Study on the Smoke Dispersion Characteristics of the Fire in Ganqing Tunnel
The study on the change rule of fire smoke in high-altitude areas of extra-long railway tunnels has important guiding significance for the optimisation of the design of extra-long railway tunnels for disaster prevention and rescue,but due to the complex geographic location and the service e environment in high-altitude areas,it is more difficult to study using experimental methods with fewer related researches.Relying on the Ganqing Tunnel Project,the numerical simulation of fire scenarios in extra-long railway tunnels in high-altitude areas is carried out based on the Fire Dynamics Simulator(FDS).By changing the longitudinal wind speed and the direction of the longitudinal wind in the tunnels,it is hoped to obtain the causative factors of fires occurring in the relying project as well as the optimal smoke-control scheme,and to compare the results with those of the simulation of causative factors of fires occurring in the plain areas.The results of the study show that the rate of smoke dispersion and the maximum temperatures and CO concentrations at characteristic altitudes are higher at high-altitudes than in plain areas.The imposition of longitudinal winds is more advantageous in the event of a fire in a tunnel at high-altitude,and as the longitudinal wind speed increases,the downwind flue gas diffusion speed increases and the upwind backflow length can be effectively controlled.Visibility in long tunnels at high-altitudes is the fastest and most influential causal factor in reaching hazard limits,and is not affected by wind speed;low visibility hazard zone exists on one side of the tunnel either with or without longitudinal wind action.The higher the longitudinal wind,the faster the flue gas diffusion,the lower the temperature at the characteristic height and the more pronounced the inhibition of high temperature flue gas diffusion.The conditions of this project suggest that the design of the fans in the downhill section of the tunnel should be strengthened and the longitudinal wind speed should be controlled not less than 3m/s.
high-altitude regionsrailway tunnelextra-long tunnelsoot dispersiondisaster-causing factorstobacco control programme
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