Series of centrifuge shaking table tests study on seismic response of subway station structures in soft soil sites

Due to the planning of the subway route, it is difficult to avoid crossing soft soil site conditions at subway stations. The seismic response of subway station structures is closely related to the surrounding soil site. In this paper, centrifuge shaking table tests were designed and carried out for subway station structures at three typical soft soil sites (all-clay site, liquefiable interlayer site, and fully liquefiable site). The test results are as follows. The structure is most severely damaged in all-clay site, while the damage is low in liquefiable interlayer site and fully liquefiable site. For liquefiable sites, site liquefaction results in a lower soil-structure stiffness ratio. Thus liquefiable interlayer site and fully liquefiable site provide a natural seismic isolation system for structures compared to all-clay site. The limits of the inter-story drift ratio of the structure were used to evaluate the post-earthquake performance stages of the model structure in the three sites. In all-clay site, the structure is in the “immediately operational” stage after the loading condition of 0.1g and 0.32g, and in the “reparable operational” stage after the loading condition of 0.52g and 0.72g. In the liquefiable interlayer site and full liquefiable site, the underground structure is in the “normal operational” stage after the loading condition of 0.1g and in the “immediately operational” stage after the loading condition of 0.32g–0.72g.