Numerical and Field Investigations of Dynamic Failure Caused by Mining-Induced Tremor Based on Focal Mechanism

The rupture mechanism of a seismic source governs the spatiotemporal distribution and intensity characteristics of the radiated stress-wave field and significantly affects the dynamic disasters of roadways triggered by seismic disturbances. In this study, we propose a method to simulate seismic sources with arbitrary rupture mechanisms based on moment-tensor theory. Subsequently, using the dynamic instability of tailentry at the 63_upper06 working face Dongtan Coal Mine induced by an “8.30” strong mining-induced tremor as the engineering context, we calibrate the characteristics of the seismic source via moment-tensor inversion. The entire process from the excitation of the strong seismic source, the propagation of stress waves, and the eventual triggering of roadway failure and instability is simulated. Concurrently, variables representing P- and S-waves are formulated based on the relationship between the vibration and propagation directions, and the roles of both waves in the dynamic instability of the tailentry are investigated. The results indicate that (1) during the mining at the 63_upper06 working face, concentrated stress is transferred to the strong seismic-source area and the advanced area of the coal wall at the tailentry, thus providing static load conditions for the occurrence of strong seismic events and the dynamic instability of the tailentry. (2) P-waves primarily exert tensile and compressive stresses along the propagation direction in the medium, thereby resulting in localized stress variations, whereas S-waves induce shear effects between adjacent wave paths because of their opposing velocity directions. (3) The “8.30” strong mining-induced tremor is characterized by tensile failure, with P-waves exhibiting the greatest intensity in the horizontal and vertical directions, and S-waves exhibiting the highest intensity at an angle of 45 ° from the seismic source, thus contributing significantly to the damage and instability of the roadway owing to the relative spatial position between the roadway and seismic source. (4) The 100 m range ahead of the coal wall at the tailentry experiences significantly greater static and dynamic disturbances compared with other areas, thus resulting in the most severe damage.