| With the continuous development of China’s economy and society,people’s demand for travel is getting higher and higher,China’s underground rail transit has been developing rapidly.At present,many cities have built a huge underground transportation network,the subway-led urban underground rail transit mode has the advantages of convenient,fast,safe and reliable,has become the preferred mode of transportation for urban residents to travel.However,once a fire occurs in the subway,the threat to the safety of the occupants is huge,because in the environment of the interval tunnel fire,the rapid spread of fire,toxic fumes are not easy to discharge,underground visibility is insufficient,passenger density and other factors.In order to solve the problem of safe evacuation of fire personnel in subway zone tunnel,FDS is used to simulate and calculate the fire scene of rectangular subway tunnel with contact channel port,and to analyze the environmental safety of fire field comprehensively.The concept of safety evacuation reliability is put forward,and the safety evacuation strategy is optimized from the aspects of time margin and safety evacuation reliability by using Pathfinder multi-intelligent body evacuation simulation platform.First,through the comparison of various subway tunnel structure forms,it is found that rectangular tunnels are less emergency measures available in the face of fire evacuation safety threats than other forms of interval tunnels,so this paper takes single-hole two-line rectangular interval tunnels as the research object.In order to ensure the safe evacuation environment of contact channels and non-accident tunnels,this paper carries on the data post-processing work on the relevant experiments carried out by the task force in advance on the fire experimental platform of the single-hole double-line tunnel.The results show that the positive pressure of nonaccident tunnel is an effective air flow anti-smoke method,which can ensure the safe exit of the contact channel and create favorable conditions for the safe evacuation of passengers.Second,according to the above-mentioned research,reference to the national standard "Subway Design Code" GB 50157-2013,the establishment of a contact channel port with a rectangular interval tunnel model,the total length of 1200 m,the train model to choose a large passenger capacity of 6A train marshalling scheme.Using FDS fire simulation calculation tool,a total of 11 kinds of fire simulation calculations were carried out under different fire occurrence locations and different ventilation and smoke exhaust modes.From the point of view of safe evacuation,the fire environment is analyzed comprehensively by co-concentration,temperature and visibility.The results show that:（1）the vertical ventilation wind speed of 2m/s can be used to curb the occurrence of flue gas reflux phenomenon and create a favorable environment for the safe evacuation of personnel.（2）Rapid reduction in visibility will first lead to adverse effects on occupants of the fire environment.（3）CO concentration in the natural ventilation conditions will be over the time in the tunnel area of more than 400 ppm this absolute hazard indicator,open vertical mechanical ventilation,in addition to the fire source downstream area 100 m range,the rest of the area CO concentration index is under the absolute hazard standard of 400 ppm,vertical mechanical ventilation can be very good to reduce the CO concentration of the tunnel fire environment,to provide favorable conditions for evacuation.（4）The effect of temperature on the safe evacuation of personnel is mainly concentrated in the fire source area 100 m range,whether to turn on vertical ventilation mode,the effect on the temperature diffusion range is not great,but will effectively curb the spread and accumulation of heat from the upper wind.（5）Compared with natural ventilation,vertical mechanical ventilation,while creating a safe evacuation environment for people with upper wind direction,also accelerates the speed of the transition of the downwind to the space area into a dangerous area,to a certain extent,adversely affects the evacuation and escape of passengers with the downwind.Third,based on the relevant index data obtained in the above-mentioned study under different tunnel fire scenarios,the safe evacuation time of personnel in each area is determined,and the visibility data is manually coupled with the Pathfinder intelligent body platform,which shows the effect of reduced visibility on the choice of evacuation route and the speed of people walking.The concept of the reliability of safe evacuation of personnel is put forward,and the calculation method is given as the basic way to judge the advantages and disadvantages of the researchers’ safe evacuation strategy.A total of 155 groups of evacuation simulations were carried out under 6 fire conditions with vertical ventilation mode on.The safe evacuation time,time margin and reliability of safe evacuation must be calculated under different schemes,and the optimal train door opening scheme and evacuation path under different fire positions,different vertical ventilation directions,and fixed load rates for different occupants are obtained.The results show that:（1）Under the 6A train grouping scheme,the fixed passenger load rate of 100% can not guarantee that personnel in the available safe evacuation time in accordance with the requirements of the specification,facing the direction of the new wind to one-sided platform to complete the evacuation.（2）Under the 6A train grouping scheme,the fixed passenger rate of 100% in addition to E1,C2 conditions,the remaining four fire scenes can ensure that personnel to the two-sided platform to complete the evacuation.（3）A1,B1,C1,D1,E1 fire scene,personnel must safely evacuate the shortest time train door opening program is to close 2,3 car doors,close 4,6 car doors,close 2,3,4,5 car doors,close 2,3,4,5 car doors,close 1,3,4,5,6 car doors.（4）In the A1,B1,C1,D1,E1 fire scene,respectively,in the fixed passenger rate of 70%,60%,70%,70%,55%of the case with the best train door opening program personnel in the direction of the new wind to the one-sided platform for evacuation or to the two-sided platform evacuation program can be achieved,from the perspective of time to consider the organization personnel quickly away from the fire source near to the two-sided platform for evacuation,From the point of view of the reliability of safe evacuation,personnel should be organized to go to the one-sided platform in the direction of the new wind for evacuation.（5）The specification provides for the determination of vertical ventilation direction of the two principles,that is,the principle of minimum downwind personnel and the principle of near-fire source platform smoke,C1,C2 operating conditions in the above two principles in the case of conflict with the adoption of different mechanical vertical ventilation direction,C1 conditions of personnel must be safe evacuation time significantly lower than C2 operating conditions,in determining the direction of vertical ventilation,should first consider the principle of the minimum downwind personnel. |
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