Abstract: Based on the Jiaozhou Bay Second Subsea Tunnel project, an antidislocation structure of the tunnel crossing the Cangkou fault subject to a maximum dislocation of 0.49 m is designed. An optimal structure design is proposed considering the serious weakening of the waterproof performance induced by the failure of the tunnel lining. The characteristics of deformation and stresses of the secondary lining′s large crosssection scheme and the porous brittle buffer material scheme are compared using the finite element method. Furthermore, the excavation quantities and the construction difficulties are compared, and the optimal design scheme of an antidislocation structure with flexible joints and porous brittle material buffering is finally selected. In addition to reducing the amount of excavation work and eliminating construction difficulty, the optimal scheme addresses the issue of the secondary lining of the traditional expanded excavation method, which is prone to devastating damage under the action of fault dislocation. This ensures the normal functionality of the water stop structure, and improves the safety of the subsea tunnel under active fault dislocation.

Key words: subsea tunnel, active fault, antidislocation structure, flexible joints, porous brittle buffer materia