The need for improved layout design criteria for deep tabular stopes

This paper was compiled to highlight the need for additional research in the area of layout design criteria for deep gold mines. It describes aspects related to two popular design criteria used in the deep gold mines of South Africa, namely average pillar stress (APS) and energy release rate (ERR). The early layout designs in the gold mines were based on trial and error and most of the recommendations of the 1924 Witwatersrand Rock Burst Committee are still valid in modern times. The introduction of APS and ERR assisted greatly to reduce areas of high stress concentrations. Both criteria are of limited use, however, as it is not clear what the maximum value of APS for remnants should be and ERR has a significant drawback as no dissipative mechanisms are incorporated to allow for non-violent failure of the rock mass. A numerical modelling study is described that illustrates the effect of total closure on the simulated APS and ERR values of remnants. It is recommended that stress measurements be conducted below remnant areas to better calibrate the numerical models. The need for additional rock mass monitoring to supplement the design criteria is also discussed.