| One of the primary safety and production problems associated with deep mining is rockbursting. The primary modes of rockbursting generally recognized in the literature are volume instabilities associated with localized stress concentrations at the mining face and shear-failure, either on pre-existing geologic discontinuities or through formation of new shearing fractures. The two approaches commonly used in the mining industry in dealing with this problem include: (1) attempts at real-time prediction using the data produced by in-mine seismic monitoring systems; and (2) mine planning through the use of numerical representations of seismic source mechanisms. This thesis addresses the latter approach and presents a methodology for employing numerical methods for representation of seismicity related to the predominant shear-failure mode.; The problem of mine seismicity is, in general, stochastic in nature due to the random distribution of geologic structure in the rock mass. A technique is presented for random generation of a "representative" rock mass using probability density functions of the structural geometry as derived from detailed line mapping. The mining-induced stress state, determined using a separate numerical analysis, is mapped onto each structural feature, and the slip potential, slip area, ride and approximate seismic moment determined using the Excess Shear Stress technique of Ryder. The extensive seismological data base available at many mines is used initially as a means of verification of the model, which is, in turn, used for relative assessments of the seismic potential of varying mining methods or sequences.; A demonstration of the method is given for a series of parameter studies of the seismicity associated with a horizontal, thin-reef, longwall excavation at great depth. The impact on seismic response of the rock mass due to variability of the geometric properties and frictional strength of the structures and to the in situ stress state are examined through the use of standard Gutenburg-Richter plots of event frequency and magnitude. A test of the model is then presented for analysis of the seismicity at the Lucky Friday Mine in Idaho, showing good comparison for reasonable values of the frictional properties of the structures. |
