Study On Safety Risk Assessment Of Shield Construction Of The Undersea Tunnel

Characterized by large amount of investment,long construction period,high degree of project complexity and high difficulty of construction technology,the undersea tunnel project is of high uncertainty and risk,and once the risk accident occurs,it will cause serious consequences.The shield construction has been widely used in building undersea tunnel owing to its characteristics such as fast tunneling speed,high degree of automation and small disturbance to the ground in the process of long-distance tunnel construction.For the sake of effectively reducing the safety risk of shield construction of undersea tunnel,this paper conducts an in-depth study on the safety risk assessment of it.The main research methods and conclusions are as follows:Through analyzing the characteristics of shield construction of the undersea tunnel,four typical working conditions were sorted out.Risk factors were identified by the comprehensive application of trace intersecting theory,fish-bone chart method and literature study method.In the meantime,questionnaireswere designed to collect the survey data to be analyzed.After the reliability and validity test,five first-level indicators including environmental factor,physical factor,construction technology,safety management factor and human factor were finally identified,and the root cause of risk was dug out layer by layer,finding out 39 second-level indicators.A safety risk assessment system highlighting the characteristics of shield construction of undersea tunnel is established.In view of the existing evaluation system,a suitable evaluation model was constructed by Bayesian network theory,fuzzy comprehensive evaluation method and the improved ALARP risk matrix method.Firstly,it adopts the Bayesian network theory to determine the risk possibility evaluation results,and then figures out the risk loss evaluation results through the fuzzy comprehensive evaluation method.Finally,the quantized value and grade of the total risk evaluation are obtained through the improved ALARP risk matrix,so as to optimize the existing safety risk assessment process of shield construction of undersea tunnel.Based on the empirical analysis of the “Suai Channel” project,it can be found that the probability of safety risk occurrence P is 55.1%,and the grade B(possible occurrence)while risk loss value C is 53.72,and grade 3(serious);Therefore,the total evaluation result R is 29.6and the grade Ⅲ(at the lower limit of the risk matrix),which lies in the acceptable range.