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Civil Design Criteria Materials & Workmanship Specification

for Civil and Structural Works

PRESENTATION OUTLINE

Geotechnical Parameters Factors of Safety for DFEs Unbalanced Load Case Instrumentation Ground Treatment Crack Repair Using Polyurethane

GEOTECHNICAL PARAMETERS

Geotechnical Parameters

DC Chapter 5 lists geotechnical parameters for design

Some parameters are conservative Higher values can be used with justification

by test data for a specific project site

3028Note 3Note

3Note

3Note

3Note

3222230530Effective Angle of Friction (degrees)

010Note 3Note

3Note

3Note

3Note

300000Effective Cohesion,c (kPa)

0Note 2Note

2Note

2Note

2Note

2Note

2

Figure 5.3 & Note 1

Figure 5.2 & Note 1

0Figure 5.1 & Note 1

0Undrained Cohesion,c

u(kPa)

0.51.01.01.01.01.01.01.01.00.71.00.5Coefficient of Earth Pressure at Rest (K0 )

192220202020201619201519Bulk Density(kN/m3)

Desig

n P

ara

meters

FillFCBBClass E

Class D

Class C

Class B

Class A

OAMF2F1EBSoil Classification


3030Note 4Note

4Note

4Note

43030Note

4Note

4Note

4Note

4Effective Angle of Friction (degrees)

00Note 4Note

4Note

4Note

400Note

4Note

4Note

4Note

4Effective Cohesion,

c (kPa)

Note 2

Note 2N/AN/AN/AN/A

Note 2

Note 2N/AN/AN/AN/A

Undrained Cohesion,c

u(kPa)

0.80.80.80.80.80.80.80.80.80.80.80.8Coefficient of Earth Pressure at Rest (K0 )

202023232424212122222424Bulk Density(kN/m3)Desig

n P

ara

mete

rs

GVIGVGIVGIIIGIIGISVISVSIVSIIISIISI

Bukit Timah Granite FormationJurong FormationSoil Classification


Coefficient of earth pressure at rest, k0 Dependent on stress history Various empirical formulae available for estimation:

Jaky: k0 = 1 - sinMayne & Kulhawy: k0 = (1-sin)(OCR)sin

Highly variable For permanent work design, it is expected that

DC values are adopted.


Subgrade modulus not given problem specific & not a soil property

Where values for the subgrade modulus are used in the calculations, the values shall be confirmed by FE or FD analyses for an appropriate range of foundation geometries Chapter 6, DC


FACTORS OF SAFETY FOR DFE

Factor of Safety for DFE

The factor of safety on working loads: The overall factor of safety shall be not less

than 2.5 The factor of safety shall be not less than 1.5

in shaft friction alone

Factor of Safety for DFEThe second requirement is not necessary: When the DFE has been installed by driving Any loose or remoulded material is removed

from the base; and the base inspected and confirmed dry before casting the concrete

If the DFE is base grouted Where the end bearing is provided by SI or SII

or GI or GII rock, and toe coring is carried out to confirm the pile/rock contact for every DFE

UNBALANCED LOAD CASE

Unbalanced Load Case

Max Water Pressure

Surcharge

GWL

GWL

Water Pressure (Varying)

Surcharge above structure if more onerous

Earth Pressure

Vertical Earth Pressure & Water Pressure

Min Water Pressure

1.5mZ

Hull Dead

Internal Dead LoadEarth Pressure

h4.5m

Wall DeflectionSame overburden v

Horizontal stress reduced, hence reduced K

h = Kv

Unbalanced Load Case

INSTRUMENTATION

Instrumentation C&C Tunnel

One Type A, B or C array for every 25m of perimeter wall or slope.

An average of one Type B or C array for every 100m of perimeter wall or slope.

An average of one Type C array for every 500m of perimeter wall or slope.

DARRAY TYPE A

0.25D 0.25D 0.25D 0.25D 0.25D 0.25D 0.25D 1D 1D

I

P

DD

ARRAY TYPE A

0.25D

ARRAY TYPE B

0.25D 0.25D 0.25D 0.25D 0.25D 0.25D 1D 1D

I

P

D


ARRAY TYPE C

0.25D 0.25D 0.25D 0.25D 0.25D 0.25D 1D 1D

I

1D1D

S

P

P P

P P

P P

I/E I/E

D

ARRAY TYPE C

0.25D 0.25D 0.25D 0.25D 0.25D 0.25D 1D 1D

I

1D1D

S

P

P P

P P

P P

I/E I/E

D


One of Type D, E or F every 25m of single tunnel.

