Study On The Safety And Reliability Of Evacuation During Long Distance Tunnel Fire

During the period of rapid development of China's infrastructure construction,road construction has made tremendous progress,and tunnel construction and operation technology has also been greatly developed.By the end of 2017,the total length of road tunnels in China has reached 15.28 or 510 meters.The length of long tunnels and extra-long tunnels accounts for about70% of the total length of road tunnels,and its number and length are increasing year by year.The tunnel is a special kind of building,especially the long-distance tunnel.Its internal space is closed,the road can be single,and the escape plan is the only one.Therefore,in the event of danger,personnel will be inevitable and have nowhere to escape.As the danger of tunnel fires is gradually recognized,its fire rescue and evacuation systems have become the focus of tunnel research.In this paper,the research on tunnel smoke diffusion is carried out.By establishing the mathematical model of smoke diffusion and the theory of personnel evacuation,the reliability study of evacuation system in tunnel fire period is transformed into the ultimate withstand time and available safe time of personnel under high temperature toxic gas.A comparative analysis between the using the smoke diffusion calculation model obtained by the theoretical research,the appropriate numerical simulation software FDS is selected as the research basis,and the boundary conditions required for the numerical model are set.The Zhaotong Yingzuiyan Tunnel in Yunnan was used for engineering application and verified by FDS simulation software.Through the different arrangements of fire locations in the tunnel fire scene,the fire exit point of the long tunnel is studied as the impact of the entrance,exit and cross-channel entrance on personnel escape.According to the numerical simulation analysis technology,the influence of the tunnel cross-channel spacing and the tunnel wind speed after the exhaust fan is started on the safety and reliability of the evacuated personnel is calculated.The temperature distribution,smoke diffusion and CO concentration change in the tunnel under different working conditions were analyzed.It was found that evacuation was the most unfavorable condition when a fire broke out at the cross-channel and the fire blocked the exit.The reliability of the analyst evacuation system should be analyzed from this most unfavorable condition.Based on the simulation study of engineering application examples,by analyzing the rescue effect of critical wind speed,it is determined that the exhaust fan should be opened so that the wind speed in the tunnel exceeds the critical wind speed.And a variety of tunnel optimization arrangements are set up to maximize the reliability of the evacuation system.In the comparative analysis of multiple optimization schemes,the optimal scheme is selected.It is found that when the exhaust fan is started,the wind speed in the tunnel reaches 3.5m/s and the cross-channel spacing in the tunnel is below 250 m,the safety of evacuation personnel can be guaranteed to the greatest extent.Figure [43] table [16] reference [64]...