## 5 Applications
### Depth Variations  
Before construction and other tunneling development, 3D modeling can predict the depth of potentially suitable foundation layers (Table 1), for example, by showing the possible distribution of sand that has a significant effect on groundwater control, by exhibiting the distribution of stable and continuous clay units that affect the potential location of tunnels.  
Figure 16: Diagrams of Es values and depth intervals (1–10 m, 10–17 m,17–35 m, and \(>\)35 m) in the study area.  
Figure 17: Diagrams of Es values at varying depths (10 m, 23 m, 35 m, and 45 m, respectively) derived from the 3D property model.  
As indicated above, ten major units were identified in the Tongzhou area, thickness maps of which could be exported from the model, such as a thickness map of the first sand layer (Unit 24), which was continuous with an average thickness of around 9 m (Figure 18) and that is widely distributed in the in Tongzhou area. Base depths of three silty clay units were indicated to be at around 8 m, 28 m, and 45 m, respectively, as derived from the model.  
Additionally, the stratigraphic structure is identified as one geological indicator to assess the potential uses of UUS based on its suitability. We summarized three types of structures (Table 2) in the project titled Standard for Geological Assessment on Urban Underground Space Resources in Beijing City (DB11/T 1895--2021, Beijing Institute of Geological Survey, 2022). The weight of this indicator was then calculated using the fuzzy mathematical method, as do other basic geological indicators, such as geotechnical properties. However, for other constraints, for example, active faults, subsidence, sand liquefaction, karst collapse, etc., weights are determined based on the analytic hierarchy  
\begin{table}
\begin{tabular}{l l c c c c c c c c c} \hline \hline \multirow{3}{*}{**Geological Units**} & \multicolumn{10}{c}{**Unit Thickness (m)**} \\ \cline{3-11}  & \multicolumn{3}{c}{**Derived from the 3D Model**} & \multicolumn{3}{c}{**Boreable Data**} & \\ \cline{3-11}  & \multicolumn{3}{c}{**Max**} & **Min** & **Mean** & **Std. Dev** & **Median** & **Variance** & **Max** & **Min** & **Mean** & **Std. Dev** \\ \hline Artificial ground & & 3.00 & 0 & 1.31 & 0.20 & 1.35 & 0.04 & 4.10 & 0.28 & 1.12 & 0.56 \\ \hline \multirow{3}{*}{The first cyclothem} & clayy silt 22 & 7.24 & 0 & 2.95 & 0.47 & 3.04 & 0.22 & 10.1 & 0.4 & 2.72 & 1.47 \\ \cline{2-11}  & silty clay 23 & 15.77 & 0 & 3.65 & 0.67 & 3.75 & 0.45 & 10.5 & 0.3 & 3.31 & 1.81 \\ \cline{2-11}  & sand 24 & 40.99 & 0 & 9.08 & 2.77 & 9.08 & 7.66 & 21.1 & 0.1 & 6.68 & 3.96 \\ \cline{2-11}  & gravel 25 & 10.68 & 0 & 2.63 & 1.58 & 2.44 & 2.49 & 11.1 & 1.0 & 4.43 & 2.42 \\ \hline \multirow{3}{*}{The second cyclothem} & clayy silt 32 & 33.38 & 0 & 4.25 & 2.30 & 3.99 & 5.30 & 12.8 & 0.5 & 3.92 & 2.30 \\ \cline{2-11}  & silty clay 33 & 37.45 & 0 & 4.49 & 0.97 & 4.43 & 0.94 & 12.8 & 0.5 & 4.66 & 2.60 \\ \cline{2-11}  & sand 34 & 31.04 & 0 & 11.79 & 1.92 & 11.97 & 3.67 & 23.0 & 1.5 & 11.88 & 3.66 \\ \cline{2-11}  & silty clay 43 & 23.67 & 0 & 4.67 & 0.78 & 4.82 & 0.61 & 13.9 & 0.4 & 5.08 & 1.82 \\ \cline{2-11}  & sand 44 & 38.42 & 0 & 9.61 & 1.73 & 9.68 & 3.00 & 21.7 & 0.7 & 8.90 & 2.66 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Interpreted thicknesses of various units derived from the 3D geological model and borehole data.  
Figure 18: Thickness map of the first sand unit (24) derived from the 3D geological model in the study area.  
process (AHP) [58]. Such an approach is consistent with the evaluation model described by [PERSON] et al. [59].  
In the study area, a multilayered structure was interpreted following the 3D model in the depth interval of 0-50 m, with double-layered developing locally or at a particular depth interval, demonstrating the heterogeneous feature of local subsoils, with relatively lower quantification result than that of a single-layered zone (Table 2).