Interface shear strength was investigated between a bentonite-polymer (B-P) geosynthetic clay liner (GCL) and a 1.5-mm textured high-density polyethylene (HDPE) geomembrane (GM). Comparative tests were conducted with a conventional GCL containing sodium bentonite. All tests were conducted to a maximum displacement of 50 mm under normal stresses of 20, 100, 250, and 400 kPa. Interfaces with the B-P GCL had lower peak shear strength than interfaces with the conventional GCL under the same normal stress. The interface strength envelope for the B-P GCL was highly non-linear with lower shear strengths occurring at 400 kPa relative to those at 250 kPa, suggesting that the mechanism controlling shear strength changes with normal stress. Extrusion of polymer hydrogel into the GCL-GM interface was identified as the likely cause for lower interface shear strength and the non-linear strength envelope for interfaces with the B-P GCL.
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