# Suitability Evaluation of Urban Underground Space Development: A Case Study of Qingdao City
## 5 Results
### Distribution of Suitability Level Zoning  
By employing both the fuzzy comprehensive evaluation model and the variable-weight analytic hierarchy process, the study obtained the final assessment outcomes regarding the suitability of urban underground space development in Qingdao City's main urban area. The study area encompasses regions within the districts of Shinan, Shibei, Laoshan, and Licang and parts of Chengyang. The suitability zoning evaluation results obtained through the fuzzy comprehensive evaluation model exhibit significant distribution characteristics within each administrative district. The areas of different suitability levels within the main urban area, along with their proportional areas within their respective administrative districts, are illustrated in Figure 11.  
Figure 11: The proportion of evaluation levels in each administrative region: (**a**) distribution of shallow underground space; (**b**) distribution of medium and deep underground spaces. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Evaluation Depth**} & \multirow{2}{*}{**Suitability Level**} & \multicolumn{4}{c}{**Comprehensive Evaluation Model**} \\  & & \multicolumn{2}{c}{**Multi-Objective Linear Function**} & \multicolumn{2}{c}{**Fuzzy Comprehensive Evaluation**} \\  & & \multicolumn{2}{c}{**Weighted Model**} & \multicolumn{2}{c}{**Model**} \\ \cline{3-5}  & & **Square Measure** & \multirow{2}{*}{**Proportion (\%)**} & **Square Measure** & \multirow{2}{*}{**Proportion (\%)**} \\  & & **(km2)** & & & \\ \hline \multirow{3}{*}{Shallow layer} & Very suitable & 69.42 & 7.18 & 47.59 & 4.92 \\  & More suitable & 429.01 & 44.35 & 62.96 & 6.51 \\ \cline{1-1}  & Generally suitable & 363.74 & 37.60 & 531.63 & 54.96 \\ \cline{1-1}  & Not suitable & 105.16 & 10.87 & 325.15 & 33.61 \\ \hline \multirow{3}{*}{Middle to deep layers} & Very suitable & 46.34 & 4.79 & 50.71 & 5.24 \\ \cline{1-1}  & More suitable & 96.73 & 10.00 & 55.98 & 5.79 \\ \cline{1-1}  & Generally suitable & 220.88 & 22.83 & 478.99 & 49.52 \\ \cline{1-1}  & Not suitable & 603.38 & 62.38 & 381.64 & 39.45 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Statistical table of suitability evaluation results for comprehensive evaluation models. Figures 12 and 13 depict the evaluation outcomes concerning the suitability of utilizing shallow and medium-deep underground space development in the main urban area of Qingdao City. Green areas indicate regions unsuitable or generally suitable for underground space development utilization, while yellow and orange areas signify areas comparatively suitable or highly suitable for underground space development utilization, respectively. From Table 6, it can be observed that areas rated as \"Highly Suitable\" are concentrated in the southern and northern districts of the research area. There are few areas in Laoshan  
Figure 12: Results of suitability evaluation for the development and utilization of shallow underground spaces in the main urban area of Qingdao City. Figure 13: Results of suitability evaluation for the development and utilization of medium and deep underground spaces in the main urban area of Qingdao City. District that are highly suitable for development, while Licang District and Chengyang District have virtually no areas rated as highly suitable. Specifically, the combined area of highly suitable and moderately suitable development zones in the southern district exceeds 40% of the total area, and in the northern district, it reaches nearly 30%, significantly higher than the other three districts. Therefore, the southern and northern districts are the key areas for the current development and utilization of shallow underground spaces in the main urban area of Qingdao. Table 7 presents the distribution of suitability evaluation levels for medium and deep underground spaces within the research area. It can be observed that areas with favorable suitability evaluation results are still predominantly concentrated in the southern and northern districts.