# Displacement Analyses of Main Structure of Parallel Pit Excavation and Analysis of Countermeasures
## 3 Parallel Pit Excavation Scheme
### Retaining Wall Deformation
#### 4.2.3 The Steel Pipe Structs' Horizontal Deformation  
Because of this paper's length constraint, only the middle column of the steel pipe in Area B is selected as the object of analysis (see Figure 5). Figure 12: Horizontal deformation of retaining wall. Under Case 1 conditions  
The horizontal deformation of the steel pipe structs is mainly caused by the redistribution of soil stress caused by the excavation of the foundation pit. Figure 14 shows the horizontal deformation of the steel pipe structs under the condition of Case 1. The deformation trends of the steel pipe structs (Struct 1, Struct 2, and Struct 4) immediately adjacent to the excavation side are the same, and they show a convex deformation to the excavation side, respectively; and Struct 1, Struct 2, and Struct 3 show deformation to the south side, while Struct 4 shows deformation to the north side. The maximum horizontal deformation values of the steel pipe Struct 1 and Struct 4 are 8.25 mm and 5.8 mm, respectively. The main reason is that the distance of the steel pipe structs from the pit edge is different. Struct 1, Struct 2, and Struct 3 are 3 m, 12 m, and 21 m from the common D-walls, while Struct 3 and Struct 4 are 24 m and 15 m from the pit in Area C. The excavation of Area C is using the slope-cut method, and the soil behind the slope limits the horizontal deformation of Struct 4. In addition, the distance of Struct 3 from the pit edge is larger, and the soil-stress redistribution has less influence on Struct 3. It can be seen that the excavation of the pit on both sides has a more obvious influence on the steel pipe structs on the adjacent excavation side, and the distance from the pit edge is the key factor affecting the deformation of the structure. Figure 14: Case 1: synchronous excavation, steel pipe structure horizontal deformation. Figure 13: Maximum vertical deformation of steel pipe structs. Under Case 2 conditions  
Under Case 2 conditions, after excavation in Area A was complete, the lateral displacement of the steel pipe struct is shown in Figure 15.  
As can be seen from Figure 16, Struct 1 after the excavation of Area A is completed, the steel pipe structs as a whole move to Area A. The closer they are to Area A, the greater the horizontal deformation of the structure, in the order of Struct 1 > Struct 2 > Struct 3 > Struct 4. The maximum lateral deformation of Struct 1 and Struct 4 is 14.86 mm and 11.06 mm, respectively. Struct 1 and Struct 2 show a convex deformation, while Struct 3 and Struct 4 show a cantilever-type deformation. The main reason is that only the top slab is applied in Area B; the top and bottom of the steel pipe structs are restrained, while the middle part is relatively free. Struct 1 and Struct 2 near Area A are most obviously influenced by the asymmetric lateral soil pressure, which makes the steel pipe structs present the deformation of the large in the middle and small on both sides. Struct 3 and Struct 4, which are far away from the  
Figure 16: Case 2: sequential excavation, steel pipe structure horizontal deformation (zone 02B excavation completed). Figure 15: Case 2: sequential excavation, steel pipe structure horizontal deformation (zone 03A excavation completed). pit, are less affected by the soil pressure but are \"pulled\" by the steel pipe structs (Struct 1 and Struct 2), which makes Struct 3 and Struct 4 show a larger deformation at the top. The above can be seen, that the steel pile structs is not only affected by the redistribution of stress in the soil on the side of the adjacent excavation, but also by the superposition of the differential deformation of the steel pile structs. b.