Interface Dynamic Shear Characteristics of Aging GMB/CCL Composite Liner

Aging degradation of the geomembrane (GMB) significantly influences the dynamic shear characteristics of the composite liner interface, which comprises the GMB and the compacted clay liner (CCL), potentially jeopardizing the dynamic stability of landfills. In this study, cyclic shear tests were performed on two types of aging GMB/CCL interfaces, concurrently with shear tests on the nonaging GMB/CCL interface for comparison. The results suggest that the impact of aging on the dynamic shear characteristics of the GMB/CCL interface is essentially governed by the surface roughness and brittleness of the GMB, with the effect degree of brittleness influenced by the normal stress. Under low normal stress, aging increased the vertical displacement, dynamic shear strength, and shear stiffness of the GMB/CCL interface. However, under high normal stress, the dynamic shear strength and shear stiffness of the aging GMB/CCL interface were more likely to be lower than those of the nonaging interface. As the displacement amplitude increased, the influence of aging on the shear stiffness of the GMB/CCL interface gradually diminished. Aging also reduced the damping ratio of the GMB/CCL interface. The difference in vertical displacement between the exposed GMB/CCL interface and the in soil GMB/CCL interface caused by brittleness was not significant. In practical engineering, when the overlying load on the GMB/CCL composite liner is relatively small, aging makes the GMB more susceptible to tearing under seismic loads, whereas with larger overlying loads, aging is more likely to increase the shear displacement, thereby increasing the likelihood of instability in landfill. Finally, based on classic models of soil, fitting models for the normalized shear stiffness and damping ratio of the GMB/CCL interface were established and validated. This study can provide reference for analyzing the dynamic stability of landfills during long-term use.