Deformations of a geosynthetic clay liner beneath a geomembrane wrinkle and coarse gravel

Experimental results are presented on the deformations of dry and hydrated geosynthetic clay liners (GCLs) when buried beneath 50 mm coarse gravel and a 1.5 mm high-density polyethylene geomembrane containing a wrinkle and then subject to simulated earth pressures. The effect of the wrinkle on GCL deformations and the effectiveness of different protection layers to minimize GCL deformations are examined. Although the wrinkle experienced a decrease in height and width, the gap beneath the wrinkle and GCL remained, even up to applied pressures of 1000 kPa. The thickness of the GCL decreased beside the wrinkle and increased beneath the wrinkle from bentonite extrusion towards the gap beneath the wrinkle. The gravel backfill itself induced large variations in the thickness of the GCL when tested without a protection layer. These variations were induced by bentonite extrusion directly beneath gravel contacts to zones in between contacts. The 1200 and 2000 g/m2 nonwoven needle-punched geotextile protection layers tested were not effective at reducing the number and magnitude of these indentations. The 150 mm thick sand protection layer tested was very effective at minimizing the number and magnitude of GCL indentations, even up to vertical pressures of 1000 kPa. Further, the beneficial redistribution of the gravel contact stresses provided by the sand protection layer ensured that majority of the GCL deformation that did occur was the result of consolidation of the bentonite (as opposed to lateral extrusion) which is preferable since the reduction in void ratio would be accompanied by a reduction in hydraulic conductivity.