Abstract: This paper will show the correlation between the shear tensile test and the direct shear test within the field of geosynthetic clay liners (GCLs). It will be proven that the former may serve as a substitute for the latter, but only for the adhesion value. GCLs are clay mineral sealing layers widespread used. They can be used in waste and contaminated soil caps and closures, landfill base liners, gas and vapor seals, vertical barriers, etc. GCLs often have bentonite encased between two geotextile layers connected by fibers, either by needle-punching or stitch-bonding. The results from peel tests and shear box tests are currently used for establishing the internal shear failure of GCLs. This paper analyzes the mechanical shear behavior of needle-punched GCLs (NP GCLs) in a zero stress condition. On the one hand, a large direct shear test (ASTM 6243-09) on NP GCLs specimens was used to study its shear behavior, specifically, assessing the adhesion value. On the other hand, the shear tensile test, showed by Maubeuge and Ehrenberg (Maubeuge, K.P., Ehrenberg, H., 2000. Comparison of peel bond and shear tensile test methods for needle-punched geosynthetic clay liners. Geotextiles and Geomembranes 18(2?4), 203?214), was used to study the shear tensile strength. Comparing both test methods, an average shear tensile value of 32 kPa was obtained which is closer to the average adhesion value of 30 kPa. The dominant failure mechanisms are not depending on the test conditions (e.g. dry or hydrated conditions). However, it strongly depends on the type of carrier geotextiles and their connections.

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