Evaluation of the Water Retention Behaviour of Geosynthetic Clay Liners
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Geosynthetic clay liners (GCL) are a composite material commonly used as hydraulic barriers in landfill liners. Due to their dependence on hydration for proper function, the water retention curve (WRC) of a GCL is important. The inherent difficulty in obtaining the WRC, including the range of suction and composite material, has limited the number of GCL WRCs in the literature. In order to quantify the large range of suctions, a dual testing technique was developed, which uses a high capacity tensiometer to measure suctions for the low suction range (0 - 500 kPa) and a relative humidity sensor for the high suction range (3,000 - 1,000,000 kPa). In total, four different GCL products were tested, varying in both materials (woven and nonwoven geotextiles) and construction methods (thermal treatment and needle punching). The dual technique method was used to establish both wetting and drying curves that were presented as gravimetric, volumetric and bulk GCL void ratio WRCs. The WRCs of the different GCL products showed significant variation between their wetting and drying curves indicating that both needle punching and thermal treatment have a significant effect on the swelling behaviour of the GCL and its WRC. Theoretical equations were fit to the experimental data establishing the parameters that can be used for numerical modeling of these four GCL products.