近距离煤层群重复采动下裂隙分布特征对端面顶板稳定性的影响研究

Study on the Influence of Fracture Distribution Characteristics on the Stability of End Face Roof Under Repeated Mining of Close-Distance Coal Seam Group

为研究近距离煤层群重复采动下覆岩裂隙分布特征对端面顶板稳定性的影响,综合运用数字图像相关技术(DIC)、三轴力学特征试验、数值模拟等方法,对近距离煤层群重复采动下裂隙分布特征进行分析。研究结果表明:三轴应力状态下围压提升会造成煤体试样峰值强度和弹性模量的增加;随着围压的增大,试样的破坏角增大,易导致煤壁片帮,从而诱发端面顶板灾变;单一煤层开采时,顶板破断主要位于工作面煤壁处的顶板位置;下位煤层开采前,岩层受上位煤层采动的影响,裂隙数量和密度进一步增加,分布范围变大,上位煤层裂隙的张开度和密度要明显高于下位煤层;工作面覆岩裂隙依次经历“产生—发育—闭合—再发育—贯通—再闭合”的动态循环变化过程。研究结果可为相似条件下近距离煤层开采端面顶板稳定性控制提供理论支撑。

In order to study the influence of fracture distribution characteristics of overlying rock on the stability of end face roof under repeated mining of close-distance coal seam group,the fracture distribution characteristics under repeated mining of close-distance coal seam group were analyzed by using digital image correlation technology(DIC),triaxial mechanical characteristic test and numerical simulation.The results show that the increase of confining pressure under triaxial stress state will increase the peak strength and elastic modulus of coal samples.With the increase of confining pressure,the failure angle of the sample increases,which easily leads to the spalling of the coal wall,thus inducing the disaster of the end face roof.When mining a single coal seam,the roof breakage is mainly located in the roof position at the coal wall of the working face.Before the mining of the lower coal seam,the number and density of fractures in the rock strata are further increased and the distribution range becomes larger due to the influence of the mining of the upper coal seam.The opening and density of the upper coal seam fractures are significantly higher than those of the lower coal seam.The overlying rock fracture in the working face undergo a dynamic cyclic change process of“generation-development-closure-redevelopment-penetration-reclosure”in turn.The research results can provide theoretical support for the stability control of end face roof in close distance coal seam mining under similar conditions.