Methane drainage has become an integral part of modern coal mining operations in low-permeable coal seams, thus some measures such as hydraulic fracturing and stress reducing are used to improve the permeability of coal scams and secure the safety and effectiveness of coal mining activities. In the paper, a coupled gas flow model which incorporated stress, damage and permeability evolution was briefly described and employed to simulate the changes of gas pressure around the boreholes in low-permeable coal seam under hydraulic fracturing, and the seepage mechanism of gas flow was analyzed. Numerical simulations show that the content of gas release was remarkably increased and the gas pressure around the borehole was obviously reduced, which is well agreement with the field findings. The work in the present paper is of great significance to further investigate and understand the mechanism of gas permeability evolution and the mechanism of gas drainage under hydraulic fracturing in both theory and practice.
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