Analysis of Rock Mass Stability Based on Mining-Induced Seismicity: A Case Study at the Hongtoushan Copper Mine in China

In deep metal mines, seismic hazards (for example, rock bursts and roof collapses) occur easily due to the influence of complicated geological conditions, high-stress environments and strong blast disturbances. A microseismic (MS) monitoring technique was used to evaluate rock mass stability in the Hongtoushan copper mine in China. The changes in the multiple MS parameters, including the apparent volume, energy index, spatial correlation length, fractal dimension and b value, during the mining process were presented. The results showed that the MS sequences decayed following Omori’s power-law and that the rock mass returned to a relatively stable state after approximately 20 days of blasting. After each stoping, the proportion of large-scale fractures increased, the MS events become more concentrated, and the long-range correlations of the rock mass weakened. These changes caused b value, fractal characteristics and spatial correlation length to decrease significantly. Although the risk of a large-scale rock mass failure was reduced, the risk of a local failure increased. As the mining process continued, stress and deformation gradually increased, and the areas with concentrated stress and large deformation were not consistent. Control measures for hazards should be implemented according to the corresponding occurrence mechanisms as determined from the differences in the rock mass physics mechanics.