## 4 IFC Data Model for Supporting Safety Risk Identification in Deep Excavation
### Evaluation of the IFC-Based Safety Risk Identification  
The effectiveness of the results generated from the CRIS prototype was evaluated by performing a manual safety risk identification seminar. Two experts and three engineering practitioners with rich domain experiences from the Center for Virtual, Safe, and Automated Construction of Hubei Province were invited to identify the potential safety risks in this project. Considering the construction information in the foundation pit excavation phase, the participants conducted safety risk identification based on construction drawings, construction plans, risk management guidelines, and other documentation. After a two-hour evaluation and discussion, the identification results--and associated suggestions, which are shown in Table 5--were given by the seminar.  
A comparison of the risk identification processes of the CRIS prototype and the seminar is shown in Table 6. Considering the main shortcomings of the traditional risk identification method (e.g., time and manpower consuming, comprehensiveness of identified risks, and subjectivity in risk-related information expression) and engineering practice, the effectiveness of the CRIS prototype is demonstrated from the following aspects: (1) the time- and manpower-saving process; (2) the accurate result by identifying more potential safety risks; and (3) the objective assessment with more related risk information.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline \multicolumn{4}{c}{**Basic Project Information**} \\ \hline Project name & \multicolumn{2}{c}{Deep excavation project of financial building,} & \multirow{2}{*}{Excavation depth} & \multirow{2}{*}{10.5 m} \\  & & Zhengdong New District. & \\ Bracing method & & Soil nailing wall and pile- anchor combined bracing system & & \\  & & & system \\  & & Potential risk list & & \\  & Risk name & Soil flow in the bottom of foundation pit & & \\
1 & & Soil property of the bottom of the foundation pit & & \\  & & 2. Entering-rock state of the retaining structure; & & \\  & Risk factors & & 3. Ratio of penetration (D/H) of the retaining structure; & \\  & & 4. Water head difference between the inside and outside of a foundation pit; & \\  & & 5. Weak stratum reinforcement state; & & \\  & & 6. Soil thickness. & & \\  & Risk results & & 1. Sudden occurence of the risk; & \\  & & 2. Soil damage and injuries. & & \\  & & 1. Entering-rock of the retaining structure; & & \\  & Measures & & 2. Weak stratum reinforcement of the bottom of the foundation pit; & \\  & & 3. Lower the water head difference between the inside and outside of a foundation pit. & \\  & Risk name & Soil flow in the bottom of the foundation pit & & Risk grade \\
2 & & Soil property of the inside and outside of a foundation pit; & \\  & & 2. Water head difference between the inside and outside of a foundation pit; & \\  & & 3. Watertightness of the retaining structure. & & \\  & & 1. An asymptotic behavior; & & \\  & & 2. Formation of caves behind the retaining structure; & & \\  & Risk results & 3. Soil subsidence in the lateral of the foundation pit; & & \\  & & 4. Movement of the retaining structure wall to the lateral of the foundation pit; & & \\  & & 5. Instability and failure of the supporting structure. & & \\  & & 1. Add waterproof curtain; & & \\ Measures & & 2. Weak stratum reinforcement of the outside of a foundation pit; & & \\  & & 3. Lower the water head difference between the inside and outside of a foundation pit. & & \\ \hline \hline \end{tabular}
\end{table}
Table 5: Manual safety risk identification results and associated suggestions (partial)