Tiefa Caol Industry Group Company has 6 high gas mines.The permeability of coal seams is low and extraction is difficult.Traditional gas drainage techniques sometimes can’t meet the requirements of methane drainage for a modern longwall operation.The alternative method to drill gas drainage holes is to drill boreholes from surface to the goaf area.Essential way of solving the gas drainage problem of low permeability coal seam is to increase coal seam permeability.Aiming at geologic conditions and production...