Numerical modeling on the seismic responses of a large underground structure in soft ground

To estimate the earthquake damages of a large subway station built in soft ground, a soil-underground structure static and dynamic coupling interaction model is advanced with the strong nonlinear properties of soil modeled by a developed viscous-plastic constitutive model. The numerical modeling results show that the large underground structure in soft site has a large vertical relative deformation during the horizontal earthquake, which could be larger than its horizontal relative deformation. The dynamic deformation responses of the components near to the middle span of the underground structure are obviously larger those of the other components at the side spans, which means that these components near to the middle span are more apt to be damaged in horizontal earthquake. According to the horizontal relative deformation and the seismic damage process of the large underground structure, which limited elastic working state and the limited elastic-plastic working state are determined, and the maximal interlayer displacement angles are suggested to be 1/430 for the limited elastic working state and 1/185 for the limited elastic-plastic working state. In addition, the seismic soil pressure coefficients on the upper side wall have significant changes. To the large underground structure shown in this paper, the seismic soil pressure coefficients on the top half of the upper side wall should be defined alone in its seismic design.