Experimental study on the monotonic shear strength of GM/CCL composite liner interface

The interface shear strength between a geomembrane (GM) and a compacted clay liner (CCL) or a geosynthetic clay liner (GCL) is of great importance for landfill stability analysis. An experimental study of the interface shear behaviour between a smooth GM (GMS) or a textured GM (GMX) and a CCL is presented in this paper. A series of monotonic shear tests was conducted using a large direct-shear apparatus. Peak and residual shear strength parameters were obtained by linear fitting of the experimental data. The shear strength of both GMS/CCL and GMX/CCL interfaces was mainly driven by the normal stress level, while the displacement rate had very little influence on the interface shear strength. The residual shear strength of the GMX/CCL interface was even higher than the peak shear strength of the GMS/CCL interface at all normal stress levels. The GM/CCL interface showed considerably higher shear strength over the GM/GCL interface; the residual strength of the GM/CCL interface was even higher than the peak strength of the GM/GCL interface at all normal stress levels. The results presented in this paper are useful for the preliminary design of landfill composite liner systems.