Shear Strength Evaluation of Soil–Geosynthetic and Geosynthetic–Geosynthetic Interfaces of Closure Cover Systems

Abstract

The use of covers containing geosynthetics as geomembranes (GM) and geosynthetic clay liners (GCL) is increasingly common in the closure of mine waste deposits. Their low hydraulic conductivity effectively minimizes water ingress into these deposits, preventing the acid drainage generation that is harmful to the ecosystem. However, these covers are susceptible to slide failure due to the low shear strength of the interface between geosynthetics and adjacent materials, which is a key design concern. This study assessed the shear strength of five interfaces, identified in cover systems with GM, GCL, and composite liner (GM and GCL). The shear strength of each interface was estimated through a large-scale direct shear testing program at low confinements (< 50 kPa), using samples of GM, GCL, granular soils (GS), and low-permeability soils (LPS). The test results were compared with other studies, aiding in identifying and understanding the mechanisms and factors influencing the interface shear strength. These factors include the gravel content and characteristics of coarse particles in GM–GS and GCL–GS interfaces, the fines content in GM–LPS interfaces, and the type of geotextile composing the GCL in GCL–GM interfaces. The findings provide valuable insights to optimize the engineering design of cover systems with geosynthetics.