Temperature Effects on Internal Shear Behavior in Reinforced GCLs

Abstract

The objective of this study was to evaluate the strength reduction of heat-treated and non-heat-treated needle-punched geosynthetic clay liners (NP GCLs) at elevated temperatures. For this purpose, a series of stress-controlled rapid-loading shear tests were performed on two NP GCLs with similar peel strength but different heat treatment. Tests were performed at temperatures of 20°C, 40°C, 60°C, and 80°C under three different normal stresses (20, 40, and 60 kPa). Internal shear behavior of NP GCLs was described as a three-mechanism conceptual model. Elevated temperature resulted in a systematic decrease in the shear stress at failure in both heat-treated and non-heat-treated NP GCLs. The internal shear strength and shear deformation mechanisms in NP GCLs are dependent on the strength of reinforcement fibers and fiber bundle–geotextile connection. Thus, the internal shear behavior of NP GCLs as a function of temperature was evaluated via changes in the tensile modulus of monofilament fibers and entanglement strength of fiber bundle–geotextile connections. In heat-treated GCLs, an increase in test temperature to 80°C reduced the tensile modulus of reinforcement fibers. In non-heat-treated GCLs, an increase in test temperature to 80°C reduced the fiber bundle–geotextile entanglement strength. These reductions in tensile modulus and fiber bundle entanglement strength corresponded to reductions in internal shear strength of NP GCLs.