## 4 Parametric Analysis
#### 4.1.2 Influence of Different Pile Diameters of Retaining Piles  
To analyze the influence of the diameter of the retaining pile of the foundation pit on the existing subway station and track structure, the diameter of the retaining pile near the station side is set to be 0.6, 0.8, 1.0, 1.2 and 1.4 m for foundation pit excavation simulation. The diameter of the retaining pile near the station side is taken as the initial condition (i.e., the pile diameter is 1.2 m). The maximum deformation curves of the station and track structures under various conditions are shown in Figure 26.  
The maximum vertical deformation of the station and track structure decreases with the increasing diameter of the retaining pile. The maximum vertical deformation of the station is between 2.68 and 2.93 mm, and the maximum deformation of the track structure is between 2.41 and 2.62 mm  
Through the analysis of foundation pit retaining pile parameters (retaining pile embedded depth and diameter), it can be seen that the embedded depth of the new deep foundation pit retaining pile has a great influence on the adjacent subway station. When the retaining pile embedded depth increases to 8 m, the maximum displacement of the station and track decreases more. The maximum displacement of the station and track changes little when the embedded depth of the retaining pile increases from 8 to 10 m. When the diameter of the retaining pile increases from 0.6 to 1.4 m, the maximum displacement of the station and track structure changes little, which indicates that the diameter of the retaining pile has little effect on the deformation of the adjacent subway station and track. Influence of Internal Support Parameters on the Deformation of the Existing Station and Track 4.2.1. Influence of Different Support Section Sizes  
To explore the influence of the interbracing stiffness of the deep foundation pit on the deformation of adjacent existing subway stations and track structures, the stiffness of interbracing is controlled by changing the cross-sectional area of interbracing based on the influence parameters of interbracing stiffness. To better study the relationship between the deformation of the station and track and the section size of the interbracing, the section size of the third interbracing is taken as the initial parameter (that is, the section size is 1.0 m \(\times\) 1.0 m). On this basis, one side of the section is changed as the comparison condition. It is assumed that the sections of the third interbracing under five conditions are A1 (0.8 m \(\times\) 1.0 m), A2 (0.9 m \(\times\) 1.0 m), A3 (1.0 m \(\times\) 1.0 m), A4 (1.1 m \(\times\) 1.0 m) and A5 (1.2 m \(\times\) 1.0 m). The maximum deformation curves of the station and track structures under various conditions are shown in Figure 27.  
The maximum vertical deformation of the station and track structure decreases with increasing interbracing section size. The maximum vertical deformation of the station is between 3.10 and 3.56 mm, and the maximum deformation of the track structure is between 2.79 and 3.20 mm. When the interbracing section of the foundation pit supporting system increases from A1 to A5, the maximum vertical displacement of the station and track structure decreases by 6%, 10%, 11% and 13% and 6%, 9%, 11% and 13%, respectively. The maximum horizontal deformation of the station and track structure decreases with increasing interbracing stiffness. The maximum vertical deformation of the station is between 3.75 and 4.31 mm, and the maximum deformation of the track structure is between 3.43 and 3.94 mm. The maximum horizontal displacement of the station and track structure decreases by 4%, 8%, 11% and 13% and 6%, 9%, 11% and 13%, respectively, when the interbracing section increases from A1 to A5. Figure 27: Maximum vertical and horizontal deformation values of stations and tracks under different interbracing section sizes. The vertical and horizontal displacements of station and track structures are less affected by the interbracing section size in the foundation pit.