# Environmental Risk Source Analysis and Classification of Zones: Subway Construction
###### Abstract
[16] proposed a cloud model and fuzzy analytic hierarchy process-based risk assessment method that established a risk assessment index system comprising four first-level indicators and seventeen second-level indicators, such as karst geological conditions, hydrogeological conditions, tunnel design, and shield construction. Adverse geological conditions were found to have the most significant impact on shield construction risk. [PERSON] et al. [17] studied the risk of urban subway tunnels crossing existing bridge pile foundations, and they identified pile foundation settlement as the primary risk. [PERSON] et al. [18] investigated the response of subway tunnels to dynamic vehicle loads and found that subway shield tunnel displacement amplitude and soil maximum settlement were significantly affected by vehicle load. [PERSON] et al. [19] analyzed the displacement changes of underground tunnels and building foundation pit excavation, and they established that the connection area between the tunnel and the foundation pit experiences minimal horizontal displacement, while the tunnel experiences significant vertical displacement, and settlement at the corner of the building adjacent to the foundation pit is relatively high. [PERSON] et al. [20] analyzed subway construction settlement when crossing existing railways and identified train live load as the main factor leading to subway construction settlement. While these studies highlight risk sources associated with individual subways in different regions of China, the actual subway construction environment typically faces multiple risk sources, necessitating the development of a method that considers the comprehensive impact of risk sources in the study area and accurately evaluates each risk source's risk level. Based on the preceding analysis and discussion, it is apparent that the distribution of environmental risk sources in subway construction varies regionally. Therefore, identifying risk sources based on regional characteristics can enhance the accuracy of results. Risk identification involves investigating and recognizing potential risks in the subway construction process and categorizing them based on risk types and impact levels. An analysis of various types of subway construction accidents reveals that most accidents occur due to surface subsidence caused by the subway construction process [21; 22]. Regional surface subsidence can be regarded as an indication of the distribution of environmental risk sources to a certain degree [23; 24; 25; 26; 27]. The research area for this study is Urumqi, which is situated at the center of Eurasia, at the northern foot of the Tianshan Mountains, and at the southern edge of the Junggar Basin. As the capital of the Xinjiang Uygur Autonomous Region, Urumqi is the political, economic, and cultural hub of the region and serves as the western bridgehead of China, playing a significant role in China's Belt and Road Initiative. With the development of Urumqi as the core economic zone, the demand for rail transit has been on the rise. According to the \"Urumqi Rail Transit Network Planning\", the planned length of Urumqi's rail transit line is 261.8 kilometers, with Line 1-7 being the main city planning line. In 2019, Urumqi Metro Line 1 was completed and put into operation, while Line 2 began construction in 2015, and the first phase of Metro Line 3 and Line 4 began construction in 2016. Conventional methods for monitoring subway settlement do not provide a comprehensive overview. Interferometric Synthetic Aperture Radar (InSAR) is a satellite-based technology that offers several advantages, including high resolution, high precision, wide range, and all-weather, all-day monitoring [28; 29; 30; 31]. It has proven successful in monitoring surface deformation in various regions. This study employs the SBAS-InSAR [32; 33; 34] analysis method to derive the surface deformation rate field during the construction of Urumqi's existing subway line 1.