The effect of organic fluid permeation on the fabric of compacted clay was investigated in order to assess whether changes in hydraulic conductivity could be estimated from changes in fabric, pore fluid characteristics, and the characteristics of clay minerals. Pore size distribution analyses were first conducted to assess the magnitude of the effect of compactive effort and moulding water content on the changes in fabric and hydraulic conductivity. Second, the effect of pore fluid characteristics on the consistency limits and free swell of kaolinite, Ca-montmorillonite, and Na-montmorillonite was investigated in an attempt to determine the effect of compositional variables. Finally, hydraulic conductivity tests were conducted with selected organic fluids and compacted kaolinite and Ca-montmorillonite specimens originally moulded with water. Nitrobenzene, acetone, phenol, benzene, and p-dioxane were used for these permeation studies. Fabric of the specimens was quantified before and after permeation with the specific pore fluid. The results indicate that changes in hydraulic conductivity correlate well with the point changes in the fabric when the moulding pore fluid and the permeation pore fluid are both water. A decrease of 20% in dry density at a fixed water content may lead to at least an order of magnitude increase in hydraulic conductivity. Tests with organic fluids indicate that changes in hydraulic conductivity are in response to changes in fabric as well as pore fluid characteristics, interaction with the clay mineral, and confining stress. Practical implications of the study are discussed.
Abstract