软岩巷道围岩裂隙范围形成力学机制及形态特征

Mechanical mechanism and morphological characteristics of fracture range formation in surrounding rock of soft rock roadway

  • 摘要: 巷道开挖后,围岩沿裂隙面的碎胀、剪胀是造成围岩大变形的重要原因,而围岩的碎胀、剪胀与围岩裂隙密切相关;研究巷道开挖后围岩裂隙分布范围,揭示裂隙分布区域边界形态特征对认识围岩变形范围、设计合适的支护方案具有重要意义。因此,为研究巷道开挖后围岩裂隙分布范围,以弹塑性力学及含单结构面岩体滑动力学模型为基础,采用室内试验、理论分析、数值模拟的方法,对巷道开挖后围岩裂隙形成力学机制、裂隙范围形态特征及影响因素进行了系统研究。结果表明:围岩侧压系数对围岩裂隙范围影响较大,相同围岩条件下,当侧压系数较小时,围岩裂隙范围呈圆形、椭圆形分布;当侧压系数较大时,围岩裂隙范围同样较大,且呈蝶形分布;侧压系数不变的情况下,巷道埋深越大,围岩裂隙范围越大;然而,埋深不能改变围岩的裂隙范围形态,只能改变其大小;结构面黏聚力和内摩擦角越小,围岩裂隙范围越大。增加结构面内摩擦角,围岩裂隙范围大幅度减小;而增加结构面黏聚力,围岩裂隙范围减小不明显。围岩应力方向发生变化时,会使围岩的裂隙范围产生旋转,当蝶形裂隙区中的蝶叶部位旋转至巷道顶板时,将会使巷道极易发生冒顶灾害,对巷道稳定维护极为不利。根据相关研究结果提出了“优化应力场分布+主动强化围岩自承能力+动态调控支护体系”的围岩控制思路;使用3DEC-BBM离散元数值模型研究了不同侧压系数下巷道开挖后围岩裂隙分布范围及形态特征,经验证,数值模拟结果与理论分析结果基本一致。

     

    Abstract: After the excavation of the roadway, the broken expansion and shear expansion of the surrounding rock along the crack surface are the important reasons for the large deformation of the surrounding rock, and the broken expansion and shear expansion of the surrounding rock are closely related to the crack of the surrounding rock. It is of great significance to study the crack range of surrounding rock after roadway excavation and reveal the morphological characteristics of crack boundary for understanding the deformation range of surrounding rock and designing appropriate support scheme. Therefore, in order to study the crack range of surrounding rock after roadway excavation, based on elastic-plastic mechanics and sliding dynamics model of rock mass with single structural plane, the mechanical mechanism of crack formation, morphological characteristics of crack range and influencing factors of surrounding rock after roadway excavation were systematically studied by means of laboratory test, theoretical analysis and numerical simulation. The results show that the lateral pressure coefficient of surrounding rock has a great influence on the crack range of surrounding rock. Under the same surrounding rock conditions, when the lateral pressure coefficient of the surrounding rock is small, the crack range of the surrounding rock is circular and elliptical. When the lateral pressure coefficient of the surrounding rock is large, the crack range of the surrounding rock is also large, and it is butterfly-shaped. Under the condition of constant lateral pressure coefficient, the greater the buried depth of the roadway, the greater the range of surrounding rock cracks; However, the buried depth can not change the shape of the crack range of the surrounding rock, but only change its size; The smaller the cohesion and internal friction angle of the structural plane, the larger the crack range of the surrounding rock. Increasing the internal friction angle of the structural plane greatly reduces the crack range of the surrounding rock; Increasing the cohesion of the structural plane means that the range of surrounding rock cracks is not significantly reduced. When the stress direction of the surrounding rock changes, the crack range of the surrounding rock will rotate. When the butterfly leaf in the butterfly crack area rotates to the roof of the roadway, it will make the roadway prone to roof fall disaster, which is extremely unfavorable to the stability and maintenance of the roadway. According to the relevant research results, the surrounding rock control idea of optimizing the distribution of stress field + actively strengthening the self-bearing capacity of surrounding rock + dynamically regulating the support system is proposed. The 3DEC-BBM discrete element numerical model is used to study the distribution range and morphological characteristics of surrounding rock fissures after roadway excavation under different lateral pressure coefficients. It is verified that the numerical simulation results are basically consistent with the theoretical analysis results.

     

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