Rock mechanics is a field of applied science which has become recognised as a coherent engineering discipline within the last two decades. It consists of a body of knowledge of the mechanical properties of rock, various techniques for the analysis of rock stress under some imposed perturbation, a set of established principles expressing rock mass response to load, and a logical methodology for applying these notions and techniques to real physical prob­ lems. Some of the areas where application of rock mechanics concepts have been demonstrated to be of industrial value include surface and subsurface construction, mining and other methods of mineral recovery, geothermal energy recovery and subsurface hazardous waste isolation. In many cases, the pressures of industrial demand for rigour and precision in project or process design have led to rapid evolution of the engineering discipline, and general improvement in its basis in both the geosciences and engineering mechanics. An intellectual commitment in some outstanding research centres to the proper development of rock mechanics has now resulted in a capacity for engineering design in rock not conceivable two decades ago. Mining engineering is an obvious candidate for application of rock mechanics principles in the design of excavations generated by mineral extrac­ tion. A primary concern in mining operations, either on surface or underground, is loosely termed 'ground control', i. e.

Inhalt

1 Rock mechanics and mining engineering.- 1.1 General concepts.- 1.2 Inherent complexities in rock mechanics.- 1.3 Underground mining.- 1.4 Functional interactions in mine engineering.- 1.5 Implementation of a rock mechanics programme.- 2 Stress and infinitesimal strain.- 2.1 Problem definition.- 2.2 Force and stress.- 2.3 Stress transformation.- 2.4 Principal stresses and stress invariants.- 2.5 Differential equations of static equilibrium.- 2.6 Plane problems and biaxial stress.- 2.7 Displacement and strain.- 2.8 Principal strains, strain transformation, volumetric strain and deviator strain.- 2.9 Strain compatibility equations.- 2.10 Stress-strain relations.- 2.11 Cylindrical polar co-ordinates.- 2.12 Geomechanics convention for displacement, strain and stress.- 2.13 Graphical representation of biaxial stress.- Problems.- 3 Rock mass structure.- 3.1 Introduction.- 3.2 Major types of structural features.- 3.3 Important geomechanical properties of discontinuities.- 3.4 Collecting structural data.- 3.5 Presentation of structural data.- 3.6 The hemispherical projection.- 3.7 Rock mass classification.- Problems.- 4 Rock strength and deformability.- 4.1 Introduction.- 4.2 Concepts and definitions.- 4.3 Behaviour of isotropic rock material in uniaxial compression.- 4.4 Behaviour of isotropic rock material in multiaxial compression.- 4.5 Strength criteria for isotropic rock material.- 4.6 Strength of anisotropic rock material in triaxial compression.- 4.7 Shear behaviour of discontinuities.- 4.8 Behaviour of discontinuous rock masses.- Problems.- 5 Pre-mining state of stress.- 5.1 Specification of the pre-mining state of stress.- 5.2 Factors influencing the in-situ state of stress.- 5.3 Methods of in-situ stress determination.- 5.4 Presentation of in-situ stress measurement results.- 5.5 Results of in-situ stress measurements.- Problems.- 6 Methods of stress analysis.- 6.1 Predictive methods for mine design.- 6.2 Principles of classical stress analysis.- 6.3 Closed-form solutions for simple excavation shapes.- 6.4 Computational methods of stress analysis.- 6.5 The boundary element method.- 6.6 The finite element method.- 6.7 The distinct element method.- 6.8 Hybrid computational schemes.- 7 Excavation design in massive elastic rock.- 7.1 General design methodology.- 7.2 Zone of influence of an excavation.- 7.3 Effect of planes of weakness on elastic stress distribution.- 7.4 Excavation shape and boundary stresses.- 7.5 Delineation of zones of rock failure.