State-of-the-art report: GCL shear strength and its measurement

This paper presents a comprehensive source of information on the shear strength and shear strength testing of geosynthetic clay liners (GCLs). Essential concepts of shear stress–displacement behavior and shear strength interpretation are presented, including long-term performance issues, followed by detailed discussions on the laboratory measurement of the shear strength of GCLs and GCL interfaces. The paper also provides recommendations for the selection of design failure envelopes for stability analyses and checklists to assist users in the specification of GCL shear testing programs. North American practice is emphasized and discussions are focused primarily within the context of landfill bottom liner and cover systems. Conclusions are drawn with regard to GCL shear strength behavior and current GCL strength testing practice, improvements for GCL strength testing and reporting are suggested, and future research needs are identified.