and rock during construction and possible changes in their

properties during excavation, transport, placement and further treatment.

Groundwater

i) the depth, thickness, extent and permeability of water bearing strata in the ground and

joint systems in rock;

ii) the elevation of the groundwater surface or piezometric surface of aquifers and their

variation over time and actual groundwater levels including possible extreme levels and

their periods of recurrence;

iii) the porewater pressure distribution;

iv) the chemical composition and temperature of groundwater;

v) the scope and nature of groundwater lowering work;




vi) the harmful effects of the groundwater on excavations or on slopes, for example the risk

of hydraulic failure, excessive seepage pressure or erosion;

vii) necessary measures to protect the structure, for example waterproofing, drainage and

measures to protect against aggressive water;

viii) the effects of groundwater lowering, desiccation, impounding on the surroundings;

ix) the capacity of the ground to absorb water injected during construction;

x) whether it is possible to use local groundwater, given its chemical constitution, for

construction purposes;

xi) is there any existing groundwater control in the vicinity of the site, which will need to be

considered;

xii) near tidal waters, groundwater monitoring over a tidal cycle.

Constructability

i) the effects of construction traffic and heavy loads on the ground;

ii) the prospective methods of dewatering and/or excavation, effects of precipitation,

resistance to weathering, and susceptibility to shrinkage, swelling and disintegration.

Further information on the planning of ground investigations can be found in UK Site Investigation

Steering Group (1993). (10)

4.3 Ground investigations proposals

4.3.1 Phasing of ground investigation Ground investigation for road projects is typically undertaken in a three phased approach as follows:

• Phase 1: Often referred to as the Preliminary Ground Investigation. Undertaken in the early

stages of a project for route selection and concept design and/or for scheme preliminary

design for construction tendering purposes.

• Phase 2: Often referred to as the Detailed Ground Investigation. Usually undertaken at the

beginning of a scheme construction contract to provide additional earthwork and structure

specific information for verification of the preliminary design and or update of the design to

be taken to construction.

In some circumstances there could be other phases of ground investigation prior to scheme

construction.

• Phase 3: Often referred to as the Construction Ground Investigation. Usually undertaken

during scheme construction for controlling and monitoring purposes. For example to

investigate particular ground conditions and verify the extent of construction works such as




the treatment of solution cavities or for the installation of piezometers to monitor groundwater

levels associated with dewatering of a deep excavation.

The composition and the extent of the ground investigations should reflect the amount and quality of

available historic exploratory hole information, the particular stage of a project and also the ground

risks as established from a Geotechnical Risk Assessment (discussed in Manual Part 1 Chapter 8)

and reflected in the Geotechnical Category of the project (discussed in Manual Part 1 Section 3.3).

4.3.2 Guidelines for overall coverage of exploratory holes spacings

and depths It is to be noted that the term exploratory holes is used here as it covers all forms of possible

investigative holes, including boreholes, trial pits and trial trenches, that the geotechnical practitioner

may wish to use in a ground investigation.

The geotechnical practitioner should plan each phase of ground investigation to supplement

information already available to ensure that an appropriate level of geotechnical information and data

are available at the particular project stage. The information obtained must be sufficient to enable

the geotechnical practitioner to assess the geotechnical risks relative to the project stage. The

ground investigation would normally be required to establish the soil, rock and groundwater

conditions, and if present the level of contamination and provide for the determination of the

properties of the soil and rock.

The type, frequency and spacing of exploratory holes required for a particular phase of investigation

will depend on the quantity and quality of information already available, the variability of subsurface

conditions, the type of earthworks and structures proposed and the Geotechnical Category of the

project. It is to be noted that, where appropriate the geotechnical practitioner should incorporate in

situ cone penetration testing (ref Section 6.3) within the overall ground investigation design to provide

overall value for money in obtaining the information required on the ground and groundwater

conditions at a site.

For the likes of route selection studies and conceptual design, overall coverage of exploratory holes

(comprising good quality available historic exploratory holes and any required Phase 1 ground

investigation to supplement those data) of up to 300m spacing may be appropriate. For simple

schemes in areas of generally uniform or simple subsurface conditions it may be appropriate to adopt

a greater spacing of up to 500m. For the purpose of preparing a preliminary design for a scheme

then an overall reduced spacing of possibly some 200m may be appropriate with at least one

exploratory hole at important structures such as a bridge foundation. The overall coverage of

exploratory holes and the extent of any Phase 1 ground investigation to supplement available historic

records should, however, be limited to that necessary for making basic design decisions.

For scheme detailed design a much denser spacing of exploratory holes (comprising good quality

available historic records, any Phase 1 ground investigation previously undertaken and any required

Phase 2 ground investigation to supplement those data) will be required. The locations of exploratory

holes and the depths of the investigations should reflect the expected ground conditions, the

dimensions of the structures and earthworks and the engineering problems. Guidelines on the layout

of exploratory holes for detailed design of scheme structures and earthworks are given in Table 2.

Guidelines on the minimum depths requirements for the exploratory holes below the lowest point of




the structure foundation or earthwork are given in Table 3. The precise numbers of exploratory holes,

their locations and depths must, however, be determined by a suitably experienced geotechnical

practitioner based on the project specific geotechnical risk assessment and guidelines provided in

this document, in particular Table-2 & 3.

When selecting the exploratory holes locations, the following should be observed:

i) The investigation points should be arranged in such a pattern that the soils and rock stratification can be assessed across the site.

ii) The investigation points for structures and any buildings should be placed at critical points relative to the shape, structural behaviour and expected loading.

iii) For linear structures the exploratory holes should be arranged at adequate offsets to the centreline depending on the overall width of the structure, such as an embankment footprint or a cutting.

iv) For structures on or near slopes and changes in the terrain (including excavations), the exploratory holes should be located so that the stability of the slope or cut can be assessed. Where anchorages are installed, due consideration should be given to the extent and likely stresses in their load transfer zone.




Table 2: Guidelines for overall exploratory holes spacings for detailed design

Scheme element /

geotechnical hazard

Scheme element

size/layout

Exploratory hole (typically boreholes, trial pits and possibly in situ cone penetration tests where appropriate)

Minimum requirements (1) Additional considerations

Bridge foundations - Advice on the design of the ground investigation

should be sought from a geotechnical practitioner

with knowledge and experience in bridge design

and construction.

1. Additional exploratory holes to be provided in areas of variable sub-

surface conditions.

2. Additional exploratory holes to be provided for unusual foundation

shape and loading.

For piers or abutments

less than 25m wide

One exploratory hole at each foundation

For piers or abutments

over 25m wide

Two exploratory holes at each foundation

Tunnel - Advice on the design of the ground investigation


with knowledge and experience in tunnel design

and construction.

-

- One exploratory hole at each portal and/or launch and

reception shafts.

One exploratory hole at intermediate shafts

Exploratory holes at 25 to 50m intervals along the

tunnel alignment depending on the initial geological

assessment and/or terrain.

Retaining walls For retaining walls less

than 25m length

One exploratory hole at each retaining wall 1. Additional exploratory holes inside and outside the wall line to define

conditions at the toe of the wall and in the zone behind the wall to

estimate lateral loads, engulfing slope failure and anchorage

capacities. For retaining walls over

25m length,

Spacing between exploratory holes should be no

greater than 25m at each retaining wall.

Gantry signs - One exploratory hole at each foundation. -




Scheme element /

geotechnical hazard

Scheme element

size/layout



Cuttings

For cuttings of less than

25m length

One exploratory hole at each cutting. 1. Additional exploratory holes perpendicular to the cutting (typically a

minimum of 3) to be provided at critical locations and high cuts to define

the ground and groundwater conditions for stability analysis design.

2. For existing slopes affected by landslide instability there should be at

least one exploratory hole upslope of the landslide.

For cuttings of greater

than 25m length


greater than 100m at each cutting in simple ground

conditions. Reduce minimum spacing required in more

difficult ground conditions relative to complexity.

Embankments For embankments of

less than 25m length

One exploratory hole at each embankment. 1. Additional exploratory holes perpendicular to the embankment to be

provided at critical locations and high embankments (typically a

minimum of 3) to define the ground and groundwater conditions for

settlement and stability analysis design. For embankments of

greater than 25m

length


greater than 100m at each embankment in simple

ground conditions. Reduce minimum spacing required

in more difficult ground conditions relative to

complexity.

Carriageways - Spacing between exploratory holes along the

carriageway alignment generally should not exceed

250m.

1. Some of the exploratory holes should be off-set from the centreline.

2. The spacing and locations of the exploratory holes should be reduced

in the case of complex ground and groundwater conditions (eg sabkha)

to ensure that the vertical and horizontal boundaries of the distinct soil

and rock units within the project limits are defined. Use may be made

of boreholes sunk for other scheme elements such as embankments,

cuttings and structures.

3. In addition to boreholes, the excavated trial pits shall be utilized to

collect bulk samples from subgrade. CBR and other field/laboratory

tests shall be carried out on samples collected at/below subgrade

instead of zone planned to be excavated for pavement construction.

Culverts - One exploratory hole at each major culvert 1. Additional exploratory holes should be provided for long culverts or in

areas of very variable subsurface conditions.




Scheme element /

geotechnical hazard

Scheme element

size/layout



Non-destructive

crossings

For crossings less than

25m length

Two exploratory holes, one at each end of the crossing

(close to crossing ends at the launch and reception

locations/pits).

1. Additional exploratory holes should be provided for long crossings or

in areas of very variable subsurface conditions.

Non-destructive

crossings (continued)

For crossings of

greater than 25m

length

Two exploratory holes, one at each end of the crossing

(close to the crossing ends at the launch and reception

locations/pits).

One borehole at crossing centre point.

1. Additional exploratory holes should be provided for long crossings or

in areas of very variable subsurface conditions.

Low rise buildings

(e.g. toll plaza or road

maintenance depot),

shades or other

landscaping

structures.

- One exploratory hole at building/structure location 1. Additional exploratory holes to be provided in areas of variable sub-

surface conditions.

2. Additional exploratory holes to be provided for unusual foundation

shape and loadings.

Landslides - Advice on the design of the ground investigation


with knowledge and experience in the

investigation and interpretation of landslides, their

management and in the design and construction

of remediation measures.

At minimum three boreholes along critical section

perpendicular through the landslide to establish

ground model including groundwater conditions for

analysis. One borehole should be upslope of the area

of instability.

-

Natural cavities - Advice on the design of the ground investigation



-




Scheme element /

geotechnical hazard

Scheme element

size/layout



investigation and interpretation of natural cavities,

their management and in the design and

construction of remediation measures.

Materials borrow

areas

- One exploratory hole every 1,000m2 of borrow area 1. Additional exploratory holes should be provided areas of variable

subsurface conditions.

Note:

(1) The provided spacing in table-2 are between two similar type of exploratory holes and should be finalized in conjunction with the depth requirements provided in Table-3.




Table 3: Guidelines for exploratory holes depths

Scheme element /

geotechnical hazard

Foundation type Depth of exploratory holes below the lowest point of the structure foundation or earthwork

Minimum depth requirements (Dmin ) (1) Additional considerations

B = breadth (m), L = length (m), Dia = diameter (m), H = height (m)

Bridge (abutments

and piers)

Spread foundation For L<2B take Dmin = greater of 5m or 2B

For L>4B take Dmin = greater of 6m or 3B

For L between 2B and 4B interpolate between the

above.

1. Extend exploratory hole depth in unfavourable ground conditions

such as weak or compressible strata.

Pile foundations For single piles Dmin = 5m or 3Dia of the pile

whichever is the greater in competent strata (below

the estimated depth of the pile toe)

For pile groups Dmin must also be greater than B for

the area circumscribing the pile group area in

competent strata.

1. Extend exploratory hole depth in unfavourable ground conditions

such as weak or compressible strata.

2. If tension piles are needed the depth of investigation should be

as for pile foundations.

Tunnel - Advice on the design of the ground investigation


with knowledge and experience in tunnel design

and construction.

If vertical alignment is known Dmin = 1Dia to 2Dia of the

tunnel below tunnel invert.

-

Retaining walls Gravity and cantilever

walls (spread footing)

Dmin = 5m or 2B whichever is the greater.

In the case of piled footings the same as bridge pile

foundations applies.

1. Extend exploratory hole depth in situations with sloping ground

behind retaining wall.

2. Extend exploratory hole depth to provide sufficient information to

allow comprehensive stability assessment of engulfing slope

failures of the retaining wall.

3. Extend exploratory hole depth in unfavourable ground

conditions such as weak or compressible strata.

Embedded walls Dmin = 1.5H for the wall retained height




Scheme element /

geotechnical hazard



Gantry signs

Spread footings Dmin = 5m or 2B whichever is the greater. -

Pile foundations For single piles Dmin = 5m or 3Dia of the pile

whichever is the greater in competent strata.

For pile groups Dmin must also be greater than B for the

area circumscribing the pile group area in competent

strata.

-

Cuttings - Dmin = 2m or 0.4H for the cutting whichever is the

greater, below the base of the cutting.

1. Extend exploratory hole depth to provide sufficient information to

allow comprehensive stability assessment of cutting slope.

Embankments - Dmin = 5m or 1.2H for the embankment whichever is

the greater, below embankment founding level.

1. Exploratory holes should extend to a depth where the additional

stress owing to the embankment is less than 10% of the imposed

load at its base.

2. Exploratory holes should be extended in unfavourable ground

conditions such as weak or compressible strata to competent

strata.

Carriageways (at

grade sections)

- Dmin = 4m below the proposed formation level. 1. Exploratory holes should be extended in unfavourable ground


strata.

Culverts Ground bearing Dmin = 4m below the invert level or 1.5B of the trench

whichever is the greater

1. For major culverts Dmin = 5m or 3B of the trench whichever is

the greater should apply.

Piled For single piles Dmin = 5m or 3Dia of the pile

whichever is the greater in competent strata.

For pile groups Dmin must also be greater than B for

the area circumscribing the pile group area in

competent strata.

-




Scheme element /

geotechnical hazard



Non-destructive

crossings

- Dmin = 4m below crossing invert level or 3Dia

whichever is the greater.

-

Low rise buildings

(e.g. toll plaza or road

maintenance depot),

shades or other

landscaping

structures.

- Dmin = 5m or 3 times width of the spread footing

whichever is the greater, below building founding level.

For pile foundations criteria for bridge pile foundations

should be adopted.

1. Exploratory holes should extend to a depth where the additional

stress owing to the building is less than 10% of the imposed load

at its base.

2. Exploratory holes should be extended in unfavourable ground


strata.

Landslides - Advice on the design of the ground investigation



investigation and interpretation of landslides, their

management and in the design and construction of

remediation measures.

Dmin has to prove the depth of the landslide together

with the geological sequence of soils and rocks that

make up the landslide and the affected slope.

1. Geomorphological mapping and assessment of the landslide

should be initially carried out and used to design the ground

investigation and should also be used to assist in development

of the ground model.

Natural cavities - Advice on the design of the ground investigation



investigation and interpretation of natural cavities,

their management and in the design and

construction of remediation measures.

Dmin has to prove the bedrock cover to potential or

known cavities to between 3 and 5 times the

anticipated cavity width.

1. Geophysical survey mapping and assessment of the natural

cavities should be initially carried out and used to design the

ground investigation and also be used to assist in development

of the ground model.

Materials borrow

areas

- Dmin = base of the deposit or to the depth required to

provide the quantity of materials needed.

-




Note:

(1) It is designer responsibility to ensure that required criteria of investigation shall be fulfilled during the design stage. In-case, investigation results may require further additional

number of boreholes and/or few boreholes may require to extend up to greater depth, efforts shall be made to execute it during design stage. However, if due to time or other

constrains the additional/extended boreholes cannot be executed during design stage along with main investigation, then particular additional scope can be added to verification

stage investigation (construction stage). Approval and agreement with authority reviewer shall be required in this regard and design Consultant shall undertake full responsibility

of the design, errors and associated risks due to non-compliance to the investigation requirements at design stage (if any).




4.4 Soils and rocks sampling and testing to obtain

engineering parameters for use in geotechnical design

4.4.1 General The derivation of engineering parameters for soils and rocks for use in geotechnical design will

usually form an important part of a geotechnical investigation. It is essential, therefore, that in

designing a ground investigation the geotechnical practitioner duly considers the soils and rock

properties that need to be investigated and the engineering parameters that will be required for

design of both permanent earthworks and structures and any temporary measures required for their

construction, for example support to a deep excavation. He can then design within the ground

investigation a programme of in situ testing, soils and rock sampling for subsequent laboratory

testing and in special cases possibly even field trials to enable him to derive the parameters required.

The type, quantity and sophistication of the geotechnical test data required for a project will depend

on the nature of the ground and the importance and sensitivity of the structure or earthwork. For

most projects in Abu Dhabi, in situ standard penetration testing (SPT) with bulk sampling of soils for

classification and chemical testing will form the basis of the ground investigation. In bedrock, cores

will normally be taken for laboratory determination of the rock unconfined compressive strength. For

some major structures, such as bridges, the consequences of a foundation failure or excessive

settlement are likely to be severe. In those cases more sophisticated in situ and laboratory testing

may be appropriate to provide the data required for specialist modelling of the ground structure

interaction during and post construction and possibly also during extreme events such as an

earthquake. Before embarking on a programme of expensive tests careful consideration should be

given to the aims, applicability and cost benefits of such testing.

Table 4 provides a list of the main soils properties and engineering parameters that might be required

to be determined for use in design, together with symbols and units used for those properties in later

sections of this manual.

Table 5 provides a list of the main rock properties and engineering parameters that might be required

to be determined for use in design, together with symbols and units used for those properties in later

sections of this manual.




Table 4: Soils properties/engineering parameters, symbols and units

Symbol Units Soils property/engineering parameters

Classification properties


wI % Liquid limit (LL) Collectively referred to as Atterberg limits

wp % Plastic limit (PL)

Ip % Plasticity index (PI)

γ Mg/m3 Bulk density/Mass density

γd Mg/m3 Dry density (maximum γdmax or minimum γdmin)

- - Particle size distribution (PSD) – fine and coarse

ρs Mg/m3 Particle density

- % Organic content (O)

Compaction/compaction related and CBR properties

- - Moisture content/dry density relationship (COMP)

- % California Bearing Ratio (CBR)

Chemical properties

- - pH, sulphate and chloride, as appropriate



Electrochemical properties



Shear strength properties

cu kPa (kN/m2)* Undrained shear strength

cr kPa (kN/m2)* Remoulded shear strength

c’ kPa (kN/m2)* Drained cohesion intercept Peak effective shear strength

’ degrees Drained angle of shear resistance

cr’ kPa (kN/m2)* Drained residual cohesion intercept Residual effective shear strength

r’ degrees Drained residual angle of shear resistance

c’crit kPa (kN/m2)* Critical state cohesion intercept (usually zero)

Critical state effective shear strength

’crit degrees Critical state angle of shear resistance





Consolidation and elastic properties

mv m2/MN Coefficient of volume compressibility (one dimensional)

cv m2/yr Coefficient of consolidation (one dimensional)

Eu MPa (MN/m2)* Young’s modulus of elasticity (undrained)

E’ MPa (MN/m2)* Young’s modulus of elasticity (drained)

E’0.01 MPa (MN/m2)* Young’s modulus of elasticity (small strain)

G MPa (MN/m2)* Shear modulus

Gmax MPa (MN/m2)* Very low strain shear modulus

ν - Poisson’s ratio (νu – undrained, ν’ – drained)

Ko - Coefficient of earth pressure at rest

ks kN/m3 Modulus of subgrade reaction

Permeability

k m/s Coefficient of permeability, horizontal (kh), vertical (kv) as appropriate

Notes:

* Units in brackets also commonly used.




Table 5: Rock properties/engineering parameters, symbols and units


Classification properties


n % Porosity

γ Mg/m3 Density

Chemical properties (Chem) (as appropriate)

- - pH, sulphate and chloride, as appropriate



CaCO3 % Carbonate content (total)

Electrochemical properties (EChem)



Strength and mass properties

I - Point load index, axial (Ia), diametral (ld), lump (Il)

UCS MPa Uniaxial compressive strength

- MPa Tensile strength

m and s - Rock material constants

RMR - Rock mass rating

j - Mass factor j

c’ MPa Discontinuity drained cohesion intercept

Discontinuity peak effective strength

’ degrees Discontinuity drained angle of shear resistance

cr’ MPa Discontinuity drained residual cohesion intercept

Discontinuity residual effective shear strength

r’ degrees Discontinuity drained residual angle of shear resistance

Elastic properties

E MPa Young’s modulus of elasticity

Es MPa Young’s modulus of elasticity (small strain/initial modulus)

G MPa Shear modulus

Gs MPa Shear modulus (small strain/initial modulus)





ν - Poisson’s ratio

4.4.2 Difficulties in parameter determination It is to be recognised that only a very small proportion of the ground that will be influenced by the

proposed structures and earthworks is tested in situ or sampled during a ground investigation. Also,

only a selection of the samples recovered are usually tested in the laboratory. Therefore, testing

must be carried out using reliable and repeatable techniques that will yield parameters representative

of the bulk of the soil or rock in situ.

Soil parameters can be derived from in situ testing, laboratory testing and field trials. There are,

however, several factors that will influence the measured values, many of which are inherent or

unavoidable. The geotechnical practitioner should be aware and appreciate the magnitude of these

influences on the required parameter and where necessary take these into account based on his

experience and published knowledge. The factors which affect the measured soil and rock

parameters can be categorised as follows:

i) natural variability

ii) sampling and testing procedures

iii) interpretation.

4.4.2.1 Natural variability Lateral and vertical variability on a large scale will lead to scatter of test results. There may also be

small scale variability in the likes of sabkha and lagoonal muds that could require particular

consideration. Soils are also typically anisotropic with, particularly, their compressibility and

permeability being different in the vertical and horizontal directions. The orientation of soil testing

may, therefore, need to be considered also with respect to the proposed structures and earthworks.

With regards to soil laboratory testing for the likes of shear strength and consolidation properties

owing to the non-linear stress-strain behaviour of soils it is essential that testing is carried out over

the appropriate working stress range of the proposed construction.

Fabric features such as local cementing in sands and laminations in lagoonal clays can also have a

significant influence on measured engineering properties. It is therefore important to recognise the

presence of such fabric within the soil and be aware of the possible influence it has on the test

results.

The stress history that a soil has undergone will also affect the way it responds to an imposed load.

