Metro Fire Risk Analysis And Evacuation Simulation Based On Smoke Simulation

Metro is an important part of the urban public transportation system.The space of metro station is relatively closed,and the passenger flow is extremely crowded at peak hour.Therefore,there are various kinds of hazard hidden in the system.Metro fire is one of the disasters most likely to cause serious casualties.It is of great significance to conduct fire risk assessment and emergency evacuation strategy research from the aspects of prevention and control measures.The numerical simulation of flue gas distribution and evacuation is already comprehensive,but the analysis of the interaction between these two factors is still very lacking.In this dissertation,AHP method is firstly adopted to evaluate the fire risk of metro system.Then the smoke flow and evacuation of metro station fire are analyzed by numerical simulation method.The specific research content is as follows:(1)Fault tree method is adopted to identify fire risk hazard of metro station.The evaluation model of fire prevention and control measures is established by fuzzy consistency matrix and analytic hierarchy process.After that the qualitative and quantitative evaluation of the existing safety risks and the prevention with control measures of metro stations has been realized;(2)the smoke flow and temperature field of the metro station fire are simulated numerically.The effects of the parameters of the station ventilation system on the flue gas flow and temperature distribution were analyzed.According to the simulation results of smoke movement,the time conditions of emergency evacuation are given.(3)based on the cellular automata model and considering the rules of human behavior,the author programmed the evacuation simulation for the situation that the station platform has not been affected by smoke;Taking the interaction between smoke diffusion and evacuation into consideration,the software MassMotion is used to simulate the evacuation under the condition of smoke diffusion on the station platform.After that the relationship between the number of evacuees under different conditions and evacuation time is obtained.The results show that the fuzzy analytic hierarchy process after quantitative evaluation is more objective than the old method.It is concluded that proactive protecting measure are the most important fire control measures.In terms of smoke simulation,the design of dual blowers can effectively slow down the diffusion of toxic and harmful gases.Even under this condition,the CO concentration in the middle escalator will still exceed the safe concentration after a certain period of time.In the process of evacuation,stairs and escalators are easy to form a bottleneck,and the existing station structure can not meet the requirements of the standard.Accordingly,the effective total width of stairs and the evacuation capacity of emergency exit should be appropriately increased.