Study On The Risk Of Crowded Stampede In Subway Station Based On Pedestrian Extrusion Force And Stability

With the increasing acceleration of urbanization in China,the proportion of urban rail transit in the whole urban public transportation is rising year by year.During morning and evening rush hours,pedestrian congestion often occurs in some stations with large passenger flow,especially in transfer stations.Once accidents occur,it is easy to cause pedestrian stampede accidents.Therefore,it is necessary to carry out a systematic study on the risk of stampede accidents in subway stations.If there is a scientific and reasonable method to quantify risks and evaluate risks,it will not only provide decision support for station passenger flow control,but also information service for passenger travel selection to guide passenger flow requirements.Based on above cognitions,this paper systematically studies the quantification and assessment method of the stampede risk in subway stationsBased on the basic theories of crowd pressure and pedestrian stability,this paper uses numerical simulation and simulation techniques to establish the relationship between basic motion parameters and mechanical parameters of pedestrians.Combining with the psychological parameters of pedestrians obtained from on-the-spot investigation,this paper proposes an approach for measuring and evaluating the crowd stampede risk in subway stationsThe main research contents and results are as follows:(1)The risk characteristics of crowded stampede accidents in subway stations are statistically analyzed to obtain the main parameters of risk assessmentBased on the statistical analysis of major crowded stampede accidents in domestic subway stations in recent years,this paper summarizes two types of risk characteristics of crowded stampede accidents:First,there are two fixed forms of injury:crushing and stability imbalance;Second,there are two kinds of typical occurrence precursors:the high local density of the crowd and the spread of panic mood.Based on these risk characteristics in subway stations,the basic input parameters of the risk assessment model are proposed,including the local density of the crowd,the quantity of pedestrians and psychological factors(2)An EMFP assessment model for the risk of stampede in subway stations is establishedAn assessment model(EMFP model)for pedestrian swarm and jostlement risk in subway stations is established,which takes into account four factors:Environment Factors,Motion Factors,Force Factors and Psychological Factors.For the psychological factors of pedestrians,the influence function of pedestrian density and residence time on pedestrian psychology is used to characterize,and the parameters of two pedestrian risk perception functions,density-panic degree k(?)and joint time-anxiety j(t),are calibrated by using questionnaire data.For the factors of aggregation environment condition,movement condition and stress condition,based on pedestrian crushing pressure model and stability model,the functional relationship between pedestrian basic parameters and risk index in different scenes is established,crushing risk index and instability risk index are calculated,and the corresponding relationship between index value interval and classification of crowded trampling risk level is analyzed and determined.(3)A simulation model of pedestrian crushing force under high-risk scenes in subway stations is establishedBased on Discrete Element Method(DEM)and improved social force model,a simulation model of high-density pedestrian flow is established,and a simulation model program is written by using FISH language built in the discrete particle flow simulation platform PFC2D to realize the simulation calculation of crowded pedestrian flow under two high-risk scenarios of "platform-upper door" and "passageway-upper stairs" in subway stations.The control variable method was used to study the relationship between the four risk index assessment coefficients of maximum crushing force Fmax,average crushing force Fave maximum crushing resultant force Fmax and average speed v and the three basic pedestrian parameters of pedestrian number Q,initial density ?0 and expected speed v0.The global general optimization algorithm package in the multivariate nonlinear regression analysis software 1stOpt was used to perform multivariate nonlinear regression on the simulation data.(4)The pedestrian stability model under the condition of one-legged support is establishedA human body dynamics model based on a single inverted pendulum is established,and the dynamics equation under the state of single foot support for human walking is obtained by Lagrange method.Taking the crushing force of pedestrians as external disturbance and acting on the centroid position of human body,the dynamic stability assessment method of human body based on energy is adopted to obtain the crushing force threshold value of pedestrians moving at a certain speed when forward or backward instability occurs,which is used to evaluate the dynamic stability of pedestrians suffering from the maximum crushing resultant force in the crowd moving at an average speed.(5)The risk of stampede in two scenes in Xizhimen Station of Beijing Subway was evaluatedAccording to the EMFP risk assessment model,the risk scenarios of"platform-upper door" and "passageway-upper stairs" in Xizhimen station of Beijing subway are evaluated for crowded stampede risk.It is found that the pedestrian risk level at the upper door of line 4 is medium risk level(level 3)during the morning peak hours on weekdays,and the transfer channel on the west side of north hall of line 2 and the bottleneck of the stairs on line 13 are safety level(level 6).