Identification And Evaluation Of Safety Risk In Construction Process Of Metro Shield Tunnel

In recent years,with the rapid development of China's subway construction,subway construction process of the existence of security risk management is not in place the problem gradually emerged.Safety as the main line of subway construction project,which runs through the whole process of subway construction,is the lifeline of construction projects.Shield method is a common method of subway construction.As the construction of subway shield tunneling has the characteristics of more professional,wide sector,long construction period and environmental impact,there are more risks in shield machinery and equipment,materials management,construction management,environment and personnel.In order to deal with the possible accidents in the construction process of subway shield tunnel,this paper identifies and evaluates the safety risk of subway shield tunnel construction process,and uses the method of risk and operability to systematically identify the risk factors,and analyzes the relationship between risk factors,and establishes the safety risk evaluation index system of subway shield tunnel construction process.Based on the established evaluation index system,the rough set is used to reduce the attribute index,the core evaluation index system is established,at the same time,BP neural network model is constructed to evaluate the safety risk of subway shield tunnel construction process,and to provide theoretical reference for further ensuring the safety of subway tunnel construction.Research work of this paper includes the following aspects:(1)Based on the background,the purpose and significance of the research,this paper discusses the research status of safety identification and evaluation of subway tunnel construction at home and abroad,and analyzes the current situation of the research,puts forward the research contents and research methods of the paper,and gives the technical roadmap of the paper.(2)Combined with the construction process of shield tunnel,analyzes the advantages and disadvantages of subway shield construction,and according to the characteristics of shield tunnel construction,the hazard and operability(HAZOP)analysis method is used to comprehensively identify the risk of shield construction at different stages from shield equipment related machinery and equipment,construction management and environment,also the safety risk evaluation index system of the construction process of the subway shield tunnel with 50 second indexes is initially established.Based on this,established the interpretative structural modeling(ISM)of shield construction early preparation stage,shield initiation and test excavation stage,shield normal stage and shield entry and exit stage,and analyzed the relationship between the indicators of each stage(3)Based on the non-linear and non-periodic characteristics of the construction data of the shield tunnel,the idea of risk evaluation model based on RS-BP neural network is proposed,and the feasibility and applicability of the model are explained from two aspects.According to the safety risk evaluation index system,using the rough set theory to reduce the index,and established the core index system with 24 risk indexes.And the index system is used as the pre-system of BP neural network to establish BP neural network evaluation model to evaluate the subway shield tunnel construction process risks.Through the training and testing of the sample,the error of the model reaches a predetermined range.Finally,the validity and maneuverability of this model are verified by taking Dalian Metro Line 4 as an example,and the countermeasures are put forward for the risk of each stage of shield tunnel construction.