Combined gas drainage practice at upper corner of high-intensity fully mechanized caving face

In view of traditional single upper corner gas control technology cannot effectively solve problem of severe over-limit of gas at upper corner of high-intensity fully mechanized caving face, taking Wangjialing Coal Mine as engineering background, the paper puts forward a scheme of combined gas drainage by use of upper corner inserted(buried) pipe and high-level directional boreholes. To INSERT INTO (bury) pipe at upper corner, gas drainage pipe is laid in return air lane of working face. The pipe extends along direction of return air lane to upper corner and forms a stable negative pressure zone at the pipe mouth to extract gas at the upper corner. Artificial air flow is formed through suction to disturb cyclotron vortex at the upper corner and reduce gas concentration. At the same time, in drilling site of the return air lane of the working face, the high-level directional borehole is constructed to drill in direction of cutting holes of working face, and the borehole track is extended in fissure zone of goaf through directional drilling technology to extract high concentration gas in the goaf. The application results show that after the combined gas drainage of upper corner inserted(buried) pipe and high-level directional borehole, gas drainage pure volume is stable at 3.40-6.20 m3/min, with an average value of 4.91 m3/min; gas volume fraction in upper corner of the working face decreases in steps, and finally stabilizes at 0.30%-0.52%, with an average value of 0.42%. The gas control effect in upper corner is significant.