Vahid Jamali - Ph.D. Student, Faculty of Civil and Environmental Engineering, Shiraz University of Technology, Iran,
Ali Lashkari - Associate Professor, Faculty of Civil and Environmental Engineering, Shiraz University of Technology, Iran

Behavior of interfaces forming between granular soils and structural materials is an influential factor in design and performance of offshore and onshore engineering structures such as sub-sea pipelines, piles, foundations and steel sheet piles. Shear strength and volume change response of soil-structure interfaces are not only limited to the soil intrinsic characteristics, but also depend on the magnitude of normal effective stress, surface roughness of structure, and normal stiffness [1-2].In this paper, the mechanical behaviors of interfaces between two angular sands and rough steel were studied using modified direct shear apparatus. It is shown that the peak and residual shear strengths as well as the maximum dilation of sand-steel interfaces depend on sand mean particle size.