Three-dimensional analysis of lenticular orebodies using displacement discontinuity elements.

摘要

The most appropriate numerical techniques for the analysis and design of excavations, pillars and mining sequences in lenticular orebodies is the displacement discontinuity method (DDM). This thesis examines three important facets of the DDM and makes improvements in these areas that affect the efficiency of the method in its application to the crack-type problems, arising in the mining of lenticular or seam deposits.;The introduction of the concept of node sharing between adjacent elements into the DDM, is the first aspect covered in the thesis. The node-sharing formulation of the DDM was made possible after the introduction of a new and unified framework for evaluating the singular boundary integrals that exist in the Green's functions of the displacement discontinuity method. The new integration method is based on the continuation approach.;The formulation of a new displacement discontinuity element---the enhanced displacement discontinuity (EDD) element---was the second major undertaking of the thesis. This new formulation provides information on the in-plane (confinement) stresses in an element, something the conventional DDM does not consider. The EDD element creates an automated and more flexible way of modelling different degrees of confinement, expected to occur in unmined orebody zones (i.e. pillars and abutments). With the inclusion of confinement into the formulation of the enhanced DD element, it can be readily used to analyse yielding pillars, since all components of the stress tensor at a point in a material are explicitly taken into account.;Finally, the thesis looked at the development of a methodology in the EDDM for modelling the post-peak behaviour of pillars. The progressive failure procedure was incorporated into the EDDM to create a program for simulating post-failure pillar response. The progressive failure procedure relies on a simple quasi-elastic constitutive relationship, and uncomplicated failure criteria to model failed pillar material.