estimating uae sed. rocks ucs from emp. correlations

8/12/2019 Estimating UAE sed. Rocks UCS from emp. correlations

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Estimating Unconfined Compressive Strength of

Sedimentary Rocks in the United Arab Emirates

from Generated Empirical Correlations

By

Hussain Osama Salah

University of Sharjah

College of Engineering

Civil and Environmental Engineering Department

Supervisors

Dr. Maher Omar

Prof. Abdullah Shanableh

Program: Master of Science in Civil Engineering

9th

of December 2013


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I




By

Hussain Osama Salah

A thesis submitted in partial fulfillment of the requirements for the

degree of Master of Science in Civil Engineering

In the Department of Civil & Environmental Engineering

University of Sharjah

Approved By

Dr. Maher Omar Chairman

Associate Professor of Civil Engineering, University of Sharjah

Prof. Abdulla Shanableh Co-Supervisor

Professor of Civil Engineering, University of Sharjah

Dr. Radhi Al-Zubaidi MemberAssociate Professor of Civil Engineering, University of Sharjah

Prof. Mousa Attom Member

Professor of Civil Engineering, American University of Sharjah

9th

of December 2013


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II

To my father who has been my teacher and advisor .

To my mother who has been my rock in l i fe.

To my sisters and brother who have been my l ife companions.

To al l scientif ic researchers who devote their lives to making the world a

better place.


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III

ACKNOWLEDGEMENTS

I would like to express my deepest and warmest gratitude to all those who helped me

complete this research. I would especially like to give my deepest thanks to my supervisors;

Dr. Maher Omar, Prof. Abdullah Shanableh, and Eng. Ali Tahmaz, who spent so much effort

reviewing, making suggestions and helping me in carrying out this study.

I would also like to thank, Eng. Yousef Al-Soboh, Director of Baynunah Engineering lab,

Abu Dhabi, Eng. Mohammed Obaid, Director of Matrix lab, Dubai, and Eng. Imad Al-Sharif,

Director of the Arab Center of Engineering Studies (ACES) Dubai for their assistance and

contribution. Additionally, I would like to thank everyone who was involved, directly or

indirectly, in completing this work.

I would also like to thank the examiners; Dr. Radhi Al-Zubaidi, the internal examiner, and

Prof. Mousa Attom, the external examiner, for their reviews, remarks, and comments on this

work. Their input was of great help in producing this research as it is now.

Finally, I would like to express my warmest, deepest and heartfelt gratitude to my family for

their love, support, patience and encouragement.


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IV




By: Hussain Osama Salah

Supervisors: Dr. Maher Omar and Prof. Abdullah Shanableh

ABSTRACT

A laboratory study was conducted to develop a database and models for predicting the

unconfined compressive strength of sedimentary rocks. A large number of rock samples from

different sites in the United Arab Emirates were collected and tested for the development of

the database and evaluation of models. Reliable empirical relationships were developed for

estimating the unconfined compressive strength of UAE rocks based on results obtained from

the following mechanical and physical tests that were performed on rock samples: unconfined

compressive strength, point load strength index, Schmidt rebound, Brazilian splitting and

ultrasonic pulse velocity tests. These were conducted to determine the mechanical properties

of rock specimens, while the bulk specific weight and moisture content test was conducted to

determine the physical properties of rock specimens.

Twenty nine relations were selected from more than a hundred and thirty generated relations

developed. Each relation was the result of a statistical analysis and the application of the

Mean Average (MA) data smoothing algorithm and Least Absolute Residuals (LAR) robust

regression wherever that was necessary. In addition, four general relationships were

developed relating unconfined compressive strength to moisture content, unit weight, point

load strength index and type of rock.

Keywords:Unconfined Compressive Strength; Modulus of Elasticity; Empirical Relations,

Laboratory Testing.


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V

Table of Contents

Chapter 1 Introduction............................................................................................................ 1

1.1. Background ..................................................................................................................... 1

1.2. Problem Statement .......................................................................................................... 2

1.3. Objectives ........................................................................................................................ 2

1.4. Scope of Study ................................................................................................................ 3

1.5. Engineering Significance ................................................................................................ 4

1.6. Limitations of the Study .................................................................................................. 4

Chapter 2 Literature Review .................................................................................................. 5

2.1. Definition and History of Rock Mechanics and Engineering ......................................... 5

2.1.1. Definition of Rock Mechanics and Engineering ...................................................... 5

2.1.2. History of Rock Mechanics and Engineering ........................................................... 6

2.2. Main Areas of Interest in Rock Mechanics and Rock Engineering ................................ 7

2.2.1. Interests in Rock Slopes Stability ............................................................................. 7

2.2.2. Interests in Shafts, Tunnels, Caverns and Underground Mines ............................... 8

2.2.3. Interests in Rock Foundations .................................................................................. 9

2.3. Software Usage in Rock Mechanics and Engineering .................................................. 11

2.4. Brief about Sedimentary Rocks .................................................................................... 12

2.5. Geological History of the United Arab Emirates and Its Rocks ................................... 14

2.6. Rock Classification ....................................................................................................... 17

2.7. Unconfined Compressive strength (UCS) of Rocks ..................................................... 19

2.7.1 Background .............................................................................................................. 19

2.7.2. Relations between UCS and Mechanical Properties .............................................. 21

2.7.2.1 Relations between UCS and Point Load Strength Index (Is(50)) ..................... 21

2.7.2.2. Relations between UCS and Schmidt Hammer Rebound Number .................. 23

2.7.2.3 Relations between UCS and Brazilian Splitting Tensile Strength .................... 25

2.7.2.4 Relations between UCS and Ultrasonic Pulse Velocity ................................... 26

2.7.2.5 Relations between UCS and Modulus of Elasticity .......................................... 28

2.7.3. Relations between UCS and Physical Properties ................................................... 31

2.7.3.1 Relations between UCS and Bulk Specific Weight .......................................... 31

2.7.3.2. Relations between UCS and Moisture Content ............................................... 32


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Chapter 3 Experimental Program ........................................................................................ 33

3.1. Introduction ................................................................................................................... 33

3.2. Sample Collection ......................................................................................................... 33

3.3. Sample Transporting and Storing .................................................................................. 36

3.4. Sample Identification .................................................................................................... 38

3.5. Sample Preparation ....................................................................................................... 39

3.6. Sample Testing .............................................................................................................. 40

3.6.1. Mechanical Tests Done .......................................................................................... 40

3.6.1.1. The Point Load Test. ........................................................................................ 40

3.6.1.2. The Schmidt Hammer Test .............................................................................. 42

3.6.1.3. Brazilian Splitting Test .................................................................................... 42

3.6.1.4. Ultrasonic Pulse Velocity Test......................................................................... 43

3.6.1.5. UCS and E Test ................................................................................................ 43

3.6.2. Physical Tests Done ................................................................................................ 45

3.6.2.1. Moisture Content Test...................................................................................... 45

3.6.2.2 Specific Weight Test ......................................................................................... 45

3.6.3. Order of Testing...................................................................................................... 45

Chapter 4 Results, Analysis and Discussion ........................................................................ 47

4.1. Introduction ................................................................................................................... 47

4.2. Test Results ................................................................................................................... 47

4.2.1. Mechanical Test Results ......................................................................................... 47

4.2.1.1 The Schmidt Hammer Test ............................................................................... 47

4.2.1.2 The Point Load Strength Index Test. ................................................................ 48

4.2.1.3. The Ultrasonic Pulse Velocity Test ................................................................. 48

4.2.1.4. The Brazilian Splitting Tensile Test ................................................................ 49

4.2.1.5. The UCS Test ................................................................................................... 49

4.2.1.6. The Youngs Modulus of Elasticity Test ......................................................... 50

4.2.2. Physical Tests Results ............................................................................................ 53

4.2.2.1. The Moisture Content Test. ............................................................................. 53

4.2.2.2 The Unit Weight Test........................................................................................ 53

4.3 Generated Relations ....................................................................................................... 54

4.3.1. UCS Relations with Mechanical Properties ........................................................... 55

4.3.1.1. UCS vs. HR....................................................................................................... 55


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VII

4.3.1.3 UCS vs. Vp ........................................................................................................ 63

4.3.1.5. E vs. UCS ......................................................................................................... 68

4.3.2 Multiple Regression Models .................................................................................... 71

Chapter 5 Summary, Conclusion and Final Recommendations....................................... 76

