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Geotechnical Engineering

 

Interstate Technical Group on Abandoned Underground Mines
Fourth Biennial Abandoned Underground Mine Workshop

Abstract: Numerical Modelling, a Key Engineering Tool for Long-Term Site Stability Assessment

Marc C. Bétournay
Natural Resources Canada

Evaluating long-term rock mass degradation is of primary importance in understanding the potential for movements which can affect surface integrity and the infrastructure that may be present.

A powerful tool is required to return a representative evaluation of long-term behavior and be successful in anticipating the location of rock mass movements. This tool must also take into consideration the particular nature of the rock mass on site, existing openings, and potential failure modes. Conventional theoretical rock mechanics approaches (e.g. beams, plates, arches, etc.) will not adequately represent actual shallow stope failure behavior, i.e. the nature, extent or relative potential for shallow stope failures in discontinuous or weak rock masses, which host the majority of failures. Only in certain circumstances such as intact rock failure can these be considered.

Numerical modelling is the most flexible and representative technique that can be routinely applied. It provides the possibility of obtaining approximate solutions to the behavior of surface and/or underground excavations while considering a number of influencing factors. However, the selection of a particular numerical code depends on proper understanding of the case and the anticipated failure mechanisms.

This presentation will briefly introduce the technique, and focus on particular application of modelling types (finite elements, boundary elements, distinct elements) to mining and rock mass conditions (metal and non-metal) and how they can represent and approximate the possible failure mechanisms. This technique will be compared to limit equilibrium equations and empirical approaches in order to outline its advantages and disadvantages. Case studies will be presented in which the effect of variable types of rock masses and openings is measured on a local scale and a regional scale, and the impact their displacements has on existing infrastructure.

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Updated: 04/07/2011

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