Experimental Study On The Risk Of High-density Crowd In Rail Transit Station

With the acceleration of China’s urbanization and the growth of population,the traffic congestion in big cities is becoming increasingly serious,and the passenger flow of rail transit continues to increase.The crowd safety problem in the station is gaining attention.The subway system is relatively an enclosed place,and it is easy to cause casualties in the crowded areas once an emergency occurs.In this study,combined with the layout of facilities in the station and the characteristics of passenger flow evacuation,a crowd experiment was set up with various risk factors concerned.The corresponding indicators were used to evaluate the risks of different types of crowd in order to study the influence of various factors on crowd risks and the evolution law of high-density passenger flow risks.Finally,a risk quantification method suitable for high-density pedestrian flows in rail transit stations is proposed,and the effectiveness of the method is verified according to actual scenarios.The results of the experiments are helpful for operators to take reasonable passenger flow control measures.The risk indicators and the proposed risk quantification method can be useful for crowd risk analysis.The main research contents and results of the thesis are as follows:(1)We have summarized the risk factors,areas of vulnerability and types of risk for crowds in rail transit stations.Combined with the characteristics of facilities and passengers in rail transit stations,the crowd risk factors are divided into two categories: facility factors and passenger factors.Combined with the data of crowd risk accidents in the station in recent years,the risk prone areas in the station are counted,and the crowd risk is divided into three categories: stampede risk,crush risk and retention risk.Three kinds of indicators are proposed as the quantification methods of population risk,and combined with risk factors and risk categories,the problems to be studied in population risk experiment are put forward.(2)Two scenarios of high-density crowd experiments are designed: the bottleneck evacuation scenario and the stress measurement scenario.Various factors such as obstacle types and layout,exit location and initial passenger speed were considered in the bottleneck evacuation experiments and simulated the fall of a passenger in front of a bottleneck in a high-density crowd.The effect of sudden changes in speed on human forces at different densities was considered in the pressure measurement experiments.Highly accurate pedestrian trajectory data were extracted using existing computer vision models and pedestrian crowding forces were measured empirically using TACTILUS(real time pressure distribution measurement system).(3)Three types of risk indicators were used to evaluate and analyze the risk to the crowd in different experimental scenarios.Using the method of variance analysis,the influence of different obstacle types and different obstacle layouts on crowd evacuation efficiency was studied from the perspectives of individual evacuation time and individual evacuation distance.A density entropy index was proposed to describe the spatial fluctuation of high-density crowd density.Using density,speed,pedestrian Angle,density entropy,speed entropy,Angle entropy and other indicators to study the bottleneck effect,obstacle effect,different exit positions,different initial speed of passenger flow,passengers fall before the bottleneck and other factors on the stampede risk.By measuring the squeezing pressure,the effect of the sudden change of crowd velocity on the human body under different densities was studied,and the pressure-density curves under normal and extreme conditions were obtained.(4)An effective method for quantifying crowd risk in rail stations is proposed.In terms of crowd evacuation efficiency,the circumnavigation coefficient is proposed to describe the rationality of obstacle layout.In the aspect of crowd stampede risk,the quantification method of crowd stampede risk considering the degree of crowding and chaos is put forward.In terms of crowd crush risk,the quantification method of crowd crush risk under normal and emergency conditions is proposed.Finally,the effectiveness of the method is verified by evaluating the risk of the crowd in the typical scene of the station.