Abstract: In order to investigate the deformation characteristics of the clay-concrete interface under pre-peak tangential cyclic shear stress conditions, a specially developed soil-structure interface cyclic shear apparatus was utilized. Initially, direct shear tests were conducted on the clay-concrete interface under four normal pressures: 50, 100, 150 kPa, and 200 kPa. These tests determined the peak shear stress of the interface under each normal pressure. Subsequently, two shear stress amplitudes below and three shear stress amplitudes above the peak shear stress were set under each normal pressure, and cyclic shear tests of the clay-concrete interface were performed. Based on the experimental outcomes, three key indicators were established: cumulative displacement, secant stiffness and tangential plastic work. The evolution of these indicators with increasing cycles was analyzed, and a comparison was made to assess the impact of normal pressure on the cyclic shear curve at a constant shear stress amplitude. The experimental findings reveal that under low shear stress amplitudes, the shear displacement-shear stress curve of the clay-concrete interface demonstrates elastic behavior. Conversely, under high shear stress amplitudes, the curve exhibits elastoplastic characteristics. Specifically, there exists a limit value for the cumulative displacement of the interface. Additionally, the secant stiffnesses during loading and unloading gradually increase and converge, while the tangential plastic work progressively diminishes and approaches zero. The influence of normal pressure on the cyclic shear behavior of the interface is predominantly observed during the first cycle. These research findings can contribute to the deformation analysis of cyclic shear at the pre-peak stage of the soil-sensitive structure interface. Furthermore, they provide an experimental foundation for establishing the cyclic shear constitutive model of the soil-structure interface under low shear stress conditions.

Key words: clay-concrete interface, small deformation, cyclic shear, sensitive structures