Three-dimensional nonlinear seismic response analysis of subway station crossing longitudinally inhomogeneous geology under obliquely incident P waves

Abstract

With the rapid development of underground space, more adverse site conditions are occurring in the construction of underground structures. For example, a subway station passes through longitudinally inhomogeneous geology. When the subway station crosses the interface of soft soil and hard soil, this may lead to the destruction of underground structures. In this paper, three-dimensional (3D) nonlinear seismic response analysis of subway stations crossing longitudinally inhomogeneous geology subjected to obliquely incident P waves is presented based on actual engineering background. The earthquake input method for the longitudinally inhomogeneous site that transforms the site seismic response into an equivalent nodal load is first developed and verified. The viscous-spring artificial boundary is used to simulate the radiation damping effect of infinite domain media. Subsequently, the topographic and geological effects on seismic response of engineering site are investigated. Finally, the failure mechanism of the subway station structure crossing longitudinally inhomogeneous geology under the obliquely incident P waves is revealed. The investigation demonstrates that the plastic zone of site usually appears along the interface between the hard and soft soil media, and appears on the side of the soft soil. The sidewall and bottom slab of the structure experience obvious tensile damage at the interface location between the hard and soft soil media. The results show that topographic and geological effects should be considered in seismic analysis and design of underground structures when the topography and geology change significantly.