Seismic response of a long shield tunnel crossing through multiple soil deposits

This study investigated the seismic response of a long shield tunnel crossing multiple soil deposits. The P2PSand model and practical-oriented hysteretic model were used to simulate the cyclic behaviour of liquefiable sand and soft clay, respectively. A refined tunnel model was adopted to simulate the mechanical behaviour of segmental linings. Dynamic analysis was then performed to explore the seismic response of shield tunnels passing through liquefiable sand and soft clay under transverse or longitudinal asynchronous ground motions. The joint displacement and lining force were found to be prominent near the interface between the liquefiable sand and soft clay. The counterintuitive seismic deformation mechanism of tunnel structure was then clarified. Parametric studies were carried out to elucidate the tunnel deformation mechanism. The seismic responses of the tunnel structure under longitudinal ground motions were more prominent than those under transverse ground motions. The earthquake intensities, relative densities and liquefaction potentials of sand, and clay stiffness exerted major influences on the seismic response of tunnel structure, while the interface inclinations and earthquake wave velocities had a slight impact on the tunnel seismic response.