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Specimen preparation, installation, and testing procedures are presented for testing a needle-punched geosynthetic clay liner (GCL) in a consolidation-type, fixed-ring constant-flow-rate hydraulic conductivity apparatus. The proposed approach is illustrated by reporting the results obtained for a GCL statically confined to effective stresses of ∼3 and ∼35 kPa, hydrated and permeated with distilled water and concentrated aqueous salt solutions (0.6 and 2.0 N NaCl), and sequentially permeated with concentrated aqueous salt solutions (0.6 and 2.0 N NaCl) after initial permeation with distilled water. The issue of potential preferential sidewall flow in the fixed-ring permeameter tests was then addressed by comparing results with those conducted under otherwise similar testing conditions in a double-ring and flexible-wall permeameter. Reasonable reproducibility of the test results was obtained between the different types of permeameters, suggesting that, if present, preferential sidewall flow was negligibly small and was not significant on the calculated hydraulic conductivity values. This conclusion was found to be valid for the range of permeant types (distilled water and 0.6 and 2.0 N NaCl), static-confining stresses, and hydrating mediums considered. Premature arrival of the salt solution front in the effluent (i.e., solute breakthrough) during fixed-ring hydraulic conductivity testing was explained as a probable diffusion-dominated transport mechanism through the relatively thin GCL specimens.
Environmental engineer, Trow Consulting Engineers, Ltd., Brampton, Ontario
Kerry Rowe, R
Professor, The University of Western Ontario, London, Ontario
Stock #: GTJ11420J