Numerical simulation and experimental analysis of granite residual soil-concrete interface under cyclic shear

Pile foundations are frequently subjected to dynamic loads, necessitating a thorough investigation of cyclic shear characteristics at pile-soil interfaces. To investigate the influence of soil moisture content and concrete surface roughness on the cyclic shear characteristics of interfaces, a series of cyclic shear tests were conducted using a large-scale indoor direct shear apparatus. The effects of three normal stresses (100, 200, and 300 kPa), four moisture content levels (14%, 19%, 24%, and 29%), and five concrete surface joint roughness coefficients (0.4, 5.8, 9.5, 12.8, and 16.7) on interface shear stress and volumetric strain behavior of residual soil were analyzed. Numerical simulations were employed to analyze the microstructural changes in particles. The results show that the water content has a significant effect on the interface stress-displacement curve. It shows a cyclic hardening type at low water content and a cyclic softening type at high water content. There is a critical roughness on the concrete surface. After exceeding this value, the shear strength of the interface is no longer improved. The number of force chains in the soil increases with the increase of the number of cycles and roughness. The increase of the number of particles in the force chain leads to the increase of the instability of the force chain structure. Therefore, most of the force chains are composed of three particles. The main direction of the normal and tangential contact force anisotropy is closely related to the shear direction. The main direction will deflect with the shear direction, and the deflection angle is about 35 degrees.