大同矿区坚硬顶板破断步距及变形规律研究

Study on the breaking span and deformation of hard roof in Datong mining area

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。

With the hard roof of certain working surface in Datong mining as the research subject and to solve the problem of its roof being hard to cave with strong or weak weighting, the breaking span of hard rock strata which are quite different in thickness in a near distance was obtained based on the key strata theory, Vlasov thick plate theory, and thin plate theory, to explain the strata caving with different weighting of the working surface; the theoretical calculation was verified through 3DEC numerical simulation, and the change law of abutment pressure peak of coal wall and fissure in overburden strata along with the deflection of hard immediate roof was obtained. The results have shown that the breaking span of the upper roof is twice as long as the lower one, leading to strong and weak weighting; the peak changes of abutment pressure and the fractal dimension changes of fissure corresponding to the hard immediate roof deformation show periodic transformation： in which the former changes quickly in the beginning, then slowly, and steadily at last, while the latter changes slowly at first but quickly later; meanwhile, the fractal dimension of fissure shows a mutated increase each time when the hard immediate roof breaks.