Theory and experimental studies of enhanced gas drainage in the high-gas face of low permeability coal multi-seams

On the basis of model test and theory research for the problem of high gas emission when mining the key coal-seam in the multi-seams coal of the highly gas content and low permeability and the difficult actual condition of gas control,the permeability of the coal seam significantly increases because of the existence of "the vertical crevasse growth area" beside the mined direction,the curving submerged belt and the bulgy deformation band in the motherboard in coal,which is very benefit for gas drainage.The research provides theory for disposing mining holes during the process of stress-relief and gas mining in the key mining stress-relief layer of coal multi-seams.The key remote mining of Panyi Coal Mine 2371 (1) workface gas mining on the working surface reveals that the most greatly absolute gas emission quantity is 70.46 m3/min,average 56.71 m3/min.The gas drainage rate amounts to 85.2%.Besides,high concentration gas drainage rate up to 67.25% and low concentration gas just only 32.75%.The experiment result shows that the utilization of coal and gas mining together not only controls workface gas emission,but also achieves mining clean gas safely and effectively in the process of coal mining.