Grain size effect on the anisotropic shear behavior of sand–textured geomembrane interface

Abstract

A set of direct shear tests conducted to investigate the effects of sand mean grain size and geomembrane surface roughness on the shear behavior of the sand-geomembrane interface. Four types of sands with different mean grain sizes were used and the interfaces included a smooth geomembrane and four textured ones with different asperity characteristics. The samples were prepared in a direct shear box at five sedimentation angles. The experimental results showed that the peak friction angle of the soil-textured geomembrane interface was dependent on the mean grain size, inherent anisotropy, and surface roughness of the geomembrane. The shear strength of sand-textured geomembranes was two to three times larger than that of the sand-smooth geomembrane interface. The peak and residual friction angles of the sand-smooth geomembrane interface occurred at an orthogonal angle of sedimentation while it happened at higher angles for the sand-textured geomembrane interface. An increase in mean grain size increased the shear strength of the sand-textured geomembrane interface; while a reverse condition occurred for the sand-smooth geomembrane interface. The shear strength occurred at larger horizontal displacement as mean particle size increased and the effect of relative roughness on peak friction angle increased with increase in mean grain size.