One of Type E or F for every 200m of single tunnel, on average.

One of Type F for every 1000m of single tunnel, where the tunnels have an excavated diameter in excess of 3m.

Instrumentation Bored Tunnel Instrumentation Bored Tunnel

ARRAY TYPE D

Z

ARRAY TYPE E

X

C

1

T

O

2

m

0.5Z 0.25Z 0.25Z 0.25Z 0.25Z 0.25Z 0.25Z 0.25Z 0.25Z 0.5Z

Z

Instrumentation Bored Tunnel

ARRAY TYPE F

C

I/E I/E

X

X

P

P

0.5Z 0.5Z 0.25Z 0.25Z 0.25Z 0.25Z 0.25Z 0.25Z 0.25Z 0.25Z 0.5Z 0.5Z

Z

Instrumentation Bored Tunnel

ARRAY TYPE F

C

I/E I/E

X

P

PXX

P

P

P

P

P

PPP P P

0.5Z 0.5Z 0.25Z 0.25Z 0.25Z 0.25Z 0.25Z 0.25Z 0.25Z 0.25Z 0.5Z 0.5Z

Z

Type E and F arrays shall be located in areas of particular concern, taking into account the nature and sequence of construction, the presence of adjacent buildings and the assessed ground conditions. Type E and F arrays should be particularly located in areas where it is expected that the tunnel will encounter soils of the KallangFormation. The Types E and F arrays are not required to be evenly spaced.

InstrumentationWhere any part of the tunnel is directly below any part of a building or structure that is in use, the following shall be implemented as a minimum: -

A comprehensively monitored zone shall be set up within the area 50m before the tunnel reaches the building. The monitoring is required to confirm that the tunnelling is being carried out in such a way that the settlements are less than or equal to that expected from the design. The zone shall include at least two type E arrays, at 25m and 50m respectively from the building.

Instrumentation

F-Arrays

GROUND TREATMENT

Ground TreatmentSS CP4 (2001) or BS8004 (1986)

Grouting is very much an art calling for good engineering appreciation of its effectiveness. All grouting works should be supervised by an engineer experienced in grouting.

Control of grouts: Suitability of a grout is best established by trial on site.

Control of grouting operation Adequate system of recording

information on grouting pressure and flow into the ground at each injection point and sampling of grout being used.

Good quality cores of ground before and after treatment can provide useful information for judging the results of grouting.

Ground TreatmentSS CP4 (2001) or BS8004 (1986)

Ground TreatmentBS EN Requirement

Elements to be monitored for control purposes geometry and where appropriate, strength,

deformability, permeability or density of jet grouting materials

Generally impractical or impossible to measure dimensions and material properties directly.

The minimum quality control consists of reporting of jet grouting parameters and observing the spoil return on all elements.

It may be assumed that in comparable soil conditions the same jet grouting parameters produce the same element dimensions, properties and soil return.


Where comparable experiences are not available, preliminary test shall be designed and performed.

If the jet grouted elements can not be exposed, the assessment of the results should be made by coring or by direct measurement prior to setting, or by indirect tests.

Indirect tests include CPTs, SPTs, pressuremeters, cross hole geophysical tests.


Supervision fluid pressure, inclination, spoil return density of spoil return should be measured.

Parameters to be monitored: Pressure and flows of the fluid; translation and rotation speed of the

monitor. Monitoring of adjacent structures. For underpinning application, buildings to be

underpinned should be monitored.


Geometry Whenever visual inspection is not possible,

dimensions can be obtained by coring or drilling with measurement of drilling rate, inclined to the element axis.

Length can be detected by coring or drilling or penetration testing parallel to axis.

Mechanic tests Where relevant, compressive strength should

be assessed by testing 4 samples for each 1000 m3 of jet grouted structures.


Ground TreatmentCIRIA Report C514

Control of two elements: Injection parameters and spoil return.

Injection parameters to be controlled: density of grout, flow rate, fluid pressure measured at the drill head, rotation and withdrawal rate to be monitored continuously through the process.

Spoil return: Visual inspection, measurement of its density, and where appropriate, compression tests on representative samples.

Post treatment validation: geometry and physical properties.

Geometry: Visual inspection, (not practical). Alternatively core samples are used to verify cross section and length of grouted elements.

