Hydraulic Performance of Geosynthetic Clay Liners (GCLs) in Containment of Brine and Landfill Applications
The interface transmissivity (θ) and hydraulic conductivity (k) of conventional and multicomponent geosynthetic clay liners (GCLs) were examined for a range of normal stresses (i.e., 10 kPa, 25 kPa, 50 kPa and 150 kPa) when placed in contact with smooth and textured geomembranes (GMBs). Solutions that vary in ionic strength and chemical composition (i.e., RO water, synthetic landfill leachate (SL3) and synthetic high saline solution (brine)) were examined to assess their effect on GCL interface transmissivity and hydraulic conductivity. In addition, several parameters including: GMB stiffness, GMB texture, bentonite enhancement, GCL pre-hydration condition, coating orientation and texture for multicomponent GCLs, and presence of defects were examined for different normal stresses. The interface transmissivity decreased non-linearly with increasing normal stress, with most of the decrease occurring for stresses up to 50 kPa; the effect was relatively small between 50 kPa and 150 kPa. The effect of GMB stiffness and texture was minor for the GCL-GMB combinations examined at high stress levels, but could be quite significant at low stress levels. High saline solutions suppressed the swelling capacity of bentonite leading to high interface transmissivity. Bentonite enhancement and pre-hydration of GCL with RO water improved the GCL performance when hydrated and permeated with brine leading to lower interface transmissivity (θ). Coating defects in multicomponent GCLs resulted in two modes of flow for which interface transmissivity: (i) flow at the GMB-geofilm interface (θGMB/Geofilm) and (ii) flow at the geofilm- rest of GCL interface (θGeofilm/GCL). Assessment of leakage (Q) and contaminant concentration (cp) at the underlying aquifer for a hypothetical containment facility using semi-analytical and finite element approaches was conducted. The results highlighted the effect of interaction between interface transmissivity (θ) and hydraulic conductivity (k) on the estimated leakage (Q), hence the contaminant concentration (cp) at the aquifer level. The results also suggested that wrinkle and failed seam lengths have a significant effect on the performance of the contaminant facility but that this is also closely linked to the interface transmissivity.