Suction and crack propagation in GCLs subjected to drying and wetting in CaCl2-solutions

Abstract

The current study addresses the cracking and self-healing capacity of Geosynthetic clay liners (GCLs) subjected to drying and wetting in a divalent salt solution. Commercially available GCLs, initially saturated under a load of 3.92 kPa, were stepwise dried for different durations in an oven at 30 °C and rewetted afterwards in deionised water and divalent salt solutions (CaCl2) of different molarities (0.05 mol/l, 0.5 mol/l and 0.05 mol/l prehydrated). The evolution of cracks and their patterns were studied by analysing X-ray images. In parallel, the water retention behavior was tested on the raw bentonite using micro-cells and a chilled-mirror hygrometer. The morphology of the crack patterns in the GCLs was highly affected by the pore fluid, which was reasoned by reduced tensile strength caused by the salt induced aggregation. The ability to retain water at a given suction was found to be higher for the samples subjected to CaCl2-solutions in comparision to the sample saturated with deionised water. However, a calculation of the osmotic suction caused by the additional CaCl2 in the porewater shows that the matric suction of the samples subjeted to CaCl2 decreases. The crack intensitiy factor (CIF) followed a similar trend and three different drying regimes were identified.