Study on Gas Migration Law for Low Permeability Outburst Coal in the Process of Destruction

Based on the experiment and numerical simulation, the paper analyzes and studies the gas migration law of low permeability coal seams during coal and gas outburst process by using self-developed coal and gas outburst simulation experiment device and the numerical model. The results show that, under the repeated action of the in-situ stress or moving abutment pressure, the permeability of the coal body in the low permeability coal seams increased, the absorption gas desorbed, the internal gas pressure increased, and the initial growth rate was faster, gradually became smaller, and finally became slower. At the same time, the free gas moves toward the mining space with low gas pressure. When a large amount of free gas can not be diffused and transported to the outside in time, the gas pressure inside the coal body continues to rise and accumulate to a certain extent. It will jointly with the in-situ stress effect to cause coal and gas outburst. Therefore, reducing free gas pressure is the key technology of low permeability outbust coal seam.