5.1 Summary ........................................................................................................................ 76

5.2 Conclusion ...................................................................................................................... 77

5.3 Recommendations for Future Research ......................................................................... 78

References ................................................................................................................................ 79

Appendixes.............................................................................................................................. 83


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List of Tables

Table 2.1: Relation For Different Is(50) Classes 22

Table 2.2: Recent BST Relations Collected By Nazir 25

Table 2.3: Correlations Found By Yassar and Erdogan 27Table 3.1: Summary of Borehole Locations and Data 34

Table 4.1: Confidence Interval Estimate of Expected Values of HR 47

Table 4.2: Confidence Interval Estimate of Expected Values of Is(50) 48

Table 4.3: Confidence Interval Estimate of Expected Values of VP 48

Table 4.4: Confidence Interval Estimate of Expected Values of S t 49

Table 4.5: Confidence Interval Estimate of Expected Values of UCS 50

Table 4.6: Confidence Interval Estimate of Expected Values of E 50

Table 4.7: Confidence Interval Estimate of Expected Values of 53

Table 4.8: Confidence Interval Estimate of Expected Values of 53

Table 4.9: Relation Cases Codes 55

Table 4.10: Relations Between UCS and HR, General Case 56

Table 4.11: Other Relations Summary Between UCS and HR 56

Table 4.12: Relations Between UCS and Is(50), General Case 58

Table 4.13: Other Relations Summary Between UCS and Is(50) 59

Table 4.14: Relations Between UCS and VP, General Case 63

Table 4.15: Relations Between UCS and St, General Case 64

Table 4.16: Other Relations Summary Between UCS and St, 65

Table 4.17: Relations Between E and UCS, General Case 68

Table 4.18: Other Relations Summary Between E and UCS 69

Table 5.1: Summary of Direct Relations 77

Table 5.2: Summary of Multiple Regression Relations 77

Table A.1: Schmidt Hammer Test, All Results 84

Table A.2: Point Load Strength Test, All Results 86Table A.3: Ultrasonic Pulse Velocity Test, All Results 90

Table A.4: Brazilian Test, All Results 92

Table A.5: Unconfined Compression Strength Test, All Results 94

Table A.6: Modulus of Elasticity Test, All Results 98

Table A.7: Moisture Content Test, All Results 99

Table A.8: Unit Weight Test, All Results 103


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List of FiguresFigure 2.1: Rock Slope Stability 7

Figure 2.2: Felton Quarry Granite Slope Failure 8

Figure 2.3: Copiap Mining Accident 2010 9

Figure 2.4: Illustration of Rock Foundation of Burj Khalifa 10

Figure 2.5: House Poarch Foundation Stones 10

Figure 2.6: Clastic Rock Classification Scheme 13

Figure 2.7: Different Types of Sedimentary Rocks 13

Figure 2.8: Arabian Plate and UAE Position 14

Figure 2.9: Summary Stratagraphic of the UAE Foreland Basin 16

Figure 2.10: Different Compression States of Rocks 20

Figure 2.11: UCSIs(50) Linear and Power Relation By Tsiambaos and Sabatakakis 22

Figure 2.12: UCSIs(50) Stratified Relation By Tsiambaos and Sabatakakis 22

Figure 2.13: UCS vs. HRRelation By Shalabi etal. 24

Figure 2.14: UCS vs. HRRelation By Yilmaz and Sendir 24

Figure 2.15: UCS vs. BST Relation By Nazir 26

Figure 2.16: Comparison of Different Studies With Lab Work By Nazir 26

Figure 2.17: Vpvs. UCS Relation By Yassar and Erdogan 27

Figure 2.18: Vpvs. E Relation By Yassar and Erdogan 28

Figure 2.19: Average Modulus of Elasticity Calculation 28

Figure 2.20: 3D Visualization of Equation 2.7 30

Figure 2.21: Nomograph Constructed for Equation 2.7 30

Figure 2.22: UCS vs. Relation By Mohd 31

Figure 3.1: General Work Plan For Thesis 33

Figure 3.2: Sample Contribution By Place and Type 35

Figure 3.3: Envelop Borehole Locations 35

Figure 3.4: Flow Chart for Preserving and Transporting Rock Core Samples 36

Figure 3.5: Sample ID Illustration 38

Figure 3.6: Sample Ready for the Point Load Test 41

Figure 3.7: Point Load Test Different Failure Patterns 41

Figure 3.8: Failed Sample After Brazilian Test 43

Figure 3.9: Sample Ready for the UCS and E Test 44

Figure 3.10: Sample Testing Stages Flowchart 46


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Figure 4.1: Sample of Stress-Strain Diagrams of Samples 50

Figure 4.2: UCS vs. HRRelation, General Case 56

Figure 4.3: UCS vs. HRRelation, AV Case 57

Figure 4.4: UCS vs. HRRelation, AW Case 57

Figure 4.5: UCS vs. Is(50) Relation, General Case 58

Figure 4.6: UCS vs. Is(50) Relation, AV Case 59

Figure 4.7: UCS vs. Is(50) Relation, AW Case 59

Figure 4.8: UCS vs. Is(50) Relation, CA Case 60

Figure 4.9: UCS vs. Is(50) Relation, CW Case 60

Figure 4.10: UCS vs. Is(50) Relation, MA Case 61

Figure 4.11: UCS vs. Is(50) Relation, MV Case 61

Figure 4.12: UCS vs. Is(50) Relation, SA Case 62

Figure 4.13: UCS vs. Is(50) Relation, SV Case 62

Figure 4.14: UCS vs. Is(50) Relation, SW Case 63

Figure 4.15: UCS vs. VPRelation, General Case 64

Figure 4.16: UCS vs. StRelation, General Case 65

Figure 4.17: UCS vs. StRelation, AV Case 65

Figure 4.18: UCS vs. StRelation, AW Case 66

Figure 4.19: UCS vs. StRelation, CA Case 66

Figure 4.20: UCS vs. StRelation, MA Case 67

Figure 4.21: UCS vs. StRelation, SA Case 67

Figure 4.22: E vs. UCS Relation, General Case 68

Figure 4.23: E vs. UCS Relation, AV Case 69

Figure 4.24: E vs. UCS Relation, AW Case 69

Figure 4.25: E vs. UCS Relation, CA Case 70

Figure 4.26: E vs. UCS Relation, MA Case 70

Figure 4.27: Comparison of Works for Rebound Number HR 72

Figure 4.28: Comparison of Works for Point Load Strength Index Is(50) 73

Figure 4.29: Comparison of Works for Ultrasonic Pulse Velocity 74

Figure 4.30: Comparison of Works for Brazilian Strength St 74

Figure 4.31: Comparison of Works for Modulus of Elasticity E 75


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Chapter 1

Introduction

1.1. Background

A closer look at the development projects and construction boom that occurred in the last

decade in the United Arab Emirates gives thoughtful considerations about the construction of

such major projects. In every construction project, geotechnical investigations are carried out

to determine how the components of the project that interact with the soil should proceed.

Geotechnical investigations vary in complexity and prices; some of them require days of

sophisticated work, complex procedures to be followed and fortunes of money to be spent.

Therefore, geotechnical engineers thought about devising easier, less sophisticated and

cheaper ways to estimate results of some important geotechnical parameters. Estimation of

such parameters is also needed to overcome sampling and handling problems. Estimation of

parameters is typically done through generating empirical correlations that simplify

estimation of the values of parameters with considerations to safety and efficiency.

One of the most important rock parameters is the unconfined compressive strength (UCS) test

of rocks, since it is used widely in rock classifications like Rock Mass Rating (RMR),

analysis and design of rock related structures. Here, special sample preparation is involved. In

the case of sedimentary rocks, UCS testing becomes harder due to the fact that the recovered

rocks are sometimes of such geometric parameters that they are not allowed by the code to

have the test performed on them, or some rocks fail in the preparation stage before

performing the UCS test. Therefore, the need of a way to determine this important parameter

arises.


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Moreover, due to the lack of information on local rocks, the main purpose of this work is to

generate empirical relations between UCS of sedimentary rocks in the UAE and other

relevant physical and mechanical properties.

