Study On The Fire Risk Assessment And Smoke Control Of Long Highway Tunnel

With the the increasing number of the long highway tunnels abd the speeding up of traffic density year by year,tunnel fire becomes one of the most dangerous problemsfaced by highway tunnels.In order to reduce the degree of harm caused by tunnel fire and ensure the safe and healthy driving environment in the tunnel,the secure state of the tunnel operation needs to be evaluated and fire smoke in the tunnel should be effectively controlled.Taking Mi Xiliang Long Highway Tunnel as an example,the safety evaluation and smoke control of long highway tunnel were studied in this paper.In this paper,highway tunnel safety features were highlighted on the base of analysing the characteristics of highway tunnel traffic environment.Accident data was collected separately in different years taking the Qinling highway tunnel and the Xi’an to Han Zhong highway tunnel group as research objects.Then the tunnel accident spatial distribution,time distribution,the accident form distribution,and vehicles’ distribution in accidents were also studied from statistics angle.Besides,the causes of highway tunnel accidents were analysed in combination with these accident data.Finally,the highway tunnel fire causes,vehicle distribution,duration,severity and other relevant indicators were statistically analyzed based on the relevant information collected from domestic and overseasSecondly,the tunnel operation safety evaluation model combining the AHP and the Fuzzy Comprehensive Evaluation method was determined through the analysis and comparison of common evaluation methods.What’s more,the tunnel operation safety evaluation index system was built based on the analysis of the tunnel operational safety factors,and the operation security situation of the Mi Xiliang Tunnel was evaluated comprehensively combined with expert investigation.From the fire performance,smoke movement phenomenon to the analysis of theoretical model,characteristics of different ventilation methods were listed and the existing highway tunnel ventilation modes were analyzed statistically based on the introduction of tunnel fire.Combined with the Mi Xiliang Tunnel project,a numerical simulation model for tunnel fire was built with Pyro Sim software,and factors(the power of fire source,longitudinal grade,blocking ratio,etc.)that influence the critical wind speed were simulated.As a result,the critical velocity of the Mi Xiliang Tunnel was determined.Besides,the fire smoke characteristics in the Mi Xiliang Tunnel was analyzed through numerical simulation.Then the distribution characteristics of smoke in long highway tunnel was analyzed from the angles of temperature distribution changes over time,the impact of gradient on temperature distribution,the impact of longitudinal ventilation on temperature distribution,and the combined effect of gradient and longitudinal ventilation on temperature distribution.Finally,based on the tunnel ventilation network theory,the ventilation in the operational phase of the Mi Xiliang Tunnel was simulated and analyzed through the tunnel ventilation network calculation program,and the the ventilation schemes under different traffic conditions were determined.