Volume change behaviour of swelling and non-swelling clays upon inundation with water and a low dielectric constant fluid

Studies of the volume change behaviour of saturated and unsaturated fine-grained soils upon exposure to various types of fluid are of significant interest while dealing with contaminated soils. In this study, the one-dimensional volume change behaviour of two clays (Spergau kaolin and Calcigel bentonite) with dominant minerals as kaolinite and montmorillonite was studied by inundating several initially unsaturated and saturated clay specimens with water and a non-polar organic liquid (heptane). For both cases, applied vertical pressures of 25 and 100 kPa were considered under oedometric conditions. The magnitude of compression and swelling deformations of the clays were found to be strongly dependent upon the mineralogy of clays, dielectric properties of the pore-fluid, initial compaction conditions, and applied stress during the wetting process. The test results indicated distinct interactions between unsaturated clays and water. Specimens of Spergau kaolin exhibited compression with water, whereas specimens of Calcigel bentonite exhibited swelling. Compression and swelling deformations of the clays with heptane as the inundating liquid remained within about ±1.0% for both clays indicating a very minor interaction between unsaturated clays and molecules of this non-polar organic liquid. The test results emphasized the significance of attractive and repulsive forces and their impact on the volume change behaviour of clays of different mineralogy.