The Shenzhen–Zhongshan Link immersed tunnel has a total length of 6 845 m, featuring eight two-way lanes, with the widest section expanding to 12 two-way lanes. It is the world’s widest cross-section immersed tunnel and China’s first subsea interchange tunnel. Traditionally, smoke exhaust systems in immersed tunnels have relied on sidewall-concentrated exhaust technology. However, owing to the ultra-wide cross-section and multi-node characteristics of the Shenzhen–Zhongshan Link immersed tunnel, this conventional approach reduces smoke exhaust efficiency and fails to meet safety requirements for personnel evacuation in the event of a fire.

To enhance tunnel safety, a new smoke exhaust system incorporating a transverse smoke exhaust duct and sidewall exhaust ports was designed. First, in accordance with relevant specifications and the standards of the American Fire Protection Association (NFPA 502), key technical parameters such as fire design equivalency and smoke exhaust volume were determined. Then, through theoretical analysis and numerical simulation, components of the exhaust system—ncluding the jet fan, transverse exhaust duct, exhaust fan power, and axial exhaust fan room—were designed and finalized. Finally, a smoke control strategy was developed for different fire scenarios. Traditionally, the experimental verification of tunnel fires has relied on small-scale model experiments or static tests in shorter full-size tunnels. However, owing to size effects and experimental limitations, ventilation and smoke exhaust verification could not be performed under real-world conditions.

For the first time, a full-scale fire experiment was conducted at three locations in the Shenzhen–Zhongshan Link immersed tunnel to evaluate the smoke exhaust system. Static and comprehensive tests were performed under 14 working conditions. Through these on-site fire experiments, the variation patterns of the velocity and temperature fields under different conditions were analyzed. The results of the full-scale experimental study confirmed that the new smoke exhaust system in the Shenzhen–Zhongshan Link immersed tunnel meets the required smoke exhaust design standards.