Mechanical behavior and constitutive relationship of bond interface in steel plate-reinforced shield tunnels

In order to explore the mechanical properties and failure mechanism of the bond interface of steel plate rein-forced shield tunnels, a series of uniaxial tensile and uniaxial shear experiments were conducted in this study. The impact of bond interface parameters on the mechanical properties of the reinforced interface was mainly analyzed, including the failure mode, ultimate bearing capacity, average bond strength, and stress-strain relationship of the bond interface. To enable numerical simulation of the mechanical behavior at the bond interface, a stressstrain constitutive relationship equation for the bond interface is established using the least squares method. The main conclusions are as follows: For steel plate-concrete interface bonded with epoxy resin, the shear resistance of the bond interface generally surpasses the tensile resistance under the same interface pa-rameters. Tensile load predominate leads to the cohesive failure of the concrete while the interface layer remains undamaged. In contrast, shear load mainly results in the detachment between the steel plate and the interface layer. The ultimate bearing capacity and bond strength of the interface can be enhanced by decreasing the interface thickness or increasing the interface roughness. Moreover, an expansion bolt can further increase the mechanical property of the bond interface, and the improvement effect intensifies with higher expansion bolt grades. The stress-strain curve of the bond interface can be divided into three stages with elastic stage, softening stage and debond stage. The main difference of stress-strain curve under different bond interface parameters lies in the stage before the softening of the bond interface. The interface stress-strain curve is primarily influenced by the thickness of the bond interface and the grade of expansion bolts, whereas the roughness of the concrete surface has minimal effect.