## 4 Analysis and Discussion  
### Field Monitoring Results of Foundation Pit  
#### 4.1.1 Monitoring Results of Diaphragm Wall  
Figure 4 shows the monitoring results of the horizontal displacement of diaphragm wall during the excavation to the bottom of the foundation pit at the project site. The monitoring points in Figure 4 were mainly located in the northern section of the diaphragm wall of sub-pit 3A10-1, and the displacements of the wall at this location showed a typical parabolic pattern. Among them, the ZQT7 and ZQT9 monitoring points were located in the middle of this segment of the wall. The monitored maximum horizontal displacement was close to or even reached the monitoring warning value of 45 mm, which might be due to the fact that the road near this segment of the wall was subjected to loads from passing dump trucks as well as heavy equipment for a long period of time. At the project site, the construction workers reinforced the soil of the foundation pit, which limited the further development of foundation pit deformation and ensured the construction safety. The monitoring points of ZQT5 and ZQT11 were located at the edges of the wall and were affected by the shading effect of foundation pit corners, and the measured values at these points were much smaller than these at the monitoring points of ZQT7 and ZQT9. The monitoring points in Figure 4 were primarily located in the western diaphragm wall of sub-pit 3A10-1, which was affected by the pre-built diaphragm wall of the adjacent sub-pit, and this segment of the wall was all within the influence of the foundation pit corner effect. Compared with Figure 4, the monitoring values at the monitoring points in Figure 4 were consistent with the measured values at the monitoring points of ZQT5 and ZQT11 and were much smaller than those at the monitoring points of ZQT7 and ZQT9. This further verified that the zonal excavation fully utilized the foundation pit corner effect and could effectively limit the horizontal deformation of the foundation pit. Similarly, this could be demonstrated from the monitoring results of sub-pit 3A5 (Figure 4) and sub-pit 3A8 (Figure 4). It is not reasonable to simplify the zonal excavation of the foundation pit into a two-dimensional plane strain problem for design calculation, which will greatly overestimate the horizontal deformation of the foundation pit with zonal excavation. Figure 4-e illustrates the horizontal deformation of the southern diaphragm wall in sub-pit 3A10-2 as it was excavated to the bottom of the foundation pit. Monitoring points ZQT38 and ZQT39 showed maximum displacement values at the top of the wall, and the wall experienced a cantilevered dislocation pattern. The other five monitoring points also underwent large displacements at the top of the wall, although they still showed a parabolic displacement pattern. This may be attributed to the overall relocation and transfer \begin{table}
\begin{tabular}{c c c} \hline \hline
**Construction Number** & **Foundation Pit No.** & **Construction Step** \\ \hline \multirow{8}{*}{Condition 5} & & Excavate to \(-3\) m \\  & & Erection support 1 \\  & & Foundation pit 3A2 and 3A4 excavated to \(-7\) m, foundation pit \\  & & 3A1-1, 3A3-1 and 3A6 excavated to \(-6\) m \\  & & Erection support 2 \\  & & Foundation pit 3A2 and 3A4 excavated to \(-11\) m, foundation pit \\  & & 3A1-1, 3A3-1 and 3A6 excavated to \(-9\) m \\  & & Foundation pit 3A2 and 3A4 ercation support 3 \\  & & Foundation pit 3A2 and 3A4 excavated to \(-15\) m \\ \hline \multirow{8}{*}{Condition 6} & & Excavate to \(-3\) m \\  & & Erection support 1 \\  & & Excavate to \(-7\) m \\  & & Excavate to \(-7\) m \\  & & Erection support 2 \\  & & Excavate to \(-11\) m \\  & & Erection support 3 \\  & & Excavate to \(-16\) m \\ \hline \hline \end{tabular}
\end{table} 
Table 3: _Cont._of the Yuantai Building prior to the excavation and construction of sub-pit 3A10-2, and the large-scale load removal resulted in the displacement at the top of the diaphragm wall towards the foundation pit.