In some cases it may be important to understand and possibly model the stress history and to model

the stress changes that the works will cause to achieve the most accurate prediction of soil

behaviour.

4.4.2.2 Sampling and testing procedures All in situ testing and sampling techniques cause disturbance to the soil and to a greater or lesser

extent some rocks fabric. This is a combination of physical remoulding of the soil and modification

of its state of stress from that existing in situ. BS5930:1999+A2-2210(7) provides a quality

classification for soil samples (Class 1 to Class 5) and provides guidance on the soils properties that

can be reliably determined from each class of sample, ref Table 6.




Table 7 lists the types of samples that are generally most suitable for taking in Abu Dhabi soils and

provides guidance on the quality class of those samples, for cross reference with Table 6. Further

guidance on preferred methods for drilling in different soils types, achievable standards of sampling

and quality class of samples that might be obtained may be found in BS EN ISO 22475-1:2006(11).

Table 6: Quality classification for soil samples

Soil sample

quality class

Properties that can be reliably determined

Stra

ta s

eq

uen

ce

Par

ticl

e si

ze

dis

trib

uti

on

,

Att

erb

erg

limit

s,

par

ticl

e d

ensi

ty

Mo

istu

re c

on

ten

t

Bu

lk d

ensi

ty

Shea

r st

ren

gth

Def

orm

atio

n a

nd

con

solid

atio

n

Class 5 * - - - - -

Class 4 * * - - - -

Class 3 * * * - - -

Class 2 * * * * - -

Class 1 * * * * * *

Table 7: Sampling techniques for Abu Dhabi soils

Soil type Type of drilling/

exploratory hole

Sampling technique Quality

class

Aeolian sand Light cable percussion

boring (preferred method)

SPT sampler

Bulk sample

Class 4

Class 4

Rotary (usually tricone bit

open hole)

SPT sampler Class 4

Trial pit Bulk sample Class 4

Fluvial sands

/ gravels

Light cable percussion


SPT sampler (in sands)

Bulk sample

Class 4

Class 4


open hole)

SPT sampler (in sands) Class 4

Sabkha



Piston thin wall (PS-T/W)

Open-tube thin wall (OS-T/W)

Open-tube thick wall (OS-TK/W)

SPT sampler

Bulk sample

Class 1

Class 1

Class 2

Class 4

Class 4




Soil type Type of drilling/

exploratory hole

Sampling technique Quality

class


open hole)


SPT sampler

Class 1

Class 4

Lagoonal

muds



Piston thin wall (PS-T/W)


Open-tube thick wall (OS-TK/W)

SPT sampler

Bulk sample

Class 1

Class 1

Class 2

Class 4

Class 4


open hole)


SPT sampler

Class 1

Class 4

For sampling of rock strata, rotary core drilling using a double tube barrel is most widely used in Abu

Dhabi and preferably should also include use of a core liner. Core sizes H (76mm diameter) and P

(92mm diameter) are most commonly used. With drilling care a high level of core recovery can

usually be achieved. Core recovery of 90% minimum in any single core run can normally be attained,

and usually core recovery of close to 100% can be obtained. It should be noted that coring at a larger

diameter will usually provide a better recovery and quality of core compared to a smaller diameter

core in the same strata. Where high pressure dilatometer testing of rock strata is undertaken, then

the ‘pockets’ for those tests is normally achieved by coring at N size (54.5mm diameter).

To ensure that representative properties and engineering parameters are determined for soils and

rock strata which are inherently variable, a reasonable number of samples should be subjected to

laboratory testing. The precise numbers and types of tests to be undertaken must be based on a

comprehensive understanding of the scheme and the engineering parameters required for design

together with appreciation of the different deposits and variation within them encountered in the

ground investigation exploratory holes. Considerable experience is required to attain the right

balance of cost effective data.

Guidelines on the minimum number of samples to be tested for each soil stratum in a scheme

element (for example a bridge or embankment length) are given in Table 8. Guidelines on the

minimum number of samples to be tested for each rock stratum in a scheme element are given in

Table 9. Further guidance on the minimum numbers of samples to be tested may be found in BS EN

1997-2:2007(12).




Table 8: Guidelines on the minimum number of samples to be tested for particular soils laboratory tests

Soil property/engineering parameter

Number of samples to be tested in each soil stratum per scheme section

Minimum number Additional considerations

Classification tests

Moisture content (w) 5 These classification tests should be undertaken on all samples on which shear strength and or consolidation/elastic properties are determined. The classification test data will often prove helpful in explaining atypical strength or consolidation/elastic properties test results that lie outside the general data set for a particular soils stratum.

In situ density tests may be undertaken instead of/in addition to laboratory bulk density tests.

Plasticity index (Ip), liquid limit (wI) and plastic limit (wp)

5

Bulk density (mass density) (γ) 3

Particle size distribution (PSD) 5

Particle density (or specific gravity) (ρ8) 2 -

Compaction/compaction related tests & California Bearing Ratio

Dry density/moisture content relationship 3 The number of tests should be selected considering the variation of the particle size distribution and the quantity of material to be compacted. 4.5kg rammer tests are mainly undertaken with the occasional 2.5kg rammer test.

California Bearing Ratio (CBR) 3 In situ CBR tests may be undertaken instead of/in addition to laboratory CBR tests. Resilient modulus may be estimated from CBR and published correlations.

Chemical tests

Soil sulphate content, chloride content and pH

3 -

Water sulphate content, chloride content, pH 3 -

Shear strength

Undrained shear strength 3 Triaxial compression method (without measurement of pore pressure)

Effective shear strength 3 Direct shear (small shear box) method, consolidated undrained triaxial with measurement of pore pressure or consolidated drained triaxial with measurement of volume change or combination of the three methods of test. For sands shear box tests are commonly undertaken on remoulded specimens.

Residual effective shear strength 3 Direct shear (small shear box) method or ring shear or combination of the two methods of test.





Number of samples to be tested in each soil stratum per scheme section



One dimensional consolidation 3 Oedometer cell or hydraulic cell test or combination of the two methods of test

Permeability

Coefficient of permeability (k) 3 Consideration to be given to both vertical permeability (kv) and horizontal permeability (kh)

Table 9: Guidelines on the minimum number of samples to be tested for particular rock laboratory tests

Rock property/engineering parameter

Number of samples to be tested in each rock stratum per scheme section



Moisture content (w) 5 Moisture content and bulk density measurements are often carried out and reported as part of uniaxial compressive strength testing.

Bulk density (mass density) (γ) 5

Strength testing

Uniaxial compressive strength (UCS) 5 -

Point load testing 10 -

Chemical tests

Carbonate content 3 -

Soil sulphate content, chloride content and pH

3 -

Water sulphate content, chloride content, pH 3 -




4.4.2.3 Interpretation Some of the largest errors in the derivation of engineering parameters can arise in making the

interpretative step from a series of in situ or laboratory test results to the engineering parameter to

be used in design calculations. With the natural variability in soils and rocks (Sub-section 4.4.2.1)

and the overall limited extent of in situ and soils laboratory testing there is the inevitable risk that the

likes of the soils and rocks strengths and deformation characteristics are inferior to the test results.

In case where soils laboratory testing is undertaken on remoulded test specimens where larger

particle sizes are removed then those tests will give results that are inferior to the performance of

the in situ materials. Simply taking the average of all the results is seldom appropriate and a

considerable degree of engineering judgement and well-established experience is required to select

the design parameters. The determination of engineering parameters for use in design is discussed

further in Section 8.3

4.5 Guidelines for engineering parameters typically

required A summary of the soils properties and the engineering parameters typically required to be assessed

by the geotechnical practitioner for road schemes is given in Table 10.




Table 10: Engineering parameters commonly required for design and to be considered in planning a ground investigation

Structure/earthwork Design issue Material Engineering

parameters*

normally

required

Usual source of data for

parameter* derivation

Occasional other testing undertaken

and other engineering parameters*

derived In situ

testing/data

Laboratory

testing

Strata abbreviations: AS – aeolian sand, FSG – fluvial sand/gravel, S – sabkha, LM – lagoonal mud, R – rock *for parameter abbreviations refer to Table 4 &

Table 5

Structures (All) Chemical attack on

buried concrete and

steel corrosion

Soils (All) Chemical

properties

- pH, SO4, Cl

Bridge

(including

abutments and

piers), gantry

signs

Spread

footings

Sizing//bearing capacity Soil (AS, FSG) γ, ’, ks SPT N, CPT,

density tests

- Soil & rock (All) – field pressuremeter

testing.

Soil (AS, FSG) – laboratory small & large

shear box tests for ’.

Soil (S, LM) – laboratory triaxial tests for

cu and c’+ ’.

Rock γ, UCS, ks

m, s, RMR

Fracture indices,

rock exposures

preferably (or core

if no exposures

available)

UCS (and PL)

Settlement

(components, total,

differential and rate)

Soil (AS, FSG) E’ SPT N, CPT - Soil & rock (All) – field pressuremeter

testing.

Soil (AS, FSG) – field plate bearing test

for E’.

Soil(S, LM) – field testing for k and

laboratory oedometer tests for mv and cv.

Rock E’ (& Es),

RMR

Fracture indices,

rock exposures

(or core if no

exposures

available)

UCS with

strain gauges

Pile

foundations

Carrying capacity (axial

and lateral), downdrag/

negative skin friction

Soil (AS, FSG) γ , ’, ks SPT N, CPT - Soil & rock (All) – field pressuremeter

testing.



Soil (S, LM) – laboratory oedometer tests

for mv and cv and triaxial tests for cu

Rock

UCS - UCS (and PL)





parameters

normally

required


parameter derivation

Occasional other testing and

engineering parameters required

In situ

testing/data

Laboratory

testing

Bridge

(including

abutments and

piers), gantry

signs

(continued)

Pile

foundations

(continued)

Settlement/ deflection of

laterally loaded piles

Soil (AS, FSG) E’ SPT N, CPT - Soil (AS, FSG) – field plate bearing test for

E’

Rock E (& Es),

RMR

Fracture indices

rock exposures

(core if exposures

not available)

UCS with

strain gauges

Tunnels Loading on tunnel lining Soil (AS) γ , ’, E’, ν,

Ko

SPT N, CPT - Advice on parameters for design

should be sought from a geotechnical

practitioner with knowledge and

experience in tunnel design and

construction.

Soil & rock (All) – field pressuremeter

testing.

Soil (AS, FSG) – field plate bearing test for

E’



Soil (S, LM) – laboratory oedometer tests

for mv and cv and triaxial tests for cu and

c’+ ’.

Rock γ ,UCS, E (&

Es), ν, Ko,

RMR

Fracture indices

rock exposures

(core if exposures

not available)

UCS with

strain gauges

Retaining walls Gravity wall Bearing capacity Soil (AS, FSG) γ, ’, ks SPT N, CPT

density tests

- Soil & rock (All) – field pressuremeter

testing.

Rock γ, UCS, m,

s, RMR

Fracture indices

rock exposures

UCS (and PL)




(core if exposures

not available)


shear box tests for ’ (and ’r where soils

are affected by landslide.


parameters

normally

required





In situ

testing/data

Laboratory

testing

Retaining walls

(continued)

Gravity wall

(continued)

Sliding resistance Soil (AS, FSG) ’ SPT N, CPT - Soil (AS, FSG) – field plate bearing test for

E’

Soil(S, LM) – laboratory oedometer tests

for mv and cv and triaxial tests for cu and

c’+ ’.

Rock – laboratory rock shear box for c’+

’.

Rock γ, c’ + ’ - -

Stability (engulfing

failures)

Soil (AS, FSG) γ, ’

SPT N, CPT,

density

-

Cantilever/

anchored

embedded

wall

Wall stability &

engulfing stability

Soil (AS, FSG) γ, ’, ks

SPT N, CPT,

density

-

Anchorage design Soil (AS, FSG) γ, ’ SPT N, CPT,

density

-

Soil cuttings Stability Soil (AS, FSG) γ, ’ SPT N, CPT,

density

- Soil (AS, FSG) – laboratory small & large



shear box tests for c’+’ (and c’r+’r where

soils are affected by landslide).

Soil (S,LM) γ, cu , c’+ ’ Triaxial tests

(UU, CU+PWP

, CD)

Rock cuttings Stability Rock γ, c’ + ’,

RMR’

Discontinuity

spacing and

orientation rock

exposures (core if

no exposures)

UCS Rock – laboratory rock shear box for c’+

’.




Embankments Stability Soil (AS, FSG) γ, ’ SPT N, CPT,

density

- Soil (AS, FSG) – laboratory small & large


Soil (S, LM) – laboratory small shear box

tests for c’+’ & (c’r +’r where soils

affected by landslip).

Soil (S, LM) γ, cu, c’ + ’ - Triaxial tests

(UU, CU+PWP

, CD)


parameters

normally

required





In situ

testing/data

Laboratory

testing

Embankments (continued) Settlement

(components, total,

differential and rate)

Soil (AS, FSG) E’ SPT N, CPT - -

Soil (S, LM) mv, cv, k Permeability test Oedometer

Road pavement Strength, trafficability

and requirement for

capping layer

Soil (All) CBR CBR CBR -

Excavatability Excavatability Rock UCS RMR Discontinuity

spacing and

orientation, rock

exposures

preferably (or core

if no exposures

available)

- -

Structures and earthworks -

general

Groundwater flow - kv & kh Permeability test

and infiltration test

Permeability

test

Published correlations for permeability

based on particle size distribution data.

Notes

(1) Triaxial tests: UU – Unconsolidated undrained (quick undrained), CU+PWP –Consolidated undrained with porewater pressure

measurement, CD – Consolidated drained.

(2) The geotechnical practitioner will be responsible for making a final determination of the parameters required for design.




4.6 Laboratory tests for determining soils, groundwater and

rock properties and engineering parameters

4.6.1 Soils and groundwater

A list of the soils properties and engineering parameters commonly determined from laboratory tests

for Abu Dhabi road projects is given in Table 11. The table also provides guidance on the standards

that should be used for the particular laboratory test.

A list of the soils properties and engineering parameters occasionally determined from laboratory

tests for Abu Dhabi road projects is given in Table 12. The table also provides guidance on the

standards that should be used for the particular laboratory test.

A list of the groundwater properties that are commonly determined from laboratory tests for Abu

Dhabi road projects is given in Table 13. The table also provides guidance on the standards that

should be used for the particular laboratory test.

Further guidance on the selection of soils laboratory testing can be found in the AGS Guide: The

selection of geotechnical soil laboratory testing (1998) (13).




Table 11: Soil properties and engineering parameters commonly determined from laboratory tests for Abu Dhabi road projects


Test methods for laboratory measurement Cost/ complexity category(1)

Notes including comments on alternative indirect methods of engineering parameter assessment

BS ASTM AASHTO


Moisture content (w) BS1377.Part 2.Cl 3(14) D2216-10(15) - A -

Plasticity index (Ip), liquid limit (wI) and plastic limit (wp)

BS1377.Part 2.Cl 4,5(14)

D4318-10(16) T89-10(17) T90-00 (18)

A -

Bulk (mass) density (γ) BS1377.Part 2.Cl 7 (14) D7263-09(19) - A In situ tests are preferred in granular soils.

Dry density (γd) BS1377.Part 2.Cl 7 (14) D7263-09(19) - A -

Particle density (ρ8) BS1377.Part 2.Cl 8 (14) D854-10(20) T100-06(21) A Obtained by calculation if w and ρ are known.

Particle size distribution BS1377.Part 2.Cl 9 (14) D422-63 (2007)(22)

T88-10(23) A -

Shear strength

Effective stress strength parameters

(Φ’ and Φcrit’)

Direct shear (shear box) methods BS1377,Part 7,Cl 4,5 (24)

D3080-04(25)

- B/C -

Compaction/compaction related tests & California Bearing Ratio

Dry density/moisture content relationship BS1377.Part 4.Cl 3(24) D698-07 (26)

D1557-09 (27)

T099-10 (28)

T180-10(29)

A/B -

California Bearing Ratio (CBR) BS1377.Part 4.Cl 7 (24) D1883-07 (30) - A/B Direct field measurement of CBR is preferred if the ground conditions are suitable.

Maximum density (pmax) minimum density (pmax)

BS1377.Part 4.Cl 4 (24) D4253-00(2006) (31)

D4254-00(2006) (32)

- A/B -

Chemical tests







BS ASTM AASHTO

Sulphate content of soil BS1377.Part 3.Cl 5 (33) C1580-09e1(34) - A BS covers both acid soluble and water soluble sulphate. ASTM covers water soluble sulphate. The determination of water soluble sulphate is most commonly made.

Chloride content of soil BS1377.Part 3.Cl 7 (33) C1524-02a(2010) (35)

T291-94(36) A ASTM test is used for testing aggregates

pH value BS1377.Part 3.Cl 9 (33) G51-95 (2005)(37) - A -

Carbonate Content BS377.Part 3.C l6 (33) D4373-02(2007)(38)

- A ASTM provides result as Calcite (CaCO3) equivalent BS results need to be corrected to be in CaCO3 equivalent.

Magnesium value in soil - C114-11b Section 16 (39)

- B -

Water Soluble Salts in Soil BS 1377 : Part 3 : 1990 (Amd. 9028-96), and Earth Manual Des.8

- - A Shall be tested at 0.5m interval for soil above groundwater table and few samples from soil below groundwater table.

Notes:

(1) Cost/complexity category definitions:

A - Low cost routine test: Normally carried out in large numbers to classify soils and to assess consistency of soil parameters.

B - More expensive, relatively routine test: Normally carried out selectively to determine design parameters.

C - High cost complex test: Normally carried out only when absolutely necessary to establish or confirm design parameters.





Table 12: Soil properties and engineering parameters occasionally determined from laboratory tests for Abu Dhabi road projects




BS ASTM AASHTO


Dispersibility tests, pinhole crumb and dispersion methods

BS1377.Part 5.Cl 6 (40) D4647-06e1 (41) Pinhole method D4221-11 (42) Double Hydrometer

- B -

Organic content (O) BS1377.Part 3.Cl 3 (33) D2974-07a(43) - A -

Collapse potential of soils BS1377.Part 5.Cl 4 (40) D5333-03 (44) - B ASTM working group currently looking at re-working this standard (WK34531)

Chemical tests

Resistivity of soil (rs) BS1377.Part 3.Cl 10 (33)

G187-05 (45)using two electrode soil box method.

- B/C Field tests are usually preferred when practicable.

Redox potential of soil (Eh) BS1377.Part 3.Cl 11 (33)

- - B/C -

Shear strength

Undrained shear strength (cu or cr)

Laboratory vane method BS1377.Part 7.Cl 3* (46)

D4648M-10(47) lab vane. Pocket penetrometer method in development

- A * Often unrepresentative due to small scale and sample disturbance.

cu can also be assessed from classification tests such as plasticity index (Ip) and published correlations.

cu can be assessed from SPT N60 values and static cone penetration tests in many soil types.

Triaxial compression method (without measurement of pore pressure) BS1377.Part 7.Cl 8,9 (46)

D2850-03a(2007)(48)

T296-10(49) A Complementary field strength determinations from in situ tests are often useful.







BS ASTM AASHTO

Shear strength

Effective stress strength parameters

(c’, Φ’ and Φcrit’)

Direct shear (shear box) with multi-reversals BS1377. Part 7 Cl 4,5 (46)

D6528-07(50) Direct shear of cohesive soils

- B/C Φcrit can be assessed from specific classification test measured in the laboratory using modified BS test procedures

Consolidated undrained triaxial (with measurement of pore pressure) BS1377.Part 8,Cl 3 to 7 (51)

D4767-11(52)

- C

Consolidated drained triaxial (with measurement of volume change) BS1377. Part 8. Cl 3,6 & 8 (51)

D7181-11(53)

- C

Residual effective stress strength

parameters (Φr’) Direct shear (shear box) with multi-reversals BS1377. Part 7.Cl 4,5, (46)

New ASTM under development (WK3822)(54)

- C Φr’ can be assessed based on classification tests and published correlations.

Φr’ may be assessed from back analysis of failures.


One dimensional consolidation/swelling properties and pre-consolidation pressure (mv, mv(rebound),cv, cv(rebound) and pc’)

Oedometer cell test methods BS1377.Part 5.Cl 3 (40)

D2435M-11(55)

T216 -07 (56) B mv can be estimated from SPT N60 values in overconsolidated clays

mv can be estimated from static cone penetration test cone resistance

mv can also be assessed based on historical data on the performance of structures.

cv laboratory generally significantly underestimates in situ performance. A field estimate of cv can be made taking cv = k/(γwmv) based on the oedometer mv value, γw (weight density

of water = 9.81kN/m3 )and a field permeability (k) from the likes of a borehole or piezometer permeability test.

Swelling Test Methods BS1377.Part 5.Cl 4 (40)

D4546-08(57) - B

Hydraulic Cell methods BS1377.Part 6.Cl 3 (58)

D4186M-12 (59) - C







BS ASTM AASHTO

Permeability

Coefficient of Permeability (k) Constant Head Method BS1377.Part 5.Cl 5 (40)

D2434-68 (2006)(60)

T215(61) B In situ field tests are usually preferred to laboratory tests

kv and kh in layered soils can be significantly different requiring measurement in tests with suitable sample preparation, orientation and drainage.

k can be assessed from particle size distribution and published correlations.

Falling Head Method (Head K H (1982)(62))

D5084-10(63) - B

Notes:









Table 13: Groundwater properties commonly determined from laboratory tests for Abu Dhabi road projects




BS ASTM AASHTO

Chemical tests

Sulphate content of groundwater BS1377.Part 3.Cl 5 (33) D516-11 (64) - A -

Chloride content of groundwater BS1377.Part 3.Cl 7 (33)

BRE Report 279 (1995)(65)

D512-10(66) - A -

pH value BS1377.Part 3.Cl 9 (33) G51-95 (2005)(37) - A -

Total Dissolved Solids (TDS) BS 1377 : Part 3 : 1990: Cl: 8.

- - A Adequate frequency below groundwater table.

Notes:









4.6.2 Rock

4.6.2.1 Laboratory testing

A list of the rock properties and engineering parameters commonly determined from laboratory tests

for Abu Dhabi road projects is given in Table 14. The table also provides guidance on the standards

that should be used for the particular laboratory test.

A list of the rock properties and engineering parameters occasionally determined from laboratory

tests for Abu Dhabi road projects is given in Table 15. The table also provides guidance on the

standards that should be used for the particular laboratory test.

