The Influence of Asperities and Surface Roughness on Geomembrane/Geotextile Interface Friction Angle

This paper presents the results of a comprehensive study that investigated the influence of asperities and roughness on the shear responses of geomembrane/geotextile interfaces. This study was aimed at providing a scientific explanation of the effect of surface texturing on geomembrane/geotextile interfaces shear behaviour as well as to recommend the quantification of asperity and roughness characteristics which mobilises optimised shear strength for the considered interface. The GMB/GTX interface shear tests were conducted according to ASTM D5321, under saturated conditions with the "305 mm by 305 mm" direct shear box at applied normal stresses of 25-400 kPa. The experimental outcome showed that the variation in geomembrane asperity height and surface roughness (from slightly textured to highly textured geomembranes) eventually mobilised an increase of 20 degrees in the peak interface friction angle values. It was, however, observed that as the surface texturing was increased, more pronounced wear occurred which resulted in a relatively minimal increase of 6 degrees in the large displacement friction angle. In addition, the geomembrane surface with asperity height of 1.2 mm and average surface areal roughness of 75 mu m was observed to develop optimal peak friction angle for the considered geomembrane/geotextile interface. These observations were validated by means of post-shear deformation evaluation and it is anticipated that the findings presented herein would be useful in the design of geotechnical systems comprising of geomembrane/geotextile interface with enhanced stability and durability