Scale and surface morphology effects on the micromechanical contact behavior of granular materials

Scale effects and the influence of surface roughness were investigated on the contact behavior of glass specimens of the grain-grain, grain-block and block-block configurations, where the block corresponds to the limiting case of infinite contact radius. The tests were carried out using in-house micromechanical apparatuses and the results showed that both the normal and tangential stiffness increased with increasing grain diameter but also decreased with increasing equivalent surface (RMS) roughness. The interface friction increased with increasing equivalent surface roughness but did not depend heavily on grain size. Rough interfaces had extended slip displacements, thus slower degradation of stiffness.