4.6.2.2 Quality and properties of rock mass

In assessing the quality and properties of rocks and rock masses the geotechnical practitioner has

to make a distinction between the behaviour of rock material as measured in the laboratory on core

samples and the behaviour of the much larger rock masses in the field which include structural

discontinuities such as bedding planes, joints, shear zones and solution cavities. In assessing rock

mass behaviour consideration needs to be given to the following characteristics of the joints:

• spacing

• orientation

• aperture, persistence (continuity)

• tightness

• roughness, including the effects of previous movements on the joints

• any joint infilling.

Those characteristics can be assessed from logging on site of nearby rock exposures or by

orientation of recovered rock core. Guidance on the recording of rock exposures is given in

references, ISRM (1989) (67), TRL (2011) (68), TRL (2011) (69) and Hoek & Bray (1994) (70) and

the method to be adopted on a project will need to be determined by a suitably qualified and

experienced geotechnical practitioner.

Estimates of rock mass properties such as strength and stiffness may be obtained by using the

concept of rock mass classification. Further details can be found in Bieniawski (1976)(71), Bieniawski

(1989)(72), Barton (2002)(73) and Hoek et al (2002)(74).




Table 14: Rock properties and engineering parameters commonly determined from laboratory tests for Abu Dhabi road projects




BS ASTM ISRM/Other


Water content (w) - D2216-10*(15) ISRM Part 2(67) A * Normally determined as part of UCS test

Density (ρ) - Part of UCS test* ISRM Part 2(67) A * Normally determined as part of UCS test

Chemical tests

Carbonate content BS1997. Part 3.Cl6(33) D4373-02(2007)(38)

- - -

Strength

Point load (I) - D5731-08(75) Broch & Franklin (1972)(76)

A Tests are typically carried out as axial point load (Ia) or diametrical point load (Id) or lump tests

Uniaxial compressive strength (UCS) - D7012-10*(77) ISRM Part 2(67) A * test includes the determination of moisture content and bulk density.

Young’s Modulus of elasticity (E) - D7012-10*(77) ISRM Part 2(67) B Where, in-situ/laboratory tests not performed to determine modulus of elasticity (Em). For non-cohesive soil a criteria of Em = 1N and for rock stratum a criteria of (Em=J x Mr x UCS) shall be adopted.

Notes:









Table 15: Rock properties and engineering parameters occasionally determined from laboratory tests for Abu Dhabi road projects




BS ASTM ISRM/Other


Porosity - D4404-10 D4992-07(78)

ISRM Part 2(67) A -

Strength

Splitting tensile strength - D3967-08(79) ISRM Part 2(67) A -

Discontinuity peak and residual effective shear strength

- - ISRM Part 2(67) B -

Notes:








05-GROUND INVESTIGATION PROCUREMENT

Page 52

Second Edition June-2021

5 GROUND INVESTIGATION PROCUREMENT

5.1 Overview The Ground Investigation Company can have a substantial influence on the accuracy and quality of

ground investigation data, which may impact on ground interpretation, geotechnical design and the

cost of the scheme. It is important therefore that an appropriately experienced Ground Investigation

Company with qualified, trained and experienced staff and operatives is engaged to undertake any

ground investigation works. The Ground Investigation Company should also operate under an

appropriate quality assurance system. It will be usual to engage a Ground Investigation Company

through a tender process. This chapter provides guidance on tender information to be requested

from a Ground Investigation Company in order that an assessment of his technical competency can

be made as part of the tender process. The chapter also provides guidance on industry standards

for assuring the quality of ground investigation personnel and laboratory testing. Advice on the

specification of ground investigation and on the preparation of a bill of quantities for tendering and

contract purposes is also given.

5.2 Procurement of a ground investigation company The precise procedure for the procurement of a specialist ground investigation company will depend

on the stage that a project has reached in its development and implementation. The Overseeing

Organisations procurement procedure should be followed and in the case of Abu Dhabi Department

of Transport the procedure is set out in its Procurement and Contracts Manual (ref

DOT/SS/P&C/M001)(80)). The assessment of ground investigation tenders should include both

technical and financial evaluation. The technical evaluation of a Ground Investigation Company

should cover:

• methodology and approach

• compliance with local health and safety regulations and local environmental regulations

relevant to the particular aspect of work being carried out

• quality of personnel, including competency assessment of drillers (ref Section 5.2.1)

• certification requirements

• technology requirements

• documentation of operations in similar projects

• capacity to upgrade and support

• green procurement initiatives

• the ability of the company to mobilize and begin work

• time for programme completion and programme logic




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• relevant experience in the local market and available resources (plants, office, software,

tools) in the UAE

• criteria for technical presentation and interviews, if any.

Templates for the technical and health and safety evaluation of Ground Investigation Companies are

included as Table D1 and Table D2 in Appendix D. Electronic copies of the templates may be

obtained from Abu Dhabi Department of Transport.

Adherence to quality assurance procedures is of prime importance to the success of any ground

investigation, as a guarantee that specific standards are attained. The Ground Investigation

Company should operate a quality management system, which should preferably comply and be

registered to a recognised industry standard such as BS EN ISO 9001(81). The Company should

also operate an environmental management system, which should preferably by registered to an

international standard such as BS EN ISO 14001(82) and a health and safety system, preferably

registered to an international standard such as OHSAS 18001 (83).

Further information on the quality management of ground investigation may be found in UK Site

Investigation Steering Group (1993)(10). Further information on the quality of ground investigation

personnel and certification requirements are given in the following sub-Sections.

5.2.1 Quality of ground investigation personnel Geotechnical practitioners employed on ground investigations carried out by a Ground Investigation

Company must be appropriately qualified with appropriate expertise and experience in geotechnics

for the role they undertake. Defined requirements for geotechnical personnel relative to technical

education, professional qualifications and industry experience are given in the Part 1 of the Manual,

Section 2.3. Appropriate training and continued professional development of such personnel is

important for them to be able to successfully undertake their duties.

Drillers and crew should also be appropriately experienced and trained. Studies have shown that the

skill and care of the driller in applying appropriate techniques and procedures in sinking a borehole

can have a significant influence on in situ test results, for example SPT ref CIRIA Report 143

(1995)(84), and the quality of soils sample and rock core recovery. For quality control it is important,

therefore, that drillers undertaking a ground investigation are competent in the drilling techniques

used. That competency should be a combination of appropriate training and relevant drilling

experience. This should ensure that drillers are aware of the detrimental impact on data quality of

poor drilling that is to be avoided and of drilling best practice to be employed.

The competency of drillers should be reviewed on an annual basis, as such auditing can improve

the quality of work and safety. The audits should be carried out on site by suitably experienced and

qualified persons, observing the driller’s work practices and reviewing in detail an individual's ability

to carry out work in accordance with relevant standards and contract specific specifications. The

driller’s ability to make correct and accurate records and to make appropriate use of method

statements and risk assessments should also be assessed. An inspection of the driller’s rig and all

drilling tools should also be made to check that they are of the required standard. In the absence of

an independent UAE body that undertakes such audits, the audits might be made by appropriate

staff in a Ground Investigation Company as part of its quality control procedures. If and when an




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independent UAE body is set up, then it is expected that the Ground Investigation Company will

adopt independent accreditation and auditing of its drillers. Further information on the competency

assessment of drillers may be found at www.britishdrillingassociation.co.uk(85).

The following information should be sought from a Ground Investigation Company for review as part

of the technical evaluation of the company:

i) names of the geotechnical practitioners to be employed on the contract together with details

of their academic and professional qualifications and summary of their experience;

ii) names of the drillers (and drilling assistants) to be employed on the contract together with

evidence of them having been subject to an annual competency audit (or accreditation by an

independent audit body), and a summary of their experience;

iii) details of the company training and development policy and training programme for its

specialist staff and drilling crews.

5.2.2 Laboratory quality It is important for all ground investigations that there is consistency and quality of laboratory testing.

This ensures accuracy of data and reduces the risk of erroneous information that could result in

interpretation that could be overly conservative thus giving rise to unnecessary higher scheme costs

or rise to a failure with associated increase in construction or maintenance costs. It is highly desirable

and encouraged by Abu Dhabi Department of Transport – Main Roads Projects that laboratories

undertaking soils and rock testing and analytical contaminant testing should be accredited by an

independent industry recognised body such that:

i) the test work is conducted using valid, recognised, technical methods suitable for the purpose

required and of established performance characteristics, with reproducible results;

ii) the work is carried out by properly qualified and trained staff;

iii) the work is carried out on correctly functioning equipment that is calibrated so as to provide

traceability to international standards of measurement;

iv) data are consistent and of known quality being subject to quality control for accuracy and

precision by techniques that are approved by independent technical assessors.

The United Kingdom Accreditation Service (UKAS) (www.ukas.com)(86) provides accreditation of

laboratories based on international standard, ISO 17025:2005 (87) - General requirements for the

competence of testing and calibration laboratories and is recognized worldwide. The American

Association for Laboratory Accreditation (A2LA) (www.a2la.org) (88) also provides accreditation of

laboratories.

Details of any independent accreditation held and of the company’s quality assurance procedures

for testing and results reporting should be sought from a Ground Investigation Company for review

as part of the technical evaluation the company.

http://www.britishdrillingassociation.co.uk/

http://www.ukas.com/

http://www.a2la.org/




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5.3 Specification and bill of quantities Having established the scope of the ground investigation required for a scheme (Chapter 4 above)

and in order to facilitate the procurement of the ground investigation works, the geotechnical

practitioner should prepare a specification and bill of quantities. To provide for clear and concise

presentation of the requirements of the ground investigation published standards should be adopted

for the specification and bill of quantities. Use of such standards will provide for consistency and

quality of documentation and minimise the risk of the Ground Investigation Company not

understanding the requirements.

The UK Site Investigation Steering Group (1993)(89) specification and bill of quantities have

commonly been used for stand-alone ground investigation contracts in Abu Dhabi. An update of

those documents was published in 2012, ref UK Site Investigation Steering Group (2012)(90). The

published documents recognise that each and every ground investigation is unique in terms of its

aims and requirements. Consequently there is provision for the geotechnical practitioner to complete

a series of schedules that define investigation specific details including:

i) a description of the site, the anticipated ground and groundwater conditions, drawings and

documents provided;

ii) the numbers, type and location of the exploratory holes;

iii) amendments and additions to the published standard specification.

The UK Site Investigation Steering Group (2012)(90) specification and bill of quantities may be

adopted for stand-alone ground investigation works and an Excel workbook template bill of quantities

in that format is included as Appendix E. An electronic copy of the template is available from Abu

Dhabi Department of Transport.

It is to be noted that in the case of Abu Dhabi Department of Transport construction contracts, ground

investigation works to be included within such contracts will normally be specified and billed in

accordance with Abu Dhabi Department of Transport’s Standard Specification for Road Works

Manual (91) and Standard Bill of Quantities Manual (DOT/T/HW/172/2009)(92). The comprehensive

details for the specification and billing of ground investigation works provided in UK Site Investigation

Steering Group (2012)(90) may, however, provide a useful reference for the inclusion of any

additional work items required that are not covered in the Standard Specification and Standard Bill

of Quantities Manuals.

5.4 Specification of ground investigation of contaminated

land The geotechnical practitioner may occasionally require a ground investigation to be performed at a

site or part of a site with known or potentially contaminated soils and or known or potentially

contaminated groundwater. For such investigations the objectives and anticipated hazards must to

be clearly defined by the geotechnical practitioner to allow the ground investigation company to

select the appropriate plant, equipment, drilling methods, materials and protective measures. The

geotechnical practitioner should therefore include additional clauses within the ground investigation

specification related to the investigation of contaminated ground or groundwater. There should also




Page 56


be additional bill of quantities items to reflect the additional work and measures that the ground

investigation company will have to undertake compared to those for a ground investigation in

uncontaminated conditions. UK Site Investigation Steering Group (1993)(93) Guidelines for the safe

investigation by drilling of landfills and contaminated land provides advice for the investigation of

known or potentially contaminated sites and includes example additional bill of quantities items that

could be added to the standard bill of quantities described in Sub-section 5.3 above.

UK Site Investigation Steering Group (1993) (93) guidelines use a ‘traffic light’ system to categorise

sites based on the risk to human health and controlled waters as presented in Table 16.




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Table 16: Site categorisation in relation to the ground investigation of landfills and contaminated land (after UK Site Investigation Steering Group (1993)(93))

Site

designation

Broad description

GREEN Subsoil, hardcore, bricks, stone, concrete, clay, excavated road materials, glass,

ceramics, abrasives, etc.

Wood, paper, cardboard, plastics, metals, wool, cork, ash, clinker, cement, etc

Note: there is a possibility that bonded asbestos could be contained in otherwise inert

areas.

YELLOW Waste food, vegetable matter, floor sweepings, household waste, animal carcasses,

sludge, trees, bushes, garden waste, leather, etc.

Rubber and latex, tyres, epoxy resin, electrical fittings, soaps, cosmetics, non-toxic

metal and organic compounds, tar, pitch, bitumen, solidified wastes, fuel ash, silica dust,

etc.

RED All substances that could subject persons and animals to risk of death, injury or

impairment of health

Wide range of chemicals, toxic metal and organic compounds, etc; pharmaceutical and

veterinary wastes, phenols, medical products, solvents, beryllium, micro-organisms,

asbestos, thiocyanates, clyanides, dye stuffs, etc

Hydrocarbons, peroxides, chlorates, flammable and explosive materials, materials that

are particularly corrosive or carcinogenics, etc

Notes:

It should be borne in mind that discriminate dumping may have taken place on a particular landfill or

contaminated site, and therefore the above categorisation should be treated as a guide only to

determining operational procedures.

Landfill sites licensed to accept asbestos waste or other sites where significant deposits of bound or

unbound asbestos occur justifiably have a RED designation, warranting the highest level of caution.

Many contaminated sites may, however, only have very small quantities of asbestos, often present as

asbestos cement, which (while presenting a hazard) may not warrant the highest level of protection. In

these cases it may be sufficient simply to add mains water to the borehole to prevent asbestos fibres

becoming airborne and hence available for inhalation, and to wear disposable ‘paper masks suitable

for low levels of asbestos’.

The presence of radioactive materials on a site has not been included in the above categorisation and

should be considered separately subject to relevant regulations and codes of practice.

The majority of dye stuffs are likely to be in the YELLOW category. There is, however, a variety of base

materials that have been used for the manufacturing of dyes and it is possible that some of those, when

in concentrated form, could be sufficiently toxic to require a RED designation.

In those situations where a preliminary sources study has not been carried out, or the preliminary

sources study has not revealed sufficient information, then the site should be given an automatic RED

designation.




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Other references that provide information and guidance in relation to the ground investigation of

contaminated land include:

• BS 10175:2011 Investigation of potentially contaminated sites – Code of practice(94)

• AGS Guidelines for Combined Geoenvironmental and Geotechnical Investigations

(2000)(95);

• US Environmental Protection Agency (EPA) document 625/12-91/002 titled “Description and

Sampling of Contaminated Soils – A Field Pocket Guide”(96);

• ASTM D5730-04 “Standard Guide for Site Characterization for environmental purposes with

emphasis on Soil, Rock, the vadose zone and groundwater”(97).

5.5 Ground investigation company performance During a ground investigation the geotechnical practitioner should monitor the performance of the

Ground Investigation Company and provide feedback to the Overseeing Organisation that may be

helpful in respect of technical evaluation of the Company in future ground investigation tenders.

Aspects which the geotechnical practitioner should typically monitor include:

• quality of service

• timeliness of delivery

• adherence to specifications

• quality of resources deployed

• contract compliance.



06-IN-SITU TESTING AND ITS INTERPRETATION

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6 IN SITU TESTING AND ITS INTERPRETATION

6.1 Overview In situ testing usually forms an important part of any ground investigation for Abu Dhabi road projects.

This chapter provides guidance on the execution, interpretation and uses of Standard Penetration

Testing, Cone Penetration Testing, in situ density determinations and geophysical surveys.

6.2 Standard penetration testing

6.2.1 Introduction The Standard Penetration Test (SPT) is the most commonly used in situ test in Abu Dhabi and the

Arabian peninsular and is widely used around the World. The test provides an indicator of the density

and compressibility of granular soils, such as the aeolian sand deposits and fluvial sediments of Abu

Dhabi (ref Sub-section 2.2.3). It is a particularly valuable test in these types of soils as undisturbed

samples cannot be readily obtained for laboratory testing. The SPT can also be used to assess the

consistency of cohesive soils such as sabkha and lagoonal muds and also weak rocks.

The SPT is a relatively simple test that gives a numerical parameter which can be used for:

• profiling soils and weak rock;

• soil classification;

• determination of engineering parameters for use in design based on empirical design rules,

discussed further in Sub-section 6.2.4;

• direct design; discussed further in Sub-section 6.2.4.

The International Society for Soil Mechanics and Foundation Engineering (ISSMFE) (1988) (98)

published an International Reference Test Procedure for the SPT, that describes the principles

constituting acceptable test procedures from which the results are comparable. Only standards that

comply with the reference test procedure, such as BS EN ISO 22476-3: 2005 (99) and ASTM.

D1586-08a (100) should be used in ground investigations.

The SPT basically consists of driving a standard 50mm outside diameter thick-walled sampler into

the soil at the base of a borehole, using repeated blows of a 63.5kg hammer falling through 760mm.

The SPT N value is the number of blows required to achieve a penetration of 300mm, after an initial

seating drive of 150mm.

6.2.2 Influence of different practices and equipment on SPT results Apart from the soil conditions in which the test is made the main influences on SPT results are:

• driller competence and borehole construction

• the SPT equipment.

6.2.2.1 Driller competence and borehole construction Studies reported in CIRIA Report 143 (1995)(84) have shown that the quality of drilling equipment and drilling technique can produce some of the largest differences in penetration resistance in




Page 60


granular soils. The skill and care of the driller in applying appropriate techniques and procedures in the sinking the borehole can have a significant influence on the penetration resistance of the soil. The correct execution of the SPT itself is also of critical importance. For quality control it is important therefore, that drillers undertaking a ground investigation are competent in the drilling techniques and testing to be used, ref Sub-Section 5.2.1.

Best practice drilling needs to be employed to minimize the disturbance of soils to be tested by SPT. In light cable percussion boreholes most commonly used in ground investigations these include:

• Where drilling in the presence of a groundwater table a water balance should be maintained within the borehole casing. This avoids a hydraulic gradient at the base of the hole that would likely cause upward seepage and piping failure within sand and silt deposits resulting in them becoming loose.

• SPTs should be carried out below the borehole casing and not within it.

• Standard 35mm internal diameter split spoon samplers should be used.

• In very loose aeolian sands or in very soft lagoonal clays the static weight of the rods and hammer assembly will often be sufficient to push the test equipment some distance into the ground below the base of the borehole. That distance should be recorded in accordance with the test standard, otherwise the penetration resistance will be over-estimated by an unknown quantity.

Typically in Abu Dhabi drilling is undertaken in 110mm diameter casing. Whilst drilling in larger diameter boreholes is not common practice, the geotechnical practitioner should be aware that drilling in boreholes of greater than 150mm diameter may give lower SPT N values than might otherwise be the case. The geotechnical practitioner should, therefore, consider this when interpreting test data and make corrections where necessary. Further information on the influence of driller competence and borehole construction on SPT results can be found in CIRIA Report 143 (1995)(84).

6.2.2.2 SPT equipment The equipment used to carry out SPTs can have a significant influence on measured N values. In

order to minimise such influences equipment complying with recognised industry standards such as

BS EN ISO 22476-3:2005 (99) and ASTM D1586-08a (100) should only be used in ground

investigations. The energy that the SPT hammer delivers to the rods and consistency of that energy

level with each drop of the hammer are important influences on SPT results. The automatic trip

hammer provides the most consistent energy application with each hammer drop and is therefore

the preferred type of equipment to be used. The automatic trip hammer is mostly used in Abu Dhabi.

Further information on the automatic trip hammer and other types of SPT hammers commonly used

can be found in CIRIA Report 143 (1995) (84).

Energy delivered to the rods With regards to the level of energy application, this varies depending on the individual hammer used.

Energy losses are induced by the hammer assembly due to frictional and other effects, which cause

the hammer velocity at impact to be less than the free fall velocity. Further losses of energy arise

from the impact of the anvil depending on its mass and other characteristics. Following studies of




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energy imparted by hammers, it has been established that a standard rod energy ratio (Er) of 60%

of the theoretical free-fall hammer energy is appropriate for normalising penetration resistances from

different equipment and systems. This permits like for like comparison of results. The correction of

SPT N values to a standard rod energy ratio of 60% of the theoretical free-fall hammer energy is

applied in standards such as BS EN ISO 22476-3:2005 (99) and ASTM D6066-96(2004)(101). The

adjusted N value is denoted by the symbol N60.

In sands the blow count N is inversely proportional to the energy ratio (Er) of the hammer and the

correction factor that has to be applied (see Section 6.2.3 below). In order to establish the correction

factor the Er value of the particular test hammer has to be established from calibration testing. SPT

hammers should be calibrated by an appropriate specialist company on a 6 monthly basis and also

after damage, overloading or repair, as recommended in BS EN ISO 22476-3:2005 (99). Annex B of

BS EN ISO 22476-3:2005 provides a recommended method to measure the actual energy imparted

by a SPT hammer assembly to the rods. The ground investigation company should provide a copy

of the current certificate(s) of calibration for the SPT hammer(s) used during a ground investigation

and referenced to the tests undertaken as part of its factual reporting of the ground investigation.

Energy loss owing to the length of rods

With low penetration resistance (N <50) the energy transmitted down the rods in the first compressive

pulse of force will be reduced as a result of a reflective tensile wave. Studies indicate that this has

an impact on tests in sand but not in cohesive soils. For SPT in sands if the rod length is less than

10m then a further correction to that for the energy ratio of the hammer should be applied as

described in Section 6.2.3.

6.2.3 Corrections applied to SPT results

6.2.3.1 Energy delivered to the rods As discussed in Section 6.2 above for design and comparison purposes SPT N values should be

adjusted to a reference energy ratio of 60% of the theoretical free-fall hammer energy. This

adjustment is made using Equation 1:

N60 = Er x N

60

Where:

- N is the SPT blow count

- Er is the energy ratio of the SPT hammer (%)

- N60 is the adjusted N value

Equation 1: SPT N60: Correction of N values to reference energy ratio of 60% of the

theoretical free-fall hammer

6.2.3.2 Energy loss owing to length of rods in sands To correct for the energy loss associated with short rod lengths when testing sands then a further

correction (λ) to the reference energy correction given in Sub-Section 6.2.3.1 should be applied to

the SPT N results. The rod length correction factors are presented in Table 17.