1.2. Problem Statement

Rocks UCS is a very important test to be done on rock cores to give full understanding of the

rocks capabilities to accommodate proposed project loads and to do the RMR classification

analysis for rocks. Sometimes, Rock Quality Designation (RQD) of a certain core specimen

is of a level so low that it is hard to find a core piece to perform the UCS test on, since codes

require a special length to diameter ratio of (2:1) and received rocks condition usually

doesnt meet this requirement. On the other hand, other tests can be done on these rocks' core

specimens like the point load strength index, rebound hammer and many other tests.

Therefore, it is assumed that there is a need for a simpler way to determine the UCS of rocks.

As a result of all of the above, the researcher decided to write a thesis on relating the UCS of

sedimentary rocks of the UAE to other mechanical parameters like point load strength index,

Brazilian splitting strength, modulus of elasticity, rebound number and ultrasonic pulse

velocity, as well as physical properties like bulk specific weight and moisture content. All of

this in order to simplify the approach of estimating the UCS for sedimentary rocks in the

UAE.

1.3. Objectives

The main objective of this research paper is to develop empirical relations between the UCS

of sedimentary rocks in the UAE and other physical and mechanical properties of rocks. The

specific objectives of the study are to relate the rocks UCS to mechanical parameters like

point load strength index, Brazilian splitting strength, modulus of elasticity, rebound number


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and ultrasonic pulse velocity, as well as physical properties like bulk specific weight and

moisture content. All tests were performed in accordance with the American Society of

Testing and Materials procedure codes. All math works were done using the MATLAB

software.

1.4. Scope of Study

The following steps were done to fulfill the work. First, previous studies regarding the same

topic were reviewed. Next, a database with means of identification was created. Then, lab

environment was prepared to receive, store and retrieve specimens. After that, sedimentary

rock samples from different types (mudstone, crystalline gypsum, sandstone and calcarenite),

from different areas in the UAE (western region, central Abu Dhabi City and Dubai) were

acquired. Subsequently, lab tests on acquired samples were conducted. These tests include;

unconfined compressive strength, modulus of elasticity point load strength index, Schmidt

rebound, Brazilian splitting and ultrasonic pulse velocity tests, and were performed to

determine the mechanical properties of rock specimens, while the bulk specific weight and

moisture content test were performed to determine the physical properties of rock specimens.

The created database was then filled with the worked test results ready for relation generation

between data from different performed tests. Afterwards, the correctness and integrity of

found relations was checked versus previously done work regarding the same subject.

Finally, Mathematical representation of relations plots was done.

This thesis has 5 chapters; chapter 1 presents study background, problem statement,

objectives, significance of the study and study limitations. Chapter 2 presents the literature

review done for the thesis. Chapter 3 discusses methodologies of testing, lab environment and

worked data digestion. Chapter 4 presents and discusses results found in the lab. And, chapter

5 states conclusions and recommendations.


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1.5. Engineering Significance

This thesis provides new and advanced knowledge about rocks in the UAE, as it brings

together analysis of strength and different physical properties and rock types of the UAE with

standardized international studies. This work is about developing relations between UCS of

UAE sedimentary rocks with other different, easier to find parameters and widely used tests

due to the lack of information about such properties. It is hoped that this work will provide a

good tool topredict rocks UCS from other mechanical and physical parameters.

1.6. Limitations of the Study

All investigations were done on sedimentary rocks of the following types; sandstone,

mudstone and crystalline gypsum in the UAE only. Therefore, careful generalization of

generated correlations for any different rock types than the aforementioned ones and other

regions than the UAE would be much recommended. Also, this study was conducted on

samples in their as received condition.


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Chapter 2

Literature Review

2.1. Definition and History of Rock Mechanics and Engineering

2.1.1. Definition of Rock Mechanics and Engineering

After many studies in the field of rock mechanics and engineering (RME), researchers in this

field have agreed to use Judds definitionof RME, which was stated in 1964 and amended in

1974 to become as follows Rock mechanics is the theoretical and applied science of the

mechanical behavior of rock and rock masses; it is that branch of mechanics concerned with

the response of rock and rock masses to the force fields of their physical environment.This

definition is more convenient in mining works as mine excavation changes force fields that

rock masses encounter. Additionally, Brady, B. and Brown, E. (2005) noted that rock

mechanics is a diverse science based on the type of rocks considered in the study. For

example, if fragmented or weathered rocks are considered, then rock mechanics approaches

soil mechanics. On the other hand, if rocks are at inaccessible depths for mining and drilling,

rock mechanics approaches mechanical aspects of structural geology. The definition of rock

engineering can be rewritten to conform with engineering definition by Smith (2012) which

was The creative application of scientific principles to design or develop structures,

machines, apparatus, ormanufacturingprocesses, or works utilizing them singly or in

combination; or to construct or operate the same with full cognizance of their design; or to

forecast their behavior under specific operating conditions; all as respects an intended

function,economicsof operation andsafetyto life and property, to be the following The

creative application of scientific principles of rock mechanics to design or develop rock

related structures and to forecast and monitor their behavior under recommended operating


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conditions with respects of intended function,economicsof operation andsafetyto lives and

properties.

2.1.2. History of Rock Mechanics and Engineering

Jaeger (1979) and Hoek (2006) have diligently studied the history and development of RME.

They disagreed on the date of the establishment of RME as a modern discipline. Jaeger gave

examples of construction of tunnels in the Alps Mountains in the late 19 th century. He

thought that the first notice of residual stresses on rocks was back in 1874 when the German

tunnel expert, Rziha, noted the bursts and squeezing in the tunnels and galleries of the Alps

Mountains. He further stated that Heim, a professor at Zurich University and Zurich Federal

Institute of Technology, concurred with Rzihas observation. Heim suggested that the order

of magnitude of horizontal forces acting on rocks in these mountains had to be the same as

the vertical forces acting on them. Jaeger observed that the first attempt at rock mechanics

was in 1926 when Schmidt conducted a thesis of which he related what Heim suggested

about residual stresses in rocks to the newly formulated ideas about rock elasticity.

Alternatively, Hoek had a different date of the beginning of rock mechanics and engineering.

He believed that rock engineering was considered a modern discipline as early as 1773 when

Coulomb had included results of Bordeaux rocks testing results in a thesis that was read

before the French academy in Paris. Hoek also gave the construction of the Panama Canal as

an example of the development of RME. He stated that 60 slides occurred in the cuts along

the Panama Canal during its construction and its operation (1910 1964). Hoek stated that

Lutton and others have concluded in 1979 that slides have occurred because of the structural

discontinuity of rocks. Hoek also reiterated a part of Karl Terzaghispresidential speech in

the first international conference on Soil Mechanics and Foundation Engineering in 1936

about the Panama Canal slides The catastrophic descent of the slopes of the deepest cut of


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the Panama Canal issued a warning that we were overstepping the limits of our ability to

predict the consequences of our actions.

2.2. Main Areas of Interest in Rock Mechanics and Rock Engineering

One can confidently claim that RME is a science by itself that has its own areas of interest.

The following is a demonstration of some of the main areas of interest which are classified

based on a personal point of view of analysis and design logic.

2.2.1. Interests in Rock Slopes Stability

Slope stability is a branch of geotechnical engineering which deals with the assessment of

static and dynamic effects on different kinds of slopes; earth and rock-fill dams, slopes of

other types of embankments, excavated slopes and natural slopes in soil and soft rocks. (US

Army Corps of Engineers, 2003) Based on the previous definition, it could be conclude that

rock slope stability is a conjoined science between slope stability and RME as shown in

Figure 2.1. The rocks UCS plays an important role here.

The concern with the stability of rock slopes is associated with the major safety concerns of

many areas in the world which are settled next to a rock slope. This becomes more important

in the case of open mines and quarries, since any rock slope failure would result in not only

SlopeStability

RockMechanics

and

Engineering

Figure 2.1: Rock Slope Stability


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working site hazards but also possible economic consequences due to the subsequent fixing

and rehabilitation required so they could be used again as reported by Rogers (1995).

Figure 2.2 shows the failure of Felton quarry, Santa Cruz, California on November 20, 1992.

2.2.2. Interests in Shafts, Tunnels, Caverns and Underground Mines

It is easy to note the variation in sizes and applications among all main areas of interest in

RME. However, all of them share the main concept of analysis and design. As stated

previously in the definition of RME, it is concerned with the stress state in rocks before and

after the construction of rock related structures, especially in shafts and similar types of

structures where the main construction concept of them, briefly speaking, is to analyze the

stress state of the rock containing them in order to provide the design solution for the project.

