Double-hole Highway Tunnel Under Fire Mode Cross-channel Ventilation Control Research

In recent years,with the rapid development of China’s economic level,the requirements for transportation are getting higher and higher,and many special tunnels have emerged.So far,China has become the country with the largest number of tunnels and the longest total length in the world.While tunnels bring convenience to people’s lives and production,the probability of fires also increases invisibly.Due to the closed and narrow tunnel space,in the event of a fire,it is impossible to quickly realize personnel escape and fire rescue.In addition,high-temperature smoke cannot be transmitted to the outside in a confined space,and fire fighting is difficult,which inevitably leads to a greater number of casualties.Compared with ordinary length tunnels,when a special tunnel fires,people and vehicles generally choose a horizontal channel for evacuation.Therefore,the systematic analysis of the influencing factors of critical wind speed in the tunnel transverse channel and the reasonable smoke prevention wind speed to prevent the intrusion of flue gas into the transverse channel have certain theoretical guiding significance for the development of tunnel ventilation operationscheme.This paper first introduces the causes,characteristics and hazards of tunnel fires,summarizes the research status of tunnel fires at home and abroad,and puts forward the research content of this paper.Then the basic knowledge of computational fluid dynamics is introduced.The basic principle of FDS numerical simulation method and its solving steps are expounded in detail.The corresponding physical model is established according to the selected experimental scene.Then the FDS software was used to simulate the tunnel fire,and the variation law of the critical wind speed of the transverse channel under different influencing factors was studied.After analyzing the influence of different factors on the critical wind speed of the transverse channel between the tunnels,the original physical model of the tunnel is used to study the smoke of the tunnel transverse channel under the vertical air supply conditions of different tunnels and the smoke prevention wind speed in different transverse channels.Intrusion situation,combined with the change of flue gas recirculation length,smoke layer thickness temperature distribution and visibility distribution in the transverse channel,analyzes the smoke prevention effect under different smoke prevention wind speeds,and proposes a reasonable smoke prevention wind speed to prevent smoke from invading thecrosschannel.The study shows that the critical wind speed of the transverse channel and the fire source power increase by 1/4 power.The greater the fire source power,the greater the critical wind speedof the corresponding transverse channel.At the same time,the greater the longitudinal ventilation speed in the tunnel,the corresponding transverse channel criticality.The wind speed is smaller.Under different fire source powers,the critical wind speed of the transverse channel decreases with the increase of the cross-sectional area of the transverse channel,and the cross-sectional area of the transverse channel is inversely proportionaltothe criticalwindspeed.For the Yangzong tunnel studied in this paper,the ventilation and smoke control for the transverse channel leads tothefollowingconclusions:1.When the fire source is in the tunnel near the side of the cross-channel protection door and the horizontal distance of the fire source is 20 m from the junction of the horizontal channel,the wind speed of the protective door is 0m/s,and the wind speed of the tunnel is not to be greater than 1.5m/s;2.Considering the most unfavorable situation of the fire source,the fire occurs in the side lane adjacent to the cross-channel protection door and the fire source is just at the junction of the tunnel and the cross-channel.The wind speed of the tunnel is 0m/s,and the wind speed of the smoke at the protective door should be greater than 1.2m/s;3.When the fire source is in the side of the tunnel near the side of the cross-channel protection door and the fire source is just at the junction of the tunnel and the transverse channel 20 m,when the tunnel wind speed is 1.7m/s,2m/s,2.3m/s,2.88m/s,from the length of the flue gas return,The critical wind speeds are 0.8m/s,0.9m/s,1.2m/s,and 2m/s respectively.Based on the evacuation safety considerations,the wind speeds of the smoke prevention and supply at the protective doors should not be less than 0.8m/s,0.9m/s,1.2m/s,and 2m/s,respectively,to ensure thesafeevacuation ofpersonnel.Insummary,it is found that under the critical smoke exhaust speed of the tunnel,the formation of 2.0m/s smoke-proof wind speed at the cross-channel protection door can effectively prevent the intrusion of smoke and ensure the safe evacuation of personnel.At this time,the wind speed at the cross-channel protection door is the demand.Reasonable smoke prevention wind speed.The above conclusions provide a certain reference for the design of tunnel ventilation and ventilation control.Figure[72]Table[13] References[68].