Impact of displacement amplitude and frequency on the cyclic shear characteristics of residual soil-concrete interfaces

The mechanical behavior of the granite residual soil-concrete interface is critical to the overall stability and safety of geotechnical structures. To investigate the effects of shear amplitude and shear frequency on the cyclic shear characteristics of granite residual soil-concrete interfaces, a series of large-scale horizontal cyclic direct shear tests were conducted, varying shear amplitudes (1, 3, 6 and 9 mm) and shear frequencies (0.1, 0.5, 1 and 2 Hz). Key parameters, including shear stress-displacement response, maximum shear stress, and vertical displacement, were analyzed. The results indicate that maximum shear stress increases with shear amplitude, although the growth rate gradually decreases. Significant changes in vertical displacement primarily occur within the first 20 cycles, after which it stabilizes, reflecting the particle rearrangement effects during the initial cycles. Shear stiffness decreases at higher shear amplitudes, while the damping ratio exhibits a fluctuating trend, suggesting that the energy dissipation mechanism of the soil is influenced by shear amplitude. Numerical simulations further reveal that, as the number of cycles increases, the number of force chains within the soil also rises, with most force chains consisting of three particles. The principal directions of normal and tangential contact forces are closely related to the shear direction, with the principal direction deflecting approximately 35° in response to changes in shear direction.