Strengthen Pre-drainage Coal Roadway Bands CH4 Technology by Gas Injection Coordinated with Boreholes Along Seam

In order to solve the problems of large declination of extraction volume and long cycle of outburst elimination at the end of pre-drainage by using pre-drainage coal roadway bands CH4 measure in boreholes along seam of Shijiazhuang mine,the reason of causing the phenomenon is analyzed.Pre-drainage coal roadway bands CH4 technology using gas injection coordinated with boreholes is tested in 15108 air intake crossheading of Shijiazhuang coal mine.The result shows that the pressure air injection of 0.5 Mpa can maintain the average pre-drainage scalar of 1.07 m³/min at end of pre-drainage;single-hole extraction scalar increased by 2～38.6 times;the effect of injection gas in parallel bedding direction is faster than in vertical stratification direction,the different of permeability is the reason leading to the difference.