## 4 SoilWorks Numerical Simulation
### Sensitivity Analysis
#### 4.3.1 Description and Input Parameter Selection for Case 3
* Basic Assumptions (1) The excavation process is assumed to exhibit plane strain behavior. * Considering the influence range behind the retaining wall, the analysis range (B) extends at least four times the excavation depth beyond the retaining wall. The vertical range (D) is obtained by adding twice the penetration depth (3H1 + H2) to the length of the retaining wall. A uniform distributed load of 15 kN/m\({}^{2}\) is assumed to act on the ground surface. * Based on the site conditions, including the excavation depth, shape, support system configuration, and soil layer boundaries, a mesh is created for the analysis. The boundary elements of the mesh are assumed to have no horizontal or lateral displacements outside the influence range. * The stiffness of the retaining wall is reduced by 70% based on empirical experience, while the stiffness of the floor slab is reduced by 25%. * The retaining walls and floor slabs are simulated using beam elements. * The analysis is conducted using 15-node triangular elements. * Based on the observation of previous cases, when the bottom of the retaining wall penetrates the gravel layer to a certain depth (more than 1.5 m below the bottom), no significant horizontal displacements are observed; therefore, in the analysis, horizontal displacements at the bottom of the retaining wall are restricted. * Analysis Procedure  
Considering the monitoring data and construction conditions at the site, the actual excavation steps are simplified for the analysis. Since the B1F floor slab is constructed during the third excavation, its influence on the retaining wall is not considered in the analysis. The groundwater level inside the site is maintained at a depth of 1.0 m below the excavation surface during the excavation process. The construction process for case three is described as follows. The analysis model is shown in Figure 19.  
1. Perform the first-stage excavation to GL.\(-\)2.5 m;
2. Construct the 1 FL at GL.\(-\)0.0 m;
3. Perform the second-stage excavation to GL.\(-\)8.0 m;
4. Construct the B2 FL at GL.\(-\)7.025 m;
5. Perform the third-stage excavation to GL.\(-\)11.2 m;
6. Construct the B3 FL at GL.\(-\)10.225 m;
7. Perform the fourth-stage excavation to GL.\(-\)14.6 m (reaching the bottom of the excavation, analysis simulation ends at this point). \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Thickness** & \multirow{2}{*}{_E_ **(kN/m\({}^{2}\))**} & \multirow{2}{*}{_I_ **(m\({}^{4}\)/m)**} & **Reduction** & **0.7 EA** & **0.7 EI** \\
**(m)** & & & & **Factor** & **(kN/m)** & **(kNm\({}^{2}\)/m)** \\ \hline
0.8 & \(2.13\times 10^{7}\) & 0.04267 & 0.7 & \(1.19\times 10^{7}\) & 6.36 \(\times 10^{5}\) \\ \hline \hline \end{tabular}
\end{table} 
Table 13: Input parameters for diaphragm wall strength in Case Study 3. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Number** & **Floor** & **Thickness** & \(A\) & **0.25A** & **I (m\({}^{4}\)/m)** & **E (kN/m\({}^{2}\))** \\
**of Floors** & **Position** & **(cm)** & **(m\({}^{2}\)/m)** & **(m\({}^{2}\)/m)** & **I (m\({}^{4}\)/m)** & **E (kN/m\({}^{2}\))** \\ \hline
1F & GL.\(+\)0.0 m & 20 & 0.20 & 0.05 & \(6.667\times 10^{-4}\) & \(2.46\times 10^{7}\) \\ B2F & GL.\(-\)3.9 m & 45 & 0.45 & 0.1125 & \(7.594\times 10^{-3}\) & \(2.46\times 10^{7}\) \\ B3F & GL.\(-\)6.3 m & 45 & 0.45 & 0.1125 & \(7.594\times 10^{-3}\) & \(2.46\times 10^{7}\) \\ \hline \hline \end{tabular}
\end{table} 
Table 14: Input parameters for floor structure in Case Study 3.