Research and Application of Gas Extraction Technology in Goaf by Separate Sources in Roof Strike High-level Long Borehole

In high gas content mine, in order to solve the borehole design problem when using the high-level long borehole to extract the gas in goaf. Based on the dynamic migration law of overlying strata in roof during mining process,according to the vertical and lateral movement characteristics of gas,the paper put forward the separate source extraction concept of "main extraction in fault zone and auxiliary extraction in caving zone", the vertical gas migration of roof and the lateral gas migration of upper corner were respectively controlled. Through the theoretical analysis of the roof "three belts" and the numerical simulation of roof crack evolution law in 15203 working face of Mabao Coal Industry, and according to this, the design of roof strike high-level long borehole was optimized, and two auxiliary extraction boreholes were arranged in the fall belt, the horizontal extraction range was form 0 m to 15 m, and the vertical height of the final hole was 15 m; three main drilling holes were arranged in the fracture zone, with the horizontal extraction range from 15 m to 35 m and the vertical height of the final hole from 32 m to 36 m. During the test, the test holes had high gas concentration and stable flow, the effective gas extraction days were up to 60 days, and the maximum pure gas extraction volume of the drilling field was 19.8 m³/min, the gas concentration of the upper corner was controlled below 0.60%, which ensured the safety of the working face.