Gas control of air return corner of fully mechanized caving face in extremely close distance coal seam

In view of the problems such as the development of overlying rock fractures, the complexity of gas migration, and the easy overrun of gas in the corner of return air during the mining of extremely close distance coal seams.Taking the gas overlimit in the corner of return air of EIN₅6-5 fully mechanized caving face of a coal mine as the research background, the influencing factors of gas overlimit are analyzed by means of theoretical analysis, numerical simulation and field practice, and the failure process and stress distribution of overburden rock in the working face are simulated and analyzed.The gas control idea of “stages and differences” is put forward, and it is applied in practice in EIN₅6-5 fully mechanized caving face.The results show that the gas overlimit in the corner of return air of EIN₅6-5 working face is caused by the coupling of several factors, such as overlying hard roof and unreasonable gas extraction measures.The maximum height of the caving zone and fracture zone is about 8.95 m and 20.33 m, respectively.The three zones of spontaneous combustion behind the working face are 0-25 m is the scattered zone, 25-70 m is the heating oxidation zone, and within 70 m is the suffocating zone.Through the implementation of reasonable gas extraction measures, the gas extraction rate reached 77%, and no gas excess occurred in the corner of the return air and the return air lane, ensuring the safe mining of the working face.