- 7.6 Support and reinforcement of massive rock.- Problems.- 8 Excavation design in stratified rock.- 8.1 Design factors.- 8.2 Rock mass response to mining.- 8.3 Roof bed deformation mechanics.- 8.4 Roof design procedure for plane strain.- 8.5 Roof design for square and rectangular excavations.- 8.6 Improved design procedures.- 9 Excavation design in jointed rock.- 9.1 Design factors.- 9.2 Identification of potential failure modes.- 9.3 Symmetric triangular roof prism.- 9.4 Asymmetric triangular roof prism.- 9.5 Roof stability analysis for a tetrahedral wedge.- 9.6 Pragmatic design in jointed rock.- 10 Energy changes accompanying underground mining.- 10.1 Mechanical relevance of energy changes.- 10.2 Mining consequences of energy changes.- 10.3 Spherical cavity in a hydrostatic stress field.- 10.4 General determination of released energy.- 10.5 Thin tabular excavations.- 10.6 Cut-and-fill stoping.- 11 Rock support and reinforcement.- 11.1 Terminology.- 11.2 Support and reinforcement principles.- 11.3 Rock-support interaction analysis.- 11.4 Pre-reinforcement.- 11.5 Support and reinforcement design.- 11.6 Materials and techniques.- 12 Mining methods and method selection.- 12.1 Mining excavations.- 12.2 Rock mass response to stoping activity.- 12.3 Orebody properties influencing mining method.- 12.4 Underground mining methods.- 12.5 Mining method selection.- 13 Naturally supported mining methods.- 13.1 Components of a supported mine structure.- 13.2 Field observations of pillar performance.- 13.3 Tributary area analysis of pillar support.- 13.4 Design of a stope-and-pillar layout.- 13.5 Bearing capacity of roof and floor rocks.- 13.6 Stope-and-pillar design in irregular orebodies.- 13.7 Global stability of a supported mine structure.- 13.8 Yielding pillars.- Problems.- 14 Artificially supported mining methods.- 14.1 Techniques of artificial support.- 14.2 Backfill properties and placement.- 14.3 Cut-and-fill stoping.- 14.4 Backfill applications in open stoping.- 15 Longwall and caving mining methods.- 15.1 Classification of longwall and caving mining methods.- 15.2 Longwall mining in hard rock.- 15.3 Longwall coal mining.- 15.4 Sublevel caving.- 15.5 Block caving.- Problems.- 16 Mining-induced surface subsidence.- 16.1 Types and effects of mining-induced subsidence.- 16.2 Chimney caving.- 16.3 Sinkholes in carbonate rocks.- 16.4 Discontinuous subsidence associated with caving methods of mining.- 16.5 Continuous subsidence due to the mining of tabular orebodies.- 17 Blasting mechanics.- 17.1 Blasting processes in underground mining.- 17.2 Explosives.- 17.3 Energy transmission in rock.- 17.4 Elastic models of explosive-rock interaction.- 17.5 Phenomenology of rock breakage by explosives.- 17.6 Computational models of blasting.- 17.7 Transient ground motion.- 17.8 Perimeter blasting.- 18 Monitoring rock mass performance.- 18.1 The purposes and nature of monitoring rock mass performance.- 18.2 Monitoring systems.- 18.3 Examples of monitoring rock mass performance.- Appendix 1 Basic constructions using the hemispherical projection.- A1.1 Projection of a line.- A1.2 Projection of the great circle and pole to a plane.- A1.3 Determination of the line of intersection of two planes.- A1.4 Determination of the angle between two lines in a plane.- A1.5 Determination of dip direction and true dip.- A1.6 Rotation about an inclined axis.- Appendix 2 Stresses and displacements induced by point and infinite line loads in an infinite, isotropic, elastic continuum.- A2.1 A point load (the Kelvin equations).- A2.2 An infinite line load.- Appendix 3 Calculation sequences for rock-support interaction analysis.- A3.1 Scope.- A3.2 Required support line calculations.- A3.3 Available support line calculations.- Appendix 4 Limiting equilibrium analysis of progressive hangingwall caving.- A4.1 Derivation of equations.- A4.2 Calculation sequence.- Answers to problems.- References.