Correlation between Needlepunch-Reinforced Geosynthetic Clay Liner Peel Strength and Internal Shear Strength

Landfill and mining applications often involve composite liner systems consisting of a geomembrane underlain by a geosynthetic clay liner (GCL). Because of the low shear strength of hydrated bentonite, GCLs are manufactured using needlepunching, where nonwoven fibers from one geotextile are punched through the bentonite and the opposite geotextile, to provide internal reinforcement. The industry uses an index test, GCL peel strength (ASTM D6496), to assess the quality and strength of the needlepunched bond. Although design engineers commonly specify higher peel strengths for projects with stringent shear strength requirements, the published information on this subject presents conflicting results. To address this data gap, a correlation study between peel and internal shear strength was performed, involving 40 shear strength tests on hydrated GCL samples with varying peel strengths. To limit variability, one type of needlepunch-reinforced GCL was tested, with all shear samples subjected to the same hydration and consolidation. The test results indicate that, for a given set of testing conditions, a GCL's peak internal shear strength is a function of its peel strength. The results of this study will be useful to design engineers in understanding appropriate GCL peel strength values for site-specific conditions.