Study on Influence Law of Coal Permeability Anisotropy on Gas Pre-drainage in Mining Seam

To counter the problems of poor permeability and difficult gas drainage of 8^# coal seam in Xinjing Mine, study was carried out on the influence law of the permeability anisotropy upon the gas drainage in the mining seam by laboratoty experiment and field test. The laboratoty results showed that permeability of coal was the biggest along its strike, the next along its inclination and the smallest along its vertical direction, and the dominant direction of gas seepage was parallel to the coal seam strike. The field gas drainage test showed that the average gas drainage flow from the hole with the included angle of 90° to the seam strike reached 0.11 m³/min, and the average gas drainage flow from the hole with the included angle of 30° to the seam strike was only 0.015 m³/min, that is to say, the larger the included angle of the hole to the seam strike, the greater the gas drainage flow; after gas drainage for 60 days, the residual gas content in the area with the larger included angle of the hole to the seam strike decreased greatly. The research results have a certain guiding significance for the rational arrangement of the gas pre-drainage holes and the improvement of gas drainage efficiency.