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Two-dimensional numerical models have been shown to provide a conservative estimate of slope stability when open pits interact with underground voids, such as old workings. The results of using both two- and three-dimensional numerical analysis are presented, and illustrated through two brief case studies. One is on the Cresson mine in Colorado, USA, and the other on a large Chilean open pit., Two-dimensional numerical models have been shown to provide a conservative estimate of slope stability when open pits interact with underground voids, such as old workings. The results of using both two- and three-dimensional numerical analysis are presented, and illustrated through two brief case studies. One is on the Cresson mine in Colorado, USA, and the other on a large Chilean open pit.

A method of analysis is presented for the design of excavations in stratified rock masses. The method involves none of the assumptions and simplifications implicit in the elementary model. The excavation far-field rock is modelled as a transversely isotropic continuum, and the near-field rock as a set of discrete, joint-defined blocks. The resulting computational scheme is developed by coupling discrete element and boundary element analysis and is used in initial studies on the response of a bedded rock mass to development of an excavation, of the effect of the field horizontal stress component on roof behaviour, and of rock bolt performance in roof bed control., A method of analysis is presented for the design of excavations in stratified rock masses. The method involves none of the assumptions and simplifications implicit in the elementary model. The excavation far-field rock is modelled as a transversely isotropic continuum, and the near-field rock as a set of discrete, joint-defined blocks. The resulting computational scheme is developed by coupling discrete element and boundary element analysis and is used in initial studies on the response of a bedded rock mass to development of an excavation, of the effect of the field horizontal stress component on roof behaviour, and of rock bolt performance in roof bed control.

The applications of discrete fracture networks (DFNs) in mining and civil engineering are reviewed. Mining geomechanics applications include in synthetic rock mass models for estimating rock mass strengths, fragmentation and micro-seismicity in caving mines and to estimate anisotropic rock mass deformability and strength in open-cast mines, kinematic analysis of block stability in underground and open-pit excavations, determination of equivalent porous media for flow estimates and pore pressure distributions in open-cast mines, and the direct evaluation of large-scale slope stability. The use of DFNs in civil engineering is less common, but more DFN-related research has been conducted in support of nuclear waste repositories than for mining, as flow and transport properties of fractured rock and the associated predictions are of critical importance for the repositories. Challenges are discussed relating to the validation and simplification of DFN models., The applications of discrete fracture networks (DFNs) in mining and civil engineering are reviewed. Mining geomechanics applications include in synthetic rock mass models for estimating rock mass strengths, fragmentation and micro-seismicity in caving mines and to estimate anisotropic rock mass deformability and strength in open-cast mines, kinematic analysis of block stability in underground and open-pit excavations, determination of equivalent porous media for flow estimates and pore pressure distributions in open-cast mines, and the direct evaluation of large-scale slope stability. The use of DFNs in civil engineering is less common, but more DFN-related research has been conducted in support of nuclear waste repositories than for mining, as flow and transport properties of fractured rock and the associated predictions are of critical importance for the repositories. Challenges are discussed relating to the validation and simplification of DFN models.

The underground panel caving method used at the Grace mine in SE Pennsylvania to extract iron ore, in the period 1951-1977, has resulted in significant surface subsidence. Upon recovery of the water table after mining, a lake has formed over much of the subsided area. Before redevelopment of the abandoned mine site for residential and light industrial usage, an investigation of the subsidence zone of influence and the potential for further subsidence has been undertaken. The evolution of subsidence crater and trough is traced, the methology used to evaluate and validate a model outlined and its prediction of long-term residual subsidence and subsurface erosion assessed., The underground panel caving method used at the Grace mine in SE Pennsylvania to extract iron ore, in the period 1951-1977, has resulted in significant surface subsidence. Upon recovery of the water table after mining, a lake has formed over much of the subsided area. Before redevelopment of the abandoned mine site for residential and light industrial usage, an investigation of the subsidence zone of influence and the potential for further subsidence has been undertaken. The evolution of subsidence crater and trough is traced, the methology used to evaluate and validate a model outlined and its prediction of long-term residual subsidence and subsurface erosion assessed.

The ability to model frictional sliding behaviour, including unstable or stick-slip behaviour, is important for applications involving earthquake mechanics and the stability of jointed rock masses, particularly the assessment of rockburst potential. In this paper, experimentally determined rate and state variable friction constitutive laws, in which the coefficient of friction depends upon the instantaneous velocity of sliding as well as upon phenomenological state variables which evolve with ongoing slip, have been incorporated into a distinct element code in which inertial effects are fully included., The ability to model frictional sliding behaviour, including unstable or stick-slip behaviour, is important for applications involving earthquake mechanics and the stability of jointed rock masses, particularly the assessment of rockburst potential. In this paper, experimentally determined rate and state variable friction constitutive laws, in which the coefficient of friction depends upon the instantaneous velocity of sliding as well as upon phenomenological state variables which evolve with ongoing slip, have been incorporated into a distinct element code in which inertial effects are fully included.

Analysis of reinforced excavations in jointed rock requires that the functions of reinforcement be considered explicitly. This can be achieved in a computational model by calculating, for each reinforcement element, the forces generated by displacements across the discontinuity through which the element passes. Simple force-displacement relations are exploited to describe both shear and axial behaviour of reinforcement element. Large shear displacements are assumed to be accompanied by simple geometric changes in an element where it crosses a discontinuity., Analysis of reinforced excavations in jointed rock requires that the functions of reinforcement be considered explicitly. This can be achieved in a computational model by calculating, for each reinforcement element, the forces generated by displacements across the discontinuity through which the element passes. Simple force-displacement relations are exploited to describe both shear and axial behaviour of reinforcement element. Large shear displacements are assumed to be accompanied by simple geometric changes in an element where it crosses a discontinuity.

A computational scheme is presented for the analysis of stresses and displacements in highly jointed rock surrounding underground excavations. The near-field rock is modelled as a set of distinct element blocks defined by joints. The explicit formulation of the distinct element method is well suited for considering large displacements and rotations, complex joint constitutive behaviour, rock support and reinforcement, and body forces. The far-field rock is modelled as a transversely isotropic continuum through a boundary element scheme. The two methods are coupled together by satisfying the equilibrium conditions of the traction equilibrium and continuity of displacement at the interface between the two domains, at each iteration of the solution process. Verification of the scheme is demonstrated through various analyses of circular excavations in regularly jointed media., A computational scheme is presented for the analysis of stresses and displacements in highly jointed rock surrounding underground excavations. The near-field rock is modelled as a set of distinct element blocks defined by joints. The explicit formulation of the distinct element method is well suited for considering large displacements and rotations, complex joint constitutive behaviour, rock support and reinforcement, and body forces. The far-field rock is modelled as a transversely isotropic continuum through a boundary element scheme. The two methods are coupled together by satisfying the equilibrium conditions of the traction equilibrium and continuity of displacement at the interface between the two domains, at each iteration of the solution process. Verification of the scheme is demonstrated through various analyses of circular excavations in regularly jointed media.