Seismic response and damage analysis of underground structures considering the effect of concrete diaphragm wall

This paper investigates the effect of concrete diaphragm wall on the seismic response of underground structures using numerical simulation. The seismic response of a two-story subway station supported by concrete diaphragm walls located in Nanjing, southeast China was analyzed. A finite element model was developed to simulate the soil-diaphragm wall-underground structure interaction during earthquakes. This model simulated the nonlinear dynamic behavior of soils using a visco-plastic model and concrete damage using a plastic-damage constitutive model. The effect of the diaphragm wall was explored related to the burial depth of the subway station. The simulation results showed that during a strong earthquake, the diaphragm wall reduced the lateral deformation of the lower story of the structure. However, the effect was very limited to the upper story of the structure. In contrast, during a small earthquake, the diaphragm wall increased the lateral deformation of the upper story of a deeply buried structure. The concrete diaphragm wall also increased the settlement of a deeply buried structure. The earthquake damage to the underground structure increased with the increase of the burial depth. The seismic tensile damage to the diaphragm wall was found adjacent to the invert of the structure. The damage to the diaphragm wall increased the uplift potential of a shallowly buried structure during earthquakes. Findings from this paper provide guidance to the seismic design of large underground structures buried in similar grounds.