Chemo-Mechanical Behavior of Bentonite-Sand Mixtures Inundated with Organic Pore-Fluid

Abstract

ABSTRACT Bentonite-sand mixture is considered to be a potential liner material for landfill facilities owing to its excellent sorption potential and swelling characteristics. Such liner materials are expected to perform satisfactorily if the hydraulic conductivity is maintained less than 10−7 cm/s and thereby inhibiting the migration of the generated leachate. However, the performance assessment of these liners in the presence of highly concentrated organic fluids and under the overburden stresses that is usually expected in landfill conditions is scarce. Therefore, in the present work, the hydraulic performance of the bentonite-sand mixtures in the presence of the organic compounds commonly encountered in the landfill leachate is studied, which is a need of the hour. Flow tests were performed to evaluate the hydraulic conductivity of different bentonite-sand mixtures in unhydrated conditions and permeated with varied proportions of methanol-water and ethanol-water mixtures. The study reveals that the proportions of the organic pore fluids significantly influence the hydraulic conductivity of the bentonite-sand mixtures. A very good linear relationship was observed between the pore fluids’ dielectric constants and the hydraulic conductivity of the bentonite-sand mixtures. The chemo-mechanical behavior suggests that the conventional bentonite-sand mixtures perform poorly in terms of the hydraulic and swelling characteristics with the change in the dielectric constant of the organic fluids. The microstructural analysis also supports the experimental findings that as the dielectric constant of the fluid are reduced, the effective flow path through the soil increases considerably resulting in higher hydraulic conductivity.