Experimental and simulation researches of loaded stress and gas environment on dynamics properties of gas-bearing coal during impact failure process

The engineering activities of deep stratigraphic resources development and space utilization are often subjected to complex stress conditions. In terms of gas-bearing coal resource mining, the dynamic mechanical properties of coal at complex loaded stress and gas environment were researched in this paper. Through the split Hopkinson pressure bar (SHPB), the dynamics experiments were performed, in which the factors of axial static load, circumferential confining pressure, internal gas pressure, and outside impact load were considered. Based on the stress and strain results of gas-bearing coal, the dynamic compressive strength and peak failure strain characteristics with strain rates were obtained. Under different loaded conditions, both dynamic compressive strength and peak failure strain added linearly along with strain rates increasing. In fact, high strain rates were the results of comprehensive loading conditions, so the effects of them to coal mechanical properties were discussed. And the improved dynamic material model of gas-bearing coal at high strain rates was proposed, which considered pre-damage of static load, hardening effects of strain rate, and weakening role of gas. Through using this model in numerical simulation, the plastic deformation and stress distribution of coal specimens subjected to impact failure were researched, which verified the results of dynamics experiments. Dynamics achievements of gas-bearing coal at complex loaded environment will provide guides for disaster prevention and promote green mining.