Strengths and weaknesses of using elastic numerical modelling in mine design at the Callie underground mine

摘要

Site geotechnical engineers are often reliant on elastic numerical modelling to assist with mine design and the selection of appropriate stoping sequences. Although plastic numerical models are often preferred, site engineers do not have access, or the ability, to use these codes. Hence, three-dimensional elasto-plastic analyses are not viable at most sites. The challenge for the site engineers is to use the available tools most effectively, and present the results in a way that most clearly communicates the mine design requirements.A first step is to establish a mine design criteria, which should not be confused with failure criteria. Mine design criteria correlate observed conditions with modelled stress states at a specific location. An effective mine design criterion then enables the assessment of probable future ground conditions on modelled stress states. Many design criteria could be used concurrently on a single mine site, as different failure mechanisms cannot be assessed with the same criterion. Comparing actual conditions or measurements with modelled stress states is the only way to establish a correlation that could be generalised into a design criterion. During the back analysis process, the actual response of the rock mass is recorded and categorised with a damage classification system and compared to different modelling result parameters. Different correlations are evaluated, and the criterion with the most consistent performance selected to make predictions of future ground conditions.This paper shares case studies where design criteria were successfully used at the Callie underground mine, and discusses the potential application areas for future evaluations.