Shear Behaviour of Rock Joints

by Indraratna; Buddhima

• ISBN13: 9789058093073
• ISBN10: 9058093077
• Format: Hardcover
• Copyright: 2000-01-15
• Publisher: CRC Press

Summary

This title covers the fundamental properties of rock joints, the method of laboratory testing of rock joints, and shear strength assessment under different loading conditions. This work is intended as a reference text for students and practitioners in mining and rock engineering.

Table of Contents

Preface	p. IX
Characterization of Joint Surface Roughness	p. 1
Introduction	p. 1
Roughness measurement techniques	p. 2
JRC measurement	p. 2
Fractal method	p. 4
Spectral method	p. 9
Digital coordinate measuring machine	p. 11
Fourier transform method and its application to measure surface rougness	p. 14
Physical and mechanical properties of intact and jointed rocks	p. 15
References	p. 16
Shear Behaviour of Clean Rock Joints	p. 17
Introduction	p. 17
CNS and CNL concepts	p. 18
Shear apparatus for laboratory testing	p. 21
Large scale shear boxes	p. 21
Loading device	p. 21
Measurements of displacements	p. 22
Laboratory modelling of rock joints	p. 23
Selection of model material for joint	p. 23
Preparation of saw-tooth and natural specimens	p. 23
Sampling and preparation of field joint specimens	p. 24
Laboratory testing of rock joints	p. 25
Shear strength response under Constant Normal Stiffness	p. 26
Normal stress and dilation behaviour	p. 27
Effect of normal stiffness on joint shear behaviour	p. 28
Effect of stiffness on shear displacement corresponding to peak shear stress	p. 28
Effect of shear rate on the strength of joint	p. 28
Tests on soft rock joints	p. 29
Effect of shear displacement rate	p. 29
Effect of boundary condition on shear behaviour	p. 31
Behaviour of unfilled/clean regular joints under CNS	p. 36
Shear behaviour of natural (field) joints	p. 37
Stress-path response of Type I, II and III joints	p. 42
Strength envelopes for Types I, II and III	p. 44
Empirical models for the prediction of shear strength of rock joints	p. 45
Summary of behaviour of unfilled/clean joints	p. 49
Effect of shear rate on shear behaviour of joints under CNS	p. 49
Effect of boundary condition on shear behaviour	p. 50
Shear behaviour of soft unfilled joint under CNS	p. 51
References	p. 51
Infilled Rock Joint Behaviour	p. 54
Influence of infill on rock joint shear strength	p. 54
Factors controlling infilled joint shear strength	p. 55
Effect of joint type on shear behaviour	p. 56
Infill type and thickness	p. 56
Effect of drainage condition	p. 63
Infill boundary condition	p. 63
Infill-rock interaction	p. 64
Effect of external stiffness	p. 67
Normal stress and lateral confinement	p. 68
Laboratory testing on infilled rock joints	p. 68
Selection of infill material	p. 70
Preparation of infilled joint surface	p. 70
Setting-up the specimen in the shear boxes	p. 71
Application of normal load	p. 71
Shear behaviour of Type I joints	p. 74
Shear behaviour of Type II joints	p. 77
Effect of infill thickness on horizontal displacement corresponding to peak shear stress	p. 77
Effect of infill thickness on stress-path behaviour	p. 81
Effect of infill thickness on peak shear stress	p. 83
Drop in peak shear strength	p. 83
Strength envelope	p. 87
Shear strength model for infilled joints	p. 87
Remarks on infilled joint behaviour	p. 90
References	p. 91
Modelling the Shear Behaviour of Rock Joints	p. 93
Introduction	p. 93
Existing models based on CNS concept	p. 94
Model based on energy balance principles	p. 94
Mechanistically based model	p. 97
Graphical model	p. 98
Analytical model	p. 98
Requirement of a new model	p. 102
New shear strength model for soft rock joints	p. 102
Application of Fourier transform method for predicting unfilled joint dilation	p. 102
Prediction of normal stress with horizontal displacement	p. 104
Prediction of shear stress with horizontal displacement	p. 105
Effect of infill on the shear strength of joint	p. 113
Hyberbolic modelling of strength drop associated with infill thickness	p. 113
Shear strength relationship between unfilled and infilled joints	p. 115
Determination of hyperbolic constants	p. 115
Development of a computer code	p. 119
Comparison between predicted and experimental results	p. 119
Dilation	p. 119
Normal stress	p. 119
Shear stress	p. 124
Strength envelopes	p. 126
Infilled joint strength	p. 127
UDEC analysis of shear behaviour of joints	p. 127
Choice of joint models	p. 127
Continuous yielding model	p. 131
Conceptual CNS shear model	p. 132
CNL direct shear model	p. 133
Discretisation of blocks and applied boundary conditions	p. 133
Results and discussions	p. 135
Summary of shear strength modelling	p. 137
References	p. 138
Simplified Approach for Using CNS Technique in Practice	p. 140
Introduction	p. 140
Underground roadway in jointed rock	p. 140
Boundary conditions	p. 140
Roadway excavation	p. 141
Stability analysis of slope	p. 143
Limit equilibrium analysis (initial condition without bolts)	p. 145
CNS analysis (considering bolt contribution)	p. 146
CNL analysis considering joint contribution	p. 147
Highlights of Rock Joint Behaviour Under CNL and CNS Conditions, and Recommendations for the Future	p. 149
Summary	p. 149
Behaviour of unfilled joints under various rates of shear displacements	p. 150
Behaviour of unfilled joints under CNL and CNS	p. 150
Shear behaviour of unfilled and natural joints under CNS	p. 150
Behaviour of unfilled joints under CNS condition	p. 151
New shear strength model by the authors	p. 151
Recommendations for further study	p. 152
Modifications to laboratory procedures	p. 152
Field mapping	p. 152
Effective stress approach	p. 152
Bolted joints	p. 153
Scale effects	p. 153
Extension in numerical modelling	p. 154
References	p. 154
Program Code for Shear Strength Model	p. 155
Subject Index	p. 163
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