Pedestrian Flow Dynamic Characteristics And Evacuation In The Metro Hub Station Based On The Social Force Model

Metro plays a more and more important role in urban public transport service,due to its characteristics of large volume,low energy consumption,less pollution and convenient taking.It has become the first choice to solve the problem of traffic congestion.With the rapid development of metro,the metro network pattern has gradually formed,and the attraction amount of pedestrian flow continues to increase day by day.The metro hub station,as a connection point of multiple metro lines,has a relatively large gathering and distributing pedestrian flow,which therefore demands an evacuation system with a higher safety performance.The study on dynamic characteristics and evacuation of the pedestrian flow in the metro hub station has attracted the attention of scholars and research institutions around the world.The bottlenecks in the metro hub station are more likely to emerge blocking,because of the complex structure and the large pedestrian flow,which can further lead to security risks.Once the fire,earthquake,terrorist attacks and other emergencies occur,serious congestion stampede may be caused under the condition of unreasonable emergency evacuation plan.In order to reduce the occurrence of accidents and guarantee the travel safety of pedestrians in the metro hub station,the key is to conduct the preliminary research on pedestrian flow dynamic characteristics and evolution rules,to formulate the reasonable emergency evacuation strategy,and to disperse and control the heavy pedestrian flow effectively.Through the comprehensive analysis of domestic and international research status,this thesis mainly focuses on analyzing and studying the pedestrian flow dynamic characteristics and evacuation in the metro hub station based on the social force model.The main research work can be summarized as follows:Firstly,the relationship between heterogeneity and dynamic characteristics of the bidirectional pedestrian flow in straight corridors is studied.A hybrid model of pedestrian motion is established for predicting the density and motion state based on the social force model and the law of mass conservation.The effect of heterogeneity in pedestrians on the free flow velocity,the probability and the start time of breakdown of bidirectional pedestrian flows in straight corridors is analyzed.The problem of internal connections between the heterogeneity of crowd and complex dynamic characteristics is solved.A hybrid model of pedestrian motion is then established based on the social force model and the law of mass conservation,which can predict the pedestrian density and motion state in the straight corridor of the metro hub station.The safety warning ability is therefore improved.Secondly,an improved social force model considering the excitation level is established.The dynamic characteristics and capacity of unidirectional/bidirectional pedestrian flows in corridors with bottlenecks are studied.Considering influences of the realization degree of desired velocity,surrounding pedestrians and environment on the excitation level of pedestrians,an improved social force model is established.The validity of the model is further verified.The role of bottlenecks on trajectory lines,hierarchical structures and breakdown phenomenon of the unidirectional/bidirectional pedestrian flow is obtained.The relationship between outflows and motion states of the pedestrian flow is given,and then the problem of influences of corridor bottlenecks on dynamic characteristics and capacity of pedestrian flows is solved.Thirdly,a pedestrian motion model considering guides is established,and pedestrian evacuation under guides is studied.The navigational force of guides is proposed.The pedestrian motion model considering guides is therefore established based on the social force model,meanwhile comprehensively considering influences of individual behavior,mass behavior,wall and other boundary conditions on the desired directions of pedestrians who don’t flow guides.The validity of the proposed model is further verified.The influence of guides,mass behavior and desired velocity on the dynamic characteristics and ability of evacuation is investigated,and then the problem of the effect of guides on the evacuation ability in the metro hub station is solved.Fourthly,a prediction model of pedestrian distribution at the metro platform is established based on ant colony optimization algorithm.Pedestrian evacuation at the platform under fires is further studied.Comprehensively considering the effect of train timetable,the distance to the waiting area and the physical structure of the station on the waiting area choice behavior,a prediction model of pedestrian distribution at the metro platform is established.Among which,the social force model is used to drive pedestrian walk.The validity and comparision results of the prediction model are also given.The maximum threshold value of pedestrian density at the metro platform is obtained,and the influence of pedestrian distribution and fire parameters on evacuation ability is therefore solved.