FEM-BEM modeling of dynamic responses of saturated soil around fluid-filled lined tunnel with imperfect soil-lining interface under water hammer

This study employs the Finite Element Method-Boundary Element Method (FEM-BEM) to simulate the dynamic response of saturated soil around a fluid-filled circular tunnel under water hammer loading, accounting for imperfect bonding at the soil-lining interface. The governing equations for the fluid and tunnel lining are solved in the frequency domain using the finite element method, while the boundary element method is applied to the saturated soil. The dynamic response of the fluid-lining-soil coupled system is obtained accounting for the incomplete interface between the lining and the soil. The influence of the imperfect interface on the dynamic stress response in saturated soil under water hammer loading is further investigated, including its effect on the dynamic stress in the soil beneath the tunnel crown and the distribution of dynamic stress along the tunnel axis. The results show that variations in interface stiffness significantly affect the dynamic stress level in saturated soil, with a more pronounced influence at the crown compared to the valve location.