Influence of pore water chemistry on GCL self-healing with hydration from silica sand

Abstract

The self-healing of a GCL with a circular hole is examined in experiments where the GCL, overlain by geomembrane, is hydrated from a silica sand subgrade (SSS) having three different pore water chemistries. Factors considered included: hole size, subgrade initial moisture content wfdn, GCL mass per unit area, and overburden stress (20–100 kPa). GCL self-healing is better for wfdn = 16% than for wfdn = 10%, which is better than for 5%, when the SSS pore water has negligible cations (ionic strength, I < 0.1 mM). However, only the 14.3 mm-diameter hole fully self-healed and only when wfdn = 16%. In contrast, when the GCL is hydrated from SSS with pore water having an ionic strength, I, of 20 and 30 mM, the self-healing for wfdn = 5% is better than for wfdn = 10%, which is better than for wfdn = 16%, although none of the holes self-healed. When a ~0.5 m hydraulic head was applied above the GCL under σv = 20–100 kPa, a 38.1 mm-diameter hole self-healed with water having I < 0.1 mM, a 25.4 mm-diameter hole self-healed with pore water with I = 20 mM and 30 mM, but none self-healed with simulated synthetic landfill leachate (SSL). Post-hydration hydraulic conductivity (k) tests with SSL suggest that a hole up to 14.3 mm-diameter would not pose a significant adverse impact on the k compared to an intact GCL; however, this is not the case for the larger holes tested.