Abstract: To investigate the impact of the over-consolidation ratio of clay on the mechanical properties of clay-concrete interface, direct shear tests were conducted on different interfaces between weakly over-consolidated clay and concrete. Test results revealed that an increase in the over-consolidation ratio of the clay from 1 to 2 led to a 40% increase in the cohesion of the interface and a 38% increase in the internal friction angle. The shear stress-shear displacement relationship followed a hyperbolic model before the interface reached shear failure. Once the shear stress reached shear failure, the interface fractured, entering a divergent state characterized by sliding. With a higher over-consolidation ratio, the shear strength, initial tangential stiffness coefficient, and failure ratio of the interface gradually increased. The shear strength of the interface conformed to the Mohr-Coulomb failure criterion. Empirical formulas were developed to describe the relationship between the over-consolidation ratio and the cohesion, internal friction angle, and slope and intercept within the coordinate system of ΔL/τ-ΔL. These formulas were combined with the Mohr-Coulomb failure criterion to establish a simple constitutive model for the interface. The rationality of this model was verified using the test data, making it applicable as a reference for other related engineering projects.

Key words: weakly over-consolidated clay, direct shear test, contact surface, over-consolidation ratio, shear strength, hyperbolic model