FABRIC AND ENGINEERING BEHAVIOR OF ORGANIC-SATURATED CLAYS.

Interactions between clay particles and organic pore fluids occur frequently in chemical waste disposal site environments. Laboratory experiments have identified the formation of clay tactoids in organic-saturated clay materials. At low pressures, tactoids impart granular fabrics and corresponding granular geotechnical behaviors to clays. As pressures increase, tactoidal clay materials pass through several unique stages of deformation: dilatant stage, pore space compression stage, tactoid breakage stage, and individual particle behavior stage. The response of a tactoidal clay to stress is dependent upon clay mineralogy and pore fluid chemistry; each stage of deformation for several organic fluid/clay mineral combinations has been quantified by compressibility, void ratio, and permeability measurements. Scanning electron microscopic examination of stressed samples confirms this multistage behavior. The occurrence of tactoids imparts a more open fabric to clay materials, resulting in increased permeability and greater friction angle.