Study On The Safe Evacuation Of Bus Fire In A Long Road Tunnel

In the public urban road transportation network,long and large road tunnels and large-capacity buses are increasing to meet people’s travel needs,increase passenger capacity,and improve transportation capacity and operational efficiency.But it also brings greater security risks at the same time.Among them,the bus fire in the tunnel is one of the most prone and most harmful disasters.Therefore,it is necessary to deeply study the evolution of the bus fire in the long road tunnel and the evacuation strategy in the tunnel,so as to provide guidance and reference for the prevention and rescue of the bus fire in the tunnel.This paper takes the bus fire in a super long highway tunnel in Shenzhen as an object,and uses a combination of theoretical analysis,fire numerical simulation,personnel evacuation simulation and model verification to study the fire safety evacuation problem.The main research contents include:(1)The smoke flow characteristics of the fire of the external bus in the long road tunnel under different ventilation conditions;(2)The influence of the cross-channel parameters of long and large highway tunnels on the evacuation time and safety of personnel under bus fire conditions;(3)The smoke flow law of the fire inside the bus in the tunnel and the influence of the window opening time on the spread of smoke;(4)The safety of evacuation based on the coordination of the smoke spread and the evacuation process under the fire conditions inside the bus;(5)Characteristics of evacuation behavior of passengers in vehicles based on the coupling effect of smoke spread and evacuation process under internal fire conditions.The research results show that:(1)When the heat release rate of the bus fire is 30 MW,the critical wind speed of the flue gas in the rectangular cross-section tunnel is 3.2m / s;longitudinal ventilation forms eddy currents and annular isotherms in the right-angle area near the fire source.The temperature gradient of the cross-section tunnel is reduced,and the maximum temperature of the flue gas in the right-angled area of the ceiling appears to be a minimum at a certain longitudinal wind speed;the vortex on the wall of the archsection tunnel near the fire source is not obvious,and the flue gas field is more stable,but the slope in the tunnel strengthens and accelerates the trend and process of smoke spreading in the upward direction;(2)When the distance between two crosswalks in the tunnel is 250 m,it is beneficial to improve the evacuation efficiency of the exits.The width of the crosswalk is 2.5m,which can reduce the total evacuation time.When the tunnel has a slope and a fire occurs under natural ventilation,the evacuation time of the crosswalks with a distance of 500 m is less than the security clearance time;(3)When a 1MW ultra-fast fire occurs inside the bus,the first obvious peak of the smoke concentration,velocity and temperature at the front door will appear at 38.0s;Qpening the window after 30 s can suppress the development of the fire inside the bus;When the front door is not used for evacuation after 30 s,it can ensure that the personnel evacuation process is within a safe range;(4)Based on the coordination of the fire development and the evacuation process,the influence of the smoke in the bus on the choice of evacuation path is reflected in the 5s after the evacuation;(5)Consider the coupling of the spread of smoke and the evacuation process.By adjusting the path and selecting exits,evacuation safety is no longer limited to the determination of evacuation time.In this paper,the research on the influence of the window opening conditions of the bus in the tunnel on the internal fire smoke flow characteristics and personnel evacuation process and the evacuation time safety judgment method based on the coupling effect are of certain innovation.The research work in this paper was supported by the Shenzhen Banyin Channel Project.The research results provide a direct reference for the fire safety design and emergency rescue plan of the tunnel project,as well as provide a new idea for the analysis of the evacuation behavior of the fire inside the tunnel and the optimization of the algorithm,which is of great significance to improve the safety of the operation of the bus in the tunnel.