## 4 Results
### Weights of Indicators
It was important to note that the Baiyangdian Lake region occupied 34.72% of the space classified as grade I and 0.81% of the space classified as grade II. Some scholars have suggested that larger lakes could have an impact on the use of shallow underground space [17]. In order to account for this,  
grade III, and grade IV accounted for 29.08%, 25.61%, 37.59%, and 7.72%, respectively. Based on the evaluation result, it was found that most of Rongcheng and Xiongxian, particularly the Rongcheng regions, were considered good or moderately suitable for underground space utilization. On the other hand, the regions around the central-eastern areas of Anxin were found to be less suitable due to issues with the bearing capacity and compression modulus of soils. As a result, the compression modulus of soils (\(-5\)--\(-10\) m), bearing capacity of soils (\(-5\)--\(10\) m), and compression modulus of soils (\(-10\)--\(15\) m) were given higher weights in assessing underground space suitability compared to other sub-indicators. For the deep layer (L\({}_{2}\)) within a depth of \(-15\)\(\sim\)\(-30\) m, grade I accounted for about 28.27% of the total acreage, grade II accounted for 13.79%, grade III accounted for 29.91%, and grade IV accounted for 28.03% (Figure 15). The analysis showed that the most suitable regions were mainly located near the west of Rongcheng and the central-north of Xiongxian. On the other hand, the regions around Baiyangdian Lake were found to be less suitable due to factors such as soil bearing capacity, ground elevation, and groundwater buried depth. Among these factors, the weights assigned to bearing capacity of soils (\(-15\)--\(-30\) m), ground elevation, and groundwater buried depth were relatively high, indicating their significant influence on the suitability of underground space, accounting for 28.89%, 26.22%, and 25.60%, respectively, compared to other sub-indicators. For the sub-deep layer (L\({}_{3}\)), which was within a depth of \(-30\)--\(-50\) m, the area occupied by grade I, grade II, grade III, and grade IV was 29.32%, 12.37%, 20.64%, and 37.67%, respectively. This indicated that the majority of the central-eastern regions of Rongcheng and Xiongxian were highly suitable for underground space utilization due to factors such as soil bearing capacity, groundwater buried depth, and ground elevation (Figure 16). Among these factors, the weights assigned to soil bearing capacity (\(-30\)--\(-50\) m), groundwater buried depth, and ground elevation were relatively higher at 28.62%, 23.57%, and 23.55%, respectively, compared to other sub-indicators. For the deep layer (L\({}_{4}\)) within a depth of \(-50\)--\(-100\) m, approximately 28.46% of the total area was classified as grade I, 13.57% as grade II, 29.52% as grade III, and 28.45% as grade IV (Figure 17). The assessment result revealed that the regions with good suitability were primarily located near the west of Rongcheng and the central-north of Xiongxian. On the other hand, the regions with poorer suitability were found around the central-east of Anxin, mainly due to factors such as groundwater buried depth, ground elevation, and compression modulus of soils. These factors, groundwater buried depth, ground elevation, and compression modulus of soils (\(-50\)--\(100\) m), were assigned higher weights, indicating their significance in determining underground space suitability, accounting for 31.02%, 30.66%, and 15.09%, respectively, compared to other sub-indicators.