Numerical investigation of anisotropic and time-dependent behaviours of foliated rock mass

Abstract

Squeezing ground conditions have become a major challenge faced by underground hard rock mines exploiting reserves at greater depth and in a high-stress environment. This thesis investigates the influence of various parameters on the severity of squeezing ground conditions in foliated rock mass utilizing continuum numerical modelling in FLAC3D finite difference code. A series of numerical simulations were carried out for selected cases of two mines subject to squeezing ground conditions to investigate the rock mass failure mechanisms, the influence of various geological, mining and stress parameters, time dependence and the role of rock reinforcements. The numerical models were calibrated using field data and underground observations. The numerical models were successful in capturing the observed failure mechanisms at the two mines. The calibrated numerical models were used to investigate the influence of varying interception angle, excavation shape, excavation over-break, mining depth and parallel excavations on the severity of squeezing ground conditions utilizing ubiquitous joint model. The time dependence in the numerical models was simulated by using the power ubiquitous model and the role of various rock reinforcement elements was simulated by using structural elements. The results of the numerical simulations were found to be in good agreement with the underground convergence data and observations. The modelling methodology used in the thesis can be used to improve the understanding of the anisotropic and time-dependent behaviour of the foliated rock mass to various mining conditions. The methodology can also be used to evaluate performance of various rock reinforcement strategies and elements that are used in squeezing ground conditions.