Effect of different groundwater levels on seismic response of subway stations shallowly buried in the sand foundation

Sand liquefaction caused by earthquakes is one of the serious threats to underground stations. The change in groundwater level may have a great influence on the seismic behavior of underground stations buried in sand foundations. In this paper, a 3D numerical model for the soil-structure interaction system was established by applying the fully nonlinear finite difference program FLAC3D. The impact of different groundwater levels on the seismic behavior of underground stations was explored in numerical analyses. The fluid-solid coupling and different seismic intensities were taken into consideration in the model. The numerical results demonstrate that the decrease of groundwater level significantly restrains the uplift of the underground station and the liquefaction of the site. The dynamic soil pressure around the sidewall under a higher water table is larger than that under a low water table. Under the earthquake, the ground peak acceleration increases as the groundwater level decreases. For the station structure, the decrease of groundwater level is unfavorable to the shear resistance of the middle columns. However, the effect of different groundwater levels on the axial stress of the middle columns is relatively small. The research results can be used as a reference for the seismic design of subway stations shallowly buried in the sand foundation with different groundwater levels.