Risks analysis of large diameter slurry shield tunneling in urban area

The construction of super-large tunnels generates various safety risks that can hamper the tunneling process and cause severe damages if not properly identified. This paper presents a case study on the identification and management of geological and environmental risks during the construction of the largest (a diameter of 15.8 m) slurry shield tunnel in China. Its ground conditions and settlement control were identified among the most challenging owing to a large area of mixed ground conditions, 11 fault zones and tunneling under residential areas and the city’s Metro Lines 1 and 9. In response to the severity of these risks and challenges, novel monitoring systems, ground treatment, and safety management technologies were successfully implemented throughout the tunneling process. Further, a technical framework was proposed in this study to serve as a risk management guidance for analogous tunneling operations.