Determination of Surface and Thickness Characteristics of Textured Geomembranes Using Image Analysis

Image analysis was used to determine surface topography and thickness of textured geomembranes. Images of cross sections (specimen length x thickness) of geomembranes were obtained at 50x magnification using a digital optical microscope. Thickness was determined as the distance between the top and bottom surfaces along an entire cross section. For surface analysis, profiles of top and bottom surfaces were extracted from the cross sectionimages. Amplitude, spatial, hybrid, and functional texture parameters were determined. Tests were conducted on eleven samples of HDPE and LLDPE geomembranes manufactured by co-extrusion and embossing at varying thicknesses. The geomembranes were classified into three texture categories: high, medium, and low. Anisotropy and directionality were observed for all samples to varying degrees between and within manufacturing directions, respectively. Statistical analysis of the results indicated that surface topographyof geomembranes could be determined by analyzing one surface of five specimens with 50mm length. Comparisons were made betweenimage analysis and mechanical tests for core thickness and asperity height. Image analysis and mechanical measurements were significantly different. Recommendations were made for the redesign of the mechanical devices bysizing the components in relation to the size and spacing of geomembrane texture features.