PURPOSES : This study provides fundamental information on the temperature variations in tunnel structures during severe fire events. A fire event in a tunnel can drastically increase the internal temperature, which can significantly affect its structural safety. METHODS : Numerical simulations that consider various fire conditions are more efficient than experimental tests. The fire dynamic simulator (FDS) software, based on computational fluid dynamics (CFD) and developed by the National Institute of Standards and Technology, was used for the simulations. The variables included single and multiple accidents involving heavy goods vehicles carrying 27,000 liters of diesel fuel. Additionally, the concrete material characteristics of heat conductivity and specific heat were included in the analysis. The temperatures of concrete were investigated at various locations, surfaces, and inside the concrete at different depths. The obtained temperatures were verified to determine whether they reached the limits provided by the Fire Resistance Design for Road Tunnel (MOLIT 2021). RESULTS : For a fire caused by 27,000 liters of diesel, the fire intensity, expressed as the heat release rate, was approximately 160 MW. The increase in the carrying capacity of the fire source did not significantly affect the fire intensity; however, it affected the duration of the fire. The maximum temperature of concrete surface in the tunnel was approximately 1400 ℃ at some distance away in a longitudinal direction from the location of fire (not directly above). The temperature inside the concrete was successfully analyzed using FDS. The temperature inside the concrete decreased as the conductivity decreased and the specific heat increased. According to the Fire Resistance Design for Road Tunnel (MOLIT 2021), the internal temperatures should be within 380 ℃ and 250 ℃ for concrete and reinforcing steel, respectively. The temperatures were found to be approximately 380 ℃ and 100 ℃ in mist cases at depths of 5 cm and 10 cm, respectively, inside the concrete. CONCLUSIONS : The fire simulation studies indicated that the location of the maximum temperature was not directly above the fire, possibly because of fire-frame movements. During the final stage of the fire, the location of the highest temperature was immediately above the fire. During the fire in a tunnel with 27,000 liters of diesel, the maximum fire intensity was approximately 160 MW. The capacity of the fire source did not significantly affect the fire intensity, but affected the duration. Provided the concrete cover about 6 cm and 10 cm, both concrete and reinforcing steel can meet the required temperature limits of the Fire Resistance Design for Road Tunnel (MOLIT 2021). However, the results from this study are based on a few assumptions. Therefore, further studies should be conducted to include more specific numerical simulations and experimental tests that consider other variables, including tunnel shapes, fire sources, and locations.

최근 대륙간 연결사업 추진이 증가하면서 우리나라 주변에는 한-중과 한-일 철도 또는 도로 연결사업에 대한 논의가 진행되고 있다. 이 때 적용될 수 있는 기술은 해중터널, 해저터널, 침매 터널 등이 있다. 이중에서 해중 터널은 부력에 의하여 해중에 부유하거나 지지보가 자중을 부담하여 수중에 잔교식의 형태로 건설되는 터널의 형식을 말한다. 해중터널은 일반적인 교량, 침매터널, 해저터널의 보완구조물 혹은 대체 구조물로 건설이 가능하다. 해중터널에 대한 연구는 전 세계적으로 거의 초기 단계이기 때문에 다양한 연구가 필요하다. 본 연구에서는 해중터널의 구조 성능 평가 중에 화재가 발생하였을 경우에 화재열이 해중터널에 미치는 영향성을 분석하고자 한다. 해중터널의 해석 모델은 일본에서 연구된 Funka Bay 해중 터널을 대상으로 해석을 수행하였으며, 다양한 화재가 발생하였을 경우에 화재열이 해중 터널 구조에 미치는 영향에 대해서 해석적으로 분석하였다.