Fuzzy comprehensive risk evaluation of damiao tunnel

A fuzzy comprehensive evaluation model is established to evaluate the holistic risk level of an extra-long tunnel in north China. In the risk evaluation process of the highway tunnel, the recognized risk factors are categorized into two hierarchies, the first hierarchy comprises seven main factors, while each main factor can be further decomposed into one to six sub-factors (second-hierarchy factors). The weight of the first-hierarchy factors and sub-factors of more than three in numbers are determined with AHP method executed in an expert group, while weights for sub-factors of three or less in numbers are decided by the mean value of the expert judgments. Then the judgment matrices for the first-hierarchy factors are established by expert judgment from experience and factual engineering condition. A matrix synthesis process is then adopted to work out the evaluation matrices, which are further normalized to indicate the membership grade of the tunnel's holistic constructional risk level to the preset five risk levels. The analytical result of the fuzzy comprehensive evaluation indicates that the holistic risk of the tunnel is ‘unwanted’.