impact of inherent anisotropy on the shear behavior of sand–textured geomembrane interface

In this paper, a comprehensive laboratory study was done on the shear behavior of the interface between geomembrane and an adjacent sandy layer using a modified direct shear test apparatus. the key parameters for this investigation included roughness of geomembrane surface, sedimentation angles of a specifically selected sand, and applied normal stress, for which a total of 162 tests were conducted, excluding reliability tests. as an indicator of all the mentioned samples, a formulation was obtained using response surface methodology (rsm) model. the results of the study were in line with previously published findings in this subject matter. the test results indicated that friction angle is highly influenced by the sand anisotropy where the maximum frictional resistance occurred at an orthogonal angle and decreased with the increase in the degree of induced anisotropy. the variations were more noticeable for the sand than sand–geomembrane interface with a minimum for the roughest interface that confirmed the reduction in anisotropy effects on shear strength with the increase in surface roughness.