Hydraulic conductivity of geosynthetic clay liners to inorganic waste leachate

Abstract

Hydraulic conductivity (k) tests were conducted to evaluate how the permeation of solidified/stabilized inorganic hazardous waste (SIHW) leachate affected the k values of two geosynthetic clay liners (GCLs): a natural sodium bentonite GCL (GCL-N) and a sodium-activated calcium bentonite GCL (GCL-S). The two GCLs were permeated with distilled water (DW) and a SIHW leachate. The effects of the type of bentonite, effective stress and prehydration were assessed. At effective stress of 30 kPa, the k to DW was 1.5 × 10–11 m/s and 5.1 × 10–11 m/s for GCL-N and GCL-S, respectively. In contrast, at the same effective stress, permeation with SIHW leachate caused the k to increase by factors ranging from 1.2 to 3733 for GCL-N and from 86 to 5294 for GCL-S, respectively. Compared with GCL-N, GCL-S had poorer hydraulic performance. Increasing the effective stress and prehydration with DW reduced the detrimental effect induced by permeation with SIHW leachate. Some GCL specimens maintained low k values to SIHW leachate even though the corresponding bentonites had small or modest swell indexes in SIHW leachate. The results of this study suggest that further evaluation is needed before using swell index test to assess the effect of SIHW leachate on the hydraulic performance of GCLs.