Influences of solution characteristics on permeability of stone-bentonite mixtures

Landfill is the main method for disposaling the municipal solid waste in cities around the world. In order to effectively protect the underlying ground-water resources and surrounding environments from leachate, the bottom of landfills is lined with impervious system. The compacted clay or bentonite-sand mixtures are the widely-used materials for impervious system. In this study, the impervious materials are prepared by stone chips of a quarry and bentonite. The influence mechanism of solution characteristics on permeability is analyzed through permeation tests, Zeta potential and X-ray diffraction. The results show that the permeability of stone-bentonite mixtures become larger with the increase of the ion concentration, which is mainly due to the exchange of ions in solution with sodium bentonite, the reducement of the repulsion between soil particles and the thickness of the electric double layer, and the increase of the crystal spacing of the montmorillonite layer in the bentonite.