考虑孔隙水压力及非线性Mohr-Coulomb破坏准则下浅埋土质隧道三维塌落机制的上限分析

浅埋土质隧道的稳定性研究一直是隧道工程的关键问题，而孔隙水压力的存在影响着浅埋土质隧道的安全。构建了隧道顶部为圆弧形的浅埋土质隧道的三维塌落机制，基于非线性Mohr-Coulomb破坏准则和极限分析上限法，并考虑孔隙水压力的作用，推导出浅埋土质隧道的塌落范围及支护力的最优上限解计算公式。通过与既有研究进行对比，验证了所提方法的合理性。分析了不同参数对塌落范围、塌落土体的重力及支护力的影响，结果表明：孔隙水压力对浅埋土质隧道的塌落范围、塌落土体的重力及支护力有着显著的影响；孔隙水压力对塌落范围、塌落土体重力的影响比较复杂，而支护力都随着孔隙水压力系数的增大而增大；不同参数对浅埋土质隧道的塌落范围、塌落土体的重力及支护力的影响规律不同。新方法可为浅埋土质隧道的设计优化提供理论支撑。

Upper bound limit analysis of three-dimensional collapse mechanism of shallow buried soil tunnel under pore pressure based on nonlinear Mohr-Coulomb criterion

The stability study of shallow-buried soil tunnel has always been a key problem in tunnel engineering. The existence of pore water pressure can contribute to the collapse of shallow-buried soil tunnels that has serious influence over the safety of life and property. In this paper, the three-dimensional collapse mechanism of a shallow-buried earth tunnel with a circular top arc is constructed. Based on the nonlinear Mohr-Coulomb failure criterion and the limit analysis upper bound method, the collapse range of the shallow-buried earth tunnel is derived considering the pore water pressure. The formula for solving the optimal upper limit of support force is established. Moreover, the proposed method is compared with existing research for rationality verification of the method. The effects of different parameters on the collapse range, gravity and support force of the collapsed soil are analyzed. The results show that the pore water pressure has significant impact on the collapse range of the shallow buried soil tunnel as well as the gravity and support force of the collapsed soil. The effects of pore water pressure on the collapse range and weight of the collapsed soil are complex, while the support force increases with the increase of the pore water pressure coefficient. Moreover, the collapse range, gravity and support force of shallow soil tunnel are influenced with varying degrees by different parameters. This method can provide theoretical support for the design optimisation of shallow-buried soil tunnel.