Hydraulic performance of geosynthetic clay liners under gravel cover soils

Abstract

Hydraulic performance of adhesive-bonded and needle-punched geotextile-supported geosynthetic clay liners (GCLs) was measured for specimens covered with uniformly graded fine, medium, and coarse gravel using flexible-wall permeameters. Local measurements of specimen thickness, water content, and mass per unit area were taken after each test to quantify thickness variability and bentonite migration/consolidation behavior. Control tests were also performed to measure GCL hydraulic performance under conventional testing conditions. Test results showed that the hydraulic performance of control and gravel-covered specimens of both GCL products improved with increasing confining stress. In addition, measured values of hydraulic conductivity for the gravel-covered specimens were less than the manufacturer's specification. The amount of bentonite migration generally increased with increasing cover soil particle size and rate of loading. Thickness variability and bentonite migration were generally less for the needle-punched product, which is attributed to the additional confinement provided by the reinforcement. The placement of an additional non-woven geotextile over the adhesive-bonded GCL was somewhat effective in reducing thickness variability and bentonite migration under rapid loading conditions.