# Development of a Fire Risk Assessment Program for Submerged Tunnels
## 3 Development of Quantitative Risk Assessment Program for Submerged Tunnels
### Fire Analysis Methods for Road and Railway Tunnels  
Fire analysis for road tunnels is carried out based on a one-dimensional airflow prediction program called TVSDM (Tunnel Ventilation Smoke Dynamic Model), which assumes airflow in only one axis (longitudinal direction). This program supports various ventilation strategies--such as longitudinal, transverse, and large exhaust shaft systems--and predicts the longitudinal airflow velocity in the tunnel during fire scenarios. Based on the predicted airflow, the fire intensity and corresponding flow conditions for each scenario are generated. These outputs are then used as input data for the FDS (Fire Dynamics Simulator), with an Excel-based automated system facilitating the creation of FDS input files. Users can enter tunnel geometry, length, and the number of mesh grids; the program then combines this information with the predicted airflow data to automatically generate FDS executable files for simulation.  
Figure 1 illustrates the parameter input window for road tunnel evacuation analysis. Users input basic tunnel specifications such as traffic direction, geometry, and traffic volume, along with fire intensity and evacuation delay parameters--including vehicle blockage time, fire detection time, and alarm broadcast delay. Once the number of vehicles inside the tunnel is entered, the total number of evacuees is estimated using average occupancy data by vehicle type. The evacuation passage spacing is divided into six equal segments to calculate evacuation distances, and a distance map is generated to support evacuation scenario modeling.  
In the case of railway tunnels, the SES (Shaft Effect Simulator) program is used to predict airflow during a fire in a one-dimensional manner based on parameters such as the presence of vertical shafts, train specifications, and tunnel dimensions. Similarly to road tunnels, the FDS input files are automatically generated using the Excel-based system, and the fire analysis is conducted using the predicted airflow data.  
Figure 2 shows the input interface for evacuation analysis in railway tunnels. Users input the tunnel geometry, train type, number of cars, and occupancy to calculate the total number of evacuees. Additionally, the train stopping time, door opening time, and evacuation delay time are entered to reflect evacuation delays in the simulation.  
The calculation of the Fractional Effective Dose (FED) is based on equations from previous studies, incorporating thermal exposure, visibility reduction, and CO inhalation. The FED for each evacuee is computed and converted into a value ranging from 0.1 to 1.0. This value is used to estimate fatalities and quantify the fire-related evacuation risk for both road and railway tunnels using the same methodology.  
\begin{table}
\begin{tabular}{c c c c} \hline
**Category** & **Train Operating Distance** & **Number of Fire Incidents** & **Fire Incident Rate** \\  & **(1,000,000 km)** & **(Cases)** & **(Cases/1,000,000 Train\(\cdot\)km)** \\ \hline
2015 & 121.7 & 1 & 0.0082 \\
2016 & 125.9 & 1 & 0.0079 \\
2017 & 133.7 & 2 & 0.0150 \\
2018 & 137.1 & 3 & 0.0219 \\
2019 & 138.5 & 0 & 0.0000 \\
2020 & 140.9 & 0 & 0.0000 \\
2021 & 142.4 & 1 & 0.0070 \\ Total & 1290.2 & 14 & 0.0109 \\ \hline \end{tabular}
\end{table}
Table 2: Cont.  
Figure 1: _Cont._  
Figure 1: Input windows for road tunnel evacuation analysis and FED assessment.  
Figure 2: _Cont._