## 3 Numerical Simulation
### Result Analysis  
#### 3.3.1 Deformation of Adjacent Soil  
Prior to the simulation of the construction stage, the initial state of the model was corrected for zero displacement. Moreover, the initial state stress was analyzed, with the initial stress field used for the initial state. The paper, which focuses on a pipeline adjacent to a foundation pit, mainly deals with soil deformation outside the support structure, without researching the soil deformation inside the foundation pit. Figure 6 shows the horizontal displacement induced by excavation. It can be seen from the figure that, in both layered excavation and bench excavation, the maximum horizontal displacement occurred mainly in the middle part of the foundation pit. For ease of analysis, three points were selected in the figure. Point 1 is the midpoint of the area where foundation pit excavation begins. Point 2 is the midpoint of the area near the side of the pipeline. Point 3 is the midpoint of the tapered section. All three points are located at the edge of the foundation pit. According to the numerical simulation results of layered excavation, the maximum horizontal displacement of soil was 2.7 mm when the foundation pit was excavated to a depth of 1.5 m, and the maximum point was 0.7 m below the surface; the excavation depth was 4.5 m, the maximum horizontal displacement was 4.8 mm, and the maximum point was 3.2 m away from the ground; the excavation depth reached 9.2 m, the maximum horizontal displacement was 7.6 mm, and the maximum horizontal displacement point was 11.4 m away from the ground. Figure 6a shows the horizontal displacement of the  
Figure 5: Overall calculation model of the metro station. Figure 6: Horizontal displacement after completion of excavation. (**a**) Layered excavation completed; (**b**) Bench excavation completed. soil after the excavation was completed (at a depth of 13.7 m). The maximum horizontal displacement was 11.7 mm and occurred at 15.2 m below the ground at point 2. It can be seen that, with the progress of excavation, the position of the peak point of horizontal displacement continued to decline, with the depth of decline being 46.7%, 106.7%, 140.4%, and 131.1% of the excavation depth increment. It can be found that a greater excavation depth increment led to a greater decline in the peak point of horizontal displacement. A smaller thickness of the excavation layer led to a lesser fall of the horizontal displacement point, enabling the support structure to play its full part. However, a larger depth of excavation facilitates construction. The thickness of an excavation layer should be designed on the basis of the requirements of the project. The simulation results of bench excavation show that, when the excavation progress reached half of the total workload, the maximum horizontal displacement reached 5.14 mm and occurred at point 2, 13 m below the ground. The horizontal displacement after the excavation was completed is shown in Figure 6b. The maximum horizontal displacement was 11.1 mm and occurred at a point along the width of the tapered portion (i.e., point 2 in the figure). This point with peak displacement was 15.5 m below the ground. Figure 7 shows the horizontal displacement at the three points. From the figure, it can be concluded that the displacement at point 1 was smaller than that at the other two. [PERSON] et al. [28] analyzed the spatial effect mechanism and soil stress. They believed that the soil arching effect in the areas near the corners of a pit reduced soil pressure, which contributes to deformation reduction for the support structure and soil. For a long, narrow deep foundation pit in metro transit projects, excavation at the ends of the pit sees small deformation, despite great excavation depths. The deformation control by the support structure focuses on the lateral displacement control of the continuous wall in standard sections in the middle of the pit.