Damage evolution and toughening mechanism of shield tunnel segments strengthened by epoxy-bonded thin plates considering interface effects

Abstract

Bonding steel plates is widely used for repairing damaged segment linings in the operation and maintenance of subway tunnels. The effectiveness of this method primarily relies on the bonding performance at the interface between the strengthening plate and the segment linings. A refined numerical model incorporating interface effects was developed in this study. To accurately simulate the adhesive interface, the cohesive zone model (CZM) was introduced, and a mixed-mode cohesive law was employed to characterize the interface stress in three directions. Full-scale experiments validated the proposed model. Then, the deformation response and toughening mechanism of steel plate-strengthened segment linings were analyzed. The failure evolution and debonding mechanism of the adhesive interface were examined. Finally, a series of simulation experiments were conducted to evaluate the effect of steel plate thickness and strengthening timing on structural toughness. The results indicate that bonding steel plates to the lining ring partially restores structural toughness. Interfacial debonding failure initiates at the 8° and 352° joints, propagates to the 73° and 287° joints, and ultimately manifests at the interface ends. Significant stress concentration is observed at the interface near the joints, which is the primary cause of interface debonding failure.