Safety Risk Evaluation And Application Of Ningbo Metro Quasi-rectangular Shield Construction

The development speed and construction scale of China's subway project have reached the international leading level.The construction of subway tunnels is mainly based on the shield method.However,due to the complex construction environment of underground engineering,safety accidents occur from time to time in the construction process.Therefore,strengthening the management of safety risks in subway construction has taken the top priority in the management of subway construction enterprises.In Ningbo subway project,it is the first time for the quasi-rectangular shield construction method to be applied in China.Due to its special cross-section design,it brings great risks to personnel management,machinery,construction techniques,materials and environment,which increases the difficulty of construction and risk control.Therefore,the research on risk management of Ningbo quasi-rectangular shield subway project has both theoretical and practical significance to a certain degree.Based on the relevant technology and risk management theory of subway shield construction,the main activities of subway shield construction are decomposed by WBS method,to form the work breakdown structure table of subway shield construction.The RBS method is used to analyze and study the five aspects of "Man","Machine","Material","Method" and "Environment" of 4M1 E management theory,to form a construction risk decomposition structure for subway shield construction.On this basis,taking the construction of the quasi-rectangular shield interval in Ningbo metro as an example,through the expert investigation,literature review,data collection,analysis and research,the risk identification matrix of four main construction activities including shield preparation,shield launching,shield tunneling and shield arrival is established,meanwhile,the main risk source and initial risk list of quasi-rectangular shield construction is identified,and a risk index system for the quasi-rectangular shield interval of Ningbo metro is established.The Analytic Hierarchy Process is applied to calculate the weight value of the risk evaluation index,the expert evaluation and scoring are used to fuzzy evaluate the risk factor occurrence probability and the loss caused,the fuzzy evaluation matrix and risk grade membership are constructed,the Fuzzy Comprehensive Evaluation method is used to obtain the fuzzy comprehensive evaluation values of all levels risk evaluation indexes of quasi-rectangular shield interval in Ningbo metro,according to the risk acceptance criterion,the risk level of each evaluation index is obtained,which makes the risk evaluation of the quasi-rectangular shield method subway construction project have the characteristics of qualitative and quantitative analysis.It guarantees the scientificalness and effectiveness of the construction risk assessment of the quasi-rectangular shield construction in the Ningbo metro project.According to the analysis and evaluation results of the construction safety risk of the Ningbo metro quasi-rectangular shield method,corresponding risk response measures and disposal lists have been formulated for major risk sources of level ? and above,to reduce the probability of all kinds of risk events and the loss caused by the incident,effectively avoid or control the risk of engineering construction,and achieve the project construction target.It also provides some reference for safety risk management of similar subway construction projects.