Effects of faults and stress on open stope design.

摘要

The thesis is focused on evaluating the effects of faults on the stability of open stopes. Faults are often the source for open stope overbreak and dilution. How faults affect stope stability is still not well understood. This thesis identifies and evaluates the fault characteristics that adversely affect stope stability.; The two main goals of the thesis are to: (1) Determine how faults affect the stability of stopes and to provide a method for estimating overbreak due to faults, and (2) Develop a fault factor for incorporation into the stability graph to improve the method.; To overcome the weakness in the stability graph method resulting from faults, a methodology for determining a fault factor for incorporation into an empirical design procedure for open stopes, using the stability graph method is developed. The method is applied to case histories from Kidd Mine in Canada.; Statistical tools are presented based on the likelihood ratio statistic to optimally define the boundaries between stability zones in the stability graph, and to determine the reliability of a stability graph.; The main conclusions of the thesis are as follows: (1) For stopes with nearby faults, the faults affect the stability of the stopes by their tendency to increase the zone of low stress or relaxation near the stopes. (2) For a stope with a nearby fault, the angle between the fault and the stope surface and the relative position of the fault are the most important factors controlling the severity of fault-related overbreak. (3) The effects of faults on open stope stability are influenced by stope geometry, distance of fault from stope surface and in situ stress. (4) Numerical models can be used to estimate the extent of overbreak due to a fault near a stope surface, and the parameter for measuring fault-related overbreak is defined as the increase in overbreak for a stope with a fault compared to one without a fault. The method can be used in estimating active support lengths and capacity requirements.; The application of the results of this thesis in the mining industry should lead to improved understanding of fault effects on open stope stability and increased confidence in the use of the stability graph as a robust empirical design tool. (Abstract shortened by UMI.)