# The Effect of the Water Table on the Bearing Capacity of a Shallow Foundation
## 3 Influence of Immersion on the Bearing Capacity of Shallow Buried Foundation
### Determination of Immersion Critical Groundwater Depth  
Determining the immersion critical groundwater depth is the basis for judging the impact of immersion and the boundary conditions for determining the scope of the immersion area. When the burial depth of the critical groundwater is greater than the predicted burial depth of the diving backscatter, the area is determined to be an immersion zone. The burial depth of immersion critical groundwater should be determined through field observation and local production practice experience according to soil properties, groundwater salinity, the height of soil capillary water rising zone, or the depth of building foundations. For low liquid limit clay and silt foundations, after groundwater enters the foundation bearing layer, it will affect the bearing capacity and deformation stability of the building foundation, and the degree of influence will increase with the rise of groundwater. According to the load type of the building, the type of foundation, the depth of the foundation, and the different depths of the groundwater table below the base, the additional stress, self-weight stress, and foundation bearing capacity of the foundation soil of the shallow-buried foundation are calculated. Sensitivity analysis is carried out on the safety of the building to determine the safety impact depth z of the groundwater level rise on the stability of the building foundation. At the same time, considering the rising height of capillary water, the critical groundwater level buried depth of this kind of foundation soil is determined as the foundation buried depth plus the rising height of capillary water and the safety influence depth z, as shown in Figure 5. However, the impact of the security impact depth z is not considered in the current specifications. The height of the capillary water rising area of the soil layer above the groundwater level can be directly measured in test pits and exploratory wells. Or it can be measured according to the appropriate water content of the soil layer during the growing period of crops, and the relationship curve of the soil layer water content above the groundwater level measured on-site with depth selected. Urban residential areas can be determined by comparing the relationship curve of soil moisture content above the groundwater level with the natural moisture content of the foundation-bearing layer before the reservoir is impounded. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Groundwater to** & **z/(b/2)** & **\(P_{\mathbf{z}}\) (kPa)** & **\(P_{\mathbf{cz}}\) (kPa)** & **\(f_{\mathbf{ac}}\) (kPa)** & **\(P_{\mathbf{Z}}+P_{\mathbf{CZ}}\) (kPa)** \\ \hline
0.3 & 0.4 & 100.08 & 51.24 & 147.09 & 151.32 \\
0.4 & 0.53 & 95.49 & 53.07 & 148.92 & 148.56 \\
0.5 & 0.67 & 89.66 & 54.9 & 150.75 & 144.56 \\
0.6 & 0.8 & 83.4 & 56.73 & 152.58 & 140.13 \\
0.7 & 0.93 & 76.44 & 58.56 & 154.41 & 135.00 \\
0.8 & 1.07 & 69.76 & 60.39 & 156.24 & 130.15 \\
0.9 & 1.2 & 63.38 & 62.22 & 158.07 & 125.60 \\
1 & 1.33 & 57.55 & 64.05 & 159.9 & 121.60 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Calculation results of foundation bearing capacity (b = 1.5 m, d = 2.5 m). \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Groundwater to** & **z/(b/2)** & **\(P_{\mathbf{z}}\) (kPa)** & **\(P_{\mathbf{cz}}\) (kPa)** & **\(f_{\mathbf{ac}}\) (kPa)** & **\(P_{\mathbf{Z}}+P_{\mathbf{CZ}}\) (kPa)** \\ \hline
0.5 & 0.5 & 96.54 & 54.9 & 150.75 & 151.44 \\
0.6 & 0.6 & 92.99 & 56.73 & 152.58 & 149.72 \\
0.7 & 0.7 & 88.20 & 58.56 & 154.41 & 146.76 \\
0.8 & 0.8 & 83.4 & 60.39 & 156.24 & 143.79 \\
0.9 & 0.9 & 78.19 & 62.22 & 158.07 & 140.41 \\
1 & 1 & 72.98 & 64.05 & 159.9 & 137.03 \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Calculation results of foundation bearing capacity (b = 2.0 m, d = 2.5 m).