Application of a routine moment tensor inversion capability in the development of a new design consideration for the stability of foundations of stabilising pillars in deep level gold mines and pillars in intermediate depth hard rock mines

Abstract

Results of SIMRAC project GAP 223 showed that stabilizing pillar-related back area seismicity was not related to the width of the pillar, nor to the dip spans of the stopes supported by the pillar. Pillar associated seismicity initiated in the back area at Western Deep Levels when the APS was, on average, 1.2 times the UCS of the footwall rock. Earlier work showed that pillar foundation (footwall and hangingwall) associated seismicity occurred in the range 65m – 95m behind the face. In both of these cases, the APS was not the full load that the pillar would receive. It was hypothesized that these histories of “foundation failure”, are, rather, symptoms of the yielding of the pillar foundation system. Thus the point of interest for design purposes could lie in the yield point of the pillar foundation. The aim of this project therefore was to use a moment tensor inversion technique to establish design criteria for the prediction of the yield point of stabilizing pillar/foundation system in deep level gold mines