# Model Test on the Behaviors of Deep Excavation with Lateral Confined Water
## 3 Results  
### Analysis of Lateral Pressure of diaphragm Wall  
The increment curve of the lateral pressure (combined earth pressure and water pressure) on the diaphragm wall is shown in Figure 8. Positive and negative values represent the increases and decreases in lateral pressure, respectively. Variations in soil compaction led to some discrepancies in the increment curves of lateral pressure on both sides of the excavation, but the distribution trends with depth remain similar. Specifically, in stage 1 (O), except for a few monitoring points at the top and bottom of the diaphragm wall, the lateral pressure generally shows a decreasing trend. In stage 2 (K1-K4), as the excavation progresses and the strut system is installed, the amplitude of lateral pressure changes initially decreases, but increases again after the excavation reaches the depth of the fourth soil layer (K4), which is within the lateral confined aquifer. In stage 3 (F), the rise in lateral confined water level further increases the amplitude of lateral pressure changes. Notably, lateral pressure changes are most pronounced within the confined water depth range, suggesting a significant impact on the diaphragm wall's stress and deformation characteristics. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Stage** & **Working Step** & **Operation** \\ \hline
1 & O & Raise lateral confined water level to 396 mm (\(F_{s}\) = 1.2) \\ \hline \multirow{6}{*}{2} & K1 & Excavate the first soil layer (\(-\)30 mm) \\ \cline{2-3}  & Z1 & Install the first level of strut (\(-\)10 mm) \\ \cline{2-3}  & K2 & Excavate the second soil layer (\(-\)120 mm) \\ \cline{2-3}  & Z2 & Install the second level of strut (\(-\)105 mm) \\ \cline{2-3}  & K3 & Excavate the third soil layer (\(-\)210 mm) \\ \cline{2-3}  & Z3 & Install the third level of strut (\(-\)200 mm) \\ \cline{2-3}  & K4 & Excavate the fourth soil layer (\(-\)300 mm) \\ \cline{2-3}  & Z4 & Install the fourth level of strut (\(-\)270 mm) \\ \hline
3 & F & Raise lateral confined water level to 432 mm (\(F_{s}\) = 1.1) \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Testing procedure. Figure 7: Photos of testing procedure: (**a**) before excavation; (**b**) after excavation. In stage 1, when the lateral confined water level rises to 396 mm (O), the lateral pressure decreases overall. The effect of lateral confined water pressure causes the diaphragm wall to shift inside (Figure 12), disrupting the initial contact structure between the soil and the diaphragm wall, and the earth pressure will be redistributed. However, the increase in water pressure remains smaller than the decrease in earth pressure caused by the diaphragm wall's inward displacement, leading to a reduction in the lateral pressure. The reduction in lateral pressure is most significant at a depth of 290 m, with the left and right diaphragm walls showing reductions of 5.30 kPa and 7.81 kPa, respectively, while at a depth of 530 m, the lateral pressure increment approaches zero. This indicates that within the lateral confined water depth range, the reduction in lateral pressure is most evident, but at greater depths, the effect of confined water pressure on the diaphragm wall's displacement is less significant than the restraining effect of the soil, resulting in negligible changes in lateral pressure. Stage 2 involves the soil excavation and the installation of the strut system. During the excavation of the first soil layer (K1), lateral pressure begins to decrease, with the decrease becoming less pronounced with increasing depth. This is attributed to the unloading effect of excavation [18], which disrupts the original pressure equilibrium between the inside and outside of the excavation. The diaphragm wall experiences horizontal displacement due to the pressure difference, with the top of the wall shifting inside more significantly than the bottom, resulting in a weakening of the decreasing trend of lateral pressure with depth.