Shear strength of the geomembrane–subgrade interface in heap leaching applications

Abstract

A series of large scale direct shear tests is used to examine the effectiveness of smooth, textured, and structured surface geomembranes (GMBs) with different soil subgrades for heap leach pads applications. Four different subgrades, including sand, two different coarse-grained underliners, and a clayey soil representing the layers directly underlying the GMB liner in heap leach pads, are used to examine the shear strength of the GMB-Subgrade interfaces at normal stresses between 50 and 1000 kPa. It was found that increasing the normal stresses can change the mechanisms contributing to the shear resistance at the interface. This resulted in a statistically insignificant increase in the interface friction of the GMB-Granular soils interfaces when using GMBs with surface roughness relative to the smooth GMB. Furthermore, depending on the type of subgrade, establishing the shear envelopes over a wide range of normal stresses was found to overestimate or underestimate the shear strength at the field stresses even when linear regressions present the best fit for the data.