SELECTED FACTORS INFLUENCING GCL HYDRAULIC CONDUCTIVITY

A series of confined swell and hydraulic conductivity tests were condu cted on a needle-punched geosynthetic clay liner (GCL) with water as t he hydrating medium and reference permeant. Increases in the static co nfining stress and the needle-punching both restricted GCL swell and c ontributed 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 hydr aulic 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 pe rmeant; however, highly concentrated mixtures (75 and 100% ethanol) pr oduced relative increases in GCL hydraulic conductivity arising from d ouble layer contraction. The implications are discussed.