Seismic behavior of underground station and surface building interaction system in earth fissure environment

Earth fissures, special engineering geological hazards, destroy the integrity of the ground and enlarge seismic responses of structures. Because of this, the safety of structures in the earth fissure environment is hard to guarantee, especially in bustling areas of the city in which underground stations and surface structures are affected by each other under earthquakes. In this paper, the 3D finite element models of the surface structure, underground station, and ground soil with earth fissure were built, taking into account the interaction between structures and soil. Then, the artificial boundary was verified, and seismic behaviors of earth fissure ground were compared with the test result. The experiment and the calculation result showed the same tendency. Moreover, the key parameters of the simulation model were modified, and the acceleration amplification factors of the underground station were analyzed. Finally, based on the most unfavorable condition, the failure mechanism of the underground station was analyzed. The numerical results indicate that the existence of earth fissure and surface structure amplifies the seismic responses of the underground station. The increase in floor number of surface structure and decrease in shear modulus of soil also enlarge the seismic responses of the underground station, and this amplification effect is more obvious in the earth fissure environment. The columns of the underground station in the hanging wall are one of the crucial parts to the bearing capacity of the station, and are destroyed due to the P-Δ effect and the uneven vertical settlement of the underground station. These results are significant for studying the effect of earth fissure on the seismic responses of the underground station.