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基于数值模拟与微震监测的缓倾斜煤层开采覆岩裂隙演化机制研究

Study on the fracture evolution mechanism of overlying strata in gently inclined coal seam mining based on numerical simulation and microseismic monitoring

  • 摘要: 缓倾斜煤层采动覆岩运动及裂隙发育特征较水平煤层更为复杂,直接影响地表沉陷与顶板水害防控。以丁集煤矿1632(3)缓倾斜工作面为工程背景,采用UDEC离散元数值模拟与井下微震监测系统,联合揭示采动覆岩裂隙的非对称演化机制。结果表明:顶板形成非对称应力平衡拱,其“形成—破断—再形成”的循环过程与覆岩周期性垮落运动呈实时映射关系;裂隙演化遵循“萌生—扩展—贯通”的阶段性模式,微震事件在时空上呈现“高频次-高连通性”与“低频次-低连通性”集中区的交替分布特征;裂隙空间分布呈显著非对称性,沿倾向,上倾侧裂隙密度高于下倾侧,垂向上,裂隙密度自下而上递减,上部稀疏、下部密集。数值模拟所得导水裂隙带发育高度(55.35 m)与微震监测结果(49.0±1.8 m)吻合良好(误差小于8.2%),且与理论预测值偏差控制在13.5%以内,验证了联合分析方法的可靠性。研究结果为缓倾斜煤层开采条件下地表沉陷控制及顶板水害防治提供了理论依据与工程参考。

     

    Abstract: The mining-induced movement and fracture development of overlying strata in gently inclined coal seams are more complex than those in horizontal seams and directly affect surface subsidence and roof water hazard prevention and control. Taking the 1632(3) gently inclined working face of Dingji Mine as the engineering background,this study combines UDEC discrete element numerical simulation with an underground microseismic monitoring system to reveal the asymmetric evolution mechanism of mining-induced overlying strata fractures. The key findings are as follows:The roof strata form an asymmetric stress equilibrium arch,whose formation-fracture-reformation cycle corresponds in real time to the periodic caving movement of the overlying strata. Fractures evolve through “initiation-propagation-interconnection” stages,with microseismic events showing alternating spatiotemporal clusters of high-frequency-high-connectivity and low-frequency-low-connectivity zones. Fracture distribution exhibits distinct asymmetry:along the dip direction,it is denser on the updip side and sparser on the downdip side; vertically,the fracture density decreases from bottom to top,being sparser in the upper strata and denser in the lower strata. The height of the water-conducting fracture zone obtained by numerical simulation (55. 35 m) agrees well with the microseismic monitoring result (49±1. 8 m) (error<8. 2%),and the deviation from the theoretical prediction remains within 13. 5%,verifying the reliability of the combined analysis method. These results provide a theoretical basis and engineering reference for surface subsidence control and roof water hazard prevention in gently inclined coal seam mining.

     

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