Peak Friction Behavior of Smooth Geomembrane-Particle Interfaces

An investigation of shear mechanisms at interfaces between particles and relatively smooth materials using contact mechanics and basic friction theory reveals that a combination of sliding and plowing governs dense Ottawa 20∕30 sand∕smooth high density polyethylene geomembrane peak interface shear behavior. Contact area and the corresponding shear resistance during sliding increase at a slower rate than the applied normal stress, resulting in a decreasing friction coefficient and flattening of the peak strength envelope. Plowing of soil grains results in an increasing peak friction coefficient with increasing normal stress and can produce an upward curvature of the strength envelope above a critical stress level. Plowing is primarily controlled by the relative hardness of the interface materials and by grain shape with angular particles exhibiting plowing in all normal stress ranges, whereas nearly perfect spheres exhibit only sliding. High surface hardness is shown to constrain shear behavior to a sliding mode with little contribution from plowing. These findings are consistent with results reported in the tribology literature.