# Development of a Fire Risk Assessment Program for Submerged Tunnels
## 2 Literature Review  
Research on fire safety in road and railway tunnels has been actively conducted for a long time, incorporating various experimental studies and simulation techniques. Notably, [PERSON] et al. (2015) [3] provided comprehensive insights into tunnel fire safety by addressing fire dynamics, smoke control, and evacuation strategies. Additionally, [PERSON] (2002) [4] applied quantitative risk analysis (QRA) to minimize casualties in road tunnel fires, highlighting that hazardous material transport accidents--such as those involving gasoline, propane, or TNT--pose significant risks and necessitate appropriate tunnel design and safety measures. However, submerged tunnels represent an innovative underwater transportation infrastructure that requires a distinct approach to fire safety. Unlike conventional tunnels, submerged tunnels are fully situated underwater, necessitating specialized ventilation systems, fire-resistant materials, and emergency evacuation strategies. Despite these critical requirements, research on fire safety in submerged tunnels remains insufficient. [PERSON] et al. (2015) [5] assessed the fire risk of the Mokpo-Jeuj subsea railway tunnel and determined the optimal spacing for evacuation passageways. To conduct the study, a quantitative risk assessment (QRA) was applied to analyze fire spread and evacuation scenarios within the tunnel. The findings indicated that a double-track tunnel with partition walls provides the safest evacuation environment. [PERSON] and [PERSON] (2018) [6] modified the existing quantitative risk assessment method for large tunnels to develop a quantitative fire risk assessment method specifically for small road tunnels designed for small vehicles. Through this study, they identified the optimal distance between cross passages and the most effective tunnel ventilation method, confirming that the proposed method can be utilized in the design and fire safety planning of small road tunnels. [PERSON] (2021) [7] identified key risk factors associated with fire and explosions inside submerged tunnels and proposed design considerations for fire and explosion response. The study emphasized that tunnel ventilation systems should be designed with longitudinal ventilation to manage fire and toxic gas emissions. It was suggested that the maximum airflow velocity should not exceed 10 m/s for unidirectional tunnels and 8 m/s for bidirectional tunnels. Additionally, the study highlighted the importance of enhancing structural fire resistance through the application of Double Hull Steel Lining and the necessity of implementing safety measures, such as escape bays at regular intervals and automated detection systems. [PERSON] et al. (2024) [8] conducted a study to evaluate the fire risk of the Shenzhen-Zhongshan underwater tunnel in China. A 1/30 scale model of the actual tunnel was constructed, and 140 small-scale fire experiments were carried out by varying fire intensity and ventilation fan operation modes to reproduce various scenarios. Based on the results, a new sidewall smoke extraction system was developed for optimal smoke control, which significantly improved smoke extraction efficiency. It is considered that if a quantitative fire risk assessment is additionally applied to this system, fire safety in underwater tunnels could be further enhanced. [PERSON] et al. (2024) [9] proposed a computer vision-based real-time tunnel fire risk and evacuation safety assessment system. Using YOLOv7 and DeepSORT algorithms, vehicles were classified based on size, the number of occupants, fuel load, and heat release rate, and the classified vehicles were monitored to predict fire load in real time. In addition, a digital twin was constructed to simulate fire scenarios and evacuation processes, and real-time evacuation scenarios were evaluated based on vehicle distribution and occupant information. Such real-time simulation helps enable prompt and accurate decision-making.