Experimental study on the influence factors of coal containing gas during the fracture process

The fracture mechanical characteristic of coal containing gas is one of the most important influencing factors of coal and gas outburst disaster. In this paper, by using the self-developed triaxial servo-controlled seepage equipment for thermo-fluid-solid coupling of coal containing methane, conventional triaxial compression tests of complete process of coal containing gas are carried out and the influence mechanism of factors in fracture process of coal containing gas is discussed. The result shows that: (i) gas seepage changes the mechanical characteristics of coal body and it makes the strength of coal containing gas decrease and exceeds its failure process; (ii) in the fracture process of coal containing methane, the higher is the gas pressure, the lower is the intensity strength of coal containing gas. Gas pressure promotes the spreading and stretching of inner pores and it also makes it easier to emit gas; (iii) under the same gas pressure conditions, the confining pressure is larger, the more difficult is the gas flow and the greater is the triaxial compressive strength of coal containing gas, but it will easily form a high gas pressure zone in the coal body and accumulate more gas compression energy, which is the main energy source for coal and gas outburst.