Analysis of pillar/rockmass failure and propagation dynamics due to mining in hard rock Platinum Mines

Mushangwe, Patrick Chenjerai
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The propagation of failure of a pillar system has often resulted in catastrophic consequences, this research establishes key variables that govern failure propagation in hard rock platinum mines. In order to critically analyse failure propagation, the available literature was reviewed to guide the research on key focus areas that may govern propagation. A review of the global and local geotechnical environment was done leading into detailed analysis of the data and rock mass behaviour from a case study mine to establish key variables and behaviour correlations. Available literature point towards failure largely due to mining practice issues and to some extent ground conditions. Joint orientation has been proven, in literature, to have an influence on the strength of pillar systems in particular when the joints dip adversely at 45° to the pillar / loading axis. This research also establishes that ground conditions, as described by rock mass quality and the effect of major sub-horizontal shear structures on pillar systems, have significant influence on the direction of failure propagation. This research further establishes that the failure prefers a direction 45° to the major vertical to subvertical joint set. The angle between the direction of migration and major subvertical joint is a phenomenon that had not been largely explored in terms of influence on failure propagation. The influence of mining practice issues, like pillar position and factor of safety, on failure direction is comparatively lower. This research also shows that barrier pillars should be designed taking into account the strike of major subvertical joint sets/structures in order to improve the ability to stop the propagation of failure. The analysis of the ground monitoring parameters, closure rates in particular, can be used to inform evacuation plans and reduce the impact of failure propagation on safety and production.
A research report submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in fulfillment of the requirements for the degree of Master of Science in Engineering, Johannesburg 2018
Mushangwe, Patrick Chenjerai (2018) Analysis of pillar/rockmass failure and propagation dynamics due to mining in hard rock Platinum Mines, University of the Witwatersrand, Johannesburg, <>