# Centrifuge Model Investigation of Interaction between Successively Constructed Foundation Pits
## 3 Analysis of Test Results
Figure 6: Horizontal displacement of wall No. 1. The strain gauge at the 3 m depth of diaphragm wall No. 3 was damaged during model installation and thus produced no measurements. In addition, no laser displacement meter was installed on the top of diaphragm wall No. 3, and the displacement of the top of the wall was obtained by fitting the trend line. The bending moment and displacement of wall 3 are shown in Figures 9 and 10, respectively. As shown in Figure 9, in construction steps 1-3, the bending moment of diaphragm wall No. 3 generally increased with increasing excavation depth, but the position of the maximum bending moment moved downward in construction step 1. In construction steps 4-6, the bending moment of diaphragm wall No. 3 was small, and the change was small when excavating the adjacent pits. The displacement variation law of diaphragm wall No. 3 was similar to that of diaphragm wall No. 2, but the top displacement was positive in construction steps 4-6. Because no measuring points were arranged on the far end diaphragm wall of the foundation pit constructed later, it could not be compared to diaphragm wall No. 3. The bending moment and displacement of diaphragm wall No. 3 were generally larger than those of wall No. 2, and the displacement of diaphragm wall No. 3 in each construction step was greater than that of diaphragm wall No. 2. Therefore, the entire foundation pit constructed first was likely offset toward the middle. Figure 8: Horizontal displacement of wall No. 2. Figure 7: Bending moment of wall No. 2. Figure 11 and 12 show the variations in earth pressure on both sides of diaphragm wall \(1\) with each excavation step, respectively. Figure 11 shows that in construction steps 1-3, the active earth pressure outside diaphragm wall No. 1 decreased with an increasing excavation depth of the foundation pit constructed first and showed a roughly opposite trend in construction steps 4-6. The active earth pressure of diaphragm wall No. 1 in construction steps 1-3 was greater than that in construction steps 1-4, which was consistent with the deformation of the diaphragm wall throughout the construction process [26,28,29]. Because there were few passive earth pressure measuring points in the pit, the earth pressure was likely linearly distributed from the excavation surface to the measuring points. The figure also shows that the passive earth pressure on both sides of diaphragm wall No. 1 decreased with increasing excavation depth above 18 m.  
Figure 10: Horizontal displacement of wall No. 3. Figure 9: Bending moment of wall No. 3. Figure 12: Earth pressure distribution of wall No. 1 from Step 4 to Step 6. Figures 13 and 14 show the distribution of earth pressure on both sides of diaphragm wall No. 2 in each construction step, respectively. The earth pressure gauge of diaphragm wall No. 2 was damaged at a depth of 9 m, and thus, the distribution between 4 m and 14 m was assumed to be linear. The figure shows that in construction steps 1–3, the active earth pressure and passive earth pressure decreased with an increasing excavation depth for the first foundation pit. In construction steps 4–6, the active earth pressure and passive earth pressure remained relatively constant due to the relatively constant deformation of the ground wall. Table 4 shows the axial force of two adjacent foundation pit supports in each construction step. Table 4 shows that the variation pattern of the axial force at measuring points ZC-1, ZC-2, and ZC-3 in step 1 and step 2 was consistent with that of a single foundation pit excavation [8; 9; 10]. Compared with ZC-3 and ZC-4, the axial forces of ZC-5 and ZC-6 were much smaller. On the basis of this comparison, the axial force of the support of the later excavated foundation pit was markedly smaller than that of the first excavated foundation pit. ZC-4 was under tension in the process of foundation pit excavation in the previous construction and increased with increasing foundation pit excavation depth.