Selected Factors Influencing GCL Hydraulic Conductivity

Abstract

A series of confined swell and hydraulic conductivity tests were conducted on a needle-punched geosynthetic clay liner (GCL) with water as the hydrating medium and reference permeant. Increases in the static confining stress and the needle-punching both restricted GCL swell and contributed to lower bulk GCL void ratios and hence significantly lower hydraulic conductivity values. A well defined linear-log relationship is found between the bulk void ratio and hydraulic conductivity. The number of pore volumes of permeant flow and consequently the level of chemical equilibrium is shown to have a significant effect on the hydraulic conductivity. It is shown that there is a decrease in hydraulic conductivity for small amounts of permeant flow for all ethanol/water mixtures examined. At or near chemical equilibrium, low concentration mixtures (25 and 50 ethanol) continued to produce relative decreases in GCL hydraulic conductivity due to the increased viscosity of the permeant; however, highly concentrated mixtures (75 and 100 ethanol) produced relative increases in GCL hydraulic conductivity arising from double layer contraction. The implications are discussed.