The UCS of the rock is very much needed here. Any mistake in this step might be the

deathblow of the whole structure. An example from memory is the Copiap mining accident

in Chile on August 8th, 2010 reported in Wikipedia (2012). Figure 2.3 illustrates the accident.

Figure 2.2: Felton Quarry Granite Slope Failure (Rogers, 1995)


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2.2.3. Interests in Rock Foundations

Depending on the geotechnical conditions of the site, a geotechnical engineer has only two

options: option one, to construct the project on or through soil which has its own design

considerations, or, option two, to construct the project on or through rocks which have their

different design considerations. A project constructed through rocks was addressed

previously. A project constructed on a rock bearing stratum is the one considered here.

Different design criteria are needed since the foundation supporting condition is different

than soil. A good designing manual is the US army corps of engineers' manual number EM

1110-1-2908, (1994). This manual gives a good idea about design considerations for large

military and civil engineering structures in terms of design considerations, site investigation,

rock characterization, bearing capacity, settlement considerations, different rock slopes

stability and finally construction considerations.

Figure 2.3: Copiap Mining Accident on 2010, Acquired from Wikipedia (2012)


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Also, depending on rock depth and the proposed project the design parameters would change

either to construct a small project on a shallow rock bearing stratum, or to construct a major

project on a deep rock bearing stratum like the case of Burj Khalifa in Dubai, UAE, where

piles where constructed through soil to reach the rock stratum which is about 50 meters deep.

The following Figure 2.4 illustrates how the rock foundations for Burj Khalifa look like.

Here, the rocksUCS played an important role in the design of this major project.

One must not mix between rock foundations and the base stone that is found under porches of

some houses in America. These stones serve as a raft for the house porch structural wise.

See Figure 2.5. These stones might be rock foundation if the bearing stratum beneath them

was rock.

Figure 2.5: House Porch Foundation Stones (Brooks Stone Inc. 2011)

Figure 2.4: Illustration of Rock Foundation of Burj Khalifa (Business Week, 2007)


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2.3. Software Usage in Rock Mechanics and Engineering

To facilitate the job for rock engineers and mechanics, many types of software have been

developed in the area of rock mechanics and engineering. These software programs, in a

personal point of view, are categorized in terms of the purpose of their usage. Some are used

as lab analysis software; others are used for specific types of rock-structural analysis, and

some offer rock analysis as an included accessory to the efficacy of a program.

RocLab, offered by RocScience Inc. (2013), is a simple lab analysis software program in

which small numbers of data are needed to calculate different parameters like Hoek-Brown

Classification, Hoek-Brown Criterion, Mohr-Coulomb Fit, tensile strength, uniaxial

compressive strength, global strength and deformation modulus along with major and minor

stresses chart and normal-shear stress charts

Other programs offered by RocScience Inc. offer specialized analysis software for various

types of application. For example, Examine

3D

(2013) is specialized boundary element

analysis software for rock structures like tunnels, caverns and other underground structures.

A more advanced finite element method software like TNO DIANAoffered by TNO BV

(2012) and Abacus offered by Simulia Inc. (2012) are very advanced and general finite

element analysis software that can be utilized to solve different and complex rock structural

analysis problems and designs.


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2.4. Brief about Sedimentary Rocks

In nature, rocks are categorized into three different types: igneous, metamorphic and

sedimentary rocks. It might be believed that the most dominant rock type is the sedimentary

rock as most people encounter this type in nature. But the fact is stated by Buchner, K and R.

Grapes (2011) which is; sedimentary rocks are only 8% of the total volume of the earth crust,

the area where all oceans and continents are placed.

The best definition of sedimentary rocks is stated by Hamblin, K. and Christiansen, E.,

(2009) as follows Sedimentary rocks are rocks that form from fragments derived from otherrocks and by precipitation from water. These rocks are usually classified based on their

texture and composition into two categories, clastic rocks and chemical and biochemical

rocks.

A closer look at a clastic rock reveals the composition. Clastic rocks are formed from gravel,

sand and mud fragments. The word clastic comes from the Greek word klastos, which

means broken, and that implies the process of weathering and erosion of rocks, transportation

of fragments to deposition sites and finally the precipitation process where fragments fuse

with each other to form the sedimentary rock.

The next Figure 2.6 shows clastic rocks' classification scheme which illustrates that clastic

rocks are classified into three categories based on their grain size. Conglomerates, shown in

Figure 2.7 (a), are those rocks with a grain size larger than 2 mm Rocks with grain sizes

varying between (1/162) mm are called sandstone, shown in Figure 2.7 (b). Lastly, rocks

with a grain size bellow 1/16 mm are named mudstones, shown in Figure 2.7 (c).


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On the other hand, chemical and biochemical rocks are formed from the chemical

precipitation or evaporation of salty lakes and shallow seas, from the growth process of some

organisms like coral and some types of algae, or from the decay of hydrocarbons in deep

sedimentary strata. Gypsum rock (CaSO42H2O), shown in Figure 2.7 (d), is a type of

chemical sedimentary rocks that results from the evaporation of shallow seas. An example of

chemical sedimentary rocks resulting from precipitation is Limestone, shown in Figure 2.7

(e). Coal is a sedimentary rock resulting from the decay of hydrocarbon content of organisms,

shown in Figure 2.7 (f).

a b c

d e f

Figure 2.6: Clastic Rocks' Classification Scheme after Hamblin, K. and Christiansen, E., (2009)

(a) Conglomerate (b) Sandstone (c) Mudstone (d) Gypsum rock (e) Limestone (f) Coal

Figure 2.7: Different Types Sedimentary of Rocks


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2.5. Geological History of the United Arab Emirates and Its Rocks

Understanding the geological history of UAE is of utmost importance here, because it makes

it easy to somewhat comprehend the formation of different types of geological formations in

the country, down from sabkhas to mid high elevation sand deserts to the Hajar mountains in

the eastern region of the country. Feulner (2005) conducted a research on the geological

history of the UAE and Hajar mountains. He concluded that the UAE is located in the corner

of the Arabian plate as shown in Figure 2.8 after Pierce (2002).

The UAE is highlighted in dark red. The Arabian plate is considered relatively sTable since

the Cambrian system of the Paleozoic era, about 520 million years ago, time scale-wise. The

Arabian plate includes, besides the Arabian Peninsula, the not true ocean basin, shallow

Arabian Gulf and the Zagros mountains. In the Chattian stage, about 25 million years ago, the

Arabian plate was disjointed from the AfroArabian continent to form the Red Sea.

Feulner also stated that the Precambrian history of the UAE can be known by reading the

Precambrian sediments of Saudi Arabia and Oman. It shows that the UAE has participated in

Figure 2.8: Arabian Plate and UAE Position (Dark Red) after Pierce (2002)


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the late Precambrian glaciations. The UAE was often covered with shallow sea throughout its

history.

Feulner also stated that the movements of the Afro-Arabian plate during the Paleozoic caused

it to pass near the southern pole. In the Mid-Paleozoic, the Afro-Arabian continent was joined

to other continents to form the super continent of Gondwana, which began to breakup in the

Permian and Triassic periods. The UAE attained tropical and sub-tropical latitudes since the

end of Paleozoic era.

Feulner also found that despite all the movements the UAE has made in its history; it still

appears to be tectonically sTable. The only exception is the formation of Al-Hajar Mountains

in the eastern region of the country. In general, the geological history of the UAE is just a

record of the advance and retreat of the sea in response to tectonic and climate changes

through time.

Ali, M.Y. etal. (2013) carried out valuable research on the seismic stratigraphy and

subsidence history of the UAE. In their work they presented a summary stratigraphic column

of the geological rock sequence in the UAE foreland basin. Although their research was

focused on oil bearing strata, the presentation way of their summary column is of great

interest. They found that UAEs rocks are mainly carbonate rocks with small intercepts of

sandstones, siltstones and shale.

In their study they used locally used names for formations of the UAE with tectonic

interpretation regarding geological conditions and events that contributed to making the

subsurface history of the UAE in its known form. The following Figure 2.9 shows their work

regarding the geological time of the UAE.


