Abstract
Considering the advancement in underground space construction in China, the number of single-end tunnels during the construction process has increased annually. To study the smoke-spreading characteristics of fires occurring in single-end tunnels formed during subway construction, a full-scale experiment was performed in the construction section of a subway tunnel.
The diffusion and settlement laws of smoke in a single-end tunnel were studied through the analysis of the overall temperature distribution, wind speed distribution, smoke layer height, and other tunnel parameters with on-site observation combined.
The results indicate that under natural ventilation, the diffusion velocity of smoke is slower toward the closed end than toward the through end; moreover, the velocity difference decreases with increasing distance between the ignition source and the closed end.
The decay rate of ceiling flue gas temperature is slower toward the through end than toward the closed end. The distribution of flue gas at the connected end conforms to the classical model with the exponential decay distritution, while the closed end has a clear accumulation effect, forming a dangerous section. The height of the flue gas layer at the closed end is as low as 1.5 m, which is the key aspect for consideration in flue gas control and fire emergencies.
