## 4 Results and Analysis  
### Results of Asymmetrical Construction  
#### 4.1.1 Lateral Displacement of Supporting Pile  
The displacement curves of supporting pile subjected to different construction processes are shown in Figure 7. It is seen that southern pile deforms obviously during the excavation of the southern pit. The displacement at the top of the pile is 3.48 mm towards the soil, and it is 7.11 mm at the bottom of pit after soil excavation. The maximum deformation is observed at the bottom of the pit. During the process of pile cutting above the pit bottom, little deformation is observed. When the construction of the southern connecting part is complete, the remaining part of the pile moves towards the opposite direction (away from the soil), with the maximum value of 4.98 mm at the top and 2.76 mm at the bottom. The deformation at the bottom decreases more obviously than that at the top. When the construction of the northern connecting section is completed, the deformation of the pile shows a similar change. During the whole procedure of asymmetric construction, the maximum deformation of the pile is 10.53 mm at the pit bottom, which indicates that the lateral displacement varies more significantly at the bottom of the pit.  
A similar deformation behavior is observed in the northern pile, as shown in Figure 6b. During the construction of the southern part, the deformation of the supporting pile (towards the soil) is 4.13 mm at the top and 2.23 mm at the bottom. After construction, little deformation is observed below the pit bottom, with the maximum deformation of 1.98 mm at the pit bottom. During the whole construction procedure, the maximum lateral displacement towards the soil is 6.27 mm, which occurs at the pit bottom of the tunnel structure.  
Figure 6: Comparisons of strain of top slab between numerical simulation and field investigation: (a) Case 2; (b) Case 3 and (c) Case 4 (unit: \(\mu\epsilon\)).  
The above deformation behavior is related to the mechanical characteristics of the supporting pile (see Figure 8). The supporting pile is divided into two parts by taking the bottom line of the foundation pit as the interface, known as Section _AB_ and Section _BC_. As for Section _AB_, the deformation behavior of the supporting pile is dependent on the loading cases. The supporting pile tends to move towards the direction away from foundation pit when the soil behind supporting pile is excavated. The construction of the tunnel frame structure on the other side will also cause the supporting pile to move away from the foundation pit. There is an uneven stress of the whole system, and the supporting pile is affected by earth pressure from the left side. As for the Section _BC_, the supporting pile tends to move towards the right during the whole construction period (see Figure 8), since there is a constraint at Section _AB_ due to the tunnel frame structure. Section _BC_ is extruded by the soil near the connection section due to the self-weight of the tunnel frame structure, as well as an unloading induced by soil excavation on the other side. The distribution of force greatly influences the deformation behavior of the supporting pile.  
Figure 8: The force analysis of supporting pile.  
Figure 7: Lateral deformation of supporting pile by asymmetric construction method: (**a**) southern pile and (**b**) northern pile (unit: mm).