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Figure 2.9: Summary Stratigraphic of the UAE Foreland Basin , Ali, M.Y. etal (2013)


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2.6. Rock Classification

Regardless of its different schemes, rock classification is considered beneficial in preliminary

design. It can be used as a check list for information or as an idea developer of strength and

deformation characteristics of rocks. Hoek (2006) did a good job in collecting different used

rock classification schemes in his book. The following is a brief exhibition of encountered

classification schemes in that book.

a. Terzaghis rock mass classification: This classification scheme generated in

1946 uses descriptive bases to classify rocks. In this scheme, rocks are

classified into 7 categories; intact, stratified, moderately jointed, blocky and

seamy, crushed, squeezing and swelling rock. This scheme is used to estimate

rock loads which are carried by steel sets for tunnel designing purposes.

b.

Classifications involving stand-up time: The stand-up time is the time for a

rock span being unsupported. The first researcher to propose the idea that rock

quality is related to stand-up time was Lauffer in 1958. For tunnels, the

unsupported span is the rock over the tunnel or between two supports. Some

modifications have been done on what Lauffer proposed by Pacher and others

in 1974 and are now part of the New Austrian Tunneling Method.

c.

Rock quality designation index (RQD): This classification is a quantitative

scheme developed by Deere and others in 1967. The RQD is defined as the

percentage of length of intact rock pieces longer than 100 mm in the total

length of the core. The drill bit for this classification should be of size NX (

= 54.7 mm) or larger.


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d. Rock structure rating (RSR): a quasi-quantitative scheme developed by

Wickham in 1972 to describe the quality of rock mass and to select the

appropriate support in terms of tunnel construction. This system is considered

a comprehensive system in terms of counting the different factors affecting the

quality of the rock mass which are the geological considerations, geometry of

proposed structure and effect of ground water inflow and joint conditions yield

in the RSR number of maximum value of 100.

e. Rock mass rating system (RMR): a widely used quasi-quantitative scheme to

classify rock masses developed by Bieniawski in 1976 and amended by him in

1989. This classification deals with many factors affecting the rock mass and

is one of schemes that uses strength of material or unconfined strength as a

criteria that contributes to the classification process. This scheme uses the

following factors to fulfill a classification job; strength of material, rock

quality designation (RQD), spacing, condition and orientation of

discontinuities and groundwater condition. The range of this classification is

from 0 (very poor) to 100 (very good).

f. Rock tunneling quality index (Q): a widely used quasi-quantitative scheme

developed by Barton in 1974 for rock mass characteristics and tunnel support

requirements represented by a numeric value (Q) that follows logarithmic

scale from 10-3 to 103. This scheme, unlike others, is a very advanced

classification system that takes into consideration the effects of rock quality,

joint conditions and stresses in a more rational way.

One has to be cautious when using rock classifications as there might be shortcomings of the

used scheme. Palmstorm and Broch (2006) worked on a thesis on the uses and misuses of the


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Q rock classification scheme. They concluded that the shortcomings in the Q classification

scheme make it not recommended for use when it comes to calculating the penetration rate

(PR) and the advance rate (AR) for tunnel boring machines (TBM). They also strongly

recommended against correlating different rock classification schemes through correlation

equation. Furthermore, they quoted Terzaghi's statement in his last years The geotechnical

engineer should apply theory and experimentation but temper them by putting them into the

context of the uncertainty of nature. Judgment enters through engineering geology

2.7. Unconfined Compressive strength (UCS) of Rocks

2.7.1 Background

There are three types of compressive strength tests of rocks. The first is the unconfined

compressive strength (UCS) where only the axial load is applied to a rock sample and no

lateral loads of any type are applied, mathematically speaking (UCS1> 0, UCS2= UCS3=

0). The second is the triaxial loading where not only axial loading is applied on the rock

sample, but also equal lateral loading is applied on the other two dimensions, mathematically

speaking (UCS1 > UCS2 = UCS3). The third is the true triaxial loading, similar to triaxial

loading but the difference being that lateral loads are not equal, mathematically speaking

(UCS1> UCS2> UCS3). The true triaxial loading is done using cubical load sample (Jaeger,

etal. (2007)). The following Figure (2.10) illustrates different compression types. (a) Implies

UCS, (b) implies triaxial loading and (c) implies true triaxial loading


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The most commonly used test is the UCS test as it is the easiest and less sophisticated among

all three compression test types. Other tests are needed if further understanding of rock

failure in semi-natural cases is required. But in general, rock triaxial and true triaxial are

seldom performed in the UAE. Another advantage of rock UCS test is the UCS value that is

used to determine the point bearing capacity of piles resting on rocks.

This test is performed in accordance with the American Society of Testing and Materials

(ASTM) code number D2938 (2002) requirements. Although this code was withdrawn in the

year 2005 by the ASTM, the replacement code number ASTM-D7012 (2010), which is the

unconfined compressive strength (UCS) and modulus of elasticity (E) testing procedures,

specifies that the details of the testing procedure is acquired from the withdrawn code and

using it is recommended. The following equation is used to determine the UCS,

Where (Pu) is the ultimate load the sample can take and (d) is the samples diameter

Figure 2.10: Different Compression States of Rock by Jaegar, etal. (2007)

...................................................... (2.1)


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2.7.2. Relations between UCS and Mechanical Properties

2.7.2.1 Relations between UCS and Point Load Strength Index (Is(50))

The point load strength index test is performed in accordance with the ASTM-D5731 (2008)

procedure and is meant to measure the rocks point load strength index, which is a very

important numerical parameter in terms of rock strength.

The following equation 2.2 was used to calculate the point load strength index Where (Pf) is

the failure load and (d2) is the specimens diameter

An interesting study was conducted by G. Tsiambaos and N. Sabatakakis (2004). The study

was about considerations on strength of intact sedimentary rocks, which aimed to find

correlations between point load strength index (Is(50)) with UCS (UCS) and Hoek-Brown

material constant (mi). In their study, sedimentary rocks from Greece where used. They

compared their work to the previous work of Bieniawski and the International Society of

Rock Mechanics (ISRM).

Based on their data, they concluded that the relation between point load index and UCS could

be presented through three different models. The linear model was the first one shown in

Figure 2.11 as the bold line. This model gave an accepTable value of R2 of 0.75. They

concluded that their result is similar to the one found by Bieniawski and the International

Society of Rock Mechanics (ISRM). The power model was the second one shown also in

Figure 2.11 as the dashed curve. This model showed a better relationship as R2was 0.82. The

classified linear model was the third one. They have observed that the point load index could

be categorized into three different classes (I, II and III). For each class a conversion factor

. (2.2)


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was assigned to multiply with the point load strength index value in order to get the UCS

value. The next Table 2.1 shows these classes which are shown in Figure 2.12.

Table 2.1: Relations for Different (Is(50)) Classes Tsiambaos and Sabatakakis (2004)Class Is(50) Conversion Factor (UCS = Is(50) )

I < 2 13

II 25 20III 5 < 28

Figure 2.11: UCSIs(50) Linear and Power Correlation by Tsiambaos and Sabatakakis (2004)

Figure 2.12: UCSIs(50) Classified Correlation Tsiambaos, G. & Sabatakakis, N. (2004)


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2.7.2.2. Relations between UCS and Schmidt Hammer Rebound Number

The Schmidt rebound hammer test is performed in accordance with the ASTM-D5873 (2013)

procedure and is meant to measure the rocks surface hardness either in situ or in lab to give arapid indication about the rocks strength. This test is best suited for rocks with UCS value

between 1 to 100 MPa.

Faisal Shalabi and his colleagues carried out research about estimation of rock engineering

properties using hardness tests. The main idea was to estimate some important rock properties

such as UCS, modulus of elasticity and Poissons ratio using easier and cheaper methodssuch as Schmidt hammer, shore scleroscope, abrasion, total hardness and unit weight. They

used dolomite, dolomitic limestone, shale, dolomitic marble, deopside and anhydrite from

different locations in California and New York as subject rocks for their study. All samples

were of size NX (54 mm diameter), which is the minimum requirement to perform a Schmidt

hammer test on rocks as per ASTM-D5873 (2013). They used standard practices to perform

required tests. They concluded that linear model could be used to estimate the UCS of

sedimentary rocks (Dolomite) from other properties such as Schmidt hammer rebound

number (Hr) as shown in Figure 2.13.


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Another interesting paper was about correlation of Schmidt hardness with unconfined

compressive strength for gypsum from Sivas (Turkey) by Yilmaz and Sendir (2002). They

used the exponential model to express this relation. The value of R2was as high as 0.96. The

following Figure 2.14 shows their work.

