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One of the important properties of geosynthetic clay liners (GCLs) is hydraulic conductivity. In the laboratory, hydraulic conductivity of GCLs is typically measured in flexible-wall permeameters. The most important variables in hydraulic conductivity testing of GCLs are addressed, including (i) trimming the GCL specimen; (ii) determining the thickness of the specimen; (iii) selecting the effective stress; (iv) selecting the hydraulic gradient; and (v) selecting the first wetting liquid and permeant liquid. A round-robin testing program was conducted in which 18 laboratories independently measured the hydraulic conductivity of a GCL that was permeated with water. The test specimens all came from the same GCL sample. The coefficient of variation, accounting for all sources of variability, was 42%. For experienced laboratories, this value reduced to 35%, which was identical to the variation in quality control tests performed over a 7-month period by the manufacturer on a variety of GCL samples. The round-robin test results are encouraging; there was less variability than might be expected, considering the difficulty in accurately measuring the hydraulic conductivity of relatively impermeable materials such as GCLs.
hydraulic conductivity, permeability, bentonite, geosynthetic clay liner, GCL, flexible-wall permeameter, precision, bias, variability
Professor, University of Texas, Austin, TX
Research Scientist, University of Texas, Austin, TX
Assistant Professor, University of Texas, Austin, TX