GCLs in landfill applications: influence of subgrade, temperature and confining pressure on bentonite hydration

Abstract : Geosynthetic Clay Liners (GCLs) are often used in landfills applications, for example in landfill covers. In order to act as a barrier, GCLs must hydrate and swell under a confining pressure. According to the French Committee for Geosynthetics, the water content of the bentonite must be at least 100% (wet dry weight). If GCLs are installed at their initial bentonite water content (around 10-15%), the question arises as to the duration of the hydration period (vapour migration from the subgrade). This question was addressed during experiments performed on a natural sodium bentonite GCL and aimed at examining the influence of several parameters: subgrade (sand versus clay), temperature and confining pressure. Results illustrate the strong influence of the subgrade water content and grain size on bentonite water content level and hydration kinetic. As could be expected, sandy soils allow a faster hydration and higher water content than clayey soils, but results provide quantitative information on hydration duration.