Direct shear testing of GCLs at elevated temperature and in a non-standard solution

The objective of this study was to develop, verify, and assess a direct shear apparatus to measure the internal shear strength of geosynthetic clay liners (GCLs) when exposed to elevated temperature and non-standard hydration solutions. Shear boxes were developed to facilitate testing 300-mm-square and 150-mm-square specimens. Preliminary experiments documented the effectiveness of a GCL gripping system and a 2-stage hydration procedure. Direct shear experiments were performed to evaluate the new apparatus with respect to the following variables: (i) specimen size; (ii) GCL peel strength; (iii) GCL heat treatment; (iv) test temperature; and (v) hydration solution. Direct shear results were verified via comparison to literature, which also supported the use of 150-mm-square GCL specimens to measure internal shear behavior and shear strength.  Shear tests on heat-treated and non-heat-treated GCLs at 20 °C and 80 °C yielded a 40% reduction in internal peak strength with increase in temperature. Hydration in ...