Interfacial bond performance of UHPC ‐strengthened concrete interfaces in shield tunnel linings: Experimental and numerical investigation

Abstract

Given the structural deterioration of in‐service shield tunnels, this paper investigates the mechanical properties of the interface between UHPC and segment concrete for UHPC‐based reinforcement. First, through laboratory direct shear and splitting tensile tests, the effects of interface preparation, bonding technique, normal pressure and groove geometry on the mechanical properties of the UHPC‐segment concrete interface are systematically investigated. Subsequently, a refined numerical model is constructed in ABAQUS, and the cohesive interface parameters are calibrated using a two‐step parameter calibration method. The influence of key parameters such as anchor bar size, groove size and groove wall inclination is analyzed. The results show that the interface treatment method can significantly affect the shear capacity of the UHPC‐segment concrete interface, and that the interface groove can effectively improve interfacial bearing capacity and increase failure ductility. Overall, the mechanical performance of precast UHPC bonding interfaces is generally inferior to that of cast‐in‐place UHPC interfaces, and the epoxy mortar bonding system shows the best overall performance. The proposed high‐fidelity numerical model shows good agreement with the experimental results. Further parametric analyses reveal the variation patterns of interfacial mechanical properties with anchor bar specifications, groove geometric parameters and groove wall inclination. The findings of this study can provide a theoretical basis for the optimal interfacial design of UHPC‐reinforced shield tunnels.