考虑局部失稳的盾构隧道开挖面挤出破坏数值模拟与理论分析

Numerical simulation and theoretical analysis of passive failure mechanism of shield tunnel face considering partial instability

通过数值模拟和理论分析,研究了盾构隧道开挖面挤出破坏机理。首先,利用有限元软件进行了数值模拟,揭示了隧道开挖面挤出破坏的局部失稳模式,得到了盾构隧道开挖面挤出破坏的局部失稳比和极限支护压力。此外,还进行了摩擦角和相对埋深对局部失稳比率和极限支护压力的参数敏感性分析。其次,基于极限分析方法,提出了一种考虑局部失稳模式的隧道开挖面挤出破坏新机制。新的被动破坏机理由五个圆锥台和作用在圆锥台上的分布力组成。通过对定义的角度和隧道开挖面局部失稳直径进行数值优化,计算得到挤出破坏模型的上限解,进而研究了摩擦角和相对埋深对局部失稳比的影响。比较了数值模拟和理论分析得出的局部失稳比结果。最后,将获得的被动极限支护压力与现有方法进行了比较,表明新的挤出破坏机理为极限支护压力提供了较为满意的预测结果。

Through virtue of numerical simulation and theoretical analysis the problem of passive failure mechanism of shield tunnel is studied.Firstly,the numerical simulations with finite element software are performed to reveal the partial instability modes of passive failure of a pressurized tunnel face.The partial instability ratio and limit support pressure for passive failure of shield tunnel face are obtained.Moreover,the parameter sensitivity analysis of friction angle and the relative cover depth on partial instability ratio and limit support pressure are also discussed.Secondly,a new passive failure mechanism of tunnel face considering the partial instability modes is proposed based on limit analysis methods.The new passive failure mechanism is composed of five truncated cones and a distributed force acting on the truncated cones.The distributed force is determined using a modification of the silo theory for passive modes.The upper-bound solution for passive failure mechanism are calculated by numerically optimizing with respect to the defined angles and partial instability diameter on tunnel face.Then the effects of friction angle and the relative cover depth on the partial instability ratio are conducted.he results of partial instability ratio obtained from numerical simulation and theoretical analysis in this paper are compared.Finally,the obtained passive limit support pressures and the existing approaches are compared,which indicates that new passive failure mechanism provides relatively satisfactory results for limit support pressures.