Shear strength of bentonite–polymer composite geosynthetic clay liners and geomembranes

Abstract

The interface shear strength between bentonite–polymer composite (BPC) geosynthetic clay liners (GCLs) and textured geomembrane (GM) was compared with the interface shear strength between conventional sodium (Na) bentonite GCLs (NaB GCLs) and the same GM. Four BPC GCLs were used that had polymer loading ranging from 0.12 to 1.09 g/kg. The peak shear strength of the BPC GCL/GM interface ranged from nearly identical to the interface strength of the NaB GCL/GM to as much as 14.4 times lower. The lower strengths of the BPC GCL/GM interface are attributed to the hydrated polymer gel that migrated out of the GCL and into the interface. The hydrated gel has very low shear resistance, reducing both peak and large-displacement interface shear strengths. The reduction in shear strength increased with increasing polymer loading of the BPC GCL and increasing normal stress. Inclusion of a woven slit-film geotextile in the interior of one of the BPC GCLs reduced migration of the polymer into the interface, leading to higher interface shear strength than obtained with the same BPC GCL without a slit-film geotextile.