Underground structures may be buried in liquefiable sites, which can cause complex seismic response mechanisms depending on the extent and location of the liquefiable soil layer. This study investigates the seismic response of multi-story underground structures in sites with varying distributions of liquified soil employing an advanced three-dimensional nonlinear finite element model. The results indicate that the extent and location of liquefied soil layers affect the seismic response characteristics of underground structures and the distribution of their damage. When the lower story of the subway station is buried in liquefied interlayer site, the structure experiences the most serious damage. When the structure is located within a liquefiable interlayer site, the earthquake ground motion will induce greater inter-story deformation in the structure, resulting in larger structural residual displacement. When all or part of the underground structure is buried in the liquefiable soil layer, the structural failure mode should be assessed to ensure that the underground rail transit can quickly restore functionality after an earthquake. Meanwhile, permeability effects of liquefiable soil have a significant impact on the dynamic response of subway station in the liquefiable site.

In seismic regions, many underground structures are inevitably partially embedded in liquefiable sites, which may cause complex seismic response mechanisms due to the varying distribution of liquefiable soil layers. This study investigates dynamic interaction between underground structures and liquefiable soils employing three-dimensional nonlinear finite element models. The seismic response of both standard and connection sections of the subway station-tunnel of underground structures in liquefiable sites is evaluated to reveal the seismic response patterns of the soil-structure system under different liquefiable soil distribution forms. The results revealed that compared to homogeneous liquefiable sites, liquefiable interlayer sites can cause greater seismic damage to underground structures, potentially leading to failure along the entire length of the subway station. Therefore, the post-earthquake failure modes of the structure and site should be comprehensively considered based on the site layers distribution characteristics.

When an underground structure passes through a liquefiable soil layer, the soil liquefaction may pose a significant threat to the structure. A centrifuge shaking table test was performed to research the seismic response of underground structures in liquefiable interlayer sites, and a valid numerical model was obtained through simulation model test. Finally, the calibrated numerical model was used to perform further research on the influence of various distribution characteristics of liquefiable interlayers on the seismic reaction of underground structures. The key findings are as follows. The structure faces the most unfavorable condition once a liquefiable layer is located in the middle of the underground structure. When a liquefiable layer exists in the middle of the structure, the seismic reactions of both the underground structure and model site will increase with the rise of the thickness of the liquefiable interlayer. The inter-story drift of the structure in the non-liquefiable site is much smaller than that in the liquefiable interlayer site. The inter-story drift of the structure is not only associated with the site displacement and the soil-structure stiffness ratio but also closely associated with the slippage of the soil-structure contact interface under the condition of large deformation of the site.