Interface failure of segmental tunnel lining strengthened with steel plates based on fracture mechanics

Segmental tunnel lining strengthened with steel plates is widely used worldwide to provide a permanent strengthening method. Most existing studies assume an ideal steel-concrete interface, ignoring discontinuous deformation characteristics, making it difficult to accurately analyze the strengthened structure’s failure mechanism. In this study, interfacial fracture mechanics of composite material was applied to the segmental tunnel lining strengthened with steel plates, and a numerical three-dimensional solid nonlinear model of the lining structure was established, combining the extended finite element method with a cohesive-zone model to account for the discontinuous deformation characteristics of the interface. The results accurately describe the crack propagation process, and are verified by full-scale testing. Next, dynamic simulations based on the calibrated model were conducted to analyze the sliding failure and cracking of the steel-concrete interface. Lastly, detailed location of the interface bonding failure are further verified by model test. The results show that, the cracking failure and bond failure of the interface are the decisive factors determining the instability and failure of the strengthened structure. The proposed numerical analysis is a major step forward in revealing the interface failure mechanism of strengthened composite material structures.