Research on shear strength of needle-punched GCL by simple-shear of composite liner

Geosynthetic composites are widely used in landfill liners owing to their excellent impermeability. However, translational failure along a multi-layered geosynthetic liner system is a major concern for the slope stability of landfill liners. Reasonable determination of the liner shear strength is vital for analysis of landfill stability. For this purpose, large-scale shear tests of a geosynthetic clay liner (GCL) overlying a geomembrane were performed without forcing shear failure to occur along a pre-determined failure plane. Different failure modes are obtained according to the interface and internal displacements of the GCL. The inflection point phenomenon is observed at small displacements on the shear stress versus displacement curve of hydrated needle-punched (NP) GCL. This is confirmed to be an inherent feature of hydrated GCL through experimental analysis. The shear mechanism of hydrated NP GCL is analyzed based on the inflection point phenomenon on the stress-displacement curve. The peak shear strength of a NP GCL can be divided into contributions from two components i.e., bentonite and reinforcement. A peak shear strength model that can reflect the failure mechanism is proposed considering each shear strength contribution of the GCL.