Technology research on borehole in place of roadway and its engineeringpractice in gas drainage of Huainan Mining Area

According to the complicated geological conditions of the roof strata and the characteristics of gas migration in Huainan Mining Area, the technology research on “borehole in place of roadway” was carried out. The technical principle of the high-position directional borehole with large-diameter in place of high level suction roadway was analyzed from the aspects of the development pattern of mining-induced fracture and the characteristics of borehole gas drainage. Based on the detailed roof strata information obtained by borehole drilling on the roof, one can optimize the layer layout of high-position directional borehole, drilling tool assembly and drilling parameters. The results of gas drainage show that:the borehole above the height of 38 m on the roof with a distance of 26 m with the coal wall of track roadway achieves high flux and high concentration of gas drainage. With the increase of pure gas flow rate in the high-position directional borehole, the gas volume fraction in the upper corner of the working face gradually decreases and stabilizes at about 0.03%. The average gas drainage rate of high-position directional borehole with large-diameter is 11.07 m3/min, with an average concentration of 31.39%, which is comparable to that from the adjacent high level suction roadway. The application shows that the technology of borehole in place of roadway for gas drainage on the roof is feasible. The present research can provide a reference on underground efficient gas drainage and treatment in coal mine.