Research On Safety Risk Assessment Of Subway Shield Construction Based On Dynamic Bayesian Network

As a mode of transportation,the subway has developed rapidly because of its advantages of high speed,low pollution and high traffic volume,injecting new vitality into urban public transportation.The shield construction project has the advantages of small impact on the surrounding environment,high degree of mechanization,and high geological adaptability.It is widely used in the construction of subway tunnels.Subway construction is a dynamic process,which will be affected by different factors at different stages,and these complex factors will change with the change of construction environment and risk transmission,that is,a risk may be transmitted to the next construction process under the action of some factors,or cause other risks.Therefore,for the subway tunnel project,it is necessary to consider the dynamics of safety risk factors and adopt a more scientific and reasonable method for risk assessment.Firstly,the research background,purpose and significance of shield construction safety risk are expounded.Combined with citespace software,the research status at home and abroad is analyzed and analyzed,and the research content and technical route of this paper are introduced.This paper expounds the relevant theories of shield construction,introduces the main construction characteristics,construction process flow,risk transfer theory and safety risk occurrence mechanism of shield method,and introduces the risk identification method and risk evaluation method of shield method.Secondly,based on the WBS-RBS method,the safety risk of shield construction is identified,and then the dynamic Bayesian network is used to evaluate the construction safety risk based on the list of identified risk factors.Combined with subway accidents and subway construction literature,the shield construction is identified.The risk factors are identified from two aspects : risk structure decomposition and construction process decomposition.The list of risk factors is established from the aspects of personnel operation,construction machinery,management and environment.The reliability and validity of the identified list of risk factors are tested to establish a scientific list of risk factors.Considering the dynamic nature of shield construction and the correlation between risk factors,this paper uses the interpretative structural model to determine the risk hierarchy as the initial static Bayesian network,and then uses the triangular fuzzy number to determine the prior probability value.The dynamic Bayesian network model of the three stages of shield launching,tunneling and arrival is established.The process of establishing the dynamic Bayesian network model is discussed in detail.The dynamic characteristics of the time segment of DBN are used to obtain the transmission path of construction safety risk,and the sensitivity analysis is used to find out the key factors.Finally,the Huang-Huai section of Qingdao Metro Line 6 is selected to verify the validity of the model.According to the actual situation of the project,the list of risk factors established above is adjusted,the dynamic Bayesian network model is constructed,and the forward and reverse reasoning and sensitivity analysis are carried out.The corresponding control measures are put forward for the key factors affecting the safety risk,which enriches the risk assessment method of subway shield construction and provides a certain reference basis for the dynamic risk assessment of shield construction.