## 5 Case Analysis  
### Project Overview and Data Acquisition  
The total length of Chengdu Metro Line 11 in China is 22.0 km, and it has 17 new subway stations. The engineering profiles of the 17 stations are presented in Table 4.  
Due to spatial constraints, Table 4 only reports the four most important types of station information, namely the maximum excavation depth, regional characteristics, construction units, and unfavorable conditions. The maximum excavation depth is the most important factor affecting the construction difficulty of subway station engineering. The greater the excavation depth, the higher the professional skills of the construction workers, the higher the management ability of the project managers, the higher the quality and maintenance level of the construction machinery, and the higher the quality of construction materials. In addition, the deeper the subway station project, the more easily it will experience adverse effects from the surrounding environment. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Station**} & **Maximum** & **Regional** & **Contractor** & **Adverse Conditions** \\  & **Excavation Depth** & **Characteristics** & & \\ \hline Huilong Boulevard Station & 21.26 m & Urban region under construction & CCTEB & Abandoned pipe gallery, high slope \\  & & Urban region under construction & CCTEB & Abandoned pipe gallery \\  & & Urban region under construction & & \\ Science Park East Station & 19.75 m & Urban region under construction & & \\ Science Park South Station & 25.18 m & Urban region under construction & & \\  & & Urban region under construction & & \\ Wan’an Station & 21.45 m & Urban region under construction & & \\ Lushan Boulevard Station & 28.84 m & Established & CCTEB & Under a bridge, high gas. \\  & & urban region & & \\ Shenyang Road Station & 19.45 m & & & \\  & & Established & & \\  & & urban region & & \\  & & Established & & \\  & & urban region & & \\  & & Established & & \\  & & urban region & & \\  & & Urban region under construction & & \\ Tianfu CBD East Station & 22.50 m & Urban region under construction & & \\ Guobin Boulevard station & 24.37 m & Urban region under construction & & \\  & & Urban region under construction & & \\ Lujiao Village Station & 19.57 m & Urban region under construction & & \\  & & & & \\  & & Suburban region & CCTEB & \\  & & & & \\  & & Suburban region & CCTEB & \\  & & Suburban region & CCTEB & \\  & & & & \\ Huilong Road Station & 20.75 m & Suburban region & CCTEB & \\  & & Subway line & \\  & & Suburban region & CCTEB & \\  & & Suburban region & CCTEB & \\  & & Subway station & \\  & & Suburban region & CCTEB & \\  & & Subway station & \\ \hline \hline \end{tabular}
\end{table} 
Table 4: The overview of the 17 stations. Regional characteristics reflect the availability of construction machinery and construction materials. In urban areas, due to traffic control, it is difficult to promptly obtain construction materials. In the suburbs and newly-built development zones, construction materials can easily be promptly obtained. In addition, subway station projects with different regional characteristics suffer from different unfavorable environmental factors. Relevant information about the construction unit directly reflects the risk management level of the project management team. The construction units of this project are the China Construction Third Engineering Bureau Group Co., Ltd., Wuhan, China (hereinafter referred to as CCTEB) and the China State Construction Railway Investment & Engineering Group Co., Ltd., Wuhan, China (hereinafter referred to as CSCRIE). CCTEB has rich experience in subway station engineering construction, while CSCRIE lacks relevant construction experience. Unfavorable conditions mainly include unfavorable geological conditions, unfavorable geographic conditions, and extreme weather conditions, all of which are important causes of construction safety accidents.