Effects of roughness on the shear zone of clay–concrete interface

• The failure mechanism of interface was revealed from the mesoscale and microscale . • The thickness of the shear zone at interface under roughness was determined. • The larger area of shear deformation at the contact surface is affected by roughness. • The surface characteristics (groove spacing and depth) of concrete was considered. • The surface roughness of concrete was achieved through 3D printing technology . An essential precondition for the stability of engineering structures is the characterization of the shear zone at the soil–concrete interface. Roughness is an inherent characteristic of concrete surface and a critical factor affecting the mechanical characteristics of interface. This study took into account the impact of the depth and spacing of grooves of the concrete surface on the shear zone of the clay–concrete interface. Direct shear testing of the interface under various roughness levels was conducted using PIV technology. The thickness of the shear zone under varying roughness is calculated based on the displacement of soil samples. The failure mechanism of interface was revealed from the mesoscale and microscale by digital microscope and SEM. The findings demonstrated a favorable correlation between roughness and the shear strength and thickness value of the shear zone. Roughness had an impact on cohesion; however, the internal friction angle was not significantly impacted by increasing groove depth. The soil sample at the contact surface had a large shear deformation area after failure. This area was related to the surface morphology characteristics of the concrete, and the contact surface with high roughness had a larger shear deformation area. The particles movement in the shear zone was more apparent than outside the shear zone. The generation of shear zone is the result of the soil particles resisting interface failure.