Experimental Research on Dynamic Shear Characteristics of Multi-layered Geosynthetic Composite Liners

The multi-layer geosynthetic composite liner technology is widely used in environmental protection projects such as landfills. The dynamic shear characteristics of composite liners can reflect their long-term stability under dynamic loads such as earthquakes or traffic. In this paper, an improved large-scale dynamic shear apparatus was used to conduct dynamic shear tests of the multi-layered composite liner composed of non-woven geotextile (GT), double sided textured geomembrane (GMX) and needle-punched geosynthetic clay liner (GCL). The dynamic shear characteristics of the composite liner under different normal stresses (170-1070 kPa) and displacement amplitudes (5-20 mm) are revealed. The results indicate that the dynamic shear failure of the multi-layer composite liner under dry conditions is concentrated at the GT/GMX interface, with failure modes including fiber hooking, rough grain peeling and hot-melt damage. The peak strength of the composite liner shows little correlation with the amplitude of dynamic shear displacement. The large displacement cohesion increases with the increase of the displacement amplitude, while the large displacement friction angle exhibits the opposite trend. The cohesion demonstrated by the failure surface GT/GMX interface under independent shear conditions is significantly greater than that during the overall shear of the multilayer composite liner, whereas the friction angle under single-interface shear is comparable to that during shear of the multilayer composite liner. The dynamic shear stiffness of the composite liner is positively correlated with the normal stress, and the damping ratio increases with the increase of the displacement amplitude and the number of cycles, but it slightly decreases in the later stage of large displacement under high normal stress.