Design parameters for bentonite-enhanced sand as a landfill liner

This paper considers the engineering properties of bentonite-enhanced sand (BES) mixtures in relation to their performance as landfill liners. Data on the swelling, hydraulic conductivity, strength and desiccation of such mixtures are presented. The hydraulic conductivity depends on the proportions of sand and clay, the confining stress and the permeating fluid. The drained strength of mixtures typically used as landfill liners depends primarily on the relative density and critical state friction angle of the sand component. The susceptibility to desiccation cracking is a function of the moisture content and the proportion of bentonite used in the mixture. A model for BES mixtures is proposed that can be used to predict their swelling and hydraulic conductivity in water and salt solutions. The model requires the swelling behaviour and hydraulic conductivity of the bentonite in the relevant solution, and the compressibility, porosity and tortuosity of the sand component as input parameters. Sand tortuosity is estimated. The strength can be predicted using the void ratio of the sand component calculated from the proposed model.