Small-scale fire tests in the underwater tunnel section model with new sidewall smoke extraction

The Shenzhen–Zhongshan Bridge is a 24-km-long bridge and tunnel system, including a 6.8-km-long super cross section subsea tunnel. To solve the smoke exhaust problem of a super large cross-section subsea tunnel, the tunnel has a new smoke exhaust system that combines a horizontal smoke exhaust cross section at the top and sidewall smoke exhaust holes. In order to evaluate the potential fire hazards of this type of tunnel, a 1:30 tunnel model was established and 140 small-scale experiments on underwater tunnel fires were conducted. By changing the fire power, fire location, and fan operation mode, different scenarios of submarine immersed tunnel fire were simulated and the related key parameters such as fire smoke diffusion behavior and smoke temperature distribution were studied. On this basis, the optimal smoke control strategy was proposed for different fire scenarios. The research results indicate that the new smoke exhaust system can fully utilize the smoke flow characteristics, significantly improve smoke exhaust efficiency, and increase available evacuation time, thus further enhancing the fire safety of super large cross-section subsea tunnels.