Influence of regional support systems (pillars and backfill) on local areas and internal support requirements adjacent to that regional support.

Abstract

The general influence of regional support on local stope conditions is not always well understood and a number of anomalous conditions, both positive and negative, have been reported in the vicinity of regional supports. Mining in similar rock conditions has apparently resulted in very different conditions, depending on the type of regional support used in the region. An incomplete understanding exists of the effect of regional supports on the local conditions around them and the criteria that should be adopted for the safe design of local support in the vicinity of the regional support. There are many examples in the industry of anomalous conditions in the vicinity of regional support, sometimes good and sometimes adverse, and the reasons for such conditions need to be fully investigated and understood. The topic of local support requirements adjacent to regional support is, therefore, investigated with the intention of providing recommendations and best-practice design guidelines for this potentially problematic zone in gold and platinum stopes. Extensive ground motion and closure monitoring, studies of hangingwall conditions and numerical modelling analyses were carried out for a selection of different regional support (i.e. pillar and backfill) layout and reef horizon combinations. Although evidence arose from this work of differences in conditions possibly requiring different support design, it was felt that no absolute values could be provided for relevant design parameters. Rather, it was decided that a modified support design methodology be proposed that accounts for the additional influencing factors pertaining to the zone adjacent to regional support.