Figure 2.13: UCS vs HRRelation by Shalabi, F. et al. (2007)

Figure 2.14: UCS vs HRRelation by Yilmaz and Sendir (2002)


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2.7.2.3 Relations between UCS and Brazilian Splitting Tensile Strength

The Brazilian splitting tensile strength test is performed in accordance with the ASTM-

D3967 (2008) code and is meant to measure the rocks splitting tensile strength. The codestates that rock engineers require the determination of complicated stress fields where a

combination of both compressive and tensile stresses are available. Furthermore, doing pure

tensile strength test is theoretically applicable but very hard to do on a practical level. This

test serves as an easy alternative to find this mechanical property of rocks. The following is

the equation used to calculate the strength, where (Pu) is the failure load, (L) is samples

height and (D) is the samples diameter.

Nazir, R. etal. (2013) conducted a research regarding correlating UCS to the Brazilian

splitting strength of lime stone samples. Firstly, they collected different relations from recent

studies. The following Table 2.2 summarizes these relations. Here BST stands for St.

Table 2.2: Recent StRelations Collected By Nazir, R. etal (2013)

Source Year Equation R2 Type

Kahraman etal 2012 UCS(MPa)= 10.61 St 0.50 Different rocks inc. limestone

Farah 2011 UCS(psi)= 5.11 St133.86 0.68 Weathered limestoneAltindag etal 2010 UCS(MPa)= 12.38 St

. 0.79 Different rocks inc. limestone

They also stated that one of the most agreed upon correlations is the one done by Sheorey,

where UCS equals 10 times the Brazilian splitting strength. They concluded that there is a

relation between St and UCS which is presented in Figure 2.15. They also compared

different previous work presented in Table 2.2. The following Figure 2.16 shows this

comparison.

(2.3)


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Figure 2.16: Comparison of Different Studies with lab Work by Nazir, R. et al. (2013)

2.7.2.4 Relations between UCS and Ultrasonic Pulse Velocity

This test is performed according to the ASTM-D2845 (2008) code and is meant to measure

the rocks ultrasonic pulse velocity, which can be correlated to different important rock

properties like UCS, E and Poissons ratio (). It is important to mention that this test is not

meant to measure stress wave attenuation. The sound velocity (VP) is found by the following

equation;

Where l = the length of specimen and t = is the time for a sound wave to move from the

transducer to receiver in seconds.

Figure 2.15: UCS vs. St(BTS) found relation by Nazir, R. et al. (2013)

.... (2.4)


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A paper was written by Yasar and Erdogan (2004) regarding correlating sound velocity with

the density, compressive strength and Youngs modulus of carbonate rocks. The scope of the

work was to correlate density, UCS and Youngs Modulus (E) for carbonate rocks in

different areas in Middle Turkey (Adana). The linear model was used to present these

relations. In their study, three types of rocks were used; Dolomite, Marble and Limestone.

Correlating different rock types with each other is an interesting idea since Marble is a

metamorphic rock and other rocks were sedimentary. But from their point of view, they

considered all as carbonate rocks. They concluded that there is a good linear relation between

mean P-wave sound velocity (Vp) with UCS and E. The following Table 2.3 shows their

results and the following Figures 2.17 and 2.18 show these relations.

Table 2.3: Correlations Found By Yasar, E. & Erdogan, Y. (2004)

Equation R

Vp= 0.0317 UCS + 2.0195 0.80

Vp= 0.0937 E + 1.7528 0.86

Figure 2.17: VpUCS Correlation by Yasar, E. & Erdogan, Y. (2004)


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2.7.2.5 Relations between UCS and Modulus of Elasticity

As stated previously, the ASTM merged the determination of the UCS and the modulus of

elasticity of rocks into one code starting from 2005. The code ASTM D-7012 (2010) is the

standardized procedure now to perform the modulus of elasticity E test. In this thesis, the

average modulus method was used to calculate the modulus of elasticity; which is the average

slope of the apparently straight line of the stress strain diagram. This is shown in the next

Figure 2.19.

Figure 2.18: VpE Correlation by Yasar, E. & Erdogan, Y. (2004)

Figure 2.19: Average Modulus of Elasticity Calculation as Per ASTM-D7012 (2010).


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Strain () is calculated as per the following equation, where () is the instantaneous

deformation and (L) is the sample length.

This test is done simultaneously with the UCS test. In fact, this test can be considered a

byproduct of the UCS test. Therefore it is logical to find the modulus of elasticity as a

function of the UCS. Tziallas, etal. (2009) did good research in correlating the UCS to E

through different models. They concluded that E can be determined as a function of UCS

with high R2 value equals 0.95. The following equation 2.6 is their concluded correlation;

where E and UCS are both in MPa.

They also concluded that E can be determined as a function of both UCS and the longitudinal

sound velocity Vp. The following equation 2.7 is their other concluded equation; where E is

in GPa, UCS is in MPa and Vpis in m/sec.

( )

They also visualized this correlation as a 3D diagram shown in Figure 2.20 and as a

nomograph shown in Figure 2.21.

. (2.6)

(2.7)

. (2.5)


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Figure 2.20: 3D visualization of equation 2.7 by Tziallas (2009)

Figure 2.21: Nomograph constructed for equation 2.7 by Tziallas (2009)


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2.7.3. Relations between UCS and Physical Properties

2.7.3.1 Relations between UCS and Bulk Specific Weight

The specific weight of rocks is determined according to the South Carolina department of

transportation code number SC-T-39 (2008). This procedure is considered one of the easiest

procedures done. The following equation 2.8 explains how it is calculated

Where W is the sample weight and V is the sample volume. The methodology is to measure

the total weight and divide it by the total volume which counts for all voids in the specimen.

In any case, it is assumed that the denser the specimen, the stronger it will be. A study

confirms that was carried out by Mohd, B. (2009).He also concluded that there is a good

relation between specific weight and UCS of a regression coefficient R2as high as 0.9666.

Here he correlated density to UCS. In fact, the specific weight is nothing but the density

times the acceleration of gravity (g) therefore this fixed value can be included easily in the

correlation without jeopardizing the accuracy of the results. The following Figure 2.22 shows

the found relation.

. (2.8)

Figure 2.22: UCS Relation by Mohd, B. (2009)


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2.7.3.2. Relations between UCS and Moisture Content

The moisture content is determined as per the ASTM-D2216 (2010) code. The procedure to

perform this test is described in the following chapter. The following equation 2.9 describes

how to calculate moisture content by mass.

Where Mi is the as received mass and Mov is the oven dry mass. The methodology is

summarized as measuring the masses of the rock specimen before and after placing it in the

oven for a certain time and temperature. It is believed that moisture content influences UCS.

. (2.9)


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Chapter 3

Experimental Program

3.1. Introduction

To achieve the proposed objectives of the study, lab and office works were conducted on a

set of samples from different locations in UAE. All Samples were acquired from the UAE's

coastal zone; the western region (W.R.), Abu Dhabi region (A.D.) and northern Emirates

region (N.E.). These samples were prepared and tested in accordance with the ASTM for all

tests except for the unit weight test where the code of South Carolina Department of

Transportation was used. The next Figure 3.1 shows the work plan flow. Every step of this

plan is a section of this chapter.

3.2. Sample Collection

In order to produce consistent and relaTable results, it was decided to have the sample span in

the core be of 1 meter length in order to ensure the uniformity of the tested samples. All cores

Sample Collection

SampleTransporting and

Storing

Sample Identification

Define Type and Depth ofEach Sample

Number The samples forEase of Access

SamplePreperation

Sample Testing

Mechanical Tests Physical Tests

Data Processing

Figure 3.1: General Work Plan of the Thesis


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were of size HX (76.2 mm) to avoid misleading results in mechanical tests. The following

Table 3.1 shows in detail the core locations in UTM coordinates with a summary about them.

