A Simulation Study On Emergency Evacuation Based On The Gas Attack Of Subway Station Incident

With the rapid growth momentum of urban economy and an increasing number of motor vehicles on the road,the metro rail transit has become a preferred choice of daily commute with its convenient and economical edge.But in recent years,terrorist attacks have occurred frequently,and the subway has become the first-select location for poisonous gas attacks throughout the current international landscape.Therefore,this article is aimed at proposing the rapid and effective measures to respond to terrorist attacks in the subway station,thus minimizing casualties and property losses.Firstly,it is counted that the general attributes,distribution,composition and basic travel status of subway passengers in the form of questionnaires,and a correlation analysis of the questionnaire results is made to obtain the main variables affecting people's walking habits: gender,age and education.Then,the pedestrian flow,speed,density and other data at peak periods are obtained through field observations.Both of the group and individual special path-finding behaviors are summarized according to the relevant documents recording pedestrians' normal states and walking rules under emergent conditions.These two pieces of data will be used as reference factors for the staff parameter settings in the evacuation simulation.Chlorine gas is used as an example to simulate the distribution of toxic gas diffusion by using Fluent software: no toxic gas diffuses into the observation surface in the first 30 s while it roughly distributes in the same shape and forms two blocks of asymptotic concentration between 60 s and 120 s.The residual gas near the outlet is to gradually dissipate after 120 s.The evacuation time is simulated by using Pathfinder software,and the simulation results are compared with the simulation results of the poison gas diffusion,in order to analyse the possibility whether passengers are exposed to the gas at the corresponding time nodes.The main factors affecting evacuation efficiency are identified by observing the evacuation process simulated by the software and analyzing the passengers' evacuation activity rules and path finding methods.Finally,according to the simulation results,the most important factor is the evacuation ability of the stairs from the aspect of building structure.Therefore,suggestions of widening the stairs and changing the stairs position are proposed.From the perspective of controllingthe diffusion of poison gas,the optimized improvement of exhaust system is proposed.It is also put forward that the knowledge of emergency evacuation need popularizing from the angle of personnel themselves.