## 4 Results and Discussion
### Internal Support Axial Force  
It can be seen from Figure 2b that the number of internal supports in the foundation pit group is large and the support system is complex. The internal support positions of each pit are not at the same height, so the axial force variation of the support cannot be estimated by conventional methods and engineering experience, which greatly increases the engineering risk. However, the layered construction process of the support can be considered in a numerical simulation, which is an effective way to solve this problem. Figure 6 shows the maximum supporting axial force after each excavation.  
It can be seen from Figure 6 that the maximum axial force of the support in Pit A is always far greater than that in other pits in each construction stage. After the excavation of all foundation pits, the maximum axial forces of the supports in Pit A-Pit F reach 13,350 kN, 5286 kN, 7723 kN, 8365 kN, 3540 kN, and 1257 kN, respectively. As the minimum width of Pit A is only 13.5 m, the internal supports have a strong supporting effect. In addition, Pit A is close to a building, which makes the axial force of the internal support in Pit A larger, always exceeding that in other pits in the subsequent construction stage. After Stage 2 excavation, the maximum axial force of support in Pit B is always less than that in Pit C. The excavation depth of Pit B is 22 m, and the pit-in-pit is located in the middle with a small excavation area. In contrast, Pit C is a large excavation area with a curved shape, and the excavation depth is 23.8 m. The pit-in-pit in Pit C is close to the diaphragm wall with a large excavation area. Therefore, the supports in Pit C have greater axial forces. Similarly, the maximum axial force of the support in Pit D is always greater than that in Pit E. The excavation depth of Pit F is the shallowest, only 4.5 m, so the maximum axial force of support is the smallest.  
After the process of Stage 2, the maximum axial force of the support in Pit A increases from 7000 kN to 13,270 kN, increasing by 89.6%. After Stage 3 excavation, the maximum axial force of the support continues to increase to 13,350 kN, with an increase of 0.6%. It can be seen that the second stage excavation has a significant impact on the maximum axial force in Pit A. Pit B and Pit C are close to Pit A. When they are excavated at the same time, the soil mass near Pit A receives an unloading disturbance and the supports in Pit A will bear greater axial forces. However, Pit D, Pit E, and Pit F are far away from Pit A, so their excavation has little impact on the axial force in Pit A, which could almost be ignored.  
After the construction of Stage 3, the maximum axial force in Pit C increases from 7314 kN to 7723 kN, with an increase of 5.6%, and the maximum axial force in Pit B increases from 5259 kN to 5286 kN, with an increase of 0.51%. It can be seen that the third stage excavation has a certain degree of influence on the axial force in Pit C. The excavation area of Pit D is obviously larger than that of Pit E and Pit F, and it is close to the curved Pit C, so the construction of Stage 3 mainly affects the support of Pit C. The shapes of Pit E and Pit F are similar--both are narrow and long, so the impact on the axial force in Pitts C and B is very small.  
In general, the maximum axial force of the support in Pit A is far greater than that in other pits, and the excavation of Stage 2 has a great impact on the axial force in Pit A. Pit A is close to the existing building, and the coupling effect of adjacent excavations shows  
Figure 6: Maximum axial force variation of internal support.  
the obvious impact on the maximum axial force in Pit A. In addition, the excavation of the third stage has a certain influence on the axial force in Pit C. Therefore, during the construction of the foundation pit group, full attention should be paid to the impact of adjacent pit excavation on existing supports, especially the development of the axial force of the support in Pit A.