Shaking table test on the seismic response of large-scale subway station in a loess site: A case study

摘要

More and more underground infrastructures have been built in special soil in recent years, especially in the loess area of western China. The loess, as a special soft soil, can have particular influence on the seismic characteristics of underground structures. Therefore, the seismic performance and safety evaluation of underground structures in loess area should be concerned. A series of large-scale shaking table tests were performed to investigate the damage mechanisms of a frame-type subway station structure in a loess site. The test results showed that the model soil softening and the stiffness degradation of the soil-structure system were more serious under stronger input motions. The acceleration response of the soil-structure interaction system in a loess site was more like that of a free-field when input PGA is lower. However, the soil-structure interaction phenomenon was more remarkable both in horizontal and vertical direction when higher PGA was input. The dominant frequency of the input motion had an inverse effect on the lateral soil deformation. The direct-force action mode of the dynamic earth pressure acting on underground structures presents a trumpet-type distribution. Meanwhile, the soil structure interaction exhibited complex mechanical behavior, and slipping or gapping in test cases with higher PGA may occur. The strain measured in the center pillar and middle slab of the subway station was larger than that in other components. The results provide an insight into how strong ground motion might induce the influence and a possible way to describe quantitatively the damage of subway structure in loess ground.