Earthquake response analysis of tunnels at a complex saturated site

Only a seismic analysis of tunnels at a single-phase site can be performed using the commonly used finite element software owing to the lack of a dynamic two-phase element. The seismic analysis of tunnels at a saturated site is primarily based on OpenSees or self-compiled programmes, the majority of which are limited to uniform or horizontal-layered sites owing to the related issues of the inconvenience of modelling and the limited computation scale. In this study, based on ABAQUS, a finite element model for the earthquake response analysis of twin tunnels at a complex saturated site is established by calling the user-defined element, which is developed for the dynamic analysis of two-phase media. The wave propagation towards infinity is simulated by the viscous-spring boundary, the seismic wave is inputted in the form of the equivalent nodal force, and the soil nonlinearity is considered via the equivalent linear method. Differences between the earthquake responses of tunnels at a complex saturated site and a complex single-phase site as well as those between tunnels at a complex saturated site and a horizontal-layered saturated site are investigated to emphasise the effects of dynamic solid-fluid coupling and complex topography and geology.