Application of short rockbolts in ultradeep tabular stoping

Abstract

Most rock related fatalities and injuries in South African gold mines occur in the stope face area. These mines generally do not use rockbolts to support this area. This paper describes short rockbolt applications in the stope face area in a narrow tabular ultradeep Carbon Leader stope. The project began with the geotechnical definition of the generic Carbon Leader Reef hangingwall and the design of a short rockbolt support system to stabilise this hangingwall. In the paper the implementation efficiency of the bolting system is described. The quantification of ground conditions was undertaken by comparing bolted and unbolted portions of the stope face. This was done by using hangingwall profiling and stoping width measurements. Some numerical modelling is presented showing the benefits of bolting in the Carbon Leader Reef geotechnical area. The paper then briefly covers short bolt reinforcement design problems that still have to be overcome, such as quantifying and matching the bolt requirements of strength and yieldability and the reinforcement zone of influence of bolts, which is related to bolt spacing, in seismically active conditions. Empirical data under seismically active conditions is still required for rockbolt design purposes.