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以大同矿区某工作面坚硬顶板为研究对象,针对其难以垮落并伴有大小来压的现象,采用岩层控制关键层理论、Vlasov厚板理论及薄板理论,求得了近距离厚度差异较大坚硬岩层的破断步距,解释该工作面岩层垮落大小来压现象;通过3DEC数值模拟软件验证了理论计算结果,并得到煤壁支承压力峰值、覆岩裂隙随坚硬直接顶变形挠度的变化规律。结果表明:该工作面上层较厚坚硬顶板断裂步距大致为下层较薄坚硬顶板断裂步距的2倍,易形成大小来压;且坚硬直接顶变形所对应的支承压力峰值变化与裂隙分形维数变化具有阶段性,前者呈现出“前快,中慢,后稳”趋势,后者呈现出“前慢,后快”趋势,并且在坚硬直接顶每次破断时,裂隙分形维数的增加具有突变性。
Taking the hard roof of a working face in Datong Mining Area as the research object, in view of the phenomenon that it is hard to collapse and accompanied by the size of the pressure, using the key layer theory of rock control, Vlasov thick slab theory and thin slab theory, The fracture step of the rock layer is interpreted to explain the phenomenon of the collapse of the rock face. The 3DEC numerical simulation software verifies the theoretical calculation results and obtains the variation law of the peak pressure of the coal wall support and the deformation of the overburden rock crack with the hard direct top. The results show that the fracture length of the thick and hard roof in the upper surface of the working face is roughly twice as large as that of the thin and hard roof in the lower layer, and it is easy to form the size and pressure. The peak pressure of support pressure corresponding to the rigid direct roof deformation and the fracture fractal dimension The former shows a tendency of “fast, slow, steady afterward”, while the latter shows a tendency of “slow before slow and fast afterward”, and the fracture fractal The increase in dimensionality is mutable.