Investigating the destressing mechanism of roof deep-hole blasting for mitigating rock bursts in underground coal mines

Abstract

Rock burst is one of the challenging problems restricting the safe and high-efficiency mining of deep-buried coal seams, and roof deep-hole blasting (RDHB) is commonly practiced in highly burst-prone zones in coal mines to control rock bursts. This research focuses on the interpretation of the destressing mechanisms of RDHB and its application for mitigating rock bursts. The theoretical analysis results show that RDHB reduces the local stress and stiffness of roof rock, thereby reducing the potential of coal failure and changing the energy release mode of the roof-coal-floor system. Then, a strain-softening numerical model based on the Hoek-Brown failure criterion was developed to evaluate the destressing efficiency of RDHB in selected underground coal mines. Further, RDHB was applied to an isolated coal pillar in a coal mine for mitigating rock bursts, and the stress variation of the isolated coal pillar before and after RDHB was detected using active seismic velocity tomography. The results illustrate that RDHB can effectively reduce stress concentration in the target area and drive stress to the surrounding areas. Moreover, due to the high correlation between in situ measurement results and numerical results, the numerical evaluation of RDHB efficiency may be successfully applied to regular use. Finally, a method for evaluating the destressing effect of RDHB based on blasting seismic energy was discussed and applied.