近距离煤层群联合开采覆岩破断规律研究

A Study on Overburden Fracture Laws in Close-Distance Coal Seam Group Mining

摘要: 为揭示近距离煤层群联合开采条件下的覆岩破断规律，解决二次采动时顶板控制难题，以淮北矿区许疃煤矿7₂煤与8₂煤联合开采为工程背景，采用理论分析(基于弹性地基梁与损伤力学理论，构建层间岩层稳定性判据)与FLAC3D数值模拟相结合的方法，系统研究初次与二次采动全过程覆岩塑性区、应力场的动态演化规律。结果表明：7₂煤初次采动时，工作面推进50 m基本顶初次破断，底板呈剪切破坏；推进90 m出现周期来压，覆岩破坏区呈“中间低、两端高”的马鞍形分布。8₂煤二次采动时，工作面推进40 m层间岩层转为剪切破坏，基本顶破断，周期来压强度弱化，但仍保持稳定周期性；上覆岩层经历“压实–卸压”动态过程，破坏区域向两侧转移并扩大。研究揭示了近距离煤层群二次采动覆岩破断的“层间耦合”效应与“压实–卸压”动态过程，可为煤层群联合开采顶板控制及下伏煤层巷道支护设计提供理论依据。

Abstract: To reveal the fracture laws of overburden strata under close-distance coal seam group mining and address the challenges of roof control during secondary mining, this study investigates the combined mining of the No. 7₂ and No. 8₂ coal seams in the Xutuan Coal Mine, Huaibei mining area. A methodology integrating theoretical analysis based on elastic foundation beam and damage mechanics theories to establish stability criteria for interlayer strata, and FLAC3D numerical simulation was employed to systematically study the dynamic evolution of the plastic zone and stress field in the overburden during both the initial and secondary mining stages. The results indicate that during the initial mining of the No. 7₂ coal seam, the main roof experienced its first fracture when the working face advanced 50 m, with the floor strata failing in shear. Periodic weighting occurred after an advance of 90 m, and the overburden failure zone exhibited a saddle-shaped distribution, described as “lower in the middle and higher on both sides”. During the secondary mining of the No. 8₂ coal seam, the interlayer rock strata transitioned to shear failure and the main roof fractured when the face advanced 40 m; the intensity of periodic weighting weakened, but it still maintained a stable periodicity. The overlying strata underwent a dynamic “compaction-decompression” process, causing the failure zone to shift and expand laterally. This study elucidates the “interlayer coupling” effect and the dynamic “compaction-decompression” process governing overburden fracture during secondary mining in close-distance coal seam groups, providing a theoretical basis for roof control in multi-seam mining and support design for roadways in underlying seams.