Research On Construction Risk Assessment Based On Fuzzy Fault Tree Of Deep Foundation Pit Of Subway Station

With the increasing acceleration of urbanization in China,there is an increasing phenomenon of urban traffic jams,the subway has advantages of large capacity,safety and efficiency,environmental protection and comfort,so its construction projects number increase gradually.However,the subway project has long construction cycle and complex environment,the accident controllability is poor,and the loss is huge,there are high security risks in the process of subway construction.As the most important part of subway construction,there are some serious safety hazards in deep foundation pit construction.Accidents occurred frequently,which made huge losses to the state and society,therefore,it is necessary to make the safety risk assessment for subway station deep foundation pit construction safety.Based on field survey,data collection,theory analysis,combined with accident-causing theory,deep foundation pit construction in metro station risk mechanism is firstly analyzed in this paper.Combined with literature review,deep excavation construction risk is identified,and the main risk factors are summarized and classified,"person-object-technology-environment" four kinds of primary risk factors are getted,and 54 main risk factors are futher getted.In consideration of the high complexity and characteristics of fuzziness and randomness of safety risk factors of deep foundation pit construction in subway station,the deep excavation construction risk assessment model of metro station based on fuzzy fault tree is established in this paper,experts consistency aggregation analysis is used to eliminate the fuzziness of expert opinion and judge the fuzzy events by the experts of the heterogeneous group,the failure probability of top event is obtained in the fuzzification and defuzzification process,sensitivity analysis and sorting of minimum cut sets are carried out.Then the evaluation model is applied to a construction project of metro,the analysis result shows that the "substandard chemical composition of materials" is the most important risk factor.After the model is applied,the results are compared with the LEC method which is applied to a metro project,it is verified that the evaluation model is reasonable.According to the results of the risk assessment system and the construction characteristics of deep foundation pit of the subway station,the paper puts forward the main risk countermeasures for the construction of the station from the perspective of "person-object-technology-environment".