Performance of GCLs after long-term wet–dry cycles under a defect in GMB in a landfill

Two geosynthetic clay liners (GCLs) with sodium bentonite and three GCLs with polymer-amended bentonite were subjected to wet–dry cycles selected to simulate the conditions to which a GCL on an 18° slope might be subjected: for a GCL below an exposed geomembrane wrinkle with a hole. The wetting involved water flowing over the GCL for 8 h each cycle. Three drying cycles (0.67, 7, and 14 days) were examined. After 12–18 months of wet–dry cycles, the samples were X-rayed to identify representative specimens for testing. The changes in the hydraulic conductivity, k, of the GCLs were obtained when permeated with two synthetic municipal solid waste leachates at an applied head of 0.35 m for a range of effective stresses (3–150 kPa). The results showed an up to four orders of magnitude difference in k depending on applied stress and RMD of the leachate permeant. The effects of the number and the duration of the wet–dry cycles, the GCL mass per unit area, presence/absence of polymer modification, the carrier geotextile, the number and the size of the needle-punched bundles, and the bundle thermal treatment are discussed.