Comparing Measured Hydraulic Conductivities of a Geotextile Polymer Coated GCL Utilizing Three Different Permeameter Types

The purpose of this paper is to measure hydraulic conductivities of a geotextile polymer coated GCL, permeated with water, with three different permeameters: constant-flow, fixed-wall single-ring (FWSR); flexible-wall (FW), and constant head, fixed wall double-ring (FWDR). All results, except for the samples tested with the FWSR were lower than 1.0 x 10^–11 m/s, with some scatter in the test results at the relatively low bulk GCL void ratios tested. The results for sample diameters of 58 to 70 mm varied from 3.1 x 10^–12 m/s to 9.2 x 10^–12 m/s for samples tested at similar e_B values using the FWSR and FW permeameters. Although only one test was performed with a 150 mm diameter sample using the FW permeameter method, this test was found to provide the lowest hydraulic conductivity of the GCL tested (1.9 x 10^–12 m/s). This would seem to suggest the presence of some level of sidewall leakage during testing. However, diffusion testing and compatibility testing performed on this same GCL (not reported herein) suggests predominant flow through the GCL. Attempts to identify sidewall leakage using dyes were not successful.