Mechanical properties: The designer to determine the number and type of tests required.

Available techniques: in-situ penetrometer tests, shear, compression and permeability tests on core samples and pumping tests.


Quality control of jet grouting is not fully standardized.

Air/water and grout flow can be monitored continuously - but not always done.

Water pressure, rate of lift of monitor, rotation are important parameters to measure.

A full scale trial with exposure of columns appears to be prudent.


Ground TreatmentJapanese Jet Grout Association

Jet grouting method usually guarantees the minimum strength as long as pre-determined parameters (jet pressure, flow rate, rotation speed and lifting speed) are followed.

Confirmation of improvement: in case of stopping seepage: in-situ

permeability test in case of improving the strength: in-situ load

test or axial compression test on cores. The improved soil radius can be verified by excavation or boring.

Principles of quality control Selection of jet grouting equipment and

operation parameters by carrying out full scale trials.

Monitoring operation parameters during production.

Verification after production.

Ground Treatment

Ground Treatment

One minimum trial test shall be carried out at site for each soil type (based on the DC Chapter 5 classification) to be treated.

The trial jet grouting shall consist of a minimum of six overlapping columns formed at the depth and in similar ground conditions as the proposed jet grouting.

Effectiveness of the trial grouting to be demonstrated by:

One shall be targeted at the centre of a pile, One at a point two third of a pile radius from the centre Two at the overlapping areas of the piles. Cores shall be fully logged and shall be tested for

strength and stiffness. A minimum of 3 samples shall be taken from top and

middle and bottom of each core for strength and stiffness testing.

Ground Treatment

Monitoring of ground heave / settlement during trial.

An interpretative report is to be submitted. Where necessary, method statement is to

be modified based on trial results.

Ground Treatment

The drilling and grouting plant shall be equipped with automatic, data logger collection system to allow the operating parameters to be checked and recorded continuously during drilling and grouting operation.

Ground Treatment

Quality Control During Production Drilling and grouting plant to be equipped with

pressure gauges, flow meters to allow operating parameters to be checked regularly.

Specific gravity and viscosity of effluent return to be checked using mud balance and Marsh cone at least once per pile during grouting.

Grouting mix to be checked by measuring specific gravity using mud balance at least twice a day per rig.

Monitoring of ground settlement / heave.

Ground TreatmentVerification

8 boreholes for each 1,000 m3 of treated soil. The boreholes shall be at the overlapping area SPT tests shall be done at the top, middle and bottom

of the treated zone or cone penetration tests 4 numbers of coring through the full depth of the piles

for each 1,000 m3 of treated soil. The cores shall be taken from the overlapping areas of

the piles. TCR not be less than 85%. 3 samples shall be taken from top and middle and

bottom of each core for strength and stiffness testing.

Ground Treatment

CRACK REPAIR USING POLYURETHANE

Polyurethane Grouting

A two-pass system of polyurethane grouting for repairs of wet cracks in structural concrete shall be submitted to the Engineer for acceptance. The submissions shall address injection system, quality assurance, material specifications, applications, testing and safety.

Properties of Injection Materials

Injection MaterialsProperties

Water-reactivePolyurethane Foam

FlexiblePolyurethane Epoxy

CementitiousGrout

Strength X X Elasticity/Flexibility X X X

MoistureCompatibility X

X = Not relevant = Good = Excellent

Injection Applications for Crack Repair

PU = Polyurethane CG = Cementitious Grout

Crack ConditionInjectionAim Dry Wet / Water Bearing

without PressureWater Bearing with

Pressure

Closing /Sealing

EpoxyPUCG

PUCG Water-reactive PU

RigidConnection

EpoxyCG CG -

FlexibleConnection Flexible PU Flexible PU

Water-reactive PUfollowed by flexible PU

Water Reactive Polyurethane Foam Acrylic Gel

For dry crack repair at casting yard, epoxy resin should be used. Cracks should be dry and dust free.

For wet / damp crack repair after erection, flexible, two component, low viscosity polyurethane grout should be used.

Injection Applications for Crack Repair Where water is seeping through cracks

under pressure, a two-pass grouting procedure should be adopted. The first stage should use water-reactive polyurethane foam to stop the seepage, followed by the second stage with flexible, two-component, low-viscosity polyurethane grout.

Injection Applications for Crack Repair

ThanksFor feedback on DC or M&W, please email to:

[email protected]

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