Table 17: Correction factors in sands for rod length




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Rod length below the

anvil (m)

Correction factor (λ)

>10m 1.0

6 to 10 0.95

4 to 6 0.85

<3m 0.75

In sands, therefore, the adjustment to be made to SPT N values to obtain a value corrected to a

reference energy of 60% of the theoretical free-fall hammer is made using Equation 2.

N60 = Er x N x λ

60

Where:



- λ is the correction factor related to rod length

- N60 is the adjusted N value

Equation 2: SPT N60: Correction of N values to reference energy ratio of 60% of the

theoretical free-fall hammer including allowance for rod length energy loss

6.2.3.3 Effect of overburden pressure For some SPT correlations it is necessary to further correct the SPT N60 values to take account of

the effect of overburden pressure. There are several published corrections that take account of the

effective overburden pressure at the SPT depth. The correction factors (CN) presented in BS EN ISO

22476-3:2005 (99) also take account of the type of consolidation of the deposit. Suggested CN values

to be applied to take account of overburden pressure and the type of consolidation of the deposit

are given in Table 18. The adjusted N60 value is denoted by the symbol (N1)60.

Table 18: Correction factors CN for vertical effective stress (σv’) owing to overburden of the

soils

Type of consolidation Correction factor (CN )

Normally consolidated √

98

σv’




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Overconsolidated 170 .

70 + σv’

σv’ is the vertical effective stress in kN/m2

In sands, therefore, the adjustment to be made to SPT N values to obtain a value corrected to a

reference energy of 60% of the theoretical free-fall hammer and to take account of effective

overburden pressure is made using Equation 3.

(N1)60 = Er x N x λ x CN

60

Where:



- λ is the correction factor related to rod length

- CN is the correction factor related to effective

overburden pressure

- (N1)60 is the adjusted N60 value.

Equation 3: SPT (N1)60: Correction of N values to reference energy ratio of 60% of the

theoretical free-fall hammer including allowance for rod length energy loss and for effective

overburden pressure

6.2.3.4 SPT corrections spreadsheet template A template spreadsheet for the application of corrections to SPT results is presented as Table F1 in

Appendix F. An electronic copy of the template may be obtained from Abu Dhabi Department of

Transport.

6.2.4 Engineering parameters and direct design methods

6.2.4.1 Engineering parameters SPT results have been correlated to a wide range of engineering parameters used in geotechnical design and for a wide range of soils and weak rock types. The engineering parameters that are commonly derived from SPT results and published correlations are listed in Table 19. Details of the various correlations and discussion on their application can be found in CIRIA Report 143 (1995)(84) and also in geotechnical engineering design text books such as Tomlinson (2001)(102).




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Table 19: Engineering parameters commonly derived from SPT results

Parameter Symbol Material type Required

input Granular soils Cohesive

soils

Weak rock

aeolian sands,

fluvial sands/

gravels

sabkha,

lagoonal

muds

carbonate

rock

Relative density Dr * - - (N1)60

Effective angle of

friction ’ * - - (N1)60

Undrained shear

strength cu - * * N60

Unconfined

compressive strength UCS - - * N60

Undrained Young’s

modulus Eu - * - N60

Drained (effective)

Young’s modulus E’ * * * N60

Coefficient of volume

compressibility mv - * - N60

Shear modulus at

very small strain Gmax * - - (N1)60

6.2.4.2 Direct design methods Several direct design methods have been developed for SPT. In these methods the N value

(corrected as appropriate) is the input parameter and the analysis directly gives the value to be

calculated, for example the settlement of a foundation, without any estimate of the engineering

parameters of the soil or rock. Direct design methods include:

i) estimation of settlements of shallow foundations on sands

ii) design of piles in soils and weak rocks

iii) liquefaction potential in sands

iv) estimation of sheet pile drivability in granular soils.

Details of the direct design methods and discussion on their application can be found in CIRIA Report

143 (1995)(84) and also in geotechnical engineering design text books such as Tomlinson

(2001)(102).




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6.3 Cone penetration testing

6.3.1 Introduction The cone penetration test (CPT) and the cone penetration test with pore pressure measurement

(CPTU) commonly referred to as the “piezocone test”, are widely undertaken in Abu Dhabi and

around the World. In addition, seismic or electrical sondes can be included in the CPT array to

provide information on sonic velocity or resistivity that can be correlated with engineering properties

such as stiffness. CPTU is the generally preferred method of test as the data obtained is more

versatile for interpretation of the ground conditions at a site. In the subsequent text CPT is used as

a generic term covering both CPT and CPTU unless stated otherwise. CPT can be very cost-effective

and can provide continuous data on the strata being tested with good repeatability of observations.

CPT can be used for:

• profiling soils stratigraphy and identifying the materials encountered;

• determination of engineering parameters of soils for use in design based on empirical design

rules, discussed further in Sub-section 6.3.5.1;

• direct design, discussed further in Sub-section 6.3.5.2.

In most cases, it is desirable that a CPT investigation is supplemented by exploratory holes, sampling

and testing in order to:

• provide correlations and verifications of soil type;

• provide complementary information where interpretation of CPT data is difficult, ie where

there has been partial drainage or where there have been problem soils;

• evaluate the effect of future changes in soil loading that cannot be assessed from the CPT.

The International Society for Soil Mechanics and Foundation Engineering (ISSMFE) (1989)(103)

published an International Reference Test Procedure for Cone Penetration Test (IRTP) that

describes the principles constituting acceptable test procedures for the CPT from which the results

are comparable. Only equipment and procedures that comply with the reference test procedure, as

described in international standards such as BS 1377-9:1990 (104) and ASTM D5778-07(105)

should be used for CPT investigations.

The CPT basically consists of pushing a cone attached to the end of a series of rods into the ground

at a constant rate of penetration with continuous or intermittent measurements made of the

resistance to penetration of the cone. Measurements are also made of either the combined

resistance to penetration of the cone and outer surface of a friction sleeve or the resistance of the

surface friction sleeve itself. The standard CPT cone has a 60 degree apex angle and a diameter of

35.7mm providing a 10cm2 cross-sectional base area and 150cm2 friction sleeve located above the

cone, ref Figure 1. CPT cones of 15cm2 cross-sectional base are also used, especially where

additional sensors are incorporated into the equipment. The ISSMFE IRTP(103) advises that

immediately behind the cone (position u2 on Figure 1) is the preferred location for the filter for the

measurement of pore pressure. Some equipment, however, has the filter on the cone (position u1 on

Figure 1) or behind the friction sleeve (position u3 on Figure 1).




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Figure 1: Cone penetrometer components

Electrical strain gauge load cells within the cone penetrometer measure the cone resistance (qc) and

the sleeve friction (fs) of the soils being tested as the cone is pushed into the ground.

6.3.2 Test methods Methods for undertaking CPT are set out in various international standards, including ISSMFE IRTP (1989)(103), BS 1377-9:1990(104), ASTM D3441-05(106) and ASTM D5778-07(105).

6.3.3 Factors that can affect CPT results The main factors that typically affect CPT results are listed below together with details of measures that can be taken to avoid the error from occurring or to correct the data:

• The skill and care of the CPT operator. Following the correct test procedure is fundamentally

important in ensuring quality and reliability of CPT results. Only suitably trained and

experience operators should be engaged to undertake CPT testing.

• Calibration of sensor and load cells. Accurate and up to date calibration of sensors and load

cells is essential for recording accurate CPT data. Good technical support facilities for

calibration and maintenance of the CPT equipment are therefore essential. Calibration

records should always be requested for the cone, friction sleeve, piezometer and any other

sensors such as seismic sonde. Such records should be current at time of commencement

of testing and should be repeated at the end of the investigation process to determine any

drift in readings that may have occurred over time.

• Pore water pressures. Pore water pressures around a penetrating cone influence the

measured cone resistance and sleeve friction. In clays a higher rate of penetration generates

higher pore pressures that will result in over-estimation of cone resistance and therefore

strength properties. High rates of penetration can also give increased resistance in some

sands owing to dilatancy generating high negative pore water pressures. Such rate effects

can be avoided by carrying out the test to the standard rate of penetration. ISSMFE

IRTP(103) recommends a rate of penetration of 20mm/s +/- 5mm/s.




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• De-airing of piezometers. If the piezometer within the CPT array becomes unsaturated then

it will give erroneous pore pressure readings. Piezocones should therefore be immersed in

de-aired water for at least 24 hrs prior to testing. Piezocones should be regularly replaced

with de-aired piezocone elements.

• Inclination of testing. If the test path deviates significantly off vertical then this will induce

errors in the depth of the recorded data. To minimize the risk of the test deviating off vertical

the thrust machine should be set up so as to obtain a trust direction as near as possible to

vertical. The deviation of the initial thrust direction from the vertical should not exceed 2

degrees. The axis of the test push rods should also coincide with the vertical trust direction.

The inclusion of a slope sensor in the penetrometer will also provide for monitoring and

recording the verticality of the test path. That information can then be used to make any

necessary corrections to give the correct measurement depth.

• Temperature. Changes in temperature can affect readings. In sands, temperature may

increase owing to friction between the cone penetrometer and the sand particles.

Temperature affects can be checked by taking a reading at zero-load at the beginning and

end of test at the same temperature as exists in the ground. The inclusion of a temperature

sensor in the penetrometer will also provide for monitoring and recording the temperature.

Corrections to the data can then be made based on laboratory calibrations.

• Cone penetrometer condition. General wear and tear can result in a cone penetrometer

falling out of standard to an extent that the accuracy of the test data may be affected. The

cone should be inspected prior to carrying out a CPT survey to ensure the cone is in good

condition. An appropriate inspection and maintenance schedule for the CPT equipment

should be put in place to ensure that any equipment that falls out of standard is identified and

taken out of use.

Further information on factors that can affect CPT results and measures that can be taken to

avoid the error or correct the data may be found in Luune et al (1997)(107). A summary of

frequency of checks and recalibrations that should be made for CPT to ensure quality of data is

given in Table G1 in Appendix G.

6.3.4 Presentation of results The following details should be presented in the Ground Investigation Company’s reporting of CPT:

• Measured parameters. For each CPT the measured parameters listed below should be

plotted on one sheet with a common set of scales used at any one site:

- measured cone resistance (qc)

- measured sleeve friction (fs)

- pore water pressure (u), where measured.

ISSMFE IRTP (1989)(103) gives recommendations for scales to be used, but those may be

varied where appropriate to ensure best presentation of data.




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• Derived parameters. Where possible the following parameters should be derived and also

presented:

- cone resistance corrected for pore pressure effects (qt)

- sleeve friction corrected for pore pressure effects (only valid when pore pressures

have been measured at both ends of the friction sleeve)

- friction ratio (Rf), usually in %, where Rf = fs/qc or is preferably Rf = ft/qt or more

typically Rf = fs/qt

- pore pressure ratio (Bq), where Bq = Δu/(qt –σvo)

With Δu = excess pore pressure (u-u0)

u0 = in situ equilibrium pore water pressure

σvo = in situ total vertical stress.

• On each CPT record:

- site name

- CPT reference number

- date of test

- serial number of the cone penetrometer

- position of the pore pressure filter(s) on the cone penetrometer

- groundwater level

- test Company and CPT operator name.

• In the factual report:

- plan showing the location of each CPT coordinated to an agreed Cartesian system

- description of the equipment used and name of the manufacturer(s)

- cone geometry and dimensions and any deviation from ISSMFE IRTP (1989) (103)

or the standard being used

- calibration factors for all sensors and the load range over which they apply

- capacity of each sensor

- zero readings for all sensors before and after each test, and the temperature at which

taken or alternatively the change in zero reading expressed in kPa

- type of liquid used in the pore pressure measurement system

- observed wear or damage on the cone, friction sleeve or the filter element.

- any irregularities during testing to the standard being used.

- the area ratio of the cone and the friction sleeve end areas.

- for dissipation tests it should be noted whether or not the rods were clamped or

unclamped during dissipation.

A check list of information required with CPT results to ensure and check data quality is provided as

Table G2 in Appendix G.




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6.3.5 Soils characteristics, engineering parameters, direct design

methods and other applications

6.3.5.1 Soils characteristics and engineering design parameters CPT is extremely effective for establishing soil type and soils stratigraphy, particularly when

correlated with data from boreholes. CPT results have also been correlated to a wide range of

engineering parameters used in geotechnical design and for a wide range of soil types. The

engineering parameters that are commonly derived from CPT results and published correlations are

listed in Table 20. Details of the various correlations and discussion on their application can be found

in Luune et al (1997)(107).

It should be noted that most of the correlations given in Lunne et al (1997)(107) are based on

empirical results and data derived for silica/quartz sands. In some instances, these correlations can

be in error for CPT tests in calcareous sands (carbonate content greater than 50%-70%) (Lunne et

al (1997)(107)).

In calcareous sands correction factors should be applied to take account of the crushability of the

shell content and hence higher compressibility of the deposits which often results in artificially lower

CPT cone resistance values compared to silica/quartz sands of the same relative density.

6.3.5.2 Direct design methods Several direct design methods have been developed for CPT. In these methods the qc is usually the

only input parameter from the CPT test and there are various formulae and correlations for the value

to be calculated. Design methods available using CPT data include:

i) pile load capacity and pile settlement

ii) bearing capacity and settlement of shallow foundations

iii) liquefaction potential evaluation.

Details of the design methods and discussion on their application can be found in Lunne et al

(1997)(107) and the CIRIA Cone Penetration Testing – Methods and Interpretation(108).

6.3.5.3 Other applications Other applications for which CPT data is commonly used are:

i) the estimation of SPT N values for use in SPT-based design approaches

ii) ground improvement quality control.

Details of these and other less common applications in Abu Dhabi can be found in Luune et al

(1997)(107) and the CIRIA Report Cone Penetration Testing – Methods and Interpretation(108).



06-IN SITU TESTING AND ITS INTERPRETATION

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Table 20: Soil characteristics and engineering parameters commonly derived from CPT results

Soil characteristics/

parameters(1 & 2)

Symb

ol

Material type Notes

Granular soils Cohesive soils

aeolian sands,

fluvial sands/

gravels

sabkha, lagoonal muds

CPT CPTU CPT CPTU

Soil state (1) For details of the correlations and discussion on their application see

Luune et al (1997).

(2) The general applicability of CPT and CPTU data for assessing soil

characteristics and parameters: A – high, B – moderate, C – low, - not

applicable.

(3) CPTU provides additional approaches compared to CPT to assess

this characteristic/parameter

(4) The coefficient of volume compressibility can be assessed from mv =

1/M

Soil type - B A B A

Soil stratigraphy - A A A A

In situ static pore pressure u - - - A

Unit weight/weight density

(bulk density/mass density) (γ) - - - C

Relative density (density

index) ID A/B A/B - -

Overconsolidation ratio

(OCR) - - - B B(3)

In situ horizontal stress σh C C B/C B/C(3)

Shear strength

Undrained shear strength cu - - B B(3)

Sensitivity - - - C C

Effective angle of friction ’ B B C B

Deformation




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Soil characteristics/

parameters(1 & 2)

Symb

ol

Material type Notes

Granular soils Cohesive soils

aeolian sands,

fluvial sands/

gravels

sabkha, lagoonal muds

CPT CPTU CPT CPTU

Drained (effective)

constrained modulus M B B C(4) B(4)

Coefficient of consolidation cv - - - A/B

Coefficient of permeability k - - - B

Undrained Young’s modulus Eu - - C B

Drained (effective) Young’s

modulus E’ B B - -

Shear modulus at very small

strain Gmax B B B B




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6.4 In situ density tests Soil bulk density, also known as mass density, is an important parameter required for geotechnical engineering design. As described in Section 4.4, routine sampling techniques cannot provide samples of the type and quality suitable for bulk density determination for aeolian sand deposits, which predominate in Abu Dhabi, or for fluvial sands and gravels. The bulk density of those deposits can, however, be determined by testing the soils in situ. A list of the tests that are commonly undertaken for Abu Dhabi road projects to establish soils bulk density in situ is given in Table 21. Table 21: Tests commonly undertaken for Abu Dhabi road projects for determining the in situ density of soils

Test method

BS ASTM Notes

Sand replacement

BS1377.Part 9.Cl 2.1(104) (small pouring cylinder)

D1556-07 (sand-cone method) (109)

Suitable for fine and medium grained soils (aeolian sand).

BS1377.Part 9.Cl 2.2 (104) (large pouring cylinder)

D4914-08 (sand replacement method) (110)

Suitable for fine, medium and coarse grained soils (aeolian sand and fluvial sands & gravels).

Water replacement

BS1377.Part 9.Cl 2.3(104)

D5030-04(111) Used rarely in coarse and very coarse soils wadi deposits.

Core cutter BS1377.Part 9.Cl 2.4 (104)

-

Suitable for cohesive soils free from coarse grained material. Used rarely, for example in cement stabilised fill.

Nuclear BS1377.Part 9.Cl 2.5 (104)

D6938-10 (112) Commonly used. The Ground Investigation Company requires a Federal Authority for Nuclear Regulations (FANR) licence (annual renewal) and the adoption of FANR procedures in respect of the transportation and storage of the nuclear equipment.

Suitable for fine grained materials like aeolian sand. Technique much less reliable in coarse gravelly soils.

6.5 Geophysical surveys

6.5.1 Introduction Geophysics is a very broad category of non destructive methods of ground investigation.

Geophysical techniques including electrical, gravity, magnetic, seismic or thermal are used to

measure the physical, electrical or chemical properties of the soil, rock and pore fluids. In general




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geophysical surveys are non invasive and enable correlation between known points of control. There

is, however, no one typical method that can be used in every instance. The selection of a geophysical

method has to be based on knowledge of the existing ground conditions and what information is

required to be obtained.

Data gathering and data interpretation in geophysical surveys are all important and require specialist

knowledge and experience. There are no samples to be handled or stored that can be checked at a

later point. Most of the geophysical methods require processing of the data after it is gathered in

order that an interpretation can be made. The specification of the geophysical survey is, therefore,

very important and the selected specialist company must be able to demonstrate that he is able to

provide the needed solutions.

Geophysics can provide information over a much broader area of a site than can be obtained by

ground investigation exploratory holes. It can provide mapping of the natural conditions of a site and

establish anomalous conditions that could present increase risk to road structures or earthworks.

For example, geophysics can be used to investigate possible cavities within limestone and gypsum

rich strata that could impact on construction or performance of bridge foundations. Geophysics may

also be used to determine soils stratigraphy if say a preliminary sources study has indentified a

possible buried channel or similar features that may impact on proposed earthworks or road

structure. Geophysics is, therefore, a very useful technique to reduce the risk of unknown conditions.

The Al Ain Municipality has published requirements concerning the use of geophysical surveys in

the document Geophysical Study in Al Ain Guideline Manual dated 2010(113), to which the

geotechnical practitioner should refer.

This chapter provides an overview of the geophysical techniques that are typically used in Abu Dhabi

Emirate and also other techniques that may be useful. Further detailed information on the

geophysical methods described can be found in ASTM D6429-99(2011)(114), McDowell et al

(2002)(115), Wightman et al (2003)(116), McCann et al (1997)(117), United States Department of

Interior, Bureau of Reclamation (2001)(118), and United States Department of Interior, Bureau of

Reclamation (1998)(119).

6.5.2 Planning The design and planning of geophysical surveys for transportation projects depends on a number of

factors which include:

• the physical properties of interest

• the techniques which can provide the information at the resolution required

• the geophysical tools that can perform well under the study conditions

• the techniques that can provide complementary data

• the non-geophysical control that is required for the interpretation of the acquired geophysical

survey data.

To assist in the planning of geophysical survey there are numerous references as indicated above.

Good basic guidance can be found in ASTM D6429-11 (114) Standard guide for selecting surface




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geophysical methods, ASTM D5753-05(2010) (120) Standard guide for the planning and conducting

of geophysical logging and Transportation Research Board Circular E-C130 (2008)(121)

“Geophysical methods commonly employed for geotechnical site characterization”.

Geophysical surveys can be used as a screening tool to provide a relatively quick understanding of

the ground conditions at a site. They can also be used to provide more detail on the specifics of a

site. The first aspect of planning a geophysical survey is to determine why the survey is to be

performed and what questions are to be answered when the survey is complete. For the various

geophysical methods that can be used, each has its own set of advantages and limitations. Table

22 provides a summary of the common applications of land based geophysical surveys in Abu Dhabi

and the preferred geophysical methods for that application (see also Table H1 in Appendix H). For

information on the use of geophysics in the marine environment reference should be made to

International Society for Soil Mechanics and Geotechnical Engineering (2005)(122).

Table 22: Summary of geophysical survey techniques and their application

Application Geophysical survey technique(1)

Seismic

Refraction

MASW(2) /

SASW(2)

Resistivity Ground

Penetrating

Radar

Electromagnetic

(EM)

Gravity

P – Primary method of choice S – Secondary method of choice/alternative

Unconsolidated

layer / soil

stratigraphy

P P - P S -

Rock

Stratigraphy S P - S - -

Depth to

bedrock P P P S S

Depth to water

table P - - P S -

Fractures and

fault zones S S S S P S

Soils and rock

properties P P S - -

S

(density)

Cavities / sink

holes - P P P S P

Saltwater

intrusion - - P S P -

Buried objects - - - P P/S S

Notes:

(1) Refer also to Table 1 in ASTM D6429-11(114) and Table 2 in McCann et al (1997)(117).

(2) MASW – Multichannel analysis of surface waves; SASW - Spectral analysis of surface waves




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For all the geophysics methods listed in Table 22 the interpretation of the geophysics data should

be calibrated against ground conditions at the site established from boreholes or trial pits. That

calibration should preferably be undertaken at the time of original data processing. If for some reason

this is not possible and the borehole or trial pit information is obtained at a later date then in these

situations the results of the geophysical survey should be reviewed and updated as necessary in

light of the actual ground conditions found in the exploratory holes.

