Changes in physical, hydraulic and microstructural properties of clays exposed to organics

Subramaniam, Kavitha (1996) Changes in physical, hydraulic and microstructural properties of clays exposed to organics. Masters thesis, Memorial University of Newfoundland.

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Abstract

The use of engineered clay liners for containing landfill wastes and protecting groundwater quality is based on the adsorption capacity and impermeability of the clay fabric. Excessive leachate through clay barriers is mainly due to changes in the intrinsic permeability of the clay material when exposed to contaminants. The compatibility of clay barriers with leachate is also evaluated through an assessment, of changes in the index properties and/or internal structure of the soil. One of the major factors that can affect the clay performance is the presence of organic chemicals in the leachate that typically constitute more than 55% of the total leachate generated in landfills. -- The goals of this work are to provide a better understanding of the effects of various organic fluids on clay minerals and to provide a database for clay-organic fluid interactions, so that the results may be used for the evaluation and prediction of clay barrier performance in waste containment applications. -- Three clay minerals; kaolinite, illite and smectite are investigated in this study. The chemicals used as permeants cover a wide range of dielectric constants and aqueous solubilities. These include acetic acid (acidic), aniline (basic), methanol and acetone1 (neutral polar), and carbon tetrachloride, trichloroethylene and xylene (neutral nonpolar). Permeability measurements have been carried out on the clays using a rigid wall permeameter. Microstructures have been observed using Scanning Electron Microscopy to determine the effects of these organic chemicals on the internal structure of the clays. This study also attempts to correlate in dex property tests and sediment at ion analyses with observed changes in intrinsic permeability and microstructure of the clays. Electrical properties of the permeant appear to control hydraulic conductivity and microstructure, especially for smectitic clay.

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