## 5 Orthogonal Experiment
### Analysis of Orthogonal Test Results  
From the numerical simulation in ABAQUS, the settlement cloud maps of the experimental groups at the maximum load are shown in Figure 22, and a summary of the settlement values is provided in Table 6.  
From Table 6, it is apparent that the settlement in group 4 is minimal, while the settlement in group 1 reaches the maximum. The settlement of a single pile is affected by multiple factors, so a significance analysis should be conducted for the sensitivity of each factor. The results of orthogonal tests are often processed through a range analysis. Then, the primary and secondary factors are divided and the optimal design combination is obtained. The results of the range analysis are shown in Table 7.  
From Table 7, it can be observed that the order is: B1 > A4 > C1 > D1 > E4. Therefore, the factors ranked in descending order of sensitivity are as follows: pile diameter, pile length, pile spacing, bedding thickness, and grouting pressure. The optimal combination is a pile length of 18 m, pile diameter of 0.4 m, pile spacing of 1.0 m, bedding thickness of 0.3 m, and grouting pressure of 0.6 MPa.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Level**} & \multirow{2}{*}{\begin{tabular}{c} **A** \\ **Pile Length** \\ **/m** \\ \end{tabular} } & \multicolumn{3}{c}{**Factor**} & \multirow{2}{*}{\begin{tabular}{c} **D** \\ **C** \\ **Pile Diameter/m** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **E** \\ **Pile Spacing/m** \\ \end{tabular} } & \multirow{2}{*}{\
\begin{tabular}{c} **D** \\ **Thickness of the** \\ **Bedding Layer/m** \\ \end{tabular} } & \multirow{2}{*}{
\begin{tabular}{c} **E** \\ **Grouting Pressure/MPa** \\ \end{tabular} } \\ \hline
1 & 12 & 0.4 & 1 & 0.3 & 0.3 \\
2 & 14 & 0.5 & 1.3 & 0.4 & 0.4 \\
3 & 16 & 0.6 & 1.4 & 0.5 & 0.5 \\
4 & 18 & 0.7 & 1.5 & 0.6 & 0.6 \\ \hline \hline \end{tabular}
\end{table}
Table 5: L\({}_{16}\) (4\({}^{5}\)) orthogonal test design.  
In this project, the sensitivity of pile diameter is much greater than that of other factors, which means that changing the pile diameter has a great impact on the bearing capacity of the project. Therefore, it is advisable to prioritize an adjustment to the pile diameter during the construction design. There is no significant difference between the sensitivity of bedding thickness and grouping pressure. Considering the higher material consumption associated with altering the bedding thickness, it is recommended to prioritize the adjustment to the gro  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \begin{tabular}{c} **Factor** \\ **Test** \\ **Number** \\ \end{tabular} & \begin{tabular}{c} **A** \\ **Pile Length/m** \\ \end{tabular} & \begin{tabular}{c} **B** \\ **Pile Diameter/m** \\ \end{tabular} & \begin{tabular}{c} **C** \\ **Pile Spacing/m** \\ \end{tabular} & \begin{tabular}{c} **D** \\ **Thickness of the** \\ **Bedding Layer/m** \\ \end{tabular} & \
\begin{tabular}{c} **E** \\ **Grouting** \\ **Pressure/MPa** \\ \end{tabular} &
\begin{tabular}{c} **Settling** \\ **Volume** \\ **/mm** \\ \end{tabular} \\ \hline
1 & 12 & 0.4 & 1.0 & 0.3 & 0.3 & 33.93 \\
2 & 12 & 0.5 & 1.3 & 0.4 & 0.4 & 21.41 \\
3 & 12 & 0.6 & 1.4 & 0.5 & 0.5 & 16.02 \\
4 & 12 & 0.7 & 1.5 & 0.6 & 0.6 & 12.58 \\
5 & 14 & 0.4 & 1.3 & 0.5 & 0.6 & 32.06 \\
6 & 14 & 0.5 & 1.0 & 0.6 & 0.5 & 24.05 \\
7 & 14 & 0.6 & 1.5 & 0.3 & 0.4 & 16.31 \\
8 & 14 & 0.7 & 1.4 & 0.4 & 0.3 & 13.32 \\
9 & 16 & 0.4 & 1.4 & 0.6 & 0.4 & 32.24 \\
10 & 16 & 0.5 & 1.5 & 0.5 & 0.3 & 22.0 \\
11 & 16 & 0.6 & 1.0 & 0.4 & 0.6 & 19.91 \\
12 & 16 & 0.7 & 1.3 & 0.3 & 0.5 & 14.32 \\
13 & 18 & 0.4 & 1.5 & 0.4 & 0.5 & 32.81 \\
14 & 18 & 0.5 & 1.4 & 0.3 & 0.6 & 23.29 \\
15 & 18 & 0.6 & 1.3 & 0.6 & 0.3 & 18.20 \\
16 & 18 & 0.7 & 1.0 & 0.5 & 0.4 & 17.38 \\ \hline \hline \end{tabular}
\end{table}
Table 6: Orthogonal test results of composite foundation settlement.  
Figure 22: Model settlement cloud map at maximum loading in orthogonal test.