1st Edition

Rock Failure Mechanisms Illustrated and Explained

By Chun'An Tang, John A. Hudson Copyright 2011

    When dealing with rock in civil engineering, mining engineering and other engineering, the process by which the rock fails under load should be understood, so that safe structures can be built on and in the rock. However, there are many ways for loading rock and rock can have a variety of idiosyncracies. This reference book provides engineers and researchers with the essential knowledge for a clear understanding of the process of rock failure under different conditions. It contains an introductory chapter explaining the role of rock failure in engineering projects plus a summary of the theories governing rock failure and an explanation of the computer simulation method. It subsquently deals in detail with explaining, simulating and illustrating rock failure in laboratory and field. The concluding chapter discusses coupled modelling and the anticipated future directions for this type of computer simulation. An appendix describing the RFPA numerical model (Rock Failure Process Analysis program) is also included.


    About the Authors
    Chun'an Tang has a PhD in Mining Engineering and is a Professor at the School of Civil & Hydraulic Engineering at Dalian University of Technology in China. He is an advisor for design and stablity problem modelling in mining and civil  rock engineeringand  and Chairman of the China National Group of the International Society for Rock Mechanics.

    John Hudson is emeritus professor at Imperial College, London and is active as an independant consultant for Rock Engineering Consultants. He has a PhD in Rock Mechanics and completed over a 130 rock engineering consulting assignments in mining and civil engineering. He is a fellow at the Royal Academy of Engineering in the UK and President of the International Society for Rock Mechanics.

     

    Preface
    Acknowledgements
    About the authors
    List of figures
    List of tables
    Explanatory notes

    1. Introduction
    1.1 The purpose of this book
    1.2 Why do things break?
    1.3 Rock failure in geological and recent history
    1.4 Rock failure in present day engineering
    1.5 The nature of rock – a natural material
    1.5.1 Discontinuities
    1.5.2 Inhomogeneity
    1.5.3 Anisotropy
    1.5.4 Inelasticity
    1.6 Numerical modelling of rock failure
    1.7 The content of this book

    2. Rock failure in uniaxial tension
    2.1 Introduction
    2.2 Specimen simulation
    2.3 Numerical simulation results for the uniaxial tension case
    2.4 Further studies of simulated rock failure in uniaxial tension

    3. Rock failure in indirect tension
    3.1 Generating a tensile stress through compressive loading
    3.2 Establishing the numerical simulation model for indirect tensile strength tests
    3.3 Numerical simulations of rock failure in indirect tensile strength tests
    3.3.1 The disc test
    3.3.1.1 Stress distribution in the discs
    3.3.1.2 Effect of the material properties of theload-bearing strip on the disc test
    3.3.1.3 Effect of load-bearing strip width on disc test
    3.3.1.4 Effect of specimen size on the disc test
    3.3.2 The plate test
    3.3.3 The ring test
    3.3.3.1 Stress distribution along the loadingdiameter for ring specimens
    3.3.3.2 Effect of hole diameter on the failurepattern of ring specimens
    3.3.3.3 Effect of hole diameter on the ringtest indirect tensile strength

    4. Rock failure uniaxial compression
    4.1 Introduction
    4.2 Numerical illustrations of rock failure in uniaxial compression
    4.2.1 Model description
    4.2.2 Numerical simulation results
    4.2.3 Summary of the numerical simulation observations
    4.2.3.1 The complete stress–strain curve
    4.2.3.2 Acoustic emission (AE) events and their locations
    4.2.3.3 Stress distribution and failure-induced stress redistribution
    4.3 Rock failure modes in uniaxial compression
    4.4 Factors affecting rock failure behaviour
    4.4.1 Model description
    4.4.2 Effect of end constraint in terms of the Young’s modulusof the loading platens
    4.4.3 Effect of height to width ratio (slenderness)of the specimen
    4.4.4 Class I and Class II curves in uniaxial compression
    4.4.5 The size effect

    5. Confinement and shear
    5.1 The effect of confinement
    5.2 Acoustic emission during shearing
    5.3 Biaxial loading 

    6. Effect of heterogeneity on rock failure
    6.1 Introduction
    6.2 Heterogeneity-induced stress fluctuations
    6.2.1 Discs subjected to diametral loading
    6.2.2 Rock blocks under hydrostatic stress
    6.3 Heterogeneity-related seismic patterns
    6.4 Influence of heterogeneity on crack propagation modes
    6.4.1 Numerical specimen
    6.4.2 Numerical results and discussion
    6.5 The influence of heterogeneity on the meso-scale
    6.5.1 Digital image based modelling method
    6.5.2 Numerical model based on the digital image
    6.5.3 Simulation results for uniaxial compression
    6.5.4 Influence of interface strength

