State-of-the-art report: GCL shear strength and its measurement – ten-year update

: This paper presents an invited update to our 2004 state-of-the-art report and provides 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 are presented, 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 strength 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 and recommendations are provided with regard to GCL shear strength behavior and current GCL strength testing practice, improvements for GCL strength testing are suggested, and future research needs are identified.