Hydraulic Conductivity of Geosynthetic Clay Liners Permeated with Acid Mine Drainage

Abstract

We investigated the potential use of two geosynthetic clay liners (GCLs) as basal liners for acid mine drainage (AMD) from a coal gangue impoundment. One contained natural sodium bentonite (GCL-N), while the other contained sodium-activated bentonite (GCL-S). Chemical compatibility and the effects of effective stress and type of bentonite were evaluated. The test results showed that permeation with a synthesized AMD caused the hydraulic conductivity of the GCL-N and GCL-S to increase by 33 and 104 times, respectively, at an effective stress of 10 kPa. Under an effective stress of 50 kPa, the hydraulic conductivity of the GCL-N and GCL-S permeated with AMD was 1.1 and 6.6 times higher, respectively, than the values based on permeation with distilled water. However, when the effective stress was increased to 200 kPa, the AMD had no negative effect on hydraulic performance. The difference in hydraulic conductivity because of the type of bentonite was only observed at effective stresses of 10 and 50 kPa, with the GCL-N consistently having less hydraulic conductivity than the GCL-S. Thus, the detrimental effects of AMD permeation and low quality bentonite can be countered by applying high effective stress to the GCLs. Both GCLs types may be suitable as effective basal liners for coal gangue impoundments where relatively high stress can be applied.