FIRE SAFETY | WTC


AN IMMERSED TUBE TUNNEL IN CHINA Fire safety among various aspects of design on a particular tunnel project, in China, were discussed in two papers5,6 that gave


focus to some of the particular challenges in designing such a giant immersed tube tunnel (see box: References). The project is the Shenzhen-Zhongshan (Shen-Zhong) tunnel, which is the key structure in a fixed link across the coastal


strait separating the cities. The giant immersed tube tunnel is a two--way, eight-lane link and its form is as a composite structure with steel encased in concrete. Researchers note, in one paper5


, that immersed tube tunnel structures are mostly focused on the form of reinforced


concrete structures. As such, composite structures of steel encased in concrete are rare in tunnels. Consequently, there is a lack of fire resistance standards related to hybrid forms like Shen-Zhong tunnel, which utilises steel for waterproofing and load bearing. The paper proposes a fire resistance limit standard for steel-encases concrete immersed tube tunnel structural forms. The


proposal is bases on standardised research and analysis, and high-temperature mechanical testing. In summary, it proposes:


● fire resistance time in the RABT standard temperature-time curve test to be at least two hours; ● In the main segmental tube structure, temperature of the steel (in the steel case surface) should not exceed 300°C within two hours; and,


● At the joints between adjoining tube segments, the maximum temperature of OMEGA and GINA rubber waterstops should not be more than 150°C. Above 100°C the resistance time of the waterstops should not be longer than one hour, and above 70°C should not be longer than two hours.


This research was supported with funding from the National Key Research and Development Program of China, the National Natural Science Foundation of China, and Natural Science Foundation of Chongqing. Given the scale of the fixed link crossing, the complexity of integration with the road network, and the high traffic


volumes in the design case for its use, the authors in the second paper on the project focused on fire prevention and rescue technologies. Given the high operational risk, they note, the design solution involved control of hazards, prevention of accidents, early


warning of accidents, alarms, emergency links and response, fire suppression, smoke extraction, evacuation, and more. The authors say the lessons of fire safety analysis and design on this large, complex project are a good reference for tunnel plans elsewhere in the underground transport industry.


noting that the findings are consistent with the


reference thermo-mechanical responses, with average errors of less than 5%. Further experimental verification is required, it is added.


REFERENCES


The following papers from World Tunnel Congress (WTC) 2024 primarily address the topic of Fire Safety and were the main focus for this article. 1 Lan, F., Zou, H., Wu, L., Wang, Y. & Deng, Y. (2024) ‘Study on fire smoke exhaust strategy in Daliangshan No1 super-long expressway tunnel.’ WTC 2024


2 Pauw, B.D., Timperman, C. & Devriese, S. (2024) ‘Approach in structural fire resistance of the existing North-South Railway Tunnel in Brussels.’ WTC 2024


3 Wang, L. & Yan, Z. (2024) ‘The numerical-physical coupling method in investigation of the response of the tunnel structure under fire scenarios.’ WTC 2024


4 Wei, K., Ji, L., Fu, Y. & Deng, Y (2024) ‘Research on fire compartmentation of hyperscale public area in underground rail transit hub.’ WTC 2024


The following further papers from WTC 2024 offered some discussion on aspects of fire safety with regard to a specific tunnel system: immersed tube tunnels. 5 Cao, P., Song, S., Wu, M., Jiang, S. & Liu, E. (2024) ‘Research on fire resistance limit standard of steel-encased concrete immersed tunnel structure.’ WTC 2024


6 Yang, X., Yin, L., Zhong, M. & Cheng, L. (2024) ‘Fire prevention and rescue technologies used in ultra-wide cross-section immersed tunnel.’ WTC 2024


The modelling investigation was supported by a


grant from the National Natural Science Foundation of China, and the Research Fund of State Key Laboratory for Disaster Reduction in Civil Engineering.


24 | July 2025


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