Abstract: The process of shield tunnel construction for metro is very complicated involving many potential risks. If not properly controlled, the construction will pose severe threats to public safety. In an attempt to effectively control the risks of shield tunnel construction, a risk assessment method based on trapezoidal fuzzy number and C-OWA operator is proposed. The evaluation information of experts is represented by trapezoidal fuzzy numbers, and the operational rule of fuzzy number is adopted to calculate the risk level of each potential risk factor. The risk level of evaluation indicators at all hierarchies, combined with the weight of each risk index calculated by C-OWA operator weighting method, is determined by calculating down-top of the evaluation system. The risk rating is obtained according to the risk matrix. The proposed method was applied to evaluate the construction risks of a shield tunnel construction of Shenzhen Metro Line 12, and the potential risk factors that require risk prevention measures in the project are obtained. The example shows that the proposed method is reasonable and reliable. Compared with traditional risk assessment methods, it has more advantages in dealing with complex problems involving fuzzy definition and subjectiveness.

Key words: metro shield construction, trapezoidal fuzzy number, C-OWA operator, risk assessment, Shenzhen