## 3 Study Methods and Evaluation Process
### Weighting of Evaluation Indicators
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Indicators**} & \multirow{2}{*}{\begin{tabular}{c} **Secondary** \\ **Indicators** \\ \end{tabular} } & \multicolumn{5}{c}{**Evaluation Level**} \\ \cline{3-6}  & & **I** & **II** & **III** & **IV** \\ \hline \multirow{5}{*}{\begin{tabular}{c} Hydrogeological \\ conditions (B\({}_{1}\)) \\ \end{tabular} } & Minimum depth of & 0–30 m: \(>\)30 m & 0–30 m: 25–30 m & 0–30 m: 20–25 m & 0–30 m: 20 m \\  & burial of & 30–100 m: \(>\)100 m & 30–100 m: 60–100 m & 30–100 m: 30–60 m & 30–100 m: \(<\)30 m \\  & groundwater having & 100–200 m: \(>\)200 m & 100–200 m: 150–200 m: 100–150 & 100–200 m: 100–200 m: \(<\)100 m \\  & \begin{tabular}{c} Groundwater \\ Richness (C\({}_{2}\)) \\ (C\({}_{3}\)) \\ \end{tabular} & \(<\)100 m\({}^{3}\)/d & 100–500 m\({}^{3}\)/d & 500–1000 m\({}^{3}\)/d & \(>\)1000 m\({}^{3}\)/d \\  & \begin{tabular}{c} Groundwater \\ Richness (C\({}_{2}\)) \\ (C\({}_{3}\)) \\ \end{tabular} & Category I, II & Category III & Category IV & Category V \\ \hline \multirow{2}{*}{\begin{tabular}{c} Engineering \\ geological \\ conditions (B\({}_{2}\)) \\ \end{tabular} } & Topography (C\({}_{4}\)) & i \(\leq\) 10\% & 10\% \(<\) i \(<\) 25\% & 25\% \(\leq\) i \(<\) 50\% & i \(\geq\) 50\% \\  & Distance from & General fracture \(>\) & General fracture & General fracture \(<\) 10 \\  & fracture structures & 100 m or active & 50–100 m or active & 10–50 m or active & m or active \\  & \begin{tabular}{c} (C\({}_{5}\)) \\ \end{tabular} & fracture \(>\) 500 m & fracture 250–500 m & fracture 50–250 m & fracture\(<\)50 m \\  & Lithological & Hard rock & Soft rock & clayey soil & Sandy soils \\  & assemblages (C\({}_{6}\)) & & & & \\ \hline \multirow{3}{*}{\begin{tabular}{c} Environmental \\ and \\ geological \\ conditions (B\({}_{3}\)) \\ \end{tabular} } & Landsides, slides, & Non-prone areas & Low susceptibility areas & Medium-prone areas & High vulnerability areas \\  & Quarry collapse (C\({}_{8}\)) & Non-prone areas & Low susceptibility areas & Medium-prone areas & High vulnerability areas \\  & Seawater intrusion & Unpolluted areas & Lightly infiltrated & More heavily & Severely infiltrated areas \\  & \begin{tabular}{c} (C\({}_{9}\)) \\ \end{tabular} & Unpolluted areas & areas & & & \\ \hline \multirow{3}{*}{\begin{tabular}{c} Human \\ engineering \\ activities \\ (B\({}_{4}\)) \\ \end{tabular} } & Ground space feature & \multirow{3}{*}{No special site types & Low-rise and & Distribution areas for & High-rise buildings, \\  & types (C\({}_{10}\)) & & multi-story buildings & historic landscapes, & overpasses \\ \cline{1-1}  & \
\begin{tabular}{c} Developed \\ underground works \\ (C\({}_{11}\)) \\ \end{tabular} & Works undeveloped & Smaller & Underground & Tunnels, Human \\ \cline{1-1}  &
\begin{tabular}{c} (C\({}_{11}\)) \\ \end{tabular} & & developments & pipelines & Defence \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Quantitative classification table of suitability evaluation index of underground space resources development in Weihai City. 1. To clarify the problem when analyzing a decision problem, the objective of the research problem must first be clarified. For this paper, the objective of the quality evaluation of underground space resource development must first be determined, i.e., to determine the suitability of underground space resource development according to geological conditions;  
2. Establishing a hierarchical analysis structure selecting evaluation indicators that can represent the evaluation area according to the geological characteristics of the evaluation area, grouping the factors in the system into one category according to the same characteristics, and then forming a higher level (criterion level) hierarchy according to the commonality between factors of the same category, until the highest level is formed to establish a hierarchical structure of the evaluation system;  
3.