Nonlinear boundary element analysis of a rock mass with discontinuities

A boundary element model was developed for stress/stability analysis of underground excavations in the vicinity of faults. The boundary element formulation adopts the Fictitious Stress Method for the simulation of excavation boundaries and the Displacement Discontinuity Method for the representation of faults. With the assumption that deformations and stress changes can generally be attributed to the presence of faults rather than to elastoplasticity of the rock mass, the numerical model employed a linear elastic constitutive relation for the rock, and nonlinear behaviour for the fault. This assumption is particularly justified in hard rock environment. Following a comprehensive review of constitutive models for rock joints, both deformation and peak strength models were incorporated for modelling the mechanical behaviour of the fault. Deformation or stiffness models include Goodman's constant stiffness model and Barton-Bandis' nonlinear model. The latter, considers the effect of a wide range of parameters such as coupling between shear and normal stresses and displacement, joint closure, joint separation, hardening followed by postpeak or residual behaviour. Peak strength models include Mohr-Coulomb and Barton-Bandis which employs a mobilized nonlinear shear strength envelope. An incremental, in situ stress relaxation algorithm is developed and implemented for the nonlinear analysis of the faults.;Model verification was done by a comparison of its predictions with previously published results found in the literature. The comparison showed excellent agreement. A model sensitivity analysis was then carried out to compare the response of different discontinuity models. A case study of an underground hard rock mine was conducted to examine the stability of a mining ore zone intersected by faults.;A user friendly graphical interface was developed to help generate the data and interpret the output results more efficiently.