Evaluation of the Interface Strength of Soil–Geomembrane and Multilayer Systems under High Normal Stresses

Abstract

In geotechnical structures composed of soil and geosynthetic layers, the shear strength mobilized at material interfaces is a complex parameter influenced by the properties of both the soil and the geosynthetics in contact. Therefore, evaluation through experimental testing is essential. However, most available studies have focused on relatively low normal stress ranges. In applications such as heap leach pads and landfill cells, loading levels have progressively increased, requiring assessments under higher normal stresses. In this context, this study evaluated the interface shear strength of a 2.0-mm-thick double- textured HDPE geomembrane under normal stresses ranging from 200 kPa to 1,500 kPa. Three large-scale direct shear testing programs were conducted in accordance with ASTM D5321 using a 300 mm × 300 mm shear box: (i) geomembrane against compacted soil at optimum moisture content; (ii) geomembrane against saturated compacted soil; and (iii) a multilayer system comprising compacted soil, nonwoven geotextile, and geomembrane. The results demonstrated significant differences in the Mohr–Coulomb strength parameters, with variations observed in both adhesion and friction angle, contributing to the expansion of the available database and to safer geotechnical design.