ANALYSIS OF COMPRESSIBILITY OF HARD TOP COAL UNDER HARD-AND-THICK STRATA AND CHOICE OF ITS MINING METHOD

The movement and breakage of top coal,especially its internal micro-fracture extension,are closely related to the movement regularity of its immediate roof and main roof.The hard-and-thick strata acts both as the floor of coal seam No.7 and as the roof of coal seam No.9 in Zhangshuanglou Coal Mine;and coal seam No.9 is also hard.Falling ability of coal seam No.9 and the choice of the mining method is the key to use the fully-mechanized with top-coal caving.Physical simulation is used to analyze the breakage features of the hard-and-thick strata.Nine mining methods are put forward for the upper and the lower coal seams mining;and the corresponding top-coal compressed volume of the lower coal seam is studied.At last,the rational mining method is determined as the staggered layout of coalface in the upper and the lower coal seam,with the upper coal seam is mined first and the lower coal seam is mined with the whole height.The numerical simulation and the field practice prove that the use of the fully-mechanized coalface with top-coal caving in the lower coal seam is successful.Achievements can be rationally used to guide the application of the fully-mechanized coalface with top-coal caving in the lower coal seam in the similar conditions.