Construction Risk Assessment of Super-largediameter Shield Tunnel in Karst Area Based on FAHP-TOPSIS Method

Background: In recent years, construction accidents happen frequently in shield tunnel crossing karst caves due to the complex karst geological structure. These are more obvious in super-large-diameter shield tunnel during construction. In the past, the studies and patents of risk assessment tended to be subjective since these reviews were mainly based on experience. Methods: A super-largediameter tunnel model is constructed by using calculation principle of FAHP-- TOPSIS method based on quantitative analysis and objective weighting method to conduct risk assessment in karst area based on risks evaluated in a shield tunnel project under construction in a city. The risk classification is formulated, and the risk assessment system for a super-large-diameter shield tunnel under construction in karst area is developed to perform computation for assessment. Results: The results show that the closeness of the construction risk for a shield tunnel with super- large-diameter crossing the karst area is 0.034, and the risk level is V, that is, high risk, which brings great potential safety hazard to tunnel construction. The computation results are consistent with those of site conditions to verify the feasibility and effectiveness of the method. Conclusion: The results have provided a reference for the risk assessment of similar engineering practice under construction. Article Highlights: ● At present, many researchers focus on risk assessment management of shield method, but there is a lack of research on risk assessment of shield construction in the context of cavern development, in contrast, this study carries out risk assessment of karst super-large-diameter shield construction, which is a high research innovation. ● With the help of reliable and novel research tools, this study constructs a risk assessment model based on the calculation principle of FAHP-TOPSIS method with quantitative and objective empowerment for the construction of oversized diameter shield tunnels in karst areas, which is able to calculate the risk level more accurately. ● The system constructed in this study can be applied to the field construction. The calculation results of the construction risk assessment system of super-large-diameter shield tunnel in karst area constructed in this paper were compared with the field situation, and the match was good, which can provide a reference for other similar projects and guarantee the safety of field construction, so it has a good promotion.