6.5.2.1 Seismic Seismic techniques including seismic refraction and MASW measure the travel time of direct and

indirect acoustic waves as they travel from a sound source at ground surface to a series of geophone

receptors placed in direct contact with the ground surface at a range of distances from the sound

source. The acoustic waves can be generated by a sledge hammer hitting a metal plate, by a weight

drop source or by a large vibratory weight drop source. Figure 2 shows the theory behind seismic

data gathering.

Figure 2: Refraction methodology (from Wightman et al (2003)(116))

A summary of uses and limitations of frequently used seismic methods is given in Table 23.




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Table 23: Summary of uses and limitations of frequently used seismic methods

Method Data collected and uses Limitations Additional comments

Seismic

Refraction

1. P Wave velocity

(compressional wave)

to determine velocity

differentiation of

geologic layers.

2. Able to determine

differences in material

properties for thick

layers.

3. Provides data along

continuous lines.

1. Layers must be relatively

thick in order to be “seen”.

2. Only layers of increasing

velocity can be recorded.

Weaker materials at depth,

will not be recorded.

3. The acoustic (seismic)

velocity through water (ie

the water table; 1,400 m/s)

may mask some weaker

weathered rock layers.

1. Resolution is a

function of the

source and the

geophone spacing.

MASW 1. Measures propagation

of surface waves from

which shear wave

velocity may be

interpreted.

2. Able to obtain data

below weak layers.

3. Able to delineate voids

or cavities.

1. The acoustic (seismic)

velocity through water (ie

the water table; 1,400 m/s)

may mask some weaker

weathered rock layers.

2. Penetration is limited by

the source of acoustic

waves generated.

1. Resolution is subject

to the geophone

spacing and the

acoustic frequency

being recorded by

the geophone.

2. Data can be

collected in noisy

areas using just the

traffic noise as an

acoustic source if

depth of data

collection is not too

deep.

6.5.2.2 Electrical Resistivity Electrical Resistivity surveys measure the resistivity of the earth materials relative to a current that

is induced into the ground. There are numerous types of resistivity surveys, but in general all of them

use a current induced into one electrode and measure the current received at receptor electrodes.

As the current input is known the apparent resistivity between the two or more electrodes can be

calculated. There are three commonly used resistivity arrays, the difference being in the spacing of

the receiving electrodes:

• Wenner: 4 equally spaced electrodes with the current placed on the outer electrodes and the

readings on the inner electrodes.

• Schlumberger: 4 electrodes but the inner electrodes (potential electrodes) are less than 1/5th

of the distance between the centre of the spread and the outer current electrode.




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• Resistivity profiling: where the electrode spacing is constant but the induced current is moved

along the line.

The electrical resistivity of a material depends on its porosity and the salinity of the water within the

pore spaces. The method is limited by the insertion of the electrode into the ground surface, so if the

surface material is pavement, very dense material or bedrock then the electrode locations need to

be pre-drilled. Additionally, in soil materials it may be necessary to wet the electrodes with saline

water, in order to increase the amount of electric current directed into the ground. In dry conditions,

such as dunes, this may require very large quantities of water to be available.

Electrical resistivity can be performed as point surveys using the Wenner or Schlumberger array.

Single point surveys are used primarily in corrosion surveys for steel (such as sheet pile walls) or for

determining ground characteristics for earthing design of electrical substations. Gridded surveys

along transects using profiling methods are usually performed for trying to find anomalies such as

cavities.

Electrical resistivity surveys can be used to map sand and gravel deposits, determine parameters

for cathodic protection, and map variations in groundwater salinity. They can also be used to locate

voids or cavities especially in areas where the cavities are above the water table. In areas where the

cavities are below the water table a lack of contrast between the electrical resistivity of the host rock

and groundwater can make the results more difficult to interpret. Electrical Resistivity surveys do not

provide information on rock properties.

6.5.2.3 Ground Penetrating Radar Ground Penetrating Radar (GPR) is a quick method of evaluating shallow near surface geology,

including the location of buried objects such as pipes, boulders, and near surface cavities. GPR can

be used for near surface underground utility detection since it can pick up PVC cable ducts and

similar pipelines that may not be currently active and which, therefore, would not be visible to other

pipeline detection methods. GPR is limited in its usefulness since conductive materials such as

saline water or the water table limits the depth of penetration. The method uses many different

antennae configurations so it is very important to provide the specialist geophysics survey company

with a clear directive on the purpose of the survey and the suspected ground conditions or the buried

structure that is being sought. GPR data does not require an excessive amount of processing and

therefore the specialist field engineer can usually review the survey findings as work progresses to

assess if the investigation needs are being met.

GPR surveys can be used in the evaluation of road pavement (including concrete) and bridge decks.

In those cases it does, however, need to be used in conjunction with other non-destruction testing

(NDT) and /or coring methods to obtain the necessary data for the calibration of the GPR data

(Wightman et al (2003)(116)).

6.5.2.4 Microgravity Microgravity or gravity measurement techniques measure the local variations in the gravitational pull

of the earth that the likes of underground cavities and buried channels or underground structures

can create. Measurements are made using a gravity meter, at intervals along traverses that cross

an anticipated or known area of interest. The variations in the relative gravity measured can then be

used to identify the likely position of the underground feature. The method can provide a very




Page 78


accurate sizing and depth of a void or anomaly. In order to achieve accuracy, it is important that the

microgravity survey data are correlated with other ground investigation data and information. The

microgravity method is labour intensive and requires the initial point of measurement (base station)

to be re-occupied frequently in order to monitor any drift in the recording of the instrument. Extremely

accurate elevation data is also required (+/- 3mm). The distance between readings taken along a

traverse should be based on the expected size of the void or anomaly to be detected; with close

spacing for small size voids and larger spacing for large voids. The gravitational anomaly that occurs

with a void decreases with depth. If the void is in the bedrock, the top of the bedrock surface below

the overburden soils must be taken into account; that information usually requires the use of a

second geophysical technique such as seismic refraction or MASW. Microgravity surveys can be

made in inside buildings and structures and in urban areas (ASTM D6429-11(114)).

6.5.2.5 Borehole geophysics There are several borehole geophysics techniques that can be used to identify strata stratigraphy,

establish particular geotechnical properties and for groundwater characterisation. Table H2 and

Table H3 in Appendix H provide lists of the different methods of borehole geophysical survey and

their applications. It should be noted that a number of the techniques require the use of a shielded

radioactive source. For this reason some of the methods that are listed and are available in the likes

of the US or the UK may not be available for use in the UAE owing to permitting issues. Consultation

should therefore be made with local geophysical survey companies to confirm the types of borehole

geophysical survey that can be provided.

6.5.3 Procurement of geophysical survey work Geophysical surveys and their interpretation is specialist work and accurate scope definition is

extremely important if value for money is to be obtained from the investigation work. It is also

important that an experienced specialist geophysical survey company is employed to undertake the

survey work and perform its interpretation. It can be advantageous to seek the advice of the specialist

geophysical survey company in determining the final scope of a geophysical survey. To facilitate

this, in addition to the geotechnical practitioner providing an initial indication of form of geophysical

survey required he should also provide the specialist geophysical survey company with the following:

1. Details of the known or anticipated ground conditions including groundwater level and

groundwater salinity (if available).

2. Information on what is wanted to be achieved by the geophysical survey for example the location of cavities, the determination of ground parameters, the location of salt water interface or locations of underground utilities.

3. Proposed depth of investigation from the ground surface.

4. Presentation of results. How will the data ultimately be used? Requirements for the data to

be coordinated to local grid and elevation. Requirements for the data to be presented in electronic format (for example CAD) as well as paper files.

5. Expected result presentation in terms of interpreted profiles and slices, identification of

anomalies and scale of the drawings. The level of detail required to be detected from the reported data (for example 0.5m or 10m size anomalies).




Page 79


The geophysical survey company can then advise on any changes in the scope of the geophysical

survey or technique(s) that might be employed to maximise the benefit from the proposed survey

work.

The procurement process should also include the minimum requirements of the report that should

be provided (Anderson et al (2008)(123)). This includes:

i) executive summary

ii) purpose and scope of study

iii) dates and location of survey (including base plan)

iv) personnel and organization involved

v) summary of data collection procedures used at the site.

vi) summary of data processing methodology

vii) quality and reliability of the acquired data

viii) interpretation of the data including summary of the procedure used and verification processes

(ground truth and /or modelling).

ix) conclusions and recommendations.

It is to be noted that in some instances it is most appropriate and best value for money if a phased

programme of geophysical survey work, using different techniques is undertaken. For example, for

the investigation of possible underground cavities, it might be appropriate to initially undertake a

wide area Resistivity or MASW survey of a site. Anomalies that are found would be verified using

either boreholes or diagraphy drilling to confirm the presence or otherwise of any cavities. The size

of the cavities might then be confirmed using cross-hole borehole geophysical surveys or with a

micro gravity survey.

Geophysical surveys can be included within the ground investigation standard specification and bill

of quantities described in Sub-section 5.3. In some instances it may be appropriate to include

multiple geophysical survey methods in the documentation in order to establish any significant price

differential between different techniques, for example Resistivity or MASW, as the price may vary

between sites depending on surface conditions and project requirement.

The geophysical survey contract should also include a “field release clause” that permits contract

termination if preliminary results do not justify continuation of the survey (Anderson et al

(2008)(123)). The clause might be invoked if the ground conditions differ from what was expected or

if the geophysical method does not achieve the data objectives including depth of penetration.

The Geophysical Survey Company should be required to include in any tender return evidence that

he has used the geophysical survey method proposed successfully at similar locations in similar

ground conditions. The tender should also include a method statement indicating the proposed

working method including as a minimum the following items:

i) proposed spacing of geophones or electrodes




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ii) quality assurance checks that will be performed daily

iii) methods that will be used in the analysis of the data

iv) equipment that will be used including external source, data storage and data back up during

the survey

v) staff, including CVs of team leaders for data collection and data interpretation

vi) methods to be used for interpretation of the data including details of the data processing

programs that will be used

vii) schedule of works based on a notice to proceed date.

The geotechnical practitioner should supervise the field geophysical survey work to ensure the

quality of work and to enable any changes in the scope of the geophysical survey to be made, in the

light of survey findings.



07-GROUND INVESTIGATION REPORTING

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7 GROUND INVESTIGATION REPORTING

7.1 Description of soils and rocks, borehole and trial pit

records The description of soils and rocks and the preparation of borehole and trial pit records should be

undertaken to an appropriate standard such as BS5930:1999+A2(2010) (7). An example borehole

record is included in Appendix I.

7.2 Laboratory test reporting The information required to be reported for soils and rock laboratory tests is generally given in the

relevant standard to which the test is being undertaken. Example test reporting forms are included

as Appendix J, a list of which is provided at the front of the appendix. An electronic copy of the forms

may be obtained from Abu Dhabi Department of Transport.

Laboratory testing and test reporting should be undertaken in accordance with industry recognised quality assurance and quality control procedures. For Abu Dhabi Department of Transport projects the procedures should be in accordance with the Quality Assurance and Quality Control Requirements for Road Projects (DOT-MR-M-05) (124).

7.3 Electronic transfer of geotechnical data To facilitate the electronic transfer of geotechnical data without the need for re-input of information

which can lead to transcribing errors the Association of Geotechnical & Geoenvironmental

Specialists developed its Data Interchange Format (commonly referred to as AGS format). The AGS

format provides a set of rules for the electronic transfer of geotechnical data, including exploratory

hole records together with in situ and laboratory testing results.

AGS format data files can be readily imported into geotechnical database programmes such as

Holebase and gINT. Also, there are a number of utility programs available that allow the user to

check AGS data files for errors and convert the data to Excel spreadsheets, including free

downloads. Example utility programs are;

• Keynetix: KeyAGS at www.keynetix.com(125)

• gINT software at www.gintsoftware.com(126)

When specifying the ground investigation the geotechnical practitioner should include the

requirement that the ground investigation company supplies the investigation records in AGS format

in addition to hard copy reports.

More information on the AGS format can be found in AGS (2005) (127), AGS (2011) (128) and on

the AGS web site www.ags.org.uk(129).

http://www.keynetix.com/

http://www.gintsoftware.com/

http://www.ags.org.uk/



08-GEOTECHNICAL DESIGN Page 82


8 GEOTECHNICAL DESIGN

8.1 Seismic loading Abu Dhabi is located on the Arabian Plate which is bounded by a series of well-defined tectonic

margins. The Arabian Plate itself is considered to be a stable landmass, with no known significant

seismic events over the past 2,000 years, ref Aldama-Bustos et al (2009)(120). The north-east border

of the Arabian plate, however, is an active plate boundary with relative convergence taking place

between the Arabian and Eurasian plates. As a result, continental collision is taking place along the

Zagros fold-and-thrust belt in southern Iran (about 120km from the UAE), while further east (in the

north of the Gulf of Oman) the oceanic part of the Arabian plate subducts beneath the Eurasian plate

along the Makran subduction zone, ref Figure A3 in Appendix A, Berberian (130). The transition from

the continental to the oceanic collision is accommodated, to a large extent, by the Zendan-Minab

fault, a north north-west trending zone of strike-slip and thrust faults, ref Regard et al.(131) (132). In

the south-east, the African and Arabian plates diverge across the Gulf of Aden while, in the south-

west, the Red Sea spreading boundary defines the interface between the two plates, ref Johnson

(133), Vita-Finzi(134) .

Among the above-mentioned plate boundaries, the Zagros fold-and-thrust belt zone and the Makran

subduction zone are the most likely contributors to seismic hazard for Abu Dhabi. In the past, the

Zagros region has been responsible for the generation of numerous large earthquakes of magnitude

around M7.0, while in the Makran subduction zone the largest earthquake recorded had a magnitude

M8.2. In addition, a number of active tectonic features in the Oman Mountains are also expected to

contribute to the hazard in the area. The Oman Mountains are located along the north-east margin

of the Arabian plate, in Northern Oman, and seismic activity has been noted by both field evidence

and historical seismicity, ref Kusky et al (135). The main structures of interest in the region are the

Dibba line, the Wadi Shimal and the Wadi Ham faults, ref Styles et al (136).

A number of seismic hazard studies have been performed for the United Arab Emirates and its

surroundings. Table 24 summarises the ground motion predictions obtained by different studies for

Abu Dhabi at various return periods. It is noted that significant differences exist among the

predictions of the various studies; these differences are discussed in Aldama-Bustos (137) and

Aldama-Bustos et al (138). Best estimate values provided in Table 24 are intended to provide an

indication of the seismic hazard levels for Abu Dhabi based on the latest studies; however PGA

values for engineering design according to AASHTO or IBC should be derived following the

procedures laid out in each of the codes and using the seismic hazard maps provided therein.





Table 24: Summary of seismic hazard studies results for Abu Dhabi at various return periods.

Author Peak Ground Acceleration (g)

475yrs 1,000yrs 2,475yrs

UBC (139) No seismic action required

- -

Grunthal et al (140) - GSHAP 0.24 - -

Al-Haddad et al (141) 0.05 - -

Abdalla and Al-Homoud (142) 0.10 - -

Sigbjörnsson and Elnashai (143) - 0.10 0.20

Musson et al (144) 0.035 - -

Malkawi et al (145) 0.09 - -

Pascucci et al (146) 0.04 - 0.07

Aldama-Bustos et al (138) 0.032 0.047 0.07

Best estimate 0.035 0.047 0.07

For transport infrastructure in Abu Dhabi seismic design is usually carried out following the general

principles set out in AASHTO Load and Resistance Factor Design (AASHTO LRFD) (2012)(147).

According to AASHTO LRFD (147), the definition of seismic hazard at a site shall use the peak

ground acceleration (PGA) and the short-period and long-period spectral acceleration coefficients,

Ss and S1 respectively, with a 7% probability of exceedance in 75 years (1,000yr return period).

These shall be based either on approved state ground motion maps or on a site-specific probabilistic

seismic hazard analysis generating a uniform hazard spectrum for the required probability of

exceedance. The PGA, Ss and S1 values correspondig to the 1,000-year return period shall be

multiplied by the site factors for the appropriate site class in order to define the design spectral

accelerations and design response spectrum. At present approved state seismic hazard maps for

the 1,000-year return period are not available; therefore a site-specific probabilistic seismic hazard

analysis would be required if the seismic design is to be carried out in accordance with AASHTO. It

should be noted that hazard maps for Ss and S1 provided in Appendix A are not suitable for design

according to AASHTO as these correspond to a different return period (i.e., 2,500 years).

According to AASHTO (147) each bridge shall be assigned to one of the four seismic zones set out

in the code. The seismic zone classification will depend on the value of the design long-period

spectral acceleration SD1, which is obtained from the product of the long-period spectral acceleration





coefficient S1 (for rock site conditions) and the appropriate site factor for long-period motion, Fv. For

the earthquake event the coincident traffic load is taken to be 50% of the design traffic load.

Traditionally, for building design in the Abu Dhabi region, seismic loads for use in building design of

five or more storeys were taken from the Uniform Building Code (UBC)(139) for a seismic category

of Zone 2A. It is to be noted that the UBC itself places Abu Dhabi in seismic category Zone 0, which

implies that no seismic loading is required to be taken into consideration in design. The UBC Zone

2A PGA is 0.15g at bedrock level. Soils overlying bedrock have the effect of amplifying the PGA and

therefore for design the bedrock level PGA value is normally enhanced based on the type of soil

present.

UBC was superseded in the United States by the International Building Codes (IBC) in 2000. The

IBC is updated every three years and the latest edition is IBC 2012(148). As part of a phased program

of customisation, adoption and implementation of IBC Abu Dhabi Department of Municipal Affairs

(DMA) published the guide “Abu Dhabi Guide to the Use of International Building Codes” in 2011

(149) and publication of its code International Building Codes in the Emirates of Abu Dhabi is due in

2012(150). The guide provides code users a reference for any amendments that have been made

to meet the local specifications of Abu Dhabi Emirate. Accordingly, the seismic ground motion values

shall be determined from the mapped 0.2s and 1.0s spectral accelerations, Ss and S1 respectively

(ref Figure A4 and Figure A5 in Appendix A) Abu Dhabi Guide to the Use of International Building

Codes (149).

For the development of these maps a probabilistic seismic hazard assessment was not performed

due to time constraints, ref Ghosh and Dowty (151). Instead, the hazard maps included in the IBC

for the Emirate of Abu Dhabi were based on the work of Abdalla and Al-Homoud(142). The hazard

maps in the “Abu Dhabi Guide to the Use of International Building Codes” are for 0.2s and 1.0s

spectral acceleration, for rock-site conditions, with 2% probability of exceedance in 50 years (2,475yr

return period). According to these maps, for Abu Dhabi, Ss for rock site conditions (site class B as

per IBC) shall be 0.60g and S1 0.24g, ref Table 25. The mapped values shall be multiplied by an

appropriate site factor for the relevant site class and a factor of 2/3 in order to obtain the design

spectral response acceleration parameters (SDS and SD1). The determination of the seismic design

categories shall be according to the amended tables presented in the “Abu Dhabi Guide to the Use

of International Building Codes” (149).

Table 25: Seismic design parameters for Site Class B for use in seismic design according to IBC (Abu Dhabi Guide to the Use of International Building Codes (149))

Ss S1

0.60g 0.24g

It should be noted that the ground motion parameters from the two codes, AASHTO(147) and

IBC(148), have different return periods. Maps developed for IBC(148), therefore, are not suitable for

design according to the AASHTO(147) specifications.

It is noted that where the size of the project merits, it is good practice to undertake a site specific

seismic hazard assessment in order to evaluate the appropriate ground motions to be used in the





design of transport infrastructure and buildings. It is to be noted that significant savings in

construction costs might be achieved in cases where the site specific PGA is determined to be lower

than the values given in the state ground motion maps.

In both AASHTO (147) and IBC(148) design earthquake spectral response acceleration shall

account for site class effects. All sites, therefore, need to be classified in the appropriate site class

by their stiffness; this can be determined by the average shear wave velocity, standard penetration

resistance or undrained shear strength in the upper 30m of the soil deposit, as described in the

relevant sections of the two codes. Special attention must be given to sites that are vulnerable to

liquefaction or collapse under earthquake loading, contain peats and/or highly organic clays, contain

very high plasticity clays or are composed of very thick soft clays. In such cases, the site shall be

classified as Class F and a site-specific site response analysis shall be performed for the derivation

of appropriate site factors.

In addition to possible structural failure and failure of foundation soils under excessive bearing

pressures associated with seismic loading, loose saturated granular soils may be subject to

liquefaction and loose dry soils may be subject to settlements associated with the phenomenon of

seismic densification. Both liquefaction and seismic densification can result in significant ground

settlements causing distress to and possibly even failure of highway structures and earthworks.

The potential for liquefaction and soil strength loss shall be evaluated for site peak ground

accelerations, magnitudes and source characteristics consistent with the design earthquake ground

motions. According to IBC, peak ground acceleration for the liquefaction assessment shall be

determined based on a site-specific study taking into account soil amplification effects, or, in the

absence of such a study, peak ground accelerations shall be assumed equal to SDS/2.5. The

assessment of soils liquefaction potential is typically carried out in line with the procedures outlined

in Youd et al (152) or Idriss and Boulanger (153) and involves three main steps:

i) the calculation of the cyclic stress ratio induced in the soil by the earthquake;

ii) the calculation of the cyclic resistance ratio based on in situ data, typically SPT, CPT or

shear wave velocity data;

iii) calculation of the ratio of the values from i) and ii) above that gives the factor of safety

against liquefaction.

As outlined in Youd et al (152), different empirical methods are available for the calculation of the

cyclic resistance ratio based on the type of information available. Correction factors will need to be

applied to the calculated values to take into account of factors such as the earthquake magnitude,

the fines content of the soils and the overburden pressure.

The recommended analysis is a total stress analysis in which the seismic demand (represented by

the earthquake induced stresses) is compared to the seismic capacity (undrained cyclic shear

strength of the soil, which is also called liquefaction resistance). The seismic demand will be denoted

as CSR (cyclic stress ratio), whereas seismic capacity will be denoted as CRR (cyclic resistance

ratio).

The safety factor (SF), computed as a ratio between CRR and CSR, should not be less than 1.25.

Evaluation of settlements in dry sands due to seismic densification can be carried out using guidance

available in Kramer (154). In order to conduct proper assessment of liquefaction potential,





investigations of soil characteristics are required in terms of in situ Standard Penetration Tests (SPT)

or Cone Penetration Tests (CPT). It is to be noted that CPT data is preferred for assessing potential

for liquefaction and seismic densification of loose granular strata during an earthquake event.

