2D Surface Topography Alterations of Different Geomembrane Liners: Grain Shape, Relative Density and Loading Perspectives

Abstract

Surface topography is of importance in playing a major role for the mobilized mechanical behavior, and hence, the strength-stability performance of composite layered systems containing synthetic geomembrane liner and natural granular sand. The 2D surface topography alterations of different geomembranes were experimentally be studied by performing profile relief measurements for detecting and determining 2D surface topographical characteristics of different geomembrane liner sheets produced from distinctive polymeric resins (HDPE, LLDPE, PVC) previously subjected to abrasive action of granular sand grains at different relative densities (Dr) and dissimilar particle shape (rounded or angular), and additionally at various loading conditions. The surface topographical characteristics as evident on the detected profiles including asperity features such as size, shape, and spacing of material dislocations comprised of peaks and valleys in the topographies were different and unique to geomembrane type. As such, the softer and the more flexible the geomembrane liner sheet in an order of HDPE, LLDPE, PVC becomes, the greater the abrasion has developed in that the surface topography demonstrated more severe peaks and valleys. Further, the angular features of sand grains led to the mobilization of more violent abrasive action in that angular particles were able to penetrate into the surface of geomembrane liner, and thus, gouge on a trajectory along the surface. The dimensions and spacing of peaks and valleys for the surface topography were small-scale in relatively stiffer geomembrane liner sheet of HDPE in which the surface topography did not possess sharp corners such that the transitions from peaks to valleys to peaks were smooth and rounded as compared to that of LLDPE as well as PVC geomembranes where sharp and rough transitions from peaks to valleys to peaks exhibited. The quantification of surface topography alterations of different geomembranes by means of the computed values of average roughness (Ra) determined for the measured surface topographies of the liners unveiled that the Ra (i.e. surficial topographical changes) increases with an increase in load, relative density, particle angularity of grain shape, and softness of geomembrane liner sheet.