Study of the effect of seismic performance measures on a metro station structure in liquefiable soil

Abstract

After the concept of ‘resilient city’ was introduced, the anti-seismic and resilience enhancement of underground structures gradually became an important issue in engineering. In this study, a method for enhancing the resilience of a soil–structure system subjected to earthquakes is proposed. First, a water-soil fully coupled numerical model was established to analyse the seismic behaviour and enhancement effect of a station structure subjected to an earthquake in liquefiable ground. In the analysis, an elastoplastic cyclic mobility model was used to describe the soil behaviour, whereas an interface joint element model was used to consider the soil-structure interaction. Subsequently, a non-liquefied clay replacement method was designed, and the effects of the replacement position and thickness on the floating displacement and internal force of the structure were analysed. To fully utilise the cushioning effect of the liquefiable sand and the anti-floating drainage near the station structure, a unilateral drainage diaphragm wall that does not drain in the far-field soil and drains in the near-field soil is proposed around the station structure. Based on the analysis results of different cases considering the soil replacement position, replacement thickness, distance between the unilateral drainage diaphragm wall and station structure, and buried depth of the wall, combined measures of clay replacement with unilateral drainage diaphragm wall were examined. The results show that the combination of the two measures significantly reduced the floating displacement, restrained the additional internal forces of the structure, reduced the time for the structure to reach stability after an earthquake, which is helpful to enhance the ability of self-recovery and improve the seismic resilience of the underground structure.