Shear Behavior of HDPE Geomembrane Interfaces with Tropical Soils

Abstract Understanding the mechanisms governing soil–geomembrane interface behavior is essential for defining appropriate testing conditions and obtaining reliable design parameters. This study investigates the interface shear behavior of flat-die fabricated HDPE geomembranes, focusing on the combined effects of soil type, surface texture, and support material. Smooth and textured geomembranes were tested in contact with two tropical soils: a cohesive lateritic clay and non-cohesive washed river sand. Large-scale direct shear tests were performed using a 300 mm × 300 mm apparatus under a reduced-area configuration, considering two conditions for filling the lower half-box (rigid base and soil). Results showed that, for the cohesive soil, the textured geomembrane promoted efficient interaction, with interface strength exceeding the soil’s internal strength, whereas the smooth geomembrane exhibited limited strength mobilization. In non-cohesive soil, interface strength remained lower than soil strength, even with textured surfaces. The type of support material had little influence on the behavior of the cohesive soil interface, whereas it had a significant effect on the granular soil interface. The results demonstrate that soil type governs the predominant interface interaction mechanisms, altering even the failure mode and the way shear strength is mobilized. Additionally, geomembrane surface texture enhances shear resistance by increasing interface friction and interlocking, which is particularly important in controlling soil-geomembrane interaction performance.