Practical Rock Mechanics

371 Pages·2015·81.28 MB·English

by  Steve Hencher

Practical
Rock
Mechanics
Applied Geotechnics Series
Series Editor: William Powrie,
University of Southampton, United Kingdom
PUBLISHED TITLES
David Muir Wood, Geotechnical Modelling
Hardback ISBN 978-0-415-34304-6 • Paperback ISBN 978-0-419-23730-3
Alun Thomas, Sprayed Concrete Lined Tunnels
Hardback • ISBN 978-0-415-36864-3
David Chapman et al.,Introduction to Tunnel Construction
Hardback ISBN 978-0-415-46841-1 • Paperback ISBN 978-0-415-46842-8
Catherine O’Sullivan, Particulate Discrete Element Modelling
Hardback • ISBN 978-0-415-49036-8
Steve Hencher, Practical Engineering Geology
Hardback ISBN 978-0-415-46908-1 • Paperback ISBN 978-0-415-46909-8
Martin Preene et al., Groundwater Lowering in Construction
Hardback • ISBN 978-0-415-66837-8
Steve Hencher, Practical Rock Mechanics
Paperback • ISBN 978-1-4822-1726-1
Mike Jefferies et al., Soil Liquefaction, 2nd ed
Hardback • ISBN 978-1-4822-1368-3
Paul F. McCombie et al., Drystone Retaining Walls: Design, Construction
and Assessment.
Hardback • ISBN 978-1-4822-5088-6
FORTHCOMING
Zixin Zhang et al., Fundamentals of Shield Tunnelling
Hardback • ISBN 978-0-415-53597-7
Christoph Gaudin et al., Centrifuge Modelling in Geotechnics
Hardback • ISBN 978-0-415-52224-3
Kevin Stone et al., Weak Rock Engineering Geology and Geotechnics
Hardback • ISBN 978-0-415-56071-9
Practical
Rock
Mechanics
Steve Hencher
Hencher Associates, Limited
University of Leeds,
UK and Halcrow, Hong Kong
A SPON PRESS BOOK
CRC Press
Taylor & Francis Group
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© 2015 by Taylor & Francis Group, LLC
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Version Date: 20160225
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Contents
Preface xv
Acknowledgements xvii
Specific permissions xix
Author xxi
1 Introduction to rock mechanics 1
1.1 Introduction 1
1.2 Differentiating between soil and rock 1
1.3 Mechanics of failure 2
1.4 Classification of intact rock 2
1.5 Compressive strength of weak rock 3
1.6 Origins of shear strength in intact rock 4
1.7 Shear strength parameters for the sample in Figure 1.3 5
1.8 Stability of a cut slope in weak rock 5
1.9 Discontinuities in rock masses 7
1.9.1 Introduction and relationship to geological history 7
1.9.2 Fracture development 7
1.9.3 Joints 9
1.9.4 Faults 10
1.10 The importance of discontinuities to stability 10
1.11 Early lessons and the relevance of rock mechanics 14
1.12 Application of rock mechanics 14
1.13 History of the subject area 14
1.14 Rock mechanics as a scientific discipline 14
1.15 Load changes 18
2 Fundamental mechanics 21
2.1 Definitions 21
2.1.1 Force and load 21
2.1.2 Stress 21
2.1.3 Stress transformation 23
2.2 Mohr circle representation of stress state 25
v
vi Contents
2.3 Stress concentration in underground openings 28
2.4 Stresses below foundations 30
2.5 Effective stress 30
2.6 Rock deformation and behaviour 30
2.6.1 Elastic behaviour and Young’s modulus 30
2.6.2 Rock behaviour 31
2.6.2.1 Brittle fracture and Griffith crack theory 32
2.6.2.2 Failure of rock 33
2.6.2.3 Plasticity 36
2.6.2.4 Poisson’s ratio 37
2.7 Direct shear 37
2.8 Simple shear and associated rock structures 38
2.9 Surface features on rock fractures 40
2.10 Conclusions to this section 42
3 Geological processes and the nature of rock masses 43
3.1 Introduction 43
3.2 Earth stresses 43
3.2.1 Plate tectonics 43
3.2.2 Earth stresses: Prediction, measurement and
significance to engineering projects 45
3.2.3 Measurement of stress 45
3.3 Faults 46
3.3.1 Significance of faults to ground engineering 46
