M.Sc. (Geology) / Analyses show that the effect of inter-panel lag on hanging wall instability is an important factor affecting rock-fall accidents and production losses in gold mines utilising segmented longwall mining methods. The study emphasises the effect of inter-panel lag on the development of mining-induced fractures which are considered a major contributor to hangingwall instability in geologically undisturbed ground. The geology and mining geometry at Western Deep Levels, Limited, particularly at the selected research site, is outlined. The data collection, which is facilitated by the use of stereo-photogrammetry and computer-aided data handling, is described. Three types of mining-induced fracture are evident. The effects of inter-panel lag and geological inhomogeneity on the orientation and density of the mining-induced fractures are illustrated and discussed. The effects of inter-panel lag length on energy release rate are demonstrated and discussed. Microseismic event location data analyses are used to elucidate the fracturing process that takes place in the rock ahead of the mine face. Practical suggestions regarding the reduction in number and length of inter-panel lags are made, in the light of recent developments in the field of rock-burst control.

D.Ing. (Civil Engineering) / This thesis describes an Investigation Into the nature of the fracture and deformation mechanism which occur at the edges of tabular gold mining excavation. Published Information on these phenomena Is reviewed, and the necessary underground Investigation required to consolidate the previous work Is described. It Is concluded that the rock near the reef plane at the edges of these mining excavations Is subject to stresses sufficiently high to cause It to fracture through the formation of regular patterns of shear planes. These fractures can form In the solid rock some distance ahead of the mining excavation. Nearer the mining face, extension fractures form which result In slabbing or splitting of the exposed rock. An Idealization of the observed rock behavior Is proposed, which Is then incorporated with conventional boundary element techniques Into a numerical model (SEAMS) which Is capable of analyzing two Dimensional tabular mining excavations where the rock near the reef plane at the edge of the mining excavation fractures, deforms and sheds load. A Sensitivity analysis of the numerical model Is described which Identifies those mining parameters capable of being used to advantage In controlling the size of the fracture zone.