Analysis of gas migration law in coal seam in structural zone

Coal and gas outburst is a common dynamic disaster in the process of coal seam resource recovery, which seriously affects the safety of production operations, and the tectonic zone is the main area where coal and gas outburst disasters commonly occur. In order to deeply understand the mechanism of coal and gas outburst in the structural area, taking the Wuzhuang reverse fault in Daping Coal Mine as the main research body, a two-dimensional mine geological model including the fault structure was established through the COMSOL numerical simulation software. Then the solid mechanics and Darcy’s law model were coupled to study the in-situ stress, gas pressure distribution and gas migration law of the coal seam working face at different distancesfrom the fault. The results of the study show that ① when the working face is 450 m away from the fault, the stress of the working face increases to twice the stress of the original rock, the gas flow state is laminar flow, and the gas pressure is 〖JP2〗the largest at 20 m in front of the working face; ② When the working face is 50 m away from the fault, the working face stress is increased to more than three times that of the original rock, the gas flow state changes from laminar flow to turbulent flow, and the gas pressure within 30 m infront of the working face is at a high value; ③ After mining, the gas seepage velocity increases rapidly and reaches the maximum after 1 h, which is a high-risk time period for coal and gas outburst disasters, and then the seepage velocity will gradually decrease and the risk of outburst will gradually decrease. Therefore, in order to ensure the safety of recovery, it is important to not only reduce the stress state of the coal seam by water injection and pre-excavation of pressure relief chambers prior to recovery, 〖JP2〗but also to reduce the gas pressure by hydraulic punching, gas extraction or other effective means. By studying the gas migration law in coal seams after mining, it can provide an effective basis for ventilation design and prevention of coal and gas disasters.