高偏应力煤巷围岩拉剪破裂特征及分区控制方法研究

Research on the characteristics of tensile⁃shear fracturing and zone control method for surrounding rock of coal roadway under high deviatoric stress

为获得高偏应力巷道围岩拉剪破裂特征并提出优化支护方案,以山西某矿孤岛工作面为背景,采用理论分析、数值模拟、相似模拟相结合的研究手段,分析了高偏应力条件下巷道围岩拉剪破裂分布特征及演化规律,揭示了托顶煤巷道围岩拉剪破裂机制,提出了高偏应力条件下巷道围岩沿掘进方向的全长分区控制方法。研究结果表明:(1)当侧压系数λ为0.60时,巷道围岩两帮呈“楔形”破坏,顶底出现明显卸荷并在巷道围岩四角点处产生应力集中;侧压系数λ逐渐减小至0.24的过程中,巷道围岩以两帮破坏为基础,在剪切应力作用下“蝶叶”逐渐发育,并最终形成蝶形破裂。(2)开挖破坏区围岩的浅部存在拉剪混合破裂区域,以张拉破裂为主;围岩深部为剪切破裂。围岩破裂演化过程可划分为3个阶段,分别为环自由面的自身破坏阶段、“蝶叶”孕育扩展阶段和“蝶叶”扩展稳定阶段。(3)定义了基于巷道全长分区的应力阈值,提出了掘进巷道全长分区支护方法,可为后续采煤工作面巷道的差异化支护提供理论参考。

Taking coal roadway of high deviatoric stress in a coal mine in Shanxi as the background,the distribution characteristics,evolution law and fracturing mechanism of tensile⁃shear fracturing were investigated combing the theoretical analysis,numerical and physical simulation.An innovative and optimized full⁃length zoning supporting method along the excavation direction was proposed for surrougnd rock of roadway.The results show with lateral pressure coefficient is 0.60,wedge failure occurs in two sidewalls of roadway,the roof and floor are obviously unloaded,and the stress concentration occurs at the four roadway corners.As lateral pressure coefficient gradually decreases to 0.24,the"butterfly wing"gradually developed with the failure iniating from two sidewalls under the effect of shear fracture,eventually forming a butterfly⁃shaped fracture pattern.The tensile⁃shear mixed fracture zone existed in the shallow part of the excavation damage zone,but dominated by tensile fractures.However,the shear fracture is dominant in the deep part.The fracturing evolution process of surrounding rock can be divided into three stages:self⁃destruction stage of the circular free surface,gestation and expansion stage of the"butterfly wing",and expansion and stable stage of the"butterfly wing".The stress threshold according to the full⁃length partition of roadway was defined and the full⁃length zonal control method of the roadway was put forward.This research provides theoretical basis for the differential supporting of roadway during coal mining.