Strong Mining-Induced Earthquakes Produced by the Fracturing of Key Strata during Deep Coal Mining

Abstract

As coalmines extend more deeply, strong mining-induced earthquakes occur more frequently; these seriously threaten the safety of underground miners and aboveground residents, as well as the productivity and effectiveness of mining activities. The distribution of mining-induced earthquake characteristics and hard roof breaking mechanisms are analyzed and revealed using the methods of field monitoring and theoretical analysis, and prevention and control technology were proposed and applied in a field application, for a typical dynamic disaster problem at Dongtan Coalmine. As indicated by the results, strong mining-induced earthquakes (E ≥ 105 J) were mostly related to the coordinated failure of several strata, and the migration and fracture of the overlying strata led to significant subsidence of the surface. As mining activities advance, the abutment stress within the coal seam in front of the coalface will dynamically change and be transferred more deeply into the coal seam under the influence of a mining-induced earthquake. Based on the mechanical behavior, the fracture structures of the overlying multiplicity of key strata are divided into main and subordinate “O-X” types. As the coal is exploited, the O-X scope gradually increases from the near field to the far field. As indicated by the field application, the implementation of deep-hole blasting could effectively weaken the integrity of the thick and hard rock strata and change the length of the overhang roof, so as to reduce the risk of strong mining-induced earthquakes, i.e., the incidence of strong mining-induced earthquakes above 5 × 105 J would be significantly reduced. Meanwhile, the frequency of rock strata collapse increases, and the average distance from the epicenter centrum to the coal seam is reduced to 47 m. The governing effect is good. We expect that the results of this study could provide references for dynamic disaster governance in similar mine areas.