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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
Estimating Unconfined Compressive Strength of
Sedimentary Rocks in the United Arab Emirates
from Generated Empirical Correlations
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
Estimating Unconfined Compressive Strength of
Sedimentary Rocks in the United Arab Emirates
from Generated Empirical Correlations
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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VI
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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VIII
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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IX
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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X
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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1
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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2
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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3
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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4
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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5
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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6
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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7
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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8
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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9
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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10
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
As stated previously in chapter 2, this test was done in accordance with ASTM D-5873-13.
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
As stated previously in chapter 2, this test was done in accordance with ASTM D-3967-08.
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 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
As stated previously in chapter 2, this test was done in accordance with ASTM D-2845-08.
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