Study On Dynamic Evaluation Of Evacuation Capacity Of Urban Subway

In order to alleviate the increasing passenger flow pressure of urban transportation system,many cities put the work of opening and operating subway on the agenda of urban rail transit planning.Subway has become the preferred means of transportation for more and more travelers because of its large passenger capacity,comfortable and convenient,fast environmental protection and other characteristics.But at the same time,the rapid development of subway traffic also brings many safety problems to subway operation.The subway operation space has the characteristics of limited number of entrances and exits,narrow activity space and high density of personnel,which are not conducive to disaster prevention and evacuation.Once an accident occurs,large-scale crowds are prone to panic,impatience and other psychological factors that are not conducive to evacuation.In addition,the subway station evacuation design and evacuation guidance are unreasonable,It is very easy to cause more large-scale secondary accidents such as stampede,and then cause more serious casualties and property losses.In order to avoid the large passenger flow accident caused by the subway station’s failure to deal with emergencies,it is necessary to build a scientific risk assessment model,reasonably evaluate the level of emergency evacuation capacity of subway station,and formulate reliable and complete emergency prevention measures and response measures of subway station according to the assessment results.Based on the theory of system safety analysis and safety evaluation,this paper studied and evaluated the emergency evacuation ability of subway station.By using the fault tree analysis method in system safety analysis,taking the large-scale stampede event after the subway station emergency as the top event of the fault tree,the fault tree of the subway station stampede accident was established,and the key factors such as the minimum path set and the structural importance order of the fault tree were determined.According to the requirements of relevant laws and regulations and expert experience,combined with the results of fault tree analysis,through secondary screening,the evaluation index system of subway station emergency evacuation ability was finally determined,which takes the station staff factor,evacuation passenger flow factor,disaster prevention equipment factor,environmental layout factor and emergency management factor as the first level index,and 30 secondary factors as the second level index.In order to make up for the one sidedness of index weight caused by single weighting method,AHP method and entropy weight method were respectively used to determine the weight value of each index from different subjective and objective angles,and multiplication synthesis normalization was used to fuse the subjective and objective weights,and then the combined static weight of each index was determined.The traditional static index weight is difficult to meet the dynamic change problem caused by the change of the measured value in the actual safety evaluation work.Therefore,this paper introduced the variable weight synthesis method to determine the reward and punishment interval of each index value in the actual situation,dynamically modified the static weight,and obtained the dynamic variable weight value,so as to meet the dynamic change of the index in the actual evaluation.Considering the problem of the ambiguity of the boundary of the index and the incompatibility between the index itself and the fuzzy index in the evaluation of the emergency evacuation capacity of the subway station,combined with the cloud model theory and matter element extension theory,the variable weight extension evaluation model of the evacuation capacity of the metro station was established,which included four quantitative levels of ideal,better,general and worse evacuation capacity.The evaluation model can effectively solve the problems of randomness and fuzziness of the indexes and the dynamic changes of the indexes in the evaluation of emergency evacuation capacity of metro stations,and evaluate the emergency evacuation capacity of metro stations more accurately and scientifically.Taking pangjiangjie station of Shenyang Metro Line 10 as an example,the evaluation model based on variable weight extension cloud theory was used to calculate the emergency evacuation capacity level of the station.The evaluation results showed that:the emergency evacuation capacity of Pangjiang Street station was "ideal",and according to the evaluation results,it provided guiding suggestions and measures for emergency evacuation work of Pangjiang Street station from four aspects:improving the quality of staff,early warning and control of large passenger flow,overhaul and maintenance of equipment and facilities,and publicity of safety evacuation knowledge,It provided theoretical support for the emergency prevention and emergency disposal of subway station.