If soils are found to be susceptible to liquefaction and the ensuing effects are deemed capable of

affecting the load bearing capacity or the stability of the foundations/roads/pavement, measures,

such as ground improvement and/or pile foundation (structures) shall be taken to ensure stability.

The liquefaction hazard may be neglected when one of the following conditions is fulfilled:

iv) Sands have a clay content greater than 20% with plasticity index (PI) larger than 10.

v) Sands have a silt content greater than 35% and at the same time the SPT normalized blow

count value (N1(60)) is larger than 20.

vi) Sands are clean, with SPT normalized blow count value (N1(60)) larger than 30.

8.2 Interpretative ground model The derivation of the ground model is an essential component of the geotechnical practitioner’s

evaluation of the ground and groundwater conditions at a site and his assessment of their impact on

the proposed scheme earthworks and structures. The geotechnical practitioner should develop a

detailed ground model of the relative location and thicknesses of the types of strata known or

expected to be present, of their properties and of the groundwater conditions based on his evaluation

of the available geological, hydrogeological and geotechnical data. In preparing the ground model

the geotechnical practitioner should make use of the available factual information such as the

exploratory hole records from ground investigations undertaken as part of a current or previous

schemes and published records such as geological maps. The published geology and hydrogeology

of the area will assist in the classification of the materials encountered and indicate their likely extent

both over the site and at depth. These provide useful records against which a correlation of the strata

encountered in the exploratory holes can be made.

The presentation of a detailed ground model solely in descriptive text can be difficult and hard for a

reader to understand except for the simplest of ground models. The preparation of a series of ground

model sections, both along the road alignment and typically perpendicular to it is, therefore, usually

of great value. When preparing sections the degree of uncertainty when interpolating between

investigation positions and projecting or extrapolating data should be highlighted. It is preferable that

sections are prepared to natural scale, ie same scale in both directions, but for long linear sites in

particular the sub-surface profile should be presented at a scale appropriate to the depth and

frequency of the exploratory holes and the overall length of the section. Exaggerated scales of

1(V):10(H) and 1(V):20(H) are often used. Example sections are included in Appendix J. In very

special circumstances it may be appropriate to prepare a three dimensional ground model.

Contour plans of groundwater levels and boundaries such as rockhead, strata thicknesses and

isometric views can also greatly assist the geotechnical practitioner in his interpretation of the ground

conditions at the site and highlight features such as buried channels and any sharp changes in

thickness or dip of strata that could have a significant impact on the proposed earthworks or

structures. Such plans and illustrations also greatly aid the presentation of the ground model.





8.3 Selection of geotechnical design parameters Design by calculation is the most commonly used method of geotechnical design. The calculation

may consist of an analytical analysis, use of semi-empirical rules or numerical modelling (such as

finite element or finite difference methods) for which key geotechnical parameters will be required.

The selection of geotechnical design parameters requires the knowledge and experience of the

geotechnical practitioner. When assessing geotechnical parameters from test results the

geotechnical practitioner should take into account the possible difference between the properties

obtained from the tests and those governing the behaviour of the ground mass and/or the

geotechnical earthwork or structure. The differences may be due to factors such as:

• many geotechnical parameters are not true constants but depend on stress level and the

mode of deformation;

• soil and rock structure (eg fissuring, laminations or large particles) can influence test results

differently to mass behaviour;

• time effects;

• percolating water can have a softening effect on soils or rock strength;

• dynamic loading can have a softening effect on soils and rock strength;

• brittleness of the soil and rock tested;

• the method of installation of the geotechnical structure;

• the influence of workmanship on artificially placed or improved ground;

• the effect of construction activities on the properties of the ground.

The geotechnical practitioner should also take into account the following:

• published and well recognised information relevant to the use of each type of test in the

ground conditions;

• the extent of field and laboratory investigation;

• the type and number of samples and the scatter of the results;

• the extent of the zone of ground governing the behaviour of the geotechnical structure;

• geological and other published and background information, such as data from previous

projects;

• the value of each geotechnical parameter compared with relevant published data and local

and general experience;

• the variability of the ground and variation of the geotechnical parameters that are relevant to

the design;

• the results of any large scale field trials and measurements from neighbouring constructions;

• any significant deterioration in ground material properties that may occur during the lifetime

of the structure.

Statistical approaches to the derivation of parameters are described in documents including

Designers’ Guide to EN 1997-1 Eurocode 7: Geotechnical design – General rules (155). Statistical

approaches do, however, require a sufficiently large number of test results for the method to be valid.

When statistical methods are used, BS EN 1997-1 Eurocode 7 (156) recommends that there should

be no greater than 5% probability that the determined characteristic value (defined below) of a

parameter will be worse than that value. Most often, however, there are insufficient data available

for a purely statistical approach. Parameter selection is therefore often very dependant on the





knowledge and experience of the geotechnical practitioner and is usually broadly based around

published guidelines. Mostly lower value conservative parameters are adopted for use in design, for

example the effective shear strength of a soil in assessing slope stability. For particular designs and

design circumstances however other parameter values may be needed. For example mid-range

(mean or median) values are often adopted for bulk density and deformation properties and upper

value conservative parameters may be used to assess pile drivability.

CIRIA 104 (1984)(157) uses the following terminology in respect of geotechnical design parameters:

- moderately conservative parameters, which are a conservative best estimate and

- worst credible parameters, which are the worst that the geotechnical practitioner realistically

believes might occur.

BS EN 1997-1:2004 (156) uses the terminology:

- characteristic value soil parameters, which are defined as being a cautious estimate of the

value affecting the occurrence of the limit state. This is essentially the same as the

aforementioned moderately conservative parameters.

Examples of moderately conservative and worst credible values and parameters are shown on

Figure 3.





Figure 3: Example of moderately conservative and worst credible values and parameters

8.4 Geotechnical design Geotechnical design should be undertaken where possible to published International Standards and with reference where appropriate to local Abu Dhabi and UAE design guidelines. Where a design procedure is not covered by or fully prescribed by a Standard then based on his specialist knowledge and experience the geotechnical practitioner may adopt other industry recognised and proven published design procedures and guidelines. Table 26 presents a list of typical roads structures and earthworks and their related geotechnical design issues together with the International Standards and other references commonly used for geotechnical design in Abu Dhabi road projects. Those Standards and references typically follow the traditional approach to geotechnical design based on working stress with overall factors of safety. A limit state design approach with use of partial factors of safety has been adopted for most standard geotechnical design work in Europe. Whilst this approach is not currently widely used in Abu Dhabi or the UAE region, the relevant limit state design Standards are listed in Table L1in Appendix L for reference and possible future use. Table 27 lists Abu Dhabi local guidelines which the geotechnical practitioner will need to consider in geotechnical investigations and geotechnical design.





Table 26: International Standards and references commonly used for geotechnical design in Abu Dhabi road projects

Structure/earthwork Geotechnical design issue Commonly used standards (working stress design with overall factors of safety) and references

Comments

Structures (All) Chemical attack on buried concrete and steel

BRE Special Digest 1 (2005)(65) (1) This has been superseded by BS EN 1997-1:2004 (156) in the UK

(2) For Spread footings minimum safety factor of 3.0 shall be adopted to calculate net allowable bearing capacity and total tolerable settlement shall not exceed 25mm.

(3) Pile allowable compression capacities based on ASD method shall be calculated by using minimum factor of safety (2.5 for skin friction and 3.0 for end bearing). Tension capacities shall not exceed 70% of allowable compression load.

(4) Pile strength design shall comply with LRFD bridge design specifications and guidelines set forth in ADQCC roads structures design manual TR-516.

(5) In order to calculate the compression capacity for piles socket in rock, end bearing shall be ignored.

Bridge (including abutments and piers), gantry signs

Spread footings Sizing/bearing capacity

Settlement (components, total, differential and rate)

Stability (including failure of foundations on slopes)

BS 8004:1986(1) (158)

Methods described in Tomlinson(2) (2001)(102), Bowles (1996)(159) and Hong Kong Geoguide 1 (1994)(160).

Pile foundations Carrying capacity(5) (axial and lateral), downdrag/ negative skin friction

Settlement/ deflection of laterally loaded piles

BS 8004:1986(1)(158)

Methods described in Tomlinson(3) (2008) (161).

AASHTO LRFD (2017) or Latest Edition/Interim(4)

Retaining walls Gravity wall Wall stability

Bearing capacity

Sliding resistance

Settlement ( total, differential and rate)

Stability (including slope failures)

BS 8002: 1994(1)(162)

BS 8004:1986(1)(158)

BS 8008: 1995(1) (163)

Methods described in Tomlinson (2001)(102)

Cantilever/ anchored embedded wall

Wall stability

Anchorage design

BS 8002: 1994(1)(162)

BS 8081:1989 for anchorage design(164)

CIRIA C580(165)

Methods described in Tomlinson (1994)(161).





Structure/earthwork Geotechnical design issue Commonly used standards (working stress design with overall factors of safety) and references

Comments

Soil cuttings - Stability BS 6031:2009(166)

Rock cutting - Stability BS 6031:2009(167)

Hoek & Bray (1994)(70), Transport Research Laboratory (2011)(68) .

Embankments - Stability (including internal and surface erosion)


BS 6031:2009(167)

BS 8008: 1995(1) (163)

Road pavement - Strength, trafficability, requirement of capping, settlement/collapses due to low CBR/loose layer underneath or weak subgrade, and/or presence of unsuitable/soluble material below subgrade.

Highways Agency IAN 73/06 Revision1 (2009) (168)

Excavatability - Excavatability Pettifer & Fookes (1994)(169)





Table 27: Abu Dhabi design guidelines for use in geotechnical design in Abu Dhabi road projects

Geotechnical issue Reference

Geophysical studies Abu Dhabi Department of Municipal Affairs. Geophysical Study in Al Ain (113)

Seismic loading Abu Dhabi Department of Municipal Affairs. Abu Dhabi Guide to the Use of International Building Codes(149)

Abu Dhabi Department of Municipal Affairs. International Building Codes in the Emirates of Abu Dhabi. Expected publication 2012.(150)

8.5 Ground improvement & treatment of voids/cavities The geotechnical risks and hazards shall be identified in details by performing

geophysical/geotechnical investigation at design and verification stage. In case investigation findings

indicates “unfavourable” conditions susceptible to liquefaction and/or settlement of

roads/pavement/infrastructures/structures/utilities etc. Ground improvement (such as soil

replacement, reinforcement with geosynthetics, vibro-compaction or vibro-flotation, vibro

replacement (stone columns), dynamic compaction/replacement, CMC columns (controlled modulus

columns/rigid inclusions), Rapid Impact Compaction (RIC), High Energy Impact Compaction (HEIC),

soil mixing or other applicable techniques) shall be performed prior to construction over it.

The conventional ground improvement techniques listed above are for general guidelines and should

be finalize at site by Ground Improvement Specialist in function of the soil type (gradation and

density) and the site trials results, in order to efficiently satisfy the performance criteria.

An indicative plan showing the location of the proposed improvement techniques shall be prepared

based on the findings of the existing and complementary subsurface investigation data at the project

design stage.

The following performance requirements shall be followed as guideline (post improvement);

8.5.1 Minimum criteria for Roads/Pavement: iv) Total settlement (immediate and long-term) shall not exceed 25mm at 100% design load and

shall not be considered less than 40 kN/m2 (considering vehicle load of HL-93).

v) The safety factor against liquefaction shall not be less than 1.25.

vi) The in-situ CBR of improved ground shall not be less than CBR value adopted in design and

in general shall not be less than 10% at 5mm penetration for any condition.





8.5.2 Minimum criteria for Structures/Infrastructures/Utilities

Foundation

x) Total settlement (immediate and long-term) shall not exceed 25mm (footings) and 50mm

(Raft) at 100% of design load.

xi) The safety factor against liquefaction shall not be less than 1.25.

xii) The post-improvement vertical and lateral settlements induced by earthquake loading shall

be limited to a maximum of 20 mm at the top of the ground.

xiii) Angular distortion (differential settlement) of points 5m apart shall be less than 1:500.

xiv) A minimum equivalent Young’s Elastic Modulus for the treated ground of 30MPa.

xv) SPT: Minimum N value of 30 along the improved depth of granular material.

xvi) CPT: Minimum cone tip resistance value of 10 MPa along the improved depth of granular

material.

xvii) Minimum relative density of 70%.

xviii) An effective angle of shear resistance not less than 35° for the medium dense to

dense sand (granular material).

The parameters of each locality must be checked for the material type, mineralogy, size, and for the

deposit thickness before the final decision to be made on the improvement method, level of energy

used, and spacing of improvement points. Moreover, the thickness of the soil cover, which is

important in determining the improvement method, can be checked through the pre-CPT/SPT testing

with close spacing. It shall be noted that vibrations induced by heavy machinery shall be limited,

while working next to existing structures or utilities that are sensitive to vibrations.

The efficiency of the final adopted improvement method for the project, final thickness/depth of the

improvement ground and verification of set performance criteria shall be checked by performing post

ground improvement in- situ tests (SPT, CPT, Plate load test (PLT), Zone Load test, CBR etc.).

The suitability of the soil material shall be determined by performing standard laboratory tests (such

as gradation, plasticity index (P.I), proctor, CBR, organic content, water soluble salts (WSS), total

dissolved salts (TDS), sulphate, chloride, pH and/or other.) by testing collected soil samples as per

the standard requirements provided under TR-542 (part 1 & 2).

8.5.3 Voids/Cavities Treatment

The risk of voids/cavities and highly fractured zones within right of way (ROW) and underneath the

foundation (structures/infrastructure/utilities) shall be investigated (geophysical/geotechnical) at

design stage to determine vertical/lateral extent and shall be verified at verification stage by

executing probing holes (grid spacing 10m x 10m) with the depth of each probe reaching a minimum

penetration of 10.0m below the last cavity encountered, and cavities filled with low mobility grout.





All encountered open cavities/voids/highly fractured zones shall be grouted prior to construction over

it. Grouting design and specifications shall be developed by considering the nature of material/

vertical and lateral extent and shall be design/performed by a company specialized in such works.

In addition, the subgrade layer (road/pavement) shall be reinforced with geogrid layers in order to

cater for any potential of cavities collapse, leading to excessive settlement in future. The type and

strength of geogrid shall be finalized in consultation with geogrid designer/supplier based on

effectiveness for the problem in hand and performance warranties.

8.6 Criteria to design retaining walls/foundation subjected

to overturning loads

External stability of retaining walls design and foundation subjected to overturning loads (such as

shade foundations) shall fulfil the serviceability criteria by following the minimum factor of safety i.e.

FoS = 2.0 (overturning), FoS = 1.5 (sliding) and FoS = 3.0 (Bearing Capacity). The global stability

shall not be less than 1.5.

For strength limit state the stability checks shall be in compliance with the guideline of AASHTO

LRFD and set forth in ADQCC roads structures design manual TR-516. In general, the larger

dimension from design of SLS & ULS shall be consider.

8.7 Slope Stability analysis

Slope Stability analysis shall be carried out to evaluate the stability of earth and rock-fill,

embankments, excavated slopes, and natural slopes in soil and rock. The stability of slope depends

upon certain factors and shall be considered in the analysis (analytical or empirical methods).

iv) Uncertainty in the accuracy with which the slope stability analysis represents the actual

mechanism of failure.

v) Uncertainty in the accuracy with which the input parameters (shear strength, groundwater

conditions, slope geometry, etc.).

vi) The likelihood and duration of exposure to various types of external loading.

Stability analyses must be formulated with great care. Since the available shearing resistance of

the soil depends on pore water drainage conditions, those conditions must be considered

carefully in the selection of shear strength and pore pressure conditions for the analysis. A minimum

surcharge load of 20 kPa shall be consider.





Accordingly, in static condition, the slope design shall satisfy minimum safety factor criteria of 1.5

(permanent) and 1.3 (temporary) and 1.1 for seismic case. Erosion protection measures shall be

provided as appropriate to design requirements in compliance with ADQCC standards and

specifications.

For stability analysis in rock slopes, following modes of failure shall be considered as applicable.

v) Planar failure

vi) Polygonal failure

vii) Wedge failure

viii) Toppling failure

Stereographic and kinematic analysis shall be performed as appropriate and applicable to project

specific requirements.



09-GEOTECHNICAL ASPECTS OF ROAD PAVEMENTS

Page 96


9 GEOTECHNICAL ASPECTS OF ROAD

PAVEMENTS

9.1 Overview The four main reasons for carrying out carriageway investigations and assessments are:

i) network management, the monitoring and assessment of the road pavement including the investigation of failures

ii) design of new works

iii) design of maintenance works and improvements

iv) premature failure. The investigative works typically undertaken are discussed in this chapter.

9.2 Pavement investigation and assessment

9.2.1 Introduction It is important for road pavement investigations that all condition surveys and investigation points

(such as in situ testing and pavement cores) are referenced to a permanent chainage (or features)

or to a scheme specific chainage. There are several stages and techniques to carrying out road

pavement investigations, as follows:

i) visual condition survey

ii) Boreholes, trial pits, cone penetration tests (CPT)

iii) cores

iv) dynamic cone penetrometer

v) ground penetrating radar

vi) laboratory testing

vii) testing pavement “strength”.

These stages are described in detail in the immediately following sub-Sections.

9.2.2 Visual condition survey An engineer’s survey should be carried out as the first step in a pavement investigation. The survey

should note basic features including:

• topography

• carriageway details including number of lanes, width etc




Page 97


• drainage arrangements

• surface type

• construction materials, as far as a visual survey will permit

• defects (the typical features to be observed are presented in Abu Dhabi Department of Transport’s Pavement Design Manual. (170).

The survey data should be interpreted to provide an assessment of the general condition of the road

pavement and any requirements for additional surveys.

9.2.3 Trial pits through the pavement layer Trial pits offer the opportunity for gathering most information but are also the most expensive and

disruptive survey technique. They also need careful backfilling to negate problems with local

subsidence and damage to the reinstated road pavement with the consequential disruption and risk

to road users. The trial pit sides through the pavement should be saw-cut to establish thickness and

general make up of the different layers making up the pavement. Saw cut edges in trial pits also

allow identification of the layers that are or are not rutted and to what depth with more accuracy than

can be achieved by taking rows of cores. Trial pits also allow the taking of bulk samples and in situ

testing of the foundation layers and subgrades. As trial pits permit more detailed examination of the

road pavement and subgrade than other investigative techniques they are particularly useful for

investigating pavement failures. The following information should be recorded:

• location

• general condition of the pavement at the trial pit position, preferably with a photograph

• depth of pit

• thickness of each layer and any changes in thickness or alignment across the area of the pit.

• the shape of the layers; note any rutting or deformation and in which layers it occurs

• description of each layer, material type and condition

• voiding, where evident

• bond or lack of bond between the layers making up the pavement

• depth of cracking

• any stripping of the binder from the aggregate.

• any particular difficulties with excavation, or where materials break easily under excavation.

• subbase thickness and type; take in situ tests such as Dynamic Cone Penetrometer/ CBR if possible; take bulk samples for laboratory testing

• subgrade (natural ground) and type; take in situ tests such as Dynamic Cone Penetrometer/ CBR if possible; take bulk samples for laboratory testing.

9.2.4 Asphalt cores Cores are the most effective means of gathering information on a road pavement. Where little is

known of a pavement they can be regularly spaced, but consideration should be given to the

information required. A row of closely-spaced cores may be able to detect rutting at different depths.

Cores should be taken in good, average, and poor areas, for comparison. Where cores are taken




Page 98


over cracked areas an adjacent core should always be taken in sound material. Further information

is given in Highways Agency DMRB HD29 (2008)(171). The following information should be

recorded in respect of cores taken:

• location

• general condition of the pavement at the core position, preferably with a photograph

• depth of hole

• length of core

• loss of core

• thickness of each layer

• description of each layer, material type and condition

• voiding, where evident

• bond or lack of bond between the layers making up the pavement

• depth of cracking

• any stripping of the binder from the aggregate.

9.2.5 Dynamic cone penetrometer (DCP) The DCP consists of a standard cone driven by a standard drop-weight. The equipment is low cost,

easily transportable, and easy to use. There are published correlations of blows against penetration

to give values of CBR. In pavement investigations the DCP is usually driven from the base of the

bound material. The thickness of the underlying layers can to some extent be estimated by changes

in blow count (and hence stiffness). Individual readings should not be used to define a CBR value at

a specific depth. Results should be plotted graphically as below with cumulative blows against depth.

Sections with similar gradients can be plotted. It can be seen from the example included as Figure

4 that the bound material was about 270mm thick, followed by a layer approximately 150mm thick

with a CBR of 1385 (most probably a granular subbase), there is a base layer with CBR of 30%

(possibly a relatively stiff subgrade). There is an intermediate 300mm layer of CBR 7% (probably an

upper layer of softer subgrade). Further information on DCP can be found in Highways Agency

DMRB HD29 (2008)(171).




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Figure 4: Example dynamic cone penetration test

9.2.6 Ground penetrating radar (GPR) Ground penetrating radar (GPR) is a useful technique to gather data on pavement thickness and

construction and can provide continuous information on pavement structures. It can identify

anomalies and discontinuities that coring would miss. It can also be used to build a database of

existing pavement construction; this is useful when at initial assessment stage as changes or

deficiencies in construction can be identified and compared with the incidence of defects. GPR itself

will provide little information regarding the condition of a pavement but complemented with other

forms of investigations, such as cores/trial pits, it will enable a wider assessment of pavement

condition to be made.

GPR is a non-destructive technique that operates by transmitting a pulse of electromagnetic radiation

into a pavement. The radiation penetrates into the pavement as an energy wave, with an envelope

in the shape of a cone. As the wave travels through the pavement its velocity is changed and its

strength is attenuated. Part of the signal will be reflected back by buried discontinuities or interfaces

between layers. The return signal can be interpreted to give information on the likes of layer thickness

and location of services. The accuracy of GPR is dependent on the wavelength used and the speed

of survey and should be undertaken by trained specialists. At lower speeds surveys will usually

provide much more detail on the likes of reinforcement position, joints, pipes and services, but will

be more disruptive to traffic.

Traffic speed surveys can be used to identify layer thickness and to check the consistency of layers;

cores are required to calibrate the survey data. There is usually no signal once materials, particularly

subgrades, become saturated.




