53rd U.S. Rock Mechanics/Geomechanics Symposium,
New York City, New York
2019. American Rock Mechanics Association
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ABSTRACT: Evaluating stope performance is important for improving stope stability, production efficiency, and profitability. Underground mines are Operating at greater depths where workers and excavations are exposed to hazards such as seismic events, which are not addressed by standard empirical stope analysis. A stope database was created for 114 primary stopes (2.7–3 km below ground level) mined between November 2013 and August 2018. It considers geometrical, geomechanical, operational, and seismological parameters. To assess stope performance, reconciliation between the mined and the designed stope geometries was performed for the entire stope volume and on a surface-by-surface basis. Common stope performance metrics such as overbreak (OB), underbreak (UB), and equivalent linear overbreak sloughing were measured, as were other metrics like rock and backfill overbreak. Results of the univariate analysis showed the OB for the hangingwall of stope type A and the UB for the east and west walls of stope type B were the critical underperforming parameters. Bivariate analysis showed trends linking OB to Richter scale seismic events, rock quality designation, stand-up time, and spatial distribution. Trends were also found linking UB to planned volume and borehole standoff.
Open stoping is a high-production and low-cost mining method to extract ore. To maximize revenue, stopes must be designed to minimize offset from the planned geometry while maximizing stope volume. Thus, stability and performance analyses are necessary for efficient stope design. These analyses take into account diverse factors such as the designed geometry, geomechanical attributes of the rock mass, operational parameters, and the rock mass response to mining. For deep mines that are seismically active, rock mass response can be quantified using seismic event monitoring. Mine seismicity is associated with the mining process (blasting) and high stress conditions (Brown and Hudyma, 2016). Seismicity represents a major hazard that changes the way we interact with the mining environment and it should be considered in stope stability analysis for deep mining. Existing empirical tools for stope design were not developed to account for seismically-active mines and should be used with great caution in such an environment.
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