Investigations on the seismic performance of a shield tunnel adjacent to an underground station in liquefiable ground through shaking table tests

Abstract

The seismic response of tunnels in liquefiable ground requires careful consideration of adjacent structures due to potential structure-soil-structure interaction (SSSI) effects. These interactions can significantly influence the behaviour of underground systems during earthquakes, potentially affecting structural integrity and safety. This study aims at explore the interaction effect of a large diameter shield tunnel and a shallow-buried station with rectangular section under seismic motion in liquefiable ground. For this purpose, 1 g shaking table tests of model SSSI system is designed. The model shield tunnel was manufactured with segments and joints using plexiglass, while the model rectangular station was precast using concrete embedded at a shallow layer adjacent to the tunnel. The responses of excess pore water pressure (EPWP), acceleration, displacement of the foundation in SSSI system and deformation of shield tunnel were measured and analysed in detail. The influence of relative stiffness of different structures is discussed based on finite element method. The experimental results show that the SSSI system exhibited a certain nonlinearity and plastic damage under input motions. Shear stress from two sides of the model structures caused the soil to dilate, resulting in a reduced EPWPR build-up between the two structures. Attenuation of the high-frequency components in the seismic wave was also observed in the soil between two structures. The tunnel structure exhibited a vertical stretching deformation at around 15° angle from the vertical direction. The soil beneath the station has compensated for the soil loss caused by the uplift of the model tunnel during the process of tunnel uplift under input motion with high GPA. These new findings in the case of SSSI is helpful for the design and construction of underground structures.