Research On Pedestrian Evacuation Model In Metro Stations In Case Of Fire And Smoke

Fire emergency evacuation has long been a crucial issue in public security,especially for the pedestrian evacuation at metro platform in case of fire.Plenty of elements may cause difficulties in the evacuation process,such as building structure,pedestrian facilities,the crowd density and the fire intensity.Simulation tools are commonly used to predict the evacuation process,thus it is essential to introduce the reasonable mechanism of pedestrians? motion for an evacuation model.However,many known evacuation models,which applied to practical evacuation study at metro station,ignore the impact of fire smoke,the specific smoke control facilities in metro system and the fact that stair structure make the pedestrians move in a three-dimensional space.Therefore,it can be helpful to have a more reasonable pedestrian evacuation mode l for studying the pedestrian movement mechanism and establishing evacuation software.Main contents of the study are as follows:(1)Determination of research purpose and contents.This paper firstly analyzed the current status of the study from three aspects: emergency evacuation studies of metro system in case of fire,studies on pedestrian evacuation characteristics and studies on pedestrian movement models.The research purpose and contents are determined in this paper: in case of fire emergency at platform of a 2-storey underground metro station,the evacuation process of pedestrian under fire smoke was studied from the perspective of pedestrian movement modeling.Moreover,the emergency smoke control facilities at station are considered in the proposed model.(2)Analysis of influencing factors in the pedestrian evacuation at metro stations in case of fire.In order to grasp the variables in the modeling process,three main influencing factors are discussed in detailed from the perspective of environment and evacuees,including the evacuation environment at metro stations(main evacuation facilities and equipment),the evacuees themselves and the fire and its combustion products(smoke).(3)Establishment of spatial evacuation model of metro station.Because of the three-dimensional structure of stairs,pedestrian evacuation from platform to the station hall is a process of movement in space.First,the evacuation space is drawn to be a three-dimensional grid space,and the evacuation identified as a two-stage process,including the motion on the platform and on the treads.Then,two cellular automation models are proposed to simulate the evacuees? movement and the smoke diffusion,separately.The evacuation model based on an integrated cellular automata model is established,in which the impacts from exits,other evacuees,fire and smoke are quantified based on social force theory.(4)Model simulation and application.The platform of Xiaolingwei station of Nanjing Metro Line No.2 is taken as a studied site for case study.The model parameters are calibrated and simulation experiments are conducted.The simulation experiments results show that this model is able to recognize the arching and stagnation phenomenon at downstairs,and the fundamental diagrams validate the model performance in macroscopic level.The relations between the evacuation time and the crowd density for different parameters are also analyzed.Moreover,the paper proposed methods for the improvement of facilities design based on simulation experiments.The model is proved to have great values on practice.