Table 3.1: Summary of Borehole Locations and Data Northing Easting UTM UAE* Total Depth (m) of Samples

1 2767823 305716 40R N.E. 16.5 7

2 2767806 305732 40R N.E. 32 6

3 2767751 305786 40R N.E. 30 1

4 2767738 473700 40R N.E. 15 3

5 2650178 626625 39R W.R. 15 14

6 2768393 335292 40R N.E. 15 11

7 2660156 643514 39R W.R. 20 20

8 2660214 643604 39R W.R. 20 16

9 2707345 230782 40R A.D. 20 15

10 2707747 234323 40R A.D. 30 25

11 2724650 249993 40R A.D. 20 15

12 2724617 249987 40R A.D. 20 16

13 2694666 249562 40R A.D. 20 14

14 2692041 249007 40R A.D. 20 15

15 2718238 266660 40R A.D. 8 5

16 2707685 259667 40R A.D. 35 20

17 2706781 259435 40R A.D. 35 20

18 2696124 267506 40R A.D. 20 15

19 2706530 259174 40R A.D. 35 25

20 2666105 752296 39R W.R. 20 121 2704006 253194 40R A.D. 20 18

22 2702117 251995 40R A.D. 15 11

23 2706744 258934 40R A.D. 35 25

24 2701589 256627 40R A.D. 20 11

25 2703094 255158 40R A.D. 20 11

26 2706864 259161 40R A.D. 35 20

27 2706648 259576 40R A.D. 35 15

28 2699153 267310 40R A.D. 20 10

29 2783068 328432 40R N.E. 15 4

30 2783332 328266 40R N.E. 15 131 2783338 328620 40R N.E. 10 1

32 2784128 329250 40R N.E. 15 3

33 2783412 329433 40R N.E. 15 1

34 2787555 326779 40R N.E. 50 5

35 2802955 337470 40R N.E. 15 5

36 2802912 337430 40R N.E. 15 5

37 2802818 337489 40R N.E. 15 2

38 2802960 337425 40R N.E. 30 4

39 2813801 345495 40R N.E. 25 3

Total Number of Samples 419

*N.E. stands for Northern Emirates, A.D. stands for Abu Dhabi and W.R. stands for Western Region


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Figure 3.2 shows the contribution of samples by location and type where Figure 3.3 shows

envelop of borehole locations.

73%

15%

12%

Sample ContributionBy Place

Abu Dhabi

Northern Emirates

Westren Region

21%

45%

34%

Sample ContributionBy Type

Crystalline Gypsum

Mudstone

Sandstone

(a) (b)

Figure 3.2: Sample Contributions (a) by Place, and (b) by Rock Type

Figure 3.3: Zone of Borehole Locations, Acquired from Google Maps (2013)


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3.3. Sample Transporting and Storing

To ensure the integrity of the acquired cores, the ASTM-D5079 (2008) practice code was

used in transporting and preserving rock core samples. This code gives very detailed

procedures for samples from the time they are recovered from cores till the deposition of the

samples or storing for a certain period of time for future testing. The code provides a nice

flow chart for personnel in charge of all stages of core recovery, transporting, testing and

storage. The following Figure 3.4 shows this flow chart which is quoted with alteration from

the code.

1. Sample RecoveryFrom Drill

2. Handling 3. Core Photography

4. Initial Logging

5. Sample Protection

Routine CareSpecial CareCritical CareSoil Like Care

6. Preparation ofStorage and Shipping

Containers

7. Transportation 8. Storage9. Specimen

Preparation

10. Testing

Figure 3.4: ASTM Flow Chart For Preserving and Transporting Rock Core Samples (2008)


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Some geotechnical laboratories cooperated in granting all studied rock core specimens.

Therefore, due to their expertise, the chart steps 1 through 6 were assumed to be

professionally done. Steps 7 through 10 were done again in transporting samples from

laboratories to the university through testing of samples. Thankfully, all samples didnt

require special transportation therefore a normal truck was used to transport samples.

Regarding storing of samples, the code specifies special measurements for storing if test

results are affected by storing conditions. In this study, only the moisture content test required

special storing measurements whereas all other tests required the normal rock core box

storing measurements.

The next step was specimen preparation for tests. This step was very important as it defined

which test came before the other. Before that, all samples were identified for ease of use and

access of data collected from various tests. Identification and preparation of samples are

addressed in the next sections.

Another important step is sample protection. Although this step can be considered as sample

identification related step because it involves some identification, this identification is

required to determine how the sample processing should proceed. This identification means

extra protection measures for every class. Class one is the routine care which is for cores of

1.5 meters run and larger. If cores are less than 3 meters run, they are stored in structurally

sound core boxes. If they are longer than 3 meters run, they are placed in slightly wider and

longer PVC pipes. Here, core runs of 1 meter were considered the base for core box storing.

The second class is the special care class. It is necessary if the moisture condition is needed.

In addition to storing in structurally sound core boxes, vinylidene chloride seal is

recommended. The third class of care is the critical care which is needed for sample

protection against shock, vibration and variations in temperature. The fourth and last class of


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care is soil like care. Logically and by the code one can consider dealing with these cores as

soil. Thankfully, only class two of care was needed as a result of the as received situation of

the cores.

3.4. Sample Identification

For ease of access, an identification system was established. Samples were given an ID of the

form XYZ-a-b. This is illustrated in the following Figure 3.5.

For example; sample ID (BY-5-08) means this sample is acquired with Baynunah labs, taken

from the 5thborehole acquired with that lab and 08 means this is the 8 thsample acquired from

that borehole.It is good to mention here that the greater the sample number, the deeper the

sample. For tabulation purposes, the ID itself represents three columns of data; XY, a and b

data columns. This made it easy to store the sample depth and type in the database

established for this purpose. Here it is good to mention that the code assigned for the three

rock types is the following; CRGP is crystalline gypsum, MUDS is mudstone and SANDS is

sandstone.

ID: XYZ-a-b

XYZ = Lab Name a = Core Number b = Sample Number

Figure 3.5: Sample ID Illustration

AC: Arab Center for Engineering Studies

GC: Gulf Laboratory

BY: Ba nunah Laborator


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3.5. Sample Preparation

Depending on the test, one can decide if the specimen requires preprocessing or not. Some

tests like the UCS and E tests require special preparation, whereas other tests dontneed any

preparation, such as the point load test. All samples were cut using the diamond rock core

cutter for the UCS and E, Brazilian splitting, and ultrasonic pulse velocity where the

geometry of the sample is required to perform these tests as explained in the next section.

In fact, only the UCS and E test needed special sample preparation. Since the height to

diameter ratio of the sample has to be 2:1 sharp with a very low margin of error. Moreover,

the two surfaces of the sample had to be parallel to each other with a very low margin of error

and vertical to the sample with, likewise, a very low margin of error. These margins and

checking methods are stated in the ASTM D-4543-08 code. This method involves three

checks of the sample, and these are; the deviation from straightness, flatness and

perpendicularity of ends checks as follows;

For straightness check, the sample was placed on a horizontal surface prepared for this check.

The sample was then rolled on that surface to check the straightness. Any sample that had a

gap more than 0.5 mm didnt meet the straightness check.The check of flatness was done as

per procedure 5.2 B of the code. In this procedure, the sample was placed on the horizontal

surface. Then a dial gage of precision 2.5 m was set in contact with the specimen. Readings

of three diameters were taken for the specimen. If the difference between maximum and

minimum readings of the diameter was less than 38 m, the sample was accepted.

For perpendicularity check, the sample was placed on the horizontal surface again with a true

square being in contact with the specimen. Then the sample is rotated to find the maximum

gap between the specimen and the square. If the gap to the length ratio was less than 1:230

then the sample met the perpendicularity requirements.


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Some samples happened to be very weak. In fact it was very hard to be prepared to meet the

ASTM-D4543 (2008), section 5.2 requirements even with best effort as the code stated,

which was using a very sharp diamond cutter and dry cutting methodology operated by a very

experienced person. The code here gave a concession for this case as the code directed to cut

the sample to desired length and apply end caps to specimen.

3.6. Sample Testing

The following is a demonstration of the detailed procedures used to perform tests. Tests are

classified into mechanical tests; point load, Schmidt hammer, Brazilian splitting, ultrasonic

pulse velocity and UCS and E tests; as well as physical tests; moisture content, and specific

weight tests. Tests are presented in that order to make it easy for the reader to navigate

through their procedures.

3.6.1. Mechanical Tests Done

3.6.1.1. The Point Load Test.

As stated previously in chapter 2, this test was done in accordance with ASTM D-5731-08.

