不整合地层下煤层开采覆岩裂隙场发育特征

Fracture development due to coal mining under unconformable overlying strata

以宁夏石嘴山矿西区3号煤层开采为工程背景,采用相似模型试验、数值模拟计算,研究深部不整合覆岩下煤层开采所引起的裂隙发育特征,并对两种方法分别得到的裂隙带形态进行对比分析。由于煤系地层与上覆地层不整合,开采扰动后应力重分布及覆岩裂隙发育具有其特殊性。研究发现:煤层开采过程中,采空区周围出现"应力拱";地层不整合面的存在阻隔了煤层开挖引起的应力重分布时的应力传递,使开采扰动后主应力在不整合面下方局部呈现应力集中现象,从而使不整合面下方附近岩体的破坏程度加剧,使裂隙带最终形态为"左高右低"的非对称"马鞍形"。

The development characteristics of fractures due to coal mining under deep unconformable overlying strata was investigated using the similar model test and DEM numerical simulation,and taking No.3 coal seam of Shizuishan in Ningxia Province as the engineering background.The comparison was performed between the results obtained from the similar model test and the DEM numerical simulation.It is realized that the development of fracture and the redistribution of stresses in overlying rock mass are both unique due to the unconformity between the coal strata and the overlying strata.It is found that the stress arch appears over the goaf in the overlying rock mass in the process of coal mining.The transmission of stresses is blocked by the unconformity of strata during the process of stresses redistribution induced by coal mining.That results in that the principle stresses concentrate at some local regions beneath the unconformity.The stresses concentration in these regions makes the failure of rock mass near the unconformity more intensive than that in other places.Finally,the saddle-shaped fractures zone which is high at left and low at right is formed over the goaf in the overlying coal strata.