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深部高应力软岩巷道失稳机理及补偿支护技术

Failure mechanisms and compensation support technology of deep high-stress soft rock roadways

  • 摘要: 深部开挖岩体应力重分布是多元应力的复合力学问题。首先,基于弹性理论叠加原理,建立了深部高应力软岩巷道开挖瞬间的围岩力学模型,研究了切向应力σ1和径向应力σ3的变化规律。其次,构建了深部高应力软岩巷道的支护力学模型,揭示了围岩的支护效应。通过物理模型试验,探究了常规支护和补偿支护下围岩σ1σ3的响应特征及相应的失稳机理。最后,通过数值模拟和现场工程应用验证了补偿支护技术的适用性。结果表明:深部高应力软岩巷道应力重分布呈现径向卸压和切向增压的趋势,开挖瞬间巷道边缘σ1变为原来的2倍,而σ3降为0。对开挖岩体进行支护后,巷道边缘σ3为围岩的支护力,σ1随支护力的增加而降低。与常规支护相比,补偿支护围岩变形量降低73.7%,破裂碎胀面积降低88.3%,裂隙长度降低11.0%。浅部围岩σ3提高68.3%,σ1峰值下降18.2%。常规支护补偿效应弱,围岩σ3大幅衰减且σ1集中程度高,促使裂隙持续张开并纵深延长,易造成围岩碎胀扩容变形。补偿支护通过NPR(Negative Poisson’s Ratio)锚索充分发挥围岩三轴强度并调动深部岩体自承力,围岩σ3补偿程度高且σ1显著降低,从而抑制裂隙的传播和穿透,进而实现围岩自稳。软岩巷道采用补偿支护技术后,NPR锚索实现恒阻,围岩变形和支护破坏程度显著降低,表明该技术对深部高应力软岩工程具有良好的控制效果。

     

    Abstract: Stress redistribution of deep excavation rock mass is a complex mechanical problem of multiple stresses. First, the mechanical model of surrounding rock at the moment of excavation of deep high-stress soft rock roadways was established based on the superposition principle of elastic theory, and the variation rules of tangential stress σ1 and radial stress σ3 were studied. Then, the supporting mechanical model of deep high-stress soft rock roadways was constructed, and the supporting effect of surrounding rock was revealed. Next, the response characteristics of σ1 and σ3 of surrounding rock and corresponding failure mechanisms under traditional support and compensation support were investigated through physical model tests. Finally, the applicability of compensation support technology was verified by numerical simulation and field engineering application. Mechanical analysis results indicated that the stress redistribution in deep high-stress soft rock roadways shows the trend of radial pressure relief and tangential pressure increase, σ1 becomes twice of the original and σ3 decreases to 0 at the moment of excavation. After supported the excavated rock mass, the σ3 of roadway edge is the support resistance of surrounding rock, and σ1 decreases with the increase of support resistance. The model test results showed that surrounding rock deformation of compensation support reduces by 73.7%, the destroyed area reduces by 88.3%, the crack length reduces by 11.0%. The σ3 of the shallow surrounding rock increases by 68.3%, and the peak value of σ1 decreases by 18.2%. The compensation effect of traditional support is weak, the σ3 attenuates greatly and the σ1 concentrates highly, which causes the crack to continue to open and extend in depth, resulting in the surrounding rock expansion deformation. Compensation support gives full play to the three-axis strength of the surrounding rock and mobilizes the self-bearing capacity of the deep rock mass by NPR cable. The compensation degree of σ3 is high and σ1 is significantly reduced, thus restraining the propagation and penetration of crack and realizing the self-stability of surrounding rock. After the compensation support technology is used in soft rock roadways, the NPR cables achieve constant resistance, the deformation of surrounding rock and the damage degree of support are significantly reduced, which indicates that this technology has a good control effect on deep soft rock engineering with high in situ stress.

     

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