Temperature and moisture effects on GCL and textured geomembrane interface shear strength

ABSTRACT: This investigation was conducted to determine the effects of temperature and moisture on the shear strength of a double nonwoven geosynthetic clay liner (GCL) and a high-density polyethylene textured geomembrane (T-GM) interface for municipal solid waste landfills. Interface direct shear tests were conducted at normal stresses representative of cover liners (10, 20 and 30 kPa) and bottom liners (100, 200 and 300 kPa). Tests were conducted at temperatures of 2, 20 and 40°C (cover liner) and 20 and 40°C (bottom liner); and at moisture contents of as-received (19%), 50 and 100%. Both peak and large-displacement (50 mm) shear strength parameters were determined. For cover liners, temperature was determined to have a greater influence on interface shear strength than moisture content, whereas bottom liner shear strength was influenced more by moisture than temperature. Measured interface shear strengths varied by up to 54% with temperature and up to 43% with moisture content. Interface friction angles were greatest at 20°C for both cover and bottom liners. Variations in the interface shear strength parameters were attributed to geosynthetic damage including surface texture of the geomembranes (quantified with optical interferometry) and bentonite extrusion. Overall, results of this testing programme indicated that both peak and large displacement GCL/T-GM interface shear strengths were influenced by temperature and moisture content representative of field service conditions.