A geomechanics study on the safe and economical extraction of the Craig Pillar at Morrison Mine was initiated in mid-2013. Historical and future mining at Morrison raised concerns that elevated in situ stress magnitudes would be encountered during pillar extraction. A multi stage FLAC3D model was developed to simulate historical mining and extraction sequence, and the model was qualitatively calibrated based on visual observations of stress induced rock mass damage. Following adequate calibration, forward projections of the pillar extraction were simulated to assess the potential for mine induced seismicity so that the associated risks, related to rock bursting and production difficulties, could be predicted, managed and mitigated. Areas of high risk were identified based on perceived probability of seismic activity and exposure of men and equipment to rock burst hazards. High risks areas were targeted for dynamic support installation and comprehensive post-blast monitoring using the mine micro-seismic system and strategically located borehole extensometers. An overview the numerical model calibration process is presented to demonstrate that, in the absence of extensive instrumentation or micro-seismic data, qualitative model calibration can be an effective tool and a reasonable method in assessing stress damage related risks to mine operations.

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