Interfacial Behaviour of Shield Tunnel Segment Strengthened by Thin Plate at Inner Surface

Abstract

The strength and stiffness of a shield tunnel segment can be improved significantly by bonding a steel plate at its inner surface. In this kind of strengthened segment, interface debonding is usually the controlling failure mode, and it strongly depends on the interfacial stresses of the adhesive layer between the segment and the steel plate. To deepen the understanding of the interfacial behaviour, this study proposes a three-dimensional fine finite element (FE) model regarding the interfacial stresses. An existing full-scale experimental result is then employed to confirm the feasibility and accuracy of the proposed model. Further, the fine finite element model is used to calculate the interfacial stress distributions and to evaluate the structural parameters on the interfacial behaviour of the strengthened segment. A high concentration of interfacial stresses exists at the vicinity of the steel plate ends and the joints, which might result in premature failure at these locations. Both the normal and shear stresses at the interface are significantly influenced by the structural parameters. The findings in this study can provide guidance for the optimal design of strengthened shield segment that can prevent premature interfacial debonding.