Complete Technology for High Efficient Gas Drainage in GassySteep and Extra-thick Coal Seam

To counter the gas occurrence characteristics in the steep and extra-thick coal seam, research was carried on the distribution regularity of the mining-induced surrounding rock fractures in the fully mechanized caving face in No. 45 coal seam at +575 m level in Wudong Mine, which provided the basis for formulating reasonable gas drainage methods. Through the adoption of the complete technology such as the gas drainage by long boreholes along the seam, the interception of the pressure-released gas, the gas drainage by high-position boreholes along roof strike and the gas drainage by buried pipes in the gob, the gas pre-drainage rate in the working face reached 42.7%, and the gas drainage rate in the face during coal mining reached 80% or more, which effectively controlled the gas emission in the face and provided a guarantee for the safe production of the face.