Research on the evolution law of overburden rock cracks on high-gas multi-seam large mining height working face

Large mining height technology is used in high-gas multi-seam mines to realize high production and high efficiency, but a difference in mining technology may lead to a change in gas emission regularity on working face. This research was carried out on the evolution law of mining overburden rock cracks on the background of coal seam occurrence conditions and overburden rock distribution characteristics on a large mining height working face in No.15 coal seam, Qinshui coalfield. The research used UDEC to numerically simulate the morphological development and displacement of overburden rock cracks on the large mining height working face at different advancing distances, and then a tracing principle-based validation method was put forward for measuring the development regularity of overburden rock cracks. According to the research, as the large mining height working face advanced to 120m, the limiting development height of the overburden rock cracks in the coal seam reached 65m, and No.8 coal seam, the upper neighboring coal seam of this large mining height working face, lied in the relief range of mining pressure. The field test data obtained by the tracer gas method validated the accuracy of the numerical simulation. Since the overburden rock cracks propagated to the upper neighboring coal seam No.8 coal seam, a gas extraction technology applying to the upper neighboring coal seam should be adopted in the stoping process on the working face.