Novel sealing concepts for landfills: mechanism and prediction of permeabilities of bentonite-sand mixtures

Abstract Landfills are commonly employed for the disposal of solid waste; however, they pose a significant risk of groundwater contamination due to leachate. To address this concern, traditional impermeable systems composed of bentonite-sand composites are employed as liners at the base of landfills. This study investigates an alternative impermeable system featuring a composite material made from quarry stone chips and bentonite aimed at enhancing leachate containment. The primary objective is to assess the effects of varying bentonite dosage and various dry densities on the permeability performance of the stone chips-bentonite mixture. GDS permeation tests are conducted to assess the permeability performance of the soil mixture comprising stone chips and bentonite. Various dosages of bentonite (ranging from 3% to 13%) and different states of dry density (between 1.76 g/cm³ and 1.95 g/cm³) are considered. The experimental results demonstrate a significant reduction in the permeability coefficient with increasing bentonite content; specifically, an impressive decrease by three orders of magnitude is observed when the bentonite dosage reaches 7%, resulting in a permeability coefficient of 10 − 7 cm/s. Conversely, decreasing the dry density while maintaining a constant bentonite admixture leads to an increase in the permeability coefficient. Additionally, this study introduces a novel evaluation method for determining the permeability coefficient of mixed soil, thereby providing valuable insights into landfill design and leachate management.