Abstract

Throughout southern Saskatchewan the upper part of unweathered Cretaceous clay is softened by glacial shear from an originally heavily overconsolidated state. Original preconsolidation pressures ranged from 10 000 to 13 000 kPa. Shear from glacial erosion created negative pore water pressures which caused an increase in water content and decrease in density. This also resulted in a reduction in apparent preconsolidation pressure. Depth profiles of water content for three sites were plotted against reference curves for the normally and overconsolidated states. From these plots the presence of softening is inferred. Softening was found at depths from 30 m to 143 m. Large blocks of intact overconsolidated clay separated by softened gouge zones as well as folds in the bedding structures have been interpreted as disturbance by glacial shear.

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