This test was performed by subjecting a rock specimen to an increasing concentrated load

until splitting of the specimen. The concentrated load was applied through coaxial conical

platens. The failure load was used to calculate the point load strength index by equation 2.2

which was used to estimate the UCS. The Figure 3.6 shows a sample ready for the test. This

test was done as follows;

A qualifying sample was of length to diameter ratio of 1:1 or more (no preparation

needed)

The diameter of the sample was then recorded

Sample was then inserted into the machine and platens were closed to form contact

with the diameter of the specimen. Here the contact point had to be in the middle if

the sample

Sample was then subject to steadily increasing load until failure occurred


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The failure load and pattern were recorded

If the failure pattern was the same as Figure 3.7 (a) the test was conducted perfectly

If the failure pattern was the same as Figure 3.7 (b) the test was rejected.

(a) (b)

Figure 3.7: Point Load Test Different Failure Patterns as Per ASTM-D5731 (2008)

(a) Accepted (b) Rejected

Figure 3.6: Sample Ready for the Point Load Test


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3.6.1.2. The Schmidt Hammer Test


This test was performed by subjecting a rock specimen to shock load without resulting in the

failure of the specimen. The shock load was applied through a rebound hammer (Schmidt

hammer). The height of the plunger after the shock was then recorded to calculate the

rebound number which was used to estimate UCS. This test was done as follows;

The rigid base was placed on a firm surface

Sample was then firmly tightened to that base

The verticality of the rebound hammer was achieved by using a vertical guide Plunger head was distanced more than one diameter from the edge

Ten shocks were given on various areas of the sample by gradually pressing the

plunger on the specimen

The average of these ten readings was calculated

Any result that deviated by more than 7 units was canceled and the averaging wasdone again to determine the rebound number (HR)

The test was rejected if the sample failed before completing the test.

3.6.1.3. Brazilian Splitting Test


This test was performed by subjecting a rock specimen to an increasing concentrated load

until splitting of the specimen. The concentrated load was applied through coaxial flat

platens. The failure load was used to calculate the tensile strength of the sample by equation

2.3 which could be used to estimate the UCS. This test was done as follows;

Samples were prepared as per ASTM D-4543-08. The thickness to diameter ratio was

to be between 0.2 and 0.75. Thickness and diameter were recorded

Samples were then marked on their diameter to ensure proper positioning in theloading machine

Then, samples were positioned in the loading frame

After that, samples were loaded until failure of samples as shown in Figure 3.9

The failure load was recorded for all samples and the strength was calculated for all

samples as per equation 2.3


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3.6.1.4. Ultrasonic Pulse Velocity Test


This test was performed by subjecting a rock specimen to an ultrasonic pulse. This pulse was

applied by a transducer and received by a receiver. The machine records the time a pulse

needed to travel from the transducer to the receiver. Then the pulse velocity was calculated

by equation 2.4 which was then used to determine some parameters for the rock of which

UCS is one of them. This test was done as follows;

Samples finely prepared as per ASTM D-4543-08. Length to diameter ratio was

recommended not to exceed 5 and at least 10 times the larger grain size. The length of

the sample was recorded

Samples were then marked for the place of transducer and receiver placement

Then, grease was applied to surface of samples, transducer and receiver to ensure noair is entrapped between the apparatus and the sample

The sample was then subjected to ultrasonic pulse. The time of travel was recorded

for each sample

The pulse velocity was then calculated by equation 2.4

3.6.1.5. UCS and E Test

As stated previously in chapter 2, UCS and E are usually done simultaneously. This test

was done in accordance with ASTM D-7012-10 methods C and D. A rock core specimen was

cut to achieve an aspect ratio of 2:1. The ends were engineered. The specimen was placed in

a loading machine. Axial load was applied gradually and increasingly on the specimen.

Deformation was measured as a function of load until peak load and failure happened. Then

Figure 3.8: Failed Sample after Brazilian Test


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the UCS was calculated by equation 2.1 and E was calculated as per equation 2.5 and Figure

2.18. Figure 3.10 shows a sample ready for the test. This test was done as follows;

Samples finely prepared as per ASTM D-4543-08. Length to diameter ratio was to be2:1 The length and diameter of sample were recorded

Samples were then placed in the loading machine connected to a computer to record

load and its corresponding deflection to construct the stress strain diagram

After that, samples were loaded until their failure

The extreme load was used to determine the UCS as per equation 2.1

The whole record was converted into stress strain diagram as per equations 2.1 and

2.5 and Figure 2.19. (E) was then calculated from the stress strain diagram

Figure 3.9: Sample Ready for the UCS and E Test


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3.6.2. Physical Tests Done

3.6.2.1. Moisture Content Test

As stated previously in chapter 2, this test was done in accordance with ASTM D-2216-10. A

test specimen was dried in an oven at a temperature of 110 5C to a constant mass. The

loss of mass due to drying is considered to be water. The water content is calculated using the

mass of water and the mass of the dry specimen. The moisture content is then calculated by

equation 2.11. The following is the detailed procedure;

Specimens masses before drying were recorded Specimens then were placed in an oven at a temperature of 110 5C for 24 4 hrs

Specimens then were removed from oven and left to cool down to room temperature

Specimens masses after drying were recorded Moisture content is calculated by equation 2.11

3.6.2.2 Specific Weight Test

As stated previously in chapter 2, this test was done in accordance with SC T 39-08.

Specimens dimensions and weight were recorded and the specific weight was calculated as

per equation 2.10.

3.6.3. Order of Testing

A closer look at the specifications of performed tests and its influence on the sample in terms

of destructivity reveals many facts. To ensure the correctness of moisture content test results,

it was decided to perform it first, just after removing the sample cover. Therefore the stage

one of testing was the moisture content.

As mentioned earlier, sample preparation for other tests required accurate measurements and

cautious cutting of samples depending on their condition. This processing was required for

geometry related tests like unit weight, ultrasonic pulse velocity, UCS and E, and Brazilian


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splitting strength tests. Also, the unit load test was the simplest test done so it was decided to

combine the unit weight test with sample preparation in one stage (stage two).

For the ultrasonic pulse velocity and The Schmidt hammer tests, it was obvious that no

sample destruction resulted. Therefore it was decided to group both tests in stage three. Stage

four was the last stage; all destructive tests were performed in this stage. It is good to mention

that the desired sample span of 1 meter facilitated the conduction of all previously mentioned

tests. Therefore, a sample segment was only tested once for stage three and four. The

following Figure 3.11 summarizes these finding in a flowchart.

Sample

Stage OneMoisture

Content

Stage TwoSample

Preparation

Unit

Weight

Stage Three USPVSchmidt

Hammer

Stage Four

Point Load

UCS and E

BrazilianSplitting

Figure 3.10: Sample Testing Stages Flowchart


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Chapter 4

Results, Analysis and Discussion

4.1. Introduction

This chapter is dedicated to presenting, analyzing and discussing lab test results. Section 4.2

presents all lab tests results with some statistical analysis and relations to rock types that were

included in the study. Section 4.3 is dedicated to the correlation analysis, in order to meet

goals and objectives set for the thesis. Section 4.4 holds a comparison between this thesiss

results and previous work results presented previously in chapter 2.

4.2. Test Results

This section presents a summary of results for all experiments done, where statistical analysis

was performed to define 95% confidence intervals estimate of the expected value from each

test. All data are presented in appendixes

4.2.1. Mechanical Test Results

4.2.1.1 The Schmidt Hammer Test

Since the capacity of the used rebound hammer varies between 10 and 90, nearly 12% of

samples failed before the fulfillment of the test. Here, 210 samples passed this test. From a

statistical analysis to determine the confidence interval of the expected value based on 95 %

confidence, the results are given in the following Table 4.1. All data is in appendix Table A.1

Table 4.1: 95% Confidence Intervals Estimates of Expected Values of (HR)

Rock Type Minimum Expected Maximum Expected

Any 15 16

Mudstone (MUDS) 13 15

Sandstone (SANDS) 15 17

Crystalline Gypsum (CRGP) 15 18


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4.2.1.2 The Point Load Strength Index Test.

In this test, the apparatus used was more sensitive, although apparatuss gauges were

analogue clock type gauges, and knowing that this test doesnt require further sampleprocessing, 419 samples were tested according to the point load test. Some samples just failed

because of fastening the apparatus on the sample.

This test is considered one of the most important tests as it is correlated directly to the UCS

of rock and is widely used for its ease of application. Nonetheless, the following Table 4.2

shows the result of the 95% confidence interval analysis for the expected value of test results

estimating uae sed. rocks ucs from emp. correlations

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