3.3.2 General 47
3.3.3 Normal faults 47
3.3.4 Thrust faulting 49
3.3.5 Reverse faults and inversion tectonics 50
3.3.6 Strike-slip faults 50
3.3.7 Fault rocks 52
3.3.8 Earthquake occurrence and prediction 53
3.4 Folding 54
3.5 Rock textures, fabrics and effect on properties 56
3.5.1 Introduction 56
3.5.2 Cooling of igneous rock 57
3.5.3 Sedimentary rock 58
3.5.3.1 Sandstone 58
3.5.3.2 Mudstone 60
3.5.3.3 Limestone 61
3.5.4 Metamorphic rock 61
3.5.5 Hydrothermal alteration 63
3.5.6 Weathering 66
3.5.6.1 General 66
3.5.6.2 Disintegration 67
3.5.6.3 Mass weathering features 69
Contents vii
3.6 Rock joints and other discontinuities 71
3.6.1 Introduction 71
3.6.2 Need for a change of approach and increased geological
input in characterising fracture networks 72
3.6.3 Starting point for dealing with rock discontinuities 73
3.6.4 Primary joints 73
3.6.4.1 Cooling (extrusive and shallow intrusive) 73
3.6.4.2 Cooling and emplacement joints (plutonic) 78
3.6.4.3 Sedimentary 80
3.6.5 Secondary, tectonic joints 80
3.6.5.1 General 80
3.6.5.2 Regional joints developed as tensile fractures 82
3.6.5.3 Hybrid joints 83
3.6.5.4 Cleavage 84
3.6.6 Tertiary joints 86
3.6.7 Joint development in geological and engineering time 88
3.6.8 Shape and extent of joints 89
3.7 Major geological structures 89
3.7.1 Evidence from the past 89
3.7.2 Evidence in the present 91
3.7.2.1 Slow processes 92
3.7.2.2 Climatic change 95
3.7.3 Faster changes 97
3.7.3.1 Rapid events 97
3.7.3.2 Rapid natural events 97
3.7.3.3 Reflections 102
4 Hydrogeology of rock masses 105
4.1 Introduction 105
4.2 Fundamental concepts and definitions 105
4.2.1 Porosity 105
4.3 Hydraulic conductivity and permeability 108
4.4 Measuring hydraulic conductivity 109
4.4.1 Difficulties 109
4.4.2 Water tests in boreholes 109
4.4.3 Lugeon testing 109
4.4.4 Pumping tests 110
4.5 Typical parameters 111
4.6 Unconfined and confined aquifers and storage 111
4.6.1 Unconfined conditions 111
4.6.2 Confined conditions 112
4.7 Compartmentalisation, aquicludes and aquitards 113
4.8 Flow paths 113
4.8.1 Flow paths in rock (unweathered) 113
4.8.2 Preferential flow paths in weathered rock 116
viii Contents
4.8.3 E stablishing hydrogeological conditions
in weathered rock profiles 117
4.9 Characterisation and prediction of
hydrogeological conditions for projects 118
4.9.1 Slopes 118
4.9.2 Underground openings 119
4.9.2.1 Setting limits for inflow 120
4.9.2.2 Predicting inflow into an underground opening 121
4.9.2.3 Experience of inflow 121
4.9.2.4 Mining 122
4.9.2.5 Nuclear waste repositories 122
4.9.3 Oil and gas 123
4.9.3.1 Dual porosity and well testing 123
4.10 Grouting 124
4.10.1 Purpose of grouting 124
4.10.2 Options and methods 124
4.11 Hydrogeological modelling 125
4.11.1 Modelling geology as isotropic 125
4.11.2 Anisotropic flow models 125
5 Characterising rock for engineering purposes 127
5.1 Introduction 127
5.2 Initial stages of site investigation 127
5.3 Field mapping 128
5.4 Trial excavations 130
5.5 Discontinuity surveys 131
5.6 Remote measurement 136
5.7 Interpretation 140
5.8 Rose diagrams 140
5.9 Stereographic interpretation 141
5.9.1 Introduction 141
5.9.2 Stereonets 143
5.9.3 Plotting data 143
5.9.3.1 Step 1: Plot a plane 144
5.9.3.2 Stage 2: Plotting a second plane and
measuring the intersecting wedge 145
5.9.3.3 Plotting large amounts of data 145
5.10 Roughness measurement 148
5.11 Ground investigation techniques 153
5.11.1 Introduction 153
5.11.1.1 Geophysics 153
5.11.1.2 Rock drilling 154
5.11.2 Sampling and storage 159
5.12 Description and classification of rocks 161
5.12.1 Introduction 161
5.12.2 Order of description 161