Thermo-Hydro-Mechanical Shear Behavior of Interfaces between a Textured Geomembrane and Geosynthetic Clay Liner

The thermo-hydro-mechanical (THM) shear behavior of the interface between a textured geomembrane (GMX) and a geosynthetic clay liner (GCL) was investigated using large-scale direct shear tests. The GCL was comprised of granular bentonite sandwiched between two non-woven geotextiles bonded by needlepunching. The geomembrane was textured high density polyethylene. Influence of normal stress, hydration condition, and temperature on interface shear behavior was evaluated, and changes in the surface characteristics of the interface were documented photographically. The peak shear strength of the GMX/GCL interface was higher under dry conditions than when hydrated. In some cases, two peak strengths were observed in the hydrated condition, whereas shearing under dry conditions consistently yielded only one peak strength. The peak shear strength and large-displacement shear strength of the GMX/GCL interface were highest at room temperature. Increasing the temperature resulted in a reduction in shear strength and less post-peak strength loss. Three failure modes were observed: GMX/GCL interfacial failure, partial interface/internal GCL failure, and internal GCL failure. Increasing normal stress and temperature caused a transition in the failure mode between interfacial failure and internal GCL failure. Extrusion of bentonite into the interface under hydrated conditions also influenced the interface strength and the failure mode.