重复采动巷道围岩裂纹跨尺度演化规律及其力学机理

Scale-span evolution law and mechanical mechanism of surrounding rock cracks in repeated mining roadway

  • 摘要: 为探究双巷布置工作面留巷受重复采动影响围岩破坏程度及劣化表征问题,以布尔台矿22205回风巷为工程背景,综合运用连续−离散耦合数值模拟、理论分析、现场观测等研究方法,研究叠加应力路径下巷道围岩裂纹分布状态以及微裂纹萌生、扩展和贯通的细−宏观跨尺度裂隙行为演化规律,阐明裂纹跨尺度演化力学机理。研究结果表明:① 裂纹演化与时间阶段存在对应关系,根据数值模拟得到围岩宏观破坏4个阶段:掘进影响稳定阶段、一次采动影响阶段、一次采动后稳定阶段、二次采动影响阶段。② 根据裂纹萌生、扩展和贯通呈现的“点、线、面”分布形式,得到剪切裂纹“点”状萌生、扩展形成“线”型破裂带,贯通闭合区域形成“面”型破碎区;两帮剪切裂纹发育以竖直方向为主,顶板以倾斜向上、底板以倾斜向下为主;拉伸裂纹在巷道浅部位置以“点”型裂纹与“线”型破裂带形式存在,两帮拉伸裂纹分布以水平方向为主。③ 叠加采动应力路径下巷道围岩主应力差决定裂纹扩展深度,主应力方向决定裂纹扩展方向,主应力差和方向共同造成巷道围岩裂纹非对称分布;裂纹从应力集中区域内萌生,导致此区域内应力集中现象向新生裂纹尖端区域转移,产生宏观裂纹,应力集中区域随最小主应力偏转方向逆时针旋转。④ 通过现场窥视将围岩裂隙分为裂隙充分发育、微裂隙萌生和围岩稳定区域,裂隙充分发育区域内裂隙分布复杂,由拉伸和剪切破坏导致,微裂隙萌生区域内裂隙发育形态呈现环向裂隙与轴向裂隙,主要由剪切破坏导致,围岩稳定区域内无裂纹。验证裂纹破坏形式与钻孔窥视结果基本吻合。

     

    Abstract: In order to explore the damage degree and deterioration characterization of surrounding rock affected by repeated mining in double roadway layout working face layout working face, the 22205 air return roadway of Buertai Colliery was taken as the engineering background, the continuum-discrete coupling numerical simulation, theoretical analysis, field observation and other research methods were comprehensively used to study the crack distribution state of roadway surrounding rock under superimposed stress path and the evolution law of micro-macro scale-span crack behavior of micro-crack initiation, propagation and penetration, and to clarify the mechanical mechanism of crack scale-span evolution. The results show that: ① There is a corresponding relationship between crack evolution and time stage. According to the numerical simulation, there are four stages of macro failure of surrounding rock: excavation influence stability stage, primary mining influence stage, stability stage after primary mining, and secondary mining influence stage. ② According to the distribution form of “point, line and surface” presented by crack initiation, propagation and penetration, It is obtained that the shear crack “point” initiates and expands to form a “line” type fracture zone, and the “surface” type fracture zone is formed through the closed area, through the closed area, the “surface” type fracture zone is formed. The development of shear cracks in the two sides is mainly in the vertical direction, the roof is inclined upward, and the floor is inclined downward. The tensile cracks exist in the shallow part of the roadway in the form of “point” crack and “line” fracture zone, and the distribution of tensile cracks in the two sides is mainly in the horizontal direction. ③ Under the superimposed mining stress path, the principal stress difference of roadway surrounding rock determines the crack propagation depth, the principal stress direction determines the crack propagation direction, and the principal stress difference and direction jointly cause the asymmetric distribution of cracks in roadway surrounding rock. Cracks are initiated from the stress concentration area, resulting in the transfer of stress concentration in this area to the new crack tip area, resulting in macroscopic cracks. The stress concentration area rotates counterclockwise with the direction of the minimum principal stress deflection. ④ Through on-site peeping, the surrounding rock fissures are divided into fissure fully developed area, micro-fissure initiation area and surrounding rock stable area. The fissure distribution in the fissure fully developed area is complex, which is caused by tensile and shear failure. The fissure development pattern in the micro-fissure initiation area presents circumferential fissure and axial fissure, which is mainly caused by shear failure, and there is no fissure in the stable area of surrounding rock. It is verified that the crack failure form is basically consistent with the drilling peep results.

     

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