Abstract
The interface friction angle is an important design parameter in geotechnical engineering applications, such as onshore and offshore foundations, retaining walls, and landfills, necessitating its accurate estimation. The influence of the surface roughness, particle shape and size, mineralogy, gradation, and breakage on the interface friction angle has been widely reported, mostly in isolation from each other. This study investigated the combined effects of surface roughness, gradation, mineralogy, and effective stress on the mobilized interface friction angle and particle breakage through large-displacement ring shear tests. Seven different sand types were sheared against two kinds of interfaces with different surface roughnesses and at varying effective stress levels. The critical state interface friction angle increased in conditions that produced greater particle breakage, including larger effective stress, surface roughness, and shear displacement. This effect was more apparent in the poorly graded sands than in the well-graded sands. With the increase in effective stress, the dependency of critical state interface friction angle on initial mean particle size decreased. The critical state interface friction angle ratio decreased with particle size, increased with angularity, and had mixed behavior with effective stress, gradation, and surface roughness, depending on the other parameters. The data presented in this paper provide insight into the coupled effects of particle size, surface roughness, and effective stress on the breakage of particles and how this influences the mobilization of strength.