## 5 Solving Pareto Optimal Solution Set and Analysis Decision
### Pareto Optimal Solution Set Analysis and Decision Making  
The multi-objective optimization model of foundation pit dewatering based on the NSGA-II algorithm is solved to obtain the Pareto optimal solution set under three different dewatering conditions. Using the multi-objective optimization evaluation system, the optimization scheme in the Pareto optimal solution set is selected as the decision optimization result from the three objectives of total dewatering cost, settlement influence coefficient, and the safety and stability of the foundation pit structure, which provides a variety of feasible schemes for the dewatering construction of the foundation pit.  
The three objectives in the foundation pit dewatering optimization model affect and interact with each other. Therefore, the specific analysis and decision making are as follows:  
1. When giving priority to the total cost of dewatering, it is important to consider the drilling and pumping costs for foundation pit dewatering. Within the optional Pareto solution set, a solution with a smaller number of pumping wells and lower total pumping capacity should be the first choice based on the dewatering multi-objective optimization evaluation system. Specifically, the operation scheme of closing the J1 and J22 pumping wells under the third optimization condition can be preferred;
2. If the focus is on the impact of dewatering on the surrounding environment, preference should be given to a dewatering scheme with a settlement impact coefficient of less than 0.53. Specifically, the operation scheme corresponding to Pareto solution No. 1 under the first optimized condition in Table 5, and the operation scheme corresponding to closing the J3 pumping well under the second optimized condition  
Figure 10: Optimization results of decision variables under the third optimization working condition.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline \begin{tabular}{c} **Schemes** \\ \end{tabular} & **Well Status** & \begin{tabular}{c} **Total Water** \\ **Inflow/(m\({}^{3}\)/d)** \\ \end{tabular} & \begin{tabular}{c} **Settlement** \\ **Value (mm)** \\ \end{tabular} & \begin{tabular}{c} **The Distance Where Water Level in** \\ **the Center of the Foundation Pit Is** \\ **Lower Than the Bottom Plate/(m)** \\ \end{tabular} & \begin{tabular}{c} **Hydraulic** \\ **Gradient Value** \\ \end{tabular} \\ \hline \begin{tabular}{c} Preliminary scheme \\ \end{tabular} & 26 wells in running & 156,000 & \textless{}15 & \textgreater{}0 & \textless{}0.9 \\ \begin{tabular}{c} The third optimized \\ working condition \\ \end{tabular} & \begin{tabular}{c} Close J19, J22 \\ \end{tabular} & 143,665 & 7.95 & 1.84 & 0.66 \\ \begin{tabular}{c} Keying condition \\ \end{tabular} & \begin{tabular}{c} Close J7, J24 \\ \end{tabular} & 143,121 & 7.95 & 1.83 & 0.65 \\ \
\begin{tabular}{c} Keying condition \\ \end{tabular} &
\begin{tabular}{c} Close J1, J22 \\ \end{tabular} & 143,036 & 7.95 & 1.83 & 0.65 \\ \hline \hline \end{tabular}
\end{table}
Table 10: Three objective optimization results of running 24 pumping wells.  
in Table 7, can ensure minimal ground settlement under the conditions of meeting the total cost requirements of dewatering and the safety and stability of the foundation pit structure;
3. When prioritizing the safety and stability of the foundation pit structure, achieving a significant drawdown of the water level in the center of the foundation pit is crucial for ensuring successful construction and enhancing structural safety. Considering the dewatering multi-objective optimization evaluation system, a preferable dewatering scheme is to maintain the water level approximately 1.5 m below the bottom plate of the foundation pit. Therefore, the operation scheme of running 25 pumping wells while closing the J16 pumping well under the second working condition is recommended to meet the maximum drawdown of the water level.