Quantitative Energy-Based Evaluation of the Intensity of Mining-Induced Seismic Activity in a Fractured Rock Mass
To elucidate the mechanism of seismic activity taking place away from extracted stopes in underground mines, this study focuses on the influence of a fracture network on the intensity of seismic activity from an energy point of view. Four seismically active regions with local geological structures and one non-active region were identified on 3880 level in the 100 and 900 Orebody areas at Copper Cliff Mine. Subsequently, cube-shaped discrete element method (DEM) models with fracture networks of the regions were generated. The stress analysis for two regions out of the four revealed that the elastic strain energy related to tensile failure quantitatively agrees well with the cumulative radiated seismic energy of the microseismic database. For the other two regions, the computed tensile failure-related strain energy was smaller than the radiated energy, leading to the postulation that the seismicity in the region was caused by violent shear rupture. The postulation was verified by quantitatively computing energy released by brittle shear failure. Then, for the seismically inactive region, the DEM analysis yielded quite small tensile failure-related strain energy. Considering these results, it was concluded that strain energy stored within rock mass with tensile failure potential can be used as an indicator for the intensity of seismicity taking place away from extracted stopes. Also, the seismic energy calculation methodology can give a reasonable estimation of seismic energy released by shear rupture taking place in geologically abnormal regions. These findings should lay a foundation for the further development of a guideline and/or simple formulation to evaluate the risk for mining-induced seismicity.