Lining cracking mechanism of old highway tunnels caused by drainage system deterioration: A case study of Liwaiao Tunnel, Ningbo, China

The drainage system deterioration is one of the important factors leading to cracking of lining structure. This paper first investigates crack patterns and water leakage through field investigations, and then reproduces the drainage system deterioration process of the tunnels and analyzes the failure mechanism of the linings by utilizing a series of fracture-based numerical models. Results reveal that the longitudinal cracks are the main cracking patterns, followed by circumferential cracks. Furthermore, lining cracks are the weak points of the lining structure and are closely related to water leakage. The deterioration of the drainage system leads to an increase in water pressure acting on the secondary lining, which leads to severe stress concentrations and cracking in the lining structure, respectively at the arch shoulder, the middle of the sidewall, and the arch foot. Finally, the paper explores the applicability of siphon drainage pipes to the treatment of water leakage. Some suggestions are also made for the prevention of water leakage in tunnel linings.