Seismic response of segmental tunnel in soil-rock strata under longitudinal excitation: experimental and numerical analysis

Tunnels passing through inhomogeneous ground conditions are particularly susceptible to significant damage during earthquakes. This study investigates the seismic response of a segmental tunnel crossing soil-rock strata under longitudinal excitation. A 1g shaking table test is conducted to model the soil-structure interaction (SSI) system. Earthquake input and observation focus on longitudinal SSI. The experimental results are then employed to calibrate a 3D finite element (FE) model, where the seismic behavior of synthetic model soil is characterized by a kinematic hardening constitutive model, and the model rock and tunnel are simulated using an elastic constitutive model. The validated FE model shows good agreement with the shaking table test results and provides insights into the longitudinal joint deformation and overall deformation patterns of the tunnel. Considering the key seismic characteristics of the tunnel, a simplified analytical model for calculating the joint extension is developed and verified against the numerical results, quantitively revealing the concentrated joint deformation caused by the ground with abruptly varying stiffness.