## 2 Test Design and Result Analysis
### Analysis of Monitoring Results
#### 2.3.2 Deformation of the Main Body and Subsidiary Structure of the Station  
(1) Deformation of the main station structure  
The deformation of each measuring point of the main structure of the subway station at different construction nodes is shown in Figure 8. During the excavation of the foundation pit from October 2018 to February 2019, the vertical deformation of adjacent subway stations was small. The main reason is that the influence of retaining pile construction and shallow soil excavation on adjacent stations is small in the early stage of foundation pit construction. During the construction period from February 2019 to May 2019, the vertical deformation of the station structure was large, and the excavation of the foundation pit had a great influence on the central position of the main structure of the station. The overall deformation trend of the station is large in the middle and small in the end. The maximum vertical deformation of the main structure of the station occurs at measuring point ZDH-7, i.e., the central position of the station. This deformation trend is consistent with the deformation trend of the numerical simulation. The maximum vertical deformation of the station is 1.43 mm. To study the vertical deformation law of the main structure of the station in the process of foundation pit construction, the time-history data of the station vertical deformation monitoring points ZDH-3, ZDH-6 and ZDH-11 are selected for analysis, as shown in Figure 9.  
Figure 7: Time\(-\)history curve of the deep horizontal displacement of the retaining pile. (**a**) Measuring point ZQT-4; (**b**) measuring point ZQT-9; (**c**) measuring point ZQT-15; (**d**) measuring point ZQT-21. According to Figure 9, during the construction of foundation pit retaining piles and temporary columns, the station has a slight subsidence trend. The deformation of the vertical displacement of the main structure of the station in the excavation stage is divided into three parts:  
(a) When the excavation depth of the foundation pit is 3.5 and 9.5 m in excavation stages 1 and 2, respectively, the deformation of the station remains stable, and there is a slight downward trend. The soil outside the foundation pit should be squeezed inward due to the excavation and unloading of the foundation pit soil, but the soil outside the pit is squeezed due to interbracing, resulting in a slight downward movement of the vertical deformation of the station structure. (b) In the third stage of excavation, i.e., the excavation depth from 9.5 to 14.5 m, the vertical displacement deformation of the station began to increase considerably. With the increasing excavation depth of the foundation pit, the retaining piles of the foundation pit are more exposed inside the foundation pit, while the active earth pressure outside the pit increases, and the supporting effect of interbracing weakens. The soil outside the foundation pit has an inward inclination trend, and the station has an upward displacement trend. (c) During excavation stages 4 and 5, the vertical deformation of the station has a clear upward trend; that is, when the excavation depth of the foundation pit is greater  
Figure 8: Vertical displacement time–history curve of each measuring point of the station. Figure 9: Vertical displacement time–history curve of the station structure. than 14.5 m, the excavation depth of the foundation pit further increases, and the vertical deformation of the station is more pronounced. In the stage of bottom slab pouring and structure construction, the station structure generally presents a floating trend, in which the bottom slab pouring stage fluctuates and sinks, and the maximum vertical deformation of the main structure of the station is 1.29 mm.