Monitoring and numerical simulation of deformation law of deep foundation pit of subway station in Lanzhou collapsible loess

Taking the deep foundation pit of Shijidadao Station of the first-stage project of Lanzhou subway line No. 1 as background, the deformation monitoring plan of its supporting structures is introduced. The monitoring items, instruments and frequencies are formulated. The in-situ monitoring is completed. According to the monitoring results, the characteristics of deformation of piles and the surrounding soils of supporting structures with time are analyzed. The results show that the design of supporting structures and the monitoring plan are reasonable. The supporting structures of bored piles and interior support can control the deformation efficiently and ensure a safe construction of the subway station. At the same time, the method of FLAC^3D is used to study the whole excavation process of the foundation pit. The calculated results are consistent with the monitoring data. This study may provide reference for the reasonable design and safety construction of deep foundation pits of subway in Lanzhou.