Effect of Pore Fluid Chemistry on Strain-Softening Behaviour of Reconstituted Plastic Clay

Proglacial Lake Agassiz clay is smectite-rich, strain-softening, and is believed to be cemented by gypsum. Five different blocks of reconstituted clay were prepared with different pore fluids to examine the effects of pore fluid chemistry on strain-softening behaviour. Specimens that were saturated with respect to gypsum displayed similar yield points and peak strengths, but significantly different strain-softening behaviour. Specimens enriched with gypsum and sodium chloride were stronger than specimens that were undersaturated with gypsum and required more axial straining before they strain-softened. The results suggest that small-strain behaviour is controlled by gypsum cementation.