Case of Rock Burst Danger and Its Prediction and Prevention in Tunneling and Mining Period at an Irregular Coal Face

Abstract

Irregular coal faces, ineluctable in coal mines within the eastern mining area in China owing to its complex geological condition, face higher rock burst danger because of their high-stress concentration and complicated spatial structure. Considering geological characteristics, rock burst liability and in situ stress in the 3303 irregular coal face at the Yangcheng coal mine, rock burst danger during tunneling and mining was analyzed to select targeted mitigation measures. The results indicate that the dynamic pressure adjustment movement (DPAM) of the roof plays an important role in the occurrence of rock bursts. Rock burst danger in tunneling of the tailgate is caused by the combination of dynamic and static stress, where the static stress is from the large depth and nearby faults, and the dynamic stress is from the DPAM of the roof above the near the 3301 mined-out area. The tunneling construction was halted for 3 months to reduce the high dynamic stress σd, and destressing large-diameter holes were drilled to reduce the static stress σ0. The rest of the tunneling construction was deemed safe. Furthermore, the rock burst danger in mining was divided into two types: I (high static stress type) and II (high dynamic stress type). The former is located at the triangular coal pillar and within a 20–150 m range ahead of the coal face. The latter acts on the tailgate caused by the intense mine seismic activity arising from the secondary DPAM. More destress holes are drilled within the danger zones of the former to release the stress fully. A combination of rigid support and flexible support (i.e., single props, double T-steel shed, bolt, anchor rope and anchor net) and monitoring is an efficient method to address the latter. The results show safe mining during the rest of the mining period. This paper provides a reference for prevention and control of rock burst for similar coal faces.