Numerical Simulation Study on Gas Drainage in Extra Long Borehole Based on COMSOL Multiphysics

By using COMSOL Multiphysics simulation software, the numerical simulation of gas pressure distribution law and total gas drainage was carried out under the condition of different gas drainage depth, different suction pressure and different pumping time in the engineering, which utilizes pre-pumping gas in kilometer drilling hole to cover the excavation of central return air roadway in south NO.5 mining area 9^# coal seam of Malan Mine. We obtain that the key area of gas drainage transfers to the region of large radial distance and the depth of the hole from the region of less radial and the shallow of the hole with the increase of the number of pumping time. The greater the depth of drilling, the greater the difficulty of gas drainage. And the appropriate increase of the negative pressure of gas drainage can effectively improve the gas drainage efficiency of the depth of the drill hole. The effective number of gas drainage time is 500 days or so when the negative pressure is 13 kPa and the total depth is 600 m; the effective number of gas drainage time is 600 days when the negative pressure is 13 kPa and the total depth of the borehole is 700 m.