Multi-scale behaviour of sand-geosynthetic interactions considering particle size effects

The continuous evolution of digital imaging and sensing technologies helps in understanding the multi-scale interactions between soils and geosynthetic inclusions in a progressively better way. In this study, advanced techniques like X-ray micro-computed tomography (mu CT) and profilometry are used to provide better understanding of the multi-scale interactions between sand and geosynthetic materials in direct shear interface tests. To cover the dilative and non-dilative interfaces and sands of different particle sizes, shear tests were carried out with a woven geotextile and a smooth geomembrane interfacing with three graded sands at different normal stresses. The shear response of different interfaces is analyzed in the light of 3D multi-scale morphology of particles and the roughness of tested geosynthetic surfaces to compare the peak and residual friction angles and shear zone thickness determined using Digital Image Correlation (DIC) technique. The average peak frictional efficiencies for sand-geotextile and sand-geomembrane interfaces are 0.84 and 0.52, respectively. The extent of the shear zone increased with the increase in particle size, with its average thickness ranging from 2.22 to 11.41 times the mean particle size. On a microscopic level, fine sands cause increased shear-induced changes on geomembrane surfaces because of their greater effective contact per unit area.