# Model Test on the Behaviors of Deep Excavation with Lateral Confined Water
## 3 Results
### Analysis of Lateral Pressure of diaphragm Wall
During the excavation of the second soil layer (K2), the lateral pressure continues to decrease overall, with a slight increase observed within a depth of 150 mm, reaching a  
Figure 8: Incremental curves of lateral pressure on diaphragm walls: (a) left side; (b) right side. maximum increment of 1.27 kPa. This increase is primarily due to the first strut restricting the inward displacement of the upper diaphragm wall, which compresses the soil behind the wall, increasing lateral pressure. When the third soil layer is excavated (K3), the lateral pressure increment curve shows similar behavior to that during the excavation of the second soil layer, but the maximum pressure increment decreases to 0.65 kPa. This reduction is due to the combined action of the first and second struts, which limit the inside displacement of the diaphragm wall while also resisting the soil and water pressures, leading to a more uniform distribution of lateral pressure and reducing localized stress concentrations. During the excavation of the fourth soil layer (K4), the reduction in lateral pressure in the upper diaphragm wall is less noticeable, but the lateral pressure on the deep diaphragm wall decreases significantly. This is because the fourth soil layer lies within the lateral confined aquifer depth, and the excavation causes a noticeable increase in the horizontal displacement of the diaphragm wall within this layer, leading to a greater reduction in lateral pressure. In stage 3, when the confined water level rises to 432 mm (F), the reduction in lateral pressure is less pronounced in the upper diaphragm wall, but more significant in the deeper sections. The primary reason for this is the increased lateral confined water pressure, which exacerbates the inside displacement of the diaphragm wall, particularly within the lateral confined aquifer depth (Figure 12), where the displacement is more pronounced, leading to a greater reduction in lateral pressure. In summary, the lateral pressure on the diaphragm wall is influenced by the coupled effects of water pressure from the confined water, soil unloading due to excavation, and stress redistribution caused by the support system. Soil excavation reduces the earth pressure on the diaphragm wall, while the rise in confined water level increases the water pressure on the diaphragm wall. The support system mitigates the fluctuations in lateral pressure caused by the changes in soil and water pressures. From the perspective of soil-water-structure interaction [19], the reason for the reduction in lateral pressure is attributed to the confined water pressure pushing the diaphragm wall inside, which in turn causes a redistribution of the earth pressure on the wall. The decrease in earth pressure due to the diaphragm wall's inward displacement exceeds the increase in water pressure caused by the rise in lateral confined water level, leading to an overall reduction in lateral pressure. Furthermore, the reduction in lateral pressure is more pronounced within the lateral confined aquifer compared to other depths.