# Environmental Risk Source Analysis and Classification of Zones: Subway Construction
## 6 Conclusions  
We employed SBAS-InSAR technology to analyze the surface subsidence performance of different areas during the construction of the Urumqi Metro Line 1 and identified the main risk sources of the subway construction environment in Urumqi. We used ArcGIS software to visualize the spatial distribution of each risk source and classify their risk levels. We then carried out a geometric superposition of the spatial distribution layers of each risk source to enable the geometric division of the environmental risk sources of subway construction in the study area. Finally, we redefined the risk index of each partition to draw the following conclusions:  
1. Four main types of risk sources affect the process of Urumqi subway construction, and these can be classified into natural conditions and human engineering activities. Each risk source control level can be divided into geological conditions (I-III) based on their spatial distribution and spatial density distribution. Additionally, the distribution of super high-rise buildings can be classified into levels I-IV, the road network distribution can be classified into levels I-IV, and the cluster building distribution can be classified into levels I-IV. 2. The environmental risk source area of subway construction in the study area is divided into 103 regions, with 12 areas having an area greater than 250,000 km\({}^{2}\). The largest partition number is 1444, and the partition number with the greatest risk is 1112. The environmental risk source and risk level of subway construction in this area are soil layer, grade I super high-rise building risk, grade I road network risk, and grade II building density risk. 3. We graded the comprehensive impact of risk sources on subway construction according to the distribution of risk sources in each sub-region. We also conducted a statistical analysis of Urumqi Metro Line 1-7 crossing the risk source zones and identified the risk control measures needed when the subway line crosses different risk levels. 4. In the future planning and construction of the Urumqi subway line, identifying the environmental risk sources of subway construction will assist the planning department in understanding the environmental risk situation surrounding the subway planning line. This information will provide a foundation for the rational planning and adjustment of regional subway lines. The subway construction company will be able to determine the environmental risk level of the subway's construction and take necessary risk control measures in advance based on the intersection of the actual subway line location and the environmental risk source zoning layer. This will help to mitigate the risk of inconsistency between the judgment results of engineering design drawings and engineering practice due to insufficient consideration of risk factors during the planning and design stage. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Zoning Risk Level** & **Risk Index Interval** & **Explanation** \\ \hline I category high-risk region & & \begin{tabular}{c} Preventive measures must be implemented for various risk sources. \\ The settlement performance of the area must be strictly monitored \\ during construction. \\ \end{tabular} \\ \hline II category high-risk region & & \begin{tabular}{c} Preventive measures must be implemented for each level I risk source. \\ \end{tabular} \\ \hline I category middle-risk region & [1.75, 2.50] & \begin{tabular}{c} Preventive measures must be identified and implemented for each \\ level I risk source to reduce risk levels \\ \end{tabular} \\ \hline I category low-risk region & [2.50, 3.75] & \
\begin{tabular}{c} The risk is on the edge of tolerance, and it is necessary to pay attention \\ to the possible impact of each level of risk source \\ \end{tabular} \\ \hline II category low-risk region & &
\begin{tabular}{c} The risk can be tolerated without taking preventive measures \\ \end{tabular} \\ \hline \hline \end{tabular}
\end{table} 
Table 8: Risk prevention measures taken for each risk zone.