    7. The effect of rock anisotropy on rock failure
    7.1 Introduction
    7.2 Numerical models

    8. Loading, unloading and the Kaiser Effect
    8.1 Introduction
    8.2 Numerical simulation

    9. Time dependency of rock failure
    9.1 Introduction
    9.2 A constitutive model for the time-dependent behaviour of rocks
    9.3 Illustrations of time-dependent micro-structural damage
    9.3.1 The creep test
    9.3.2 The relaxation test
    9.4 Degradation of building stones with time

    10. Coalescence of fractures
    10.1 Introduction
    10.2 Modelling of crack growth from crack-like flaws in compression
    10.2.1 An angled crack-like flaw
    10.2.2 Crack growth from an array of crack-like flaws
    10.2.2.1 Wing crack growth from three array flaws
    10.2.2.2 Wing crack growth from randomly distributed multi-flaws
    10.3 Crack growth from a pore-like flaw in compression 
    10.3.1 Modelling crack growth from a single hole in specimens under compression 1
    10.3.1.1 Crack growth from a single hole in specimens of different width
    10.3.1.2 Crack growth from a single hole with different diameters
    10.3.1.3 Modelling of crack growth from an array of holes in a specimen under compression

    11. Dynamic loading of rock
    11.1 Introduction
    11.2 The simulation models
    11.3 Simulation demonstration 
    11.3.1 Influence of heterogeneity on stress wave propagation
    11.3.2 Influence of stress wave amplitude on the fracture process and failure pattern

    12. Rock failure and water flow
    12.1 Introduction
    12.2 Rock failure under hydraulic pressure
    12.3 Illustrations of fluid flow in heterogeneous initially intact rock
    12.3.1 Evolution of flow paths
    12.4 Comparison with the rock degradation modelling by Yuan and Harrison (2005)
    12.5 Fluid flow in initially intact rock containing block in homogeneities

    13. Rock failure induced by thermal stress
    13.1 Introduction
    13.2 Thermally-induced rock failure
    13.3 Thermal cracking of a discring model
    13.4 Thermal cracking in models containing irregularly shaped inclusions

    14. Slope failure in rock masses
    14.1 Introduction
    14.2 Strength reduction rule and determination of safety factor
    14.3 A slope in a layered rock mass
    14.4 A slope in a jointed rock mass
    14.5 A slope in a jointed rock mass with differing joint persistence 

    15. The fracture process when cutting inhomogeneous rocks
    15.1 Introduction
    15.2 Modelling rock cutting and the failure mechanism
    15.2.1 Quasi-photoelastic fringe pattern
    15.2.2 Fracture pattern
    15.2.3 The chipping process
    15.3 The load–displacement response when cutting in homogeneous rock
    15.4 The crushed zone during rock cutting

    16. Rock failure around tunnels in jointed rock
    16.1 Introduction
    16.2 Progressive failure around a tunnel in a jointed rock mass
    16.2.1 Effect of dip angles on the stability of tunnel
    16.2.2 The effect of the lateral stress on the mode of tunnel failure
    16.2.3 Displacements at the tunnel periphery

    17. Rock failure induced by longwall coal mining
    17.1 Introduction
    17.2 Illustrations of longwall mining simulations
    17.3 The Daliuta coal mine in China
    17.3.1 The strata failure process
    17.3.2 Pillar stresses

    18. Gas outbursts in coal mines
    18.1 Introduction
    18.2 Outbursts induced by cross-cutting from rock to coal seam
    18.3 Outburst as the working face approaches high methanepressure in the coal seam

    19. Particle breakage and comminution
    19.1 Introduction
    19.2 Single particle breakage
    19.2.1 Breakage of single particle under diametral loading without confinement
    19.2.2 Breakage of single particle under diametral loading with confinement
    19.3 Multiple particle breakage
    19.3.1 Fragmentation process of a rock particle assemblage in a container
    19.3.2 Force and displacement relation duringthe breakage process
    19.3.3 Energy considerations
    19.3.4 Size distribution
    19.3.5 Influence of particle shape

    20. 3-D Modelling and ‘turtle crack formation’ in rock
    20.1 Introduction
    20.2 The three-layer model
    20.3 Fracture spacing measurements

    21. Concluding remark

    References and bibliography
    Index 
    Preface

     

    Biography

    Chun'An Tang, John A. Hudson