Seismic response of a cross interchange metro station in soft soil: Physical and numerical modeling

The expansion of the Shanghai metro grid leads to a growing demand for underground stations. This paper studies the seismic performance of a typical cross interchange station in soft soil, combining shaking table testing and numerical modeling. The cross interchange station is composed of a three-storey section, rigidly connected to a perpendicular two-storey section, leading to an abrupt change of stiffness in the conjunction area. A series of 1 g shaking table tests are conducted, using synthetic model soil (a mixture of sand and sawdust) and granular concrete with galvanized steel wires to model the soil-structure system. The experimental results are then used as a benchmark, allowing for validation of a 3D finite element (FE) model. The validated FE model is shown to compare adequately well with the shaking table tests and is subsequently used to indirectly extrapolate the results to prototype scale. The combined experimental and numerical study allows deriving insights on the dynamic response of cross interchange stations. A key conclusion is that the abrupt change of stiffness at the conjunction area leads to concentration of racking deformation at the bottom storey. This leads to significant stress concentrations on the station sidewall in the same area, revealing the increased seismic vulnerability due to the induced stiffness discontinuity. Seismic damage can be avoided by increasing the reinforcement ratio in such critical locations or by introducing deformable joints.

Automated summary

This study investigates the seismic performance of a typical cross interchange station in soft soil through shaking table testing and numerical modeling, providing insights on the dynamic response of such stations. The research concludes that the abrupt change of stiffness at the conjunction area leads to stress concentrations, suggesting that increasing reinforcement ratio in critical locations or introducing deformable joints can help avoid seismic damage.