Abstract: Risk assessment of tunnel boring machine (TBM) construction is affected by many uncertain factors. The traditional fuzzy analytic hierarchy process (FAHP) tends to weaken the influence of some prominent risk factors due to the use of linear operators for calculating risk levels, reducing the accuracy of the final assessment results. This paper introduced a nonlinear operator into the comprehensive calculation of traditional FAHP, and established a new risk assessment model for TBM construction based on the nonlinear FAHP. Based on the work breakdown structure method (WBS) and the risk breakdown structure method (RBS), a risk assessment index system for TBM construction was also established. To calculate the weight of risk factors in the risk assessment index system and to construct the fuzzy relation matrix, analytic hierarchy process (AHP) and the membership vector obtained from the expert evaluation method were adopted. Through introducing the nonlinear operator, the weight of risk factors and fuzzy relation matrix were analyzed, and on this basis the final risk level for TBM construction was obtained based on the principle of the maximum membership degree. The proposed model was successfully applied to the risk assessment of a TBM crossing the F2-2 secondary fault in Yangtaishan Tunnel of Shenzhen metro and the risk level of TBM construction crossing the fault section was determined to be level 4, which was a high risk. Finally, to further verify the reliability of the proposed model, the difference between the new risk assessment model and the traditional FAHP evaluation method was discussed based on the Yangtaishan Tunnel project.

Key words: tunnel engineering, TBM construction, risk assessment, nonlinear, fuzzy analytic hierarchy process