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This investigation was conducted to determine the variations in the dimensions of multi-component geosynthetic clay liners (GCLs). Two GCLs were tested: a sample with a relatively smooth geofilm, and a sample with a textured geofilm. Discrete effects of cyclic wetting-drying, initial moisture content, overburden pressure, temperature, and underlying subgrade soil were determined. Coupled effects of underlying subgrade soil and climatic conditions were evaluated in an outdoor simulated field environment. Cyclic wetting and drying resulted in net shrinkage of GCLs, with shrinkage strains of 11 % and 4 % in the machine and cross-machine directions, respectively. Specimens with high initial moisture contents (75 % to 125 %) underwent more shrinkage in the early wet-dry cycles than those with low initial moisture (22 % to 50 %), however, the initial moisture had no significant effect on the ultimate shrinkage. In the machine direction, strains exceeded values that would cause panel separation in the field within the first two cycles, whereas at least seven cycles were required for panel separation strains in the cross-machine direction. Temperature effects alone did not result in significant shrinkage. Specimens placed on soil subgrades without wetting or drying underwent moisture changes however experienced less shrinkage than those subjected to wet-dry cycling. The GCLs underwent significant diurnal temperature variations (up to 55°C) outdoors. However, the shrinkage of these specimens was similar to that observed in the subgrade tests. The specimens with higher initial moisture contents underwent more dimensional change than the specimens at lower moistures. The type of geosynthetic in contact with the underlying soil influenced GCL–soil systems. Woven geotextile sides on soil subgrades resulted in high moisture transfer and shrinkage.
geosynthetic clay liner, multi-component, shrinkage, panel separation, dimensional stability
Hanson, James L.
Professor, Civil and Environmental Engineering Dept., California Polytechnic State Univ., San Luis Obispo, CA
Director, Global Waste Research Institute, California Polytechnic State Univ., San Luis Obispo, CA
Olsen, Gregory R.
Staff Engineer, Hultgren-Tillis Engineers, Concord, CA