The evolution of permeability and gas extraction technology in mining coal seam

The low permeability of coal is the bottleneck of gas extraction technology.The permeability tracer test of mining coal seam was done to solve this bottleneck,the evolution law of permeability was obtained.Based on the coupling effect of stress and seepage,the numerical experiment method was used to analysis the drill hole layout how to influent the gas drainage effect.The results show that gas drill hole locate at the high permeability area,the gas pressure decrease large range relatively and gain the better extraction.The drill hole is removed when the length is less than 5 m from the working face.It is conducive to improving the safety of the working face.