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9.2.7 Laboratory testing Laboratory testing should only be carried out where there is an identified need.

Tests can be carried out to determine:

• “strength”, the stiffness modulus

• resistance to deformation (rutting)

• binder penetration.

Binder penetration is usually only relevant in the investigation of failures. It can be used to identify

what penetration was used at time of construction (ie was the binder too soft, in which case rutting

and pushing may have occurred, or too hard, in which case premature fatigue may have occurred).

It should be carried out relatively soon after construction because all binders age to a residual

penetration with time. There is little merit in carrying out binder penetration from samples from routine

investigations.

9.2.8 Testing pavement “strength” Individual techniques such as surface condition, coring, and DCP can give an indication of the overall

condition of the pavement but there are techniques that enable the overall strength of a pavement

to be measured objectively and directly in situ.

Objective assessment of pavement layers is often carried out by measuring deflections in some way.

There are a number of deflectometers available for use. Some are mounted on lorries to simulate

normal loading and to provide continuous measurements. The Falling Weight Deflectometer is widely

used and consists of a dropped weight at discrete points to simulate loads; geophones measure

deflections at different distances from the load, enabling a bowl shape to be established. It is trailer-

mounted and easily towed by a normal 4x4 type vehicle. This method also provides data on the

"strength" of different pavement layers and foundation in the form of modulus values. The data allows

the pavement to be analysed and maintenance solutions involving either inlays or overlays, or both

to be developed and adopted. The technique can also be used to determine the residual life of a

pavement.

Coring or trial pits will also be required for correlation and identification of existing layers, their

thickness and condition. For simpler schemes an assessment of this data with simple in situ testing

may be sufficient.

9.3 Subgrade investigation and assessment For new works the subgrade/foundation requires assessment and shall be carried out as per the

criteria provided in table-2 & 3 of this manual. The subgrade assessment may form part of predictive

design for new works or for maintenance or improvement design. For all cases the methods of

assessment will be similar. It is to be noted, however, that tests carried out below in-service road

pavements may give a better assessment of pavement long term performance. The subgrade

“strength” is usually assessed by measurement of its CBR.

Measurements are normally made by direct in situ tests. Soils are, however, moisture sensitive and

a direct measurement at any location may therefore vary with time. In situ tests, should therefore

normally be supplemented with laboratory tests including remoulded/soaked tests as appropriate.




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Information on the frequency of testing is given in sub-Section 4.4.2.2. It is to be noted that CBR

may also be assessed based on soils laboratory classification tests and published local correlations.

Validation in situ CBR tests should be undertaken during construction to ensure the in situ value is

no worse than has been designed for. The equipment typically used for in situ testing is conventional

CBR, drop hammer (light Falling Weight Deflectometer), or Dynamic Cone Penetrometer (DCP).

Particularly for work on existing live highways, the use on non-destructive geophysical survey

techniques might be employed as part of the overall investigation strategy to minimise traffic

disruption. Information on geophysical survey techniques is given in Section 6.5.

In case soil investigation indicates that subgrade is suspected to liquefaction and/or

excessive/differential settlement more than tolerable limits, due to unsuitable material/weak ground

condition and/or presence of water soluble content/pure salt layer underneath and/or other risks and

geo-hazards, that may affect the stability of roads/pavement and/or foundation of

structures/infrastructure/utilities, than ground improvement measures shall be taken into account, to

mitigate the effect of both liquefaction and settlement, prior to construction over it. Subgrade shall

be reinforced with geogrid layers and the requirements shall be determined at design stage. The

type and strength of geogrid shall be finalized in consultation with geogrid designer/supplier based

on the effectiveness for the problem in hand and performance warranties. For ground improvement,

requirements and criteria provided in section 8.5 of TR-509-2 shall be followed.

The suitability of the material shall be evaluated based on the criteria provided in ADQCC TR-542

(1 & 2). The sum of the organic matters’ content and the soluble salt content as a total shall not

exceed 2% in both natural soil and imported backfill.

Similarly, mitigation due to shallow groundwater table (such as capillary break, subsurface drainage

etc.) shall also be adopted at design stage. For the provision of capillary break layer (wrapped in

geotextile), the criteria of design groundwater table of minimum1.5m below formation level (TR-514-

2, Standard DWG C-5) shall be followed.



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09e1.

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OTHER REFERENCES Page 112


OTHER REFERENCES

1. Association of Geotechnical & Geoenvironmental Specialists. Safety Manual for

Investigation Sites. 2002.

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preparation of Ground Report. 2005.

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associated with the preparation of Ground Reports. 2005.

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practice in site investigation (Issue 2). 2006.

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Thomas Telford.



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18. Mayne, Paul; Auxt, Jay A.; Mitchell, James K.; Yilmaz, Recep U.S. National Report on CPT.

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Linköping, Sweden: Swedish Geotechnical Society. pp. 263-276. October 4-5, 1995.

19. NCHRP Report 368. Static Cone Penetration Testing. 2007.

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Investigations – Geotechnical Site Characterization Reference Manual. Publication No.

FHWA NHI-01-031. May 2002.

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Technical Guidance Manual. May 2007.

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guidelines for review of geotechnical reports and preliminary plans and specifications.

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http://geosystems.ce.gatech.edu/Faculty/Mayne/papers/CPT%2095%20US%20Report.pdf



APPENDIX A Pag114 Second Edition June-2021

APPENDIX A: GEOLOGICAL MAP, LITHO-STRATIGRAPHICAL

SECTION, TECTONIC SETTING MAPS AND GEOHAZARD RISK MAPS



APPENDIX A Pag115 Second Edition June-2021

Figure A1: Geological Map of the United Arab Emirates (Huntington Geology & Geophysics Ltd, 1979(1))



APPENDIX B Pag116 Second Edition June-2021

Figure A2: Abu Dhabi litho-stratigraphy (Alsharhan (2008)(2))




Figure A3: Tectonic setting of the Arabian plate (Aldama et al (138))




Figure A4: Maximum considered earthquake ground motion for the United Arab Emirates of 0.2s (Ss) spectral response acceleration (5% of critical damping), Site class B (Abu Dhabi

Guide to the Use of International Building Codes, (149))




Figure A5: Maximum considered earthquake ground motion for the United Arab Emirates of 1.0s (S1) spectral response acceleration (5% of critical damping), Site class B (Abu Dhabi

Guide to the Use of International Building Codes (149))




Figure A6: Reported Loose Soil Thickness-Abu Dhabi

(The above is for Information only, and shall be investigated further, during project specific investigation)




Figure A7: Reported Sabkha Deposit - Abu Dhabi





Figure A8: Reported Halite Deposit- Abu Dhabi





Figure A9: Reported Voids/Cavities- Abu Dhabi





Figure A10: Reported Geohazard Risk- Abu Dhabi





APPENDIX B: ABU DHABI SOILS AND ROCK STRATA TYPICAL

GEOTECHNICAL HAZARDS AND RISKS




Table B1: Abu Dhabi typical geotechnical hazards and risks

Strata/ feature Typical risk/ undesirable consequence

Soils and rock strata

Aeolian Sand Very loose and loose deposits are prone to erosion, mobility and settlement.

Possible metastable structure leading to collapse settlements.

Very loose and loose deposits can be expected to have a lower effective shear

strength compared to deposits of greater relative density. There is therefore a

greater risk of instability of slopes and of lower bearing capacity for foundations

in very loose and loose deposits compared to denser deposits.

Normally uniformly graded deposits which are difficult to compact to engineering

standards when not confined.

Depending on the origin, possible high salt content that gives rise to an

aggressive chemical environment for buried concrete and steel.

Sabkha Significant local variability (both horizontally and vertically) within the deposits

with resultant variation in material properties and differential in engineering

performance.

Some deposits can have high fines content and be highly compressible giving

rise to large settlements and large differential ground displacements. This can

adversely impact on the construction and performance of infrastructure.

Loss of strength and possible dissolution when saturated (rainfall, flash floods,

storm tides inundation, absorption of water in humid weather conditions)

resulting in ground instability under loading conditions and adverse impact on

infrastructure.

High salt content that gives rise to an aggressive chemical environment for

buried concrete and steel.

Presence of gypsum and anhydrite minerals that can undergo alternate

dehydration and rehydration due to changes in the environment. These changes

may be due to natural causes such as seasonal variation, or may be due to man

made causes such as irrigation systems. The resultant shrinkage and swelling

within the deposits that can adversely affect the engineering performance of

foundations and road pavements.

Lagoonal

Sediments

Parts of the coastal fringe in Abu Dhabi contain significant thicknesses of

Lagoonal Sediments. These vary in composition but are typically silts and clayey

silts (aragonite muds) with gypsum inclusions. They are very compressible, and

hence are unsuitable as founding layers and may cause problems during

construction.

Duricrusts Often a hardened surface due to heat, evaporation and salt content, overlying a

leached, cavernous porous or friable zone underneath may cause problems

during construction.

Fluvial

sands/gravels

Variable grading of the deposits related to their spatial location within the alluvial

fan. This gives rise to variability in the characteristics of the deposits and their

engineering performance.







Evaporites Chemically unstable and liable to volume change and dissolution



Conglomerate Difficult to excavate.

Gypsum Gypsum dissolution natural cavities, the presence of which can impact on

engineering design and construction. The collapse of cavities can impact on

engineering construction and the performance of completed engineering works.

Massive (limited discontinuities) strong units of gypsum can be difficult to

excavate. This can give rise to claims and/ or construction delays.

Sandstone/siltstone/

mudstone

Depending on the origin, possible high salt content that gives rise to an

aggressive chemical environment for buried concrete and steel.

In extreme cases with high gypsum content, strata susceptible to collapse owing

to dissolution of the gypsum.

Slopes excavated in the strata can be prone to deterioration and failure.

Calcarenite Typically is of low strength.

Depending on the origin, highly porous strata can give rise to groundwater flow

bringing in high salt concentrations that give rise to an aggressive chemical

environment for buried concrete and steel.

Limestone Stronger, massive strata can be difficult to excavate. This can give rise to claims

and/ or construction delays.

Other factors

Groundwater



Lowering of groundwater for an excavation may cause adverse settlement, for

example from:

• changes in effective stress in compressible deposits by ground loss

• unrestricted flow of water into excavations resulting in piping erosion

• loss of fines from the ground into poorly designed wells.

Seismic activity Liquefaction of some soils and associated ground settlement and lateral

spreading with adverse impact on infrastructure.

Increased loading on structures that may exceed load carrying capacities in

terms of serviceability and ultimate limit states adversely affecting structure

performance and may give rise to failure and collapse.

Flash floods Flash floods are common and occur in wadis in Al Ain desert areas and also in

developed areas with hard surfaces – e.g. Roads. Flash floods can result in

severe erosion and damage to the natural and man made environment.

Sand accumulation Construction of barriers to wind flow (eg road embankments) in areas of wind

blown sand results in deposition and accumulation of sand. This can cause

ongoing maintenance and operational difficulties.





Boreholes Ground investigation techniques commonly adopted in the region are relatively

poorly developed, commonly resulting in poor quality boreholes and non

representative borehole logs. In particular, rotary coring is common with SPTs

between drill strings and the SPTs are used as the key source of parameters.

Core recovery rates are commonly poor, and normal drilling techniques are not

able to recover the weak silty layers which are found within some of the weak

rock units. This can be significant when considering settlement of foundations.

Notes:

The term ‘high salt content’ is used in this table. Sulphates tend to dominate with concentrations of over

50% being reported (Fookes, French and Rice (1985)(172)). This affects the durability of concrete and

steel and it is essential that the aggressive conditions are understood and designed for (ref Guide to

the construction of reinforced concrete in the Gulf, CIRIA C577 (2002)(173) ).

For further information on hazards in the region refer to ”Proceedings of the Conference on Engineering

problems associated with ground conditions in the Middle East”, Quarterly Journal of Engineering

Geology, Vol II No 1 1978(174) .



APPENDIX C Pag129 Second Edition June-2021

APPENDIX C: PRELIMINARY SOURCES STUDY




Table C1: General information required for a preliminary sources study

Ref

No.

Topic Information required

1 General

topographical land

survey

a) location of site on published maps and charts

b) aerial photographs, all dated where appropriate

c) site boundaries, outlines of structures and building lines

d) ground contours and natural drainage features

e) obstructions to sight lines and aircraft movement, for example

transmission lines

f) indication of obstructions below ground

g) record of differences and omissions in relation to published maps

h) position of survey stations and benchmarks (with reduced levels)

i) climate and meteorological information.

2 Permitted use and

restrictions

a) Planning and statutory restrictions applying to the particular areas

under the Emirate Planning Regulations administered by Abu Dhabi

Municipality

b) Local Authority regulations on planning restrictions

c) tunnels rights

d) ancient monuments, burial grounds, etc

e) previous potentially contaminative uses of site and adjacent areas

f) any restrictions imposed by environmental and ecological

considerations, e.g., natural reserves and protected sites

g) oil and gas field, Royal Palaces, military bases.

3 Approaches and

access (including

temporary access)

a) road

b) by water

c) by air.

4 Ground conditions a) geological maps

b) geological memoirs or reports

c) wadi flooding, erosion, and subsidence history

d) data held by central and local authorities

e) construction and investigation records of adjacent sites

f) seismicity.

5 Sources of materials

for construction

a) natural materials

b) imported materials.

6

Drainage and

sewage

a) names of sewage, land drainage and other authorities, bye-laws

b) location and levels of existing systems (including fields, drains and

ditches), showing sizes of pipes, and whether foul, storm water or

combined

c) existing flow quantities and capacity for additional flow

d) liability to surcharging

e) charges for drainage facilities

f) disposal of solid waste

g) flood risk in wadi areas.




Ref

No.

Topic Information required

7 Services (water,

electricity, gas,

telecommunications)

a) names of authorities concerned and their requirements, bye-laws

b) location, sizes and depths of services including drawings

c) gas and water mains, pressure characteristics

d) electricity voltage, phases and frequency

e) water analysis

f) availability of water for drilling

g) storage requirements

h) water source for fire-fighting.

8 Air conditioning a) district cooling.

9 Information related to

made ground and

potential

contamination

a) history of the site, including details of occupiers and users, any

incidents or accidents relating to dispersal of contaminants

b) processes used, including their locations

c) nature and volume of raw materials, products, waste residues

d) soil and/or waste disposal activities and methods of soil and/or

handling waste

e) layout of the site above and below ground at each stage of

development, including roadways, storage areas, hard-cover areas,

and the presence of any extant structures and services

f) presence of any waste disposal tips, abandoned pits and quarries

g) presence of nearby sources of contamination from which

contaminants could migrate via air and/or groundwater onto site.




Table C2: Sources of information for a preliminary sources study

Ref

No.

Topic Source of information

1 Geography a) geographic maps for Abu Dhabi can be obtained for Abu Dhabi

Municipality can be provided in the form of base plans;

b) Google Maps and Google Earth images (these are subject to licensing);

c) the Physical Geography of Abu Dhabi, which can be downloaded

http://www.soe.ae/English/Documents/physical_geog_forweb.04.11.08.p

df (175)

2 Geology,

hydrogeology

and soils

a) geological maps: The following Geological maps published by the UAE

Ministry of Energy can be referred to for geological information about the

UAE and Abu Dhabi

• UAE - Geological Map of the United Arab Emirates 1:1,000,000.

1 sheet, 1976.

• UAE - Geohazards Overview Map of the United Arab Emirates

1:500,000. 1 sheet, 2006.

• The Ministry of Energy has also commissioned the British

Geological Survey (BGS) to prepare 1:100,000 geological maps

for the UAE with geological explanations. The maps are expected

to be published by the Ministry in 2013;

b) geological memoirs: The 1:100 000 geological maps currently being

prepared by BGS will have an accompanying series of explanatory sheet

memoirs;

c) borehole core and specimens: There are many collections of ground

investigation data for Abu Dhabi but these are not centrally archived. In

order to establish availability of information for a certain area it may be

necessary to contact several sources including local ground investigation

companies;

d) hydrogeological maps: Hydrogeological Map of the Emirate of Abu Dhabi

2005;

e) soil maps and memoirs: Soils survey information for Abu Dhabi is held by

the Environment Agency in Abu Dhabi. The soil survey comprises

mapping and classification of the various types of soils in the Emirate of

Abu Dhabi. The entire Emirate is mapped at a scale of 1:100,000. Selected

land, covering 400,000 hectares, evaluated as being suitable for irrigated

agriculture is mapped at a scale of 1:25,000. There are 21 thematic maps

identifying suitability of soils for various purposes such as agriculture,

dune, sabka, forestry and landfill

f) a series of published literature on the geology, soil and hydrogeology of

the UAE are available on line. For example UAE Interact Website

http://www.uaeinteract.com/nature/geology/index.asp,(176)

http://sepmstrata.org/UAE/AbuDhabi/UAEGallery/ABgallery.html (177)

and the Commission of the Geological Maps for the Middle East

http://www.cgmme.com (178)

3 Marine

information

a) marine information in relation to wave heights, wind speed and wind

directions is available from The National Centre for Meteorology and

Seismology.

http://www.soe.ae/English/Documents/physical_geog_forweb.04.11.08.pdf

http://www.soe.ae/English/Documents/physical_geog_forweb.04.11.08.pdf

http://www.uaeinteract.com/nature/geology/index.asp

http://sepmstrata.org/UAE/AbuDhabi/UAEGallery/ABgallery.html

http://www.cgmme.com/




Ref

No.

Topic Source of information

4 Meteorological

information

a) meteorological information for UAE is available from The National Centre

for Meteorology and Seismology.

5 Hydrological

information

a) water resource data is available from the Department of Water Resources

of the Environment Agency.

6 Aerial

photographs

a) aerial photographs of Abu Dhabi are available in hard and electronic from

Abu Dhabi Municipality.

7 Seismological

information

a) computer listings and maps of earthquakes occurring in the UAE and

elsewhere in the Middle East are available from The National Centre for

Meteorology and Seismology.




Table C3: Notes on site reconnaissance

Ref

No.

Topic Action

1 Preparatory

work

a) whenever possible, have the following available: site plan, maps or charts,

and geological maps and aerial photographs

b) ensure that permission to gain access has been obtained from both owner

and occupier and is not a restricted area

c) obtain Critical National Infrastructure Authority (CNIA) pass as needed

d) ensure safety precautions, equipment and PPE required, particularly in

respect of dune and sabkha areas

e) when undertaking site reconnaissance on potentially contaminated land,

ensure that all likely hazards have been identified, that appropriate safety

procedures are followed, and that necessary safety equipment is used.

2 General

information

a) traverse whole area, preferably on foot but by vehicle for larger sites

b) set out proposed location of work on plans, where appropriate

c) observe and record differences and omissions on plans and maps; for

example, boundaries, buildings, roads and transmission lines

d) inspect and record details of existing structures

e) observe and record obstructions; for example, transmission lines, ancient

monuments/ structures of archaeological importance, trees subject to

preservation orders, gas and water pipes, electricity cables, sewers

f) check site access arrangements, also consider the probable effects of

construction traffic and heavy construction loads on existing roads, bridges

and services

g) check and note water levels, tidal and other fluctuations due to dewatering

at or near to site

h) observe and record adjacent property and the likelihood of its being

affected by proposed works, and any activities that may have led to

contamination of the site under investigation

i) observe and record quarry workings, old workings, old structures, and any

other features that may be relevant

j) observe and record any obvious immediate hazards to public health and

safety (including to trespassers) or the environment

k) observe and record any areas of discoloured soil, polluted water,

distressed vegetation or significant odours

3

Ground

information

a) study and record surface features, on site and nearby, preferably in

conjunction with geological maps and aerial photographs, and note the

following:

i. morphology and note if site is dune, sabkha or made ground

ii. type and variability of surface conditions

iii. in areas of sabkha note areas of ponding after rain and salt

accumulation

iv. comparison of surface lands and topography with previous map

records to check for presence of fill, wind erosion, or cuttings

v. steps in surface, which may indicate geological faults or shatter

zones. In cavity areas evidence of subsidence should be looked

for: compression and tensile damage in brickwork, buildings and

roads; structures out of vertical

vi. crater-like holes in carbonate rocks, which usually indicate

swallow holes filled with soft material




Ref

No.

Topic Action

3 Ground

information

(continued)

b) assess and record details of ground conditions in quarries, cuttings and

rock outcrops on site and nearby

c) assess and record, where relevant, ground water level or levels (often

different from water course) positions of irrigation wells and occurrence of

artesian flow

d) study embankments, buildings and other structures in the vicinity having a

settlement history.

4 Site inspection

for ground

investigation

(ii) inspect and record location and conditions of access to working sites;

(iii) observe and record obstructions, such as power cables, telephone lines,

boundary fences and trenches

(iv) locate and record areas for depot, offices, sample storage, field

laboratories

(v) ascertain and record ownership of working sites, where appropriate

(vi) consider liability to pay compensation for damage caused

(vii) locate a suitable water supply where applicable and record location and

estimated flow

(viii) record particulars of lodgings and local labour, as appropriate

(ix) obtain list of permissions and notices required from Land Authorities.



APPENDIX D Pag136 Second Edition June-2021

APPENDIX D: EXAMPLE TEMPLATE EVALUATION SHEETS FOR

GROUND INVESTIGATION COMPANIES




Table D1: Example template technical evaluation sheet for Ground Investigation Companies

Technical aspect to be evaluated

Notes for preparing a list of technical information for evaluation to be submitted by the Ground Investigation Company as part of its tender

Information sought from Ground Investigation Company

Depending on the evaluation system used the headings below will vary

Po

int

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Po

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To

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po

ints

=

Po

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*

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igh

ting

Methodology and approach to ground investigation

(1) The Ground Investigation Company’s methodology and approach to the proposed ground investigation can have a substantial influence its successful execution and timely completion. Details of these should be sought as part of a tender package.

(i) Description of the Ground Investigation Company’s proposed methodology and approach to the ground investigation. (2 No A4 page sides maximum)

(ii) Preliminary method statements for key activities describing the Ground Investigation Company’s proposed methods, including temporary works and safety provision. (Each preliminary method statement shall be limited to 2No. A4 page sides maximum).

