Numerical simulation of curviplanar fractures associated with gas outbursts

Abstract

Abstract Coal and gas outburst (outburst) is a principal hazard in underground coal mining. Closely spaced curviplanar mining induced cleavage is often observed around outburst cavities in underground development faces, indicating a mechanical process of outburst development in terms of coal failure. In this paper, we employed FRACOD, a 2D explicit fracture simulation code based on displacement discontinuity method, to simulate fracture initiation and propagation around a development face to investigate the mechanism underlying the occurrence of mining-induced cleavage. A 2D model comprising a working seam, roof strata and floor strata was constructed. The simulation results show a pattern of fracture propagation ahead of the face similar to those observed in field and laboratory experiments, irrespective whether a soft inclusion is present. However, when there is a soft inclusion, more open and slipping fractures are generated. Such types of fractures are deemed to facilitate fast gas desorption and pressure building up, creating conducive conditions for outburst initiation and propagation.