Self-healing of laboratory eroded defects in a GCL on silty sand

Abstract

The self-healing of five geosynthetic clay liners (GCLs) with laboratory simulated down-slope erosion defects (quasi-circular holes and linear slits where there is little or no bentonite) upon hydration from Godfrey silty sand subgrade with wfdn = 16% under an overburden stress σv = 20 and 100 kPa is examined. While there was an up to 9.6 mm reduction in hole diameter/slit width, none of the defects fully self-healed. The self-healing of these laboratory eroded specimens with a swell index of 10.2 ± 1.7 ml/2 g after hydration is generally smaller than that of the corresponding virgin GCLs. GCLs with powdered bentonite with an initial SI of 32 ml/2 g generally self-healed better and the intact specimens had a lower hydraulic conductivity than GCLs with granular bentonite with an initial SI of 24–26 ml/2 g. Higher mass per unit area of bentonite and overburden stress led to better self-healing. Ponding of distilled (DI) water above the GCL increased self-healing of GCL slightly more than simulated synthetic landfill leachate (SSL). The post-hydration hydraulic conductivity, k, of GCL specimens with holes/slits is shown to be about 1–3 orders of magnitude higher than that of the intact GCL specimen.