(iii) Project organogram detailing lines of responsibility and communication within the team and with other parties (see Quality of personnel aspect for information to be supplied in respect of competencies, relevant experience and qualifications of key staff). (2 No A4 page sides maximum)

Compliance to EHS requirements

(1) The Ground Investigation Company should operate under an environmental management system, preferably register to BS EN ISO 14001:2005 or similar

(i) Details and copies of relevant accreditation certificates of the Ground Investigation Company’s environmental management policy and any training programme for its staff, technicians and drilling crews. (1 No. A4 page side maximum + certificates)








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Compliance to EHS requirements (continued)

(2) Appropriate environmental

management is important to negate

environmental damage and for

providing overall success of the

ground investigation. Details of the

Ground Investigation Company’s

environmental management

proposals in respect of the ground

investigation should be sought.

(i) Details of the Ground Investigation

Company’s environmental protection

measures in respect of the proposed

ground investigation works. (1 No. A4 page

side maximum)

(3) It is essential that the Ground Investigation Company appropriately manages the health and safety aspects of the ground investigation for the protection of its staff, operatives, other parties involved in the ground investigation, the public and existing infrastructure. Evidence of the health and safety competence of the Ground Investigation Company should be sought.

(i) Complete the health and safety questionnaire (Table D2 below).

(ii) Copy of the Company’s health and safety policy and its health and safety training programme for its staff, laboratory technicians and drilling crews.

(iii) Evidence of competence to carry out the ground investigation to the requirements of health and safety legislation and the named resources allocated to control and manage the health and safety risks.

(iv) A preliminary assessment of the main health and safety risks associated with the proposed ground investigation. (2No. A4 page sides maximum)








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Quality of personnel (1) The Ground Investigation Company should employ on the ground investigation appropriately qualified staff with appropriate expertise and experience in work to be undertaken and for the role for which they are named (ref Manual Part 1 Section 2.3 Definition of geotechnical practitioners)

(i) Names of the specialists to be employed on the ground investigation together with details of their academic and professional qualifications and a summary of their experience. Full curriculum vitae to be provided for senior roles such as Site Agent and Laboratory Manager.

(2) Drills and crew appropriately experienced and trained. Competence assessed and accredited by an independent industry body (ref Manual Part 2 Section 5.2.1 Quality of ground investigation personnel)

(i) Names of the drillers (and drilling assistants) to be employed on the contract together with details of their accreditation, if any, and a summary of their experience

(3) Company staff, technician and operatives training and development policy and programme (ref Manual Part 2 Section 5.2.1 Quality of ground investigation personnel)

(i) Details of the company training and development policy and its training programme for its specialist staff, laboratory technicians and drilling crews. (1 No. side A4 page maximum)

Certification requirements

(1) The Ground Investigation Company should operate under a quality assurance system, preferably register to BS EN ISO 9000:2005 or similar) (ref Manual Part 2 Section 5.2.1 Quality of ground investigation personnel).

(i) Details and copies of relevant certificates for the company’s quality assurance system. (1 No. side A4 page maximum + copies of certificates)

(ii) An example quality plan for similar previous ground investigation work.








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Certification requirements (contined)

(2) Laboratories undertaking soils and rock testing and analytical contaminant testing should be accredited by an independent industry recognised body eg UKAS or A2LA (ref Manual Part 2 Section 5.2.2 Laboratory quality).

(i) Details and copies of relevant certificates of any independent accreditation held for laboratory testing and results reporting. (1 No. side A4 page maximum + copies of certificates)

Technology requirements

(1) Where innovative or new technology is required to be used on a ground investigation the Ground Investigation Company’s knowledge and experience of that technology should be established.

(ii) Statement of knowledge and experience of the particular technology required to be used. (1 No. side A4 page maximum)

Documentation of operations in similar projects

(1) Past experience of similar ground investigation works to those proposed past similar ground investigation can have a substantial influence its successful execution and timely completion. Details of these should be sought as part of a tender package.

(i) Details of ground investigations of a similar nature which have been carried out by the Ground Investigation Company within the last five years with evidence of satisfactory completion. Details shall include how lessons learnt from previous ground investigations would be used to improve performance on the proposed ground investigation. The statement shall include up to 5No. previous investigations. (3No. sides A4 pages maximum)

Capacity to upgrade and support

(1) Possible requirements for the Ground Investigation Company to upgrade its services and provide additional support to the overall

(i) Description with evidence of the Ground Investigation Company’s capacity to upgrade and support as set out in the








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Capacity to upgrade and support (continued)

delivery of the ground investigation should be set out in the tender documentation. This might be to undertake ground investigation works outside those included in the bill of quantities or provision of other specialist staff additional drilling crews, equipment and other plant and laboratory testing and facilities.

tender documentation. (1No. A4 page maximum)

The ability of the company to mobilise and begin work

(1) A prompt start is usually important to ensuring that a ground investigation is completed in a timely manner within the specified ground investigation contract programme and the overall project programme. Details of the Ground Investigation Company’s ability to mobilise and begin work should be sought.

(i) Confirmation and details of the Ground Investigation Company’s available resources and its ability to mobilise and begin work. ( ½No. A4 page maximum)

Time for programme completion and programme logic

(1) An appropriate programme for the execution of the proposed ground investigation works with associated programme logic in terms of order of execution of those works is important for the timely execution and completion of the ground investigation and its successful completion. A preliminary resourced programme covering the main

(i) A preliminary resourced programme which shows the periods required and the sequence in which the Ground Investigation Company proposes to undertake the various parts of the ground investigation and the dates of the principle operations. The details submitted must include an easy to understand bar chart programme.








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elements of the ground investigation should be sought.

Relevant experience in the local market and available resources (plants, office, software, tools) in the UAE

(1) Relevant experience in the local market and having appropriate local resources can benefit the timely execution and successful completion of a ground investigation. Details of the Ground Investigation Company’s experience of the local market and his local UAE resources should be sought.

(i) Details of the Ground Investigation Company’s experience of working in UAE and of its local UAE resources including numbers of: - geotechnical practitioners (office & field

based) against the categories in Table A1 in Appendix A Part 1 of the Manual for Geotechnical Investigation and Geotechnical Design;

- office administration support staff; - drillers and drilling crew related to the

type of drilling rig they operate and whether they are accredited;

- laboratory staff and technicians; - numbers and types of drilling rigs and

other plant; - numbers and types of laboratory testing

machines (eg shear box and triaxial test apparatus, oedometers) together with copies of their calibrations certificates;

(ii) Confirmation of whether the Ground Investigation Company can supply AGS data together with a copy of a typical AGS data file from its database.








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Relevant experience in the local market and available resources (plants, office, software, tools) in the UAE (continued)

(iii) Copies of the Ground Investigation Company’s typical borehole, trial pit and field and laboratory test reporting records.

(iv) Details shall include how lessons learnt from previous ground investigations in UAE would be used to improve performance on this ground investigation (2no. side of A4 page maximum)



APPENDIX E Page144 Second Edition June-2021

Table D2: Example template health and safety questionnaire for Ground Investigation Companies

Question Included Response (If information is part of a separate document or continued on

a separate sheet provided please give the title and page or

clause number)

Yes No N/A

A) General information

1. Company name and Registered Address

1. Name……………………………...………………

Address………………………….……………… ……………………………………………………. ……………………………………………………. Tel………………………………………………… Fax……………………………………………… Email……………………………………………… Internet…………………………………………… Contact Name……………………………………..

2. Give the name and position in the Company of the person who has overall responsibility for ensuring adequate resources are made available for Health and Safety.

Submit an organisation chart for Health and Safety.

2. Name……………………………...………………

Position………………………….……………….. H&S Chart…………………………………….…..

3. Give the name, qualifications, and experience of the person nominated to provide specific Health and Safety advice in the execution of the contract.

3. Name……………………………...……………….

Position………………………….………………... CV Included……………………………………...

4. Summarise the main details of your safety management system.

4.

5. Do you audit Health and Safety?

5. If not go to Q.6

6. Give details of the recommendations from any audits that have been undertaken.

6.

7. How do you learn from your past Health and Safety experience?

7.




Question Included Response (If information is part of a separate document or continued on

a separate sheet provided please give the title and page or

clause number)

Yes No N/A

8. Summarise injuries, diseases and dangerous occurrences during the last three years. Provide the information in the form of an incidence rate per 100,000 employees. Identify fatalities separately.

8.

9. Summarise your arrangements for selecting and controlling sub-contractors with respect to Health and Safety.

9.

B) Project specific information

10. Information on similar projects and experience

10.

11. Ground investigation risk management experience on a project of similar size, procurement style

11.

12. A developed H&S Plan from at least one ground investigation

12.

13. Names and experience (H&S) of project team

13.

14. How competence and resource checks will be done for any sub-contractors

14.

15. Confirmation that the competent personnel are available for the project programme

15.




APPENDIX E: TEMPLATE BILL OF QUANTITIES FOR GROUND

INVESTIGATION

NOTE: APPENDICES ARE AVAILABLE IN THE PDF COPIES

.




UK Specification for Ground Investigation second edition, ref UK Site Investigation Steering Group

(2012)(90), includes a specification, a model bill of quantities and schedules that enable the

geotechnical practitioner to define investigation specific details together with associated notes for

guidance. The model bill of quantities provides a comprehensive list of items that are correlated to

the specification items. It is intended that the numbering of the model bill of quantities items remains

unaltered with items that are not required for a particular project ground investigation either marked

as “not used” or not presented in the project-specific bill of quantities. Typically the project-specific

additional items should be included at the end of each bill. The template bill of quantities for Abu

Dhabi road projects included in this appendix follow those principles so that the published standard

specification may be used with minimal changes for project-specific requirements.



APPENDIX F Page169 Second Edition June-2021

APPENDIX F: SPT CORRECTIONS SPREADSHEET TEMPLATE



APPENDIX F Page170 Second Edition June-2021

Table F1: SPT corrections spreadsheet template



APPENDIX G Page171 Second Edition June-2021

APPENDIX G: CONE PENETRATION TESTING




Table G1: Summary of typical checks and recalibrations to be made for CPT

Check or recalibration

Frequency

At start of

test

programme(1)

At start of

sounding

At end of

sounding

At three-

month

intervals

Verticality of thrust machine - * - -

Straightness of push rods * * - -

Precision of measurements * - - *

Zero load error (taking baselines) - * * -

Wear:

- dimension of cone, friction

sleeve * * - -

- roughness * * * -

- filters - - - *

Seals:

- presence of soil particles * * - -

- quality * * * -

Calibration:

- load cells and pressure

transducers * - - *

- unequal end area - - - *

- temperature - - - * Notes

(1) And regularly during a long testing programme




Table G2: Check list for information required for CPT to check data quality

Question Answer Notes

1 Type of cone penetrometer Manufacturer, capacity, type.

ISSMFE IRTP (1989)(103) standard.

2

Adhering to international

standard (ie 10cm², 60⁰, sleeve

area = 150cm² etc)

Compare with requirements in

ISSMFE IRTP (1989)(103).

3 If answer to 2 is no, what cone

is being used?

x-sect area =

cone angle =

sleeve area =

If A = 15cm², α = 60⁰

and Asl = 202cm²; ok.

4

Location of filter(s) for

measuring pore pressure and

type of fluid

5 Area ratio (a) of cone tip Normally in range a = 0.59 to 0.85.

6 End areas of friction sleeve Best if they are equal.

7 Is qc corrected for pore pressure

effects?

Compare with formulas given in

Lunne et al (1997)(107).

8 Is ƒs corrected for pore pressure

effects?

Compare with formulas given in

Lunne et al (1997)(107).

9 What is basis for σ’vo? Assumed? Based on measurement

of bulk density (ρ) on samples?

10 When were sensors (qc, u, ƒs)

last calibrated?

Compare with requirements given in

specifications or Lunne et al

(1997)(107).

11 Zero readings before and after

each test reported?

Important to check if results appear

"abnormal"

12

Where were readings zeroed?

(eg sea bottom or bottom of

borehole)

Important for overwater testing

13 Depth of any pre-drilling Explains any missing data

14

What is frequency of readings?

The commercial rate is one set

every second, ie every 2cm.

Decided by project requirements

15

For dissipation testing;

(a) were the rods clamped or

unclamped?

(b) frequency of readings

How well was the initial part of the

dissipation curve defined - faster

sampling rate to start with?



APPENDIX H Page174 Second Edition June-2021

APPENDIX H: BOREHOLE GEOPHYSICAL TECHNIQUES




Table H1: Tools and methods for subsurface investigations (from US Dept of Interior, Bureau of Reclamation (1998)(119))

Method Principle and application Limitations

Surface seismic

refraction

Determine bedrock depths and characteristic

wave velocities as measured by geophones

spaced at intervals.

May be unreliable unless velocities

increase with depth and bedrock surface

is regular. Data are indirect and

represent averages. Limited to depths of

about 30m (100ft).

High resolution

reflection

Determine depths, geometry and faulting in

deep rock strata. Good for depths of a few

thousand meters. Useful for mapping offsets

in bedrock. Useful for locating ground water.

Reflected impulses are weak and easily

obscured by the direct surface and

shallow refraction impulses. Does not

provide compression velocities.

Computation of depths to stratum

changes requires velocity data obtained

by other means.

Vibration Travel time of transverse or shear waves

generated by a mechanical vibrator is

recorded by seismic detectors. Useful for

determining dynamic modulus of subgrade

reaction for design of foundations of vibrating

structures.

Velocity of wave travel and natural period

of vibration gives some indication of soil

types. Data are indirect. Usefulness is

limited to relatively shallow foundations.

Uphole, downhole,

and cross-hole

surveys (seismic

direct methods)

Obtain velocities for particular strata;

dynamic properties and rock-mass quality.

Energy source in borehole or at surface;

geophones on surface or in borehole.

Unreliable for irregular strata or soft soils

with large gravel content. Cross-hole

measurements best suited for in-place

modulus determination.

Electrical resistivity

surveys

Locate fresh/salt water boundaries; clean

granular and clay strata; rock depth; depth to

ground water. Based on difference in

electrical resistivity of strata.

Difficult to interpret and subject to wide

variations. Difficult to interpret strata

below water table. Does not provide

engineering properties. Used up to

depths of about 30m (100ft).

Electromagnetic

conductivity surveys

Measures low frequency magnetic fields

induced into the earth. Used for mineral

exploration; locating near surface pipes;

cables, and drums and contaminated plumes.

Fixed coil spacings limited to shallow

depth. Background noise from natural

and constructed sources (manufactured)

affects values obtained.

Magnetic

measurements

Mineral prospecting and locating large

igneous masses. Highly sensitive proton

magnetometer measures Earth’s magnetic

field at closely spaced intervals along a

traverse.

Difficult to interpret quantitatively, but

indicates the outline of faults, bedrock,

buried utilities or metallic objects in

landfills.

Gravity

measurements

Detect major subsurface structures, faults,

domes, intrusions, cavities. Based on

differences in density of subsurface

materials.

Not suitable for shallow depth

determination but useful in regional

studies. Some application in locating

caverns in limestone.

Ground-penetrating

radar

Locate pipe or other buried objects, bedrock,

boulders, near surface cavities, extent of

piping caused by sink hole and leakage in

dams. Useful for high-resolution mapping of

near-surface geology.

Does not provide depths or engineering

properties. Shallow penetration. Silts,

clays, and salts, saline water, the water

table, or other conductive materials

severely restrict penetration of radar

pulses.




Table H2: Geophysical methods and techniques for logging boreholes (from US Dept of Interior, Bureau of Reclamation (1998)(119))

Method Principle and application Limitations

Electrical logging Several different methods available. Provides

continuous record of resistivity from which

material types can be deduced when correlated

with test-boring data.

Provides qualitative information. Best used with

test-boring information. Limited to uncased

hole.

Neutron radiation

logging

Provides continuous measure of natural moisture

content. Can be used with density probe to

locate failure zones or water bearing zones in

slopes.

Data from neutron probe is limited to-in-place

moisture content values. Often differs from

oven-dried moisture content and requires

correction.

Gamma-gamma

logging

Provides continuous measure of in-place density

of materials.

Data limited to density measurements. Wet

density usually more accurate than dry density.

Scintillometer (Gamma

ray logging)

Provides measure of gamma rays. Used to

locate shale and clay beds and in mineral

prospecting.

Quantitative assessments of shale or clay

formations.

Acoustic borehole

imaging

Sonic energy generated and propagated in fluid

such as air to water. Provides continuous 360

image of borehole wall showing fractures and

other discontinuities. Can be used to determine

dip.

Must be used in fluid-filled borehole unless

casing is being inspected. Tool must be

centred in the borehole. Logging speed is

relatively low between 20 and 75 mm/s (4 and

15ft/min). Imaging less clear than house

obtained with borehole cameras.

Acoustic velocity

logging

Can determine litho logic contracts, geologic

structure, cavities and attitude of discontinuities.

Elastic properties of rock can be calculated.

Compression (P-water) is generated and

measured. Used almost exclusively in rock.

Borehole must be fluid filled and diameter

accurately known. Penetration beyond

borehole wall of about a meter or so. Geologic

materials must have P-water velocities higher

than velocity of the borehole fluid.

Crosshole seismic

tests

Seismic source in one borehole; receiver(s) at

same depth in second (or more) borehole(s).

Material properties can be determined from

generated and measured compression and

shear waves. Low velocity zones underlying high

velocity zones can be detected.

Borehole spacing is critical and should be >3m

and <15m. Precise borehole spacing must be

accurately known for data to be useful.

Borehole cameras Borehole TV or film type cameras available. TV

viewed in real time. Can examine cavities,

discontinuities joints, faults, water well screen,

concrete-rock contacts, grouting effectiveness,

and many other situations.

Requires open hole. Images are affected by

water clarity. Aperture on film camera must be

preset to match reflectivity of borehole wall

materials.

Borehole caliper

logging

Used to continuously measure and record

borehole diameter. Identify zones of borehole

enlargement. Can evaluate borehole for

positioning packers for other tests. One to six

arm probe designs.

Diameter ranges from about 50 to 900mm (2 to

36in). Must calibrate caliper against known

minimum and maximum diameter before

logging. Special purpose acoustic caliper

designed for large or cavernous holes (dia) 1.8

to 30m (6 to 100ft).

Temperature logging Continuous measure of borehole fluid

temperature after fluid has stabilized. Can

determine temperature gradient with depth.

Probe must be calibrated against a fluid of

known temperature. Open boreholes take

longer to stabilize than cased holes. Logging

speed 15 to 20mm/s (3 to 4 ft/min).



APPENDIX H Pag177 Second Edition June-2021

Table H3: Borehole logs and their applications and limitations (from BS5930-1999 with 2010 Addendum(7))

Application

limitations

Log type (“1” against a particular log type means that it is suitable for the application listed)

Fo

rma

tio

n

mic

ro

Te

levie

wer

Spectr

al

gam

ma

Dia

me

ter

Flo

w m

ete

r

Flu

id

conductivity

Flu

id

tem

pera

ture

Te

levis

ion

Calip

er

Sonic

Neutr

on

Gam

ma

gam

ma

Natu

ral

gam

ma

Intr

oductio

n

Ele

ctr

ical

Resis

tivity

Sponta

ne

pote

ntia

l

Lined hole - - 1 - 1 1 1 1 1 1 1 1 1 - - -

Open hole 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

Air-filled - - 1 - - - - 1 1 - 1 1 1 1 - -

Water/mud filled 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

Diameter - - - - - - - - 1 - - - -- - - -

Casing - - - 1 - - - 1 1 - - - 1 - 1 -

Fractures/joints 1 1 - 1 1 1 1 1 1 1 - 1 - - 1 -

Cement bend - - - - - - - - - - - - - - - -

Bed boundaries 1 1 1 1 - - - 1 1 1 1 1 1 1 1 1

Bed thickness 1 1 1 - - - - 1 1 1 1 1 1 1 1 1

Bed type - - 1 - - - - - - 1 1 1 1 1 1 1

Porosity - - - - - - - - - 1 1 1 - 1 1 -

Density - - - - - - - - - - - 1 - - - -

Permeable zones 1 1 - - 1 1 1 - 1 - 1 1 - - - -

Borehole fluid quality - - - - - 1 - - - - - - - - - -

Formation fluid quality - - - - - - - - - - - - - 1 1 1

Fluid movement - - - - 1 1 1 - - - - - - - - -

Direction of dip - - - 1 - - - - - - - - - - - -

Shale /sand indication - - - - - - - - - - - - 1 - - 1



APPENDIX I Pag178 Second Edition June-2021

APPENDIX I: EXAMPLE EXPLORATORY HOLE RECORD




APPENDIX J Page181 Second Edition June-2021

APPENDIX J: EXAMPLE REPORTING FORMS FOR SOILS AND

ROCK LABORATORY TESTS




APPENDIX K Page305 Second Edition June-2021

APPENDIX K: EXAMPLE GEOLOGICAL PROFILES




APPENDIX L Page307 Second Edition June-2021

APPENDIX L: INTERNATIONAL STANDARDS - LIMIT STATE

GEOTECHNICAL DESIGN



APPENDIX L Page308 Second Edition June-2021

Table L1: International Standards – Limit state geotechnical design

Structure/earthwork Geotechnical design issue Limit state geotechnical design standards (with use of partial factors of safety)

BS EN 1997-1:2004(156)

Comments

Bridge (including abutments and piers), gantry signs

Spread footings Sizing/bearing capacity


Stability (engulfing failure of foundations on slopes)

BS EN 1997-1:2004 Section 6, Annex D, Annex F, Annex G for foundations on rock and Annex H

BS EN 1997-1:2004 Section 11

Pile foundations Carrying capacity (axial and lateral) , downdrag/ negative skin friction

Settlement/ deflection of laterally loaded piles

BS EN 1997-1:2004 Section 7

Retaining walls Gravity wall Wall stability

Bearing capacity

Sliding resistance


Stability (engulfing failures)

BS EN 1997-1:2004 Section 9, Annex C, Annex H

BS EN 1997-1:2004 Section 11 for slope stability aspects

Cantilever/anchored embedded wall

Wall stability

Anchorage design

Stability (engulfing failures)

BS EN 1997-1:2004 Section 9 & Annex C

BS EN 1997-1:2004 Section 8 for anchorage design

BS EN 1997-1:2004 Section 11 for slope stability aspects.

Soil cuttings - Stability BS EN 1997-1:2004 Section 11 & BS 6031:2009 (166)

Rock cutting - Stability BS EN 1997-1:2004 Section 11

Embankments - Stability (including internal and surface erosion)


BS EN 1997-1:2004 Section 11, BS EN 1997-1:2004 Section 12, Annex F & BS 6031:2009 (166)