Engineering rock mechanics: an introduction to the principles

458 Pages·1997·11.655 MB·English

by  Author Unknown

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Engineering rock
mechanics
an introduction to the principles

Engineering rock
I 0
mechanics
an introduction to the principles
John A. Hudson
Professor of Engineering Rock Mechanics
Imperial College of Science, Technology and Medicine
University of London, UK
and
John P. Harrison
Senior Lecturer in Engineering Rock Mechanics
Imperial College of Science, Technology and Medicine
University of London, UK
Pergamon
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0 1997 J. A. Hudson and J. P. Harrison. Published by Elsevier Science Ltd.
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For all our past, present and future students and colleagues
at Imperial College
About the authors
Professor J. A. Hudson
John Hudson graduated in 1965 from the Heriot-Watt University and
obtained his Ph.D. in 1970 at the University of Minnesota. He has spent his
professional career in rock mechanics and rock engineering-as they apply
to both civil and mining engineering-in consulting, research and teach-
ing. He has written over 100 scientific papers and been awarded the D.Sc.
degree by the Heriot-Watt University for his contributions to the subject.
From 1983 to 1993, Professor Hudson was based at Imperial College
where most of the book was written. He is now a Principal of Rock Engi-
neering Consultants, a Visiting Professor at Imperial College, and actively
engaged in applying engineering rock mechanics principles to relevant
engineering practice worldwide.
Dr J. P. Harrison
John Harrison graduated in civil engineering from Imperial College,
University of London and then worked for some years in the civil engi-
neering industry with both contracting and consulting organizations.
This was interspersed by studies leading to a Master’s degree, also from
Imperial College, in engineering rock mechanics. In 1986 he was appoint-
ed Lecturer in Engineering Rock Mechanics at Imperial College, was
promoted to Senior Lecturer in 1996 and now directs undergraduate and
post-graduate rock mechanics teaching, as well as research there.
His personal research interests are in the characterization and behaviour
of discontinuous rock masses and, for his work on novel mathematical
methods applied to the analysis of discontinuity geometry, he was awarded
the degree of Ph.D. by the University of London in 1993.
Contents
Preface xi
1. Introduction 1
1.1 The subject of rock mechanics 1
1.2 Content of this book 9
2. Geological setting 11
2.1 Rock as an engineering material 11
2.2 Natural rock environments 14
2.3 The influence of geological factors on rocks and rock masses 16
3. Stress 31
3.1 Why study stress in rock mechanics and rock engineering? 31
3.2 The difference between a scalar, a vector and a tensor 32
3.3 Normal stress components and shear stress components 32
3.4 Stress as a point property 33
3.5 The stress components on a small cube within the rock 34
3.6 The symmetry of the stress matrix 36
3.7 The state of stress at a point has six independent components 37
3.8 The principal stresses 37
3.9 All unsupported excavation surfaces are principal stress
planes 38
3.10 Concluding remarks 40
4. In situ stress 41
4.1 Why determine in situ stress? 41
4.2 Presentation of in situ stress state data 41
4.3 Methods of stress determination 42
4.4 Statistical analysis of stress state data 52
4.5 The representative elemental volume for stress 54
4.6 Predictions of natural in situ stress states based on elasticity
theory 56
4.7 Collated worldwide in situ stress data 59
viii Contents
4.8 Reasons for high horizontal stresses 62
4.9 Effect of discontinuities on the proximate state of stress 65
4.10 Glossary of terms related to stress states in rock masses 68
5. Strain 71
5.1 Finite strain 71
5.2 Examples of homogeneous finite strain 73
5.3 Infinitesimal strain 75
5.4 The strain tensor 77
5.5 The elastic compliance matrix 78
5.6 Implications for in situ stress 82
6. Intact rock 85
6.1 The background to intact rock testing 85
6.2 The complete stress-strain curve in uniaxial compression 86
6.3 Soft, stiff and servo-controlled testing machines 89
6.4 Specimen geometry, loading conditions and environmental
effects 95
6.5 Failure criteria 106
6.6 Concluding remarks 111
7. Discontinuities 113
7.1 The occurrence of discontinuities 114
7.2 Geometrical properties of discontinuities 116
7.3 Mechanical properties 134
7.4 Discussion 138
8. Rock masses 141
8.1 Deformability 141
8.2 Strength 144
8.3 Post-peak strength behaviour 147
9. Permeability 149
9.1 Fundamental definitions 149
9.2 Primary and secondary permeability 151
9.3 Flow through discontinuities 151
9.4 Flow through discontinuity networks 154
9.5 Scale effect 156
9.6 A note on effective stresses 159
9.7 Some practical aspects: grouting and blasting 160
10. Anisotropy and inhomogeneity 163
10.1 Definitions 163
10.2 Anisotropy 165
10.3 Inhomogeneity 166
10.4 Ramifications for analysis 169
11. Testing techniques 173
11.1 Access to the rock 173
Contents ix
11.2 Tailoring testing to engineering requirements 17 4
11.3 Tests on intact rock 177
11.4 Tests on discontinuities 181
11.5 Tests on rock masses 186
11.6 Standardized tests 191
12. Rock mass classification 193
12.1 Rock Mass Rating (RMR) system 193
12.2 Q-system 195
12.3 Applications of rock mass classification systems 198
12.4 Links between the classification systems and rock properties 201
12.5 Discussion 201
12.6 Extensions to rock mass classification techniques 202
12.7 Concluding remarks 206
13. Rock dynamics and time-dependent aspects 207
13.1 Introduction 207
13.2 Stress waves 208
13.3 Time-dependency 213
13.4 Time-dependency in rock engineering 221
14. Rock mechanics interactions and rock engineering
systems (RES) 223
14.1 Introduction to the subject 223
14.2 Interaction matrices 225
14.3 Interaction matrices in rock mechanics 228
14.4 Symmetry of interaction matrices 229
14.5 A rock mechanics-rock engineering interaction matrix 232
14.6 Further examples of rock mechanics interaction matrices 235
14.7 Concluding remarks 236
15. Excavation principles 239
15.1 The excavation process 239
15.2 Rock blasting 243
15.3 Specialized blasting techniques 248
15.4 Mechanical excavation 255
15.5 Vibrations due to excavation 261
16. Stabilization principles 267
16.1 The effect of excavation on the rock mass environment 267
16.2 The stabilization strategy 269
16.3 Rock reinforcement 271
16.4 Rock support 274
16.5 Stabilization of 'transitional' rock masses 279
16.6 Further comments on rock stabilization methods 282
17. Surface excavation instability mechanisms 287
17.1 Slope instability 287
17.2 Foundation instability 298