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不同条件下,隧道围岩发生破坏的机理不尽相同,有劈裂破坏、剪切破坏和重力坍塌等。根据围岩稳定性分析需要,采用理论分析和模型实验相结合的方法,验证了砂土地层中隧道失稳的机理。采用Mohr—Coulomb弹塑性本构模型,计算隧道围岩发生破坏的起始部位、破坏面的开裂方向和形状。通过隧道开挖模型实验,得到砂土地层中隧道失稳时的表观特征,验证了理论分析结果。研究结果表明,砂土地层中隧道失稳的力学破坏形式是压应力集中导致的劈裂与剪切滑移,采用Mohr—Coulomb模型来计算砂土地层中隧道围岩破坏面的特征是合理的,计算的破坏区域可以用于指导隧道支护设计。
Under different conditions, the failure mechanism of tunnel surrounding rock varies, with splitting failure, shear failure and gravity collapse. According to the need of stability analysis of surrounding rock, the mechanism of tunnel instability in sandy soil is verified by the combination of theoretical analysis and model experiment. The Mohr-Coulomb elastic-plastic constitutive model was used to calculate the initial site of tunnel wall failure and the direction and shape of failure surface cracking. Through the tunnel excavation model experiment, the apparent characteristics of the tunnel in the sand stratum are obtained, and the theoretical analysis results are verified. The results show that the mechanical failure mode of tunnel instability in sand stratum is the cleavage and shear slip caused by the compressive stress concentration. It is reasonable to calculate the characteristics of the surrounding rock failure surface in sand stratum by using Mohr-Coulomb model , The calculated failure area can be used to guide the tunnel support design.