Mode of overlying rock roofing structure in large mining height coal face and analysis of support resistance

The mining space of large mining height coal face is large, the range of movement and caving of rock strata is large and the stability of supports at coal face is low and damage rate of supports is high, which significantly affects the safe and efficient production of coal mines. By similar simulation experiment and theoretical analysis, the mode of fractured roofing structure of large mining height coal face and the method of determination of reasonable support resistance of the support was evaluated. Analysis shows that the structural mode of “combined cantilever beam–non-hinged roofing–hinged roofing” of the large mining height coal face appears at the roofing of large mining height coal face. The supporting factor of caved gangue at the gob is introduced, the calculating equations of the fractured step distance of roofing were derived and conventional calculating method of caved height of roofing was corrected and the method of determination of the length and height of each structural area of the roofing was provided. With reference to the excavating conditions at Jinhuagong coal mine in Datong minefield, the dimensions of structural areas of the roofing of the coal face were determined and analyzed, and reasonable support resistance of the height coal face was acquired. By selecting Model ZZ13000/28/60 support and with procedures of advanced pre-cracking blasting, the safe production of large mining height coal face was assured.