Oxide minerals in the sensitive post-glacial marine clays

Abstract

Oxide minerals increase the undisturbed and remoulded strengths of the sensitive marine clays. In Eastern Canada, the oxide mineral contents of sensitive post-glacial marine sediments are greatest in the near-surface, where weathering has occurred, and decrease to an approximately constant value (in the order of 1%) where unweathered. In these marine clays, crystalline hematite or magnetite dominate the iron oxide content, with little, if any, ferrihydrite. The total amorphous mineral content is very low. In Japanese quick clays, in which the minerals are of volcanic origin, ferrihydrite is the dominant iron oxide and total amorphous mineral content is not known. In order for the small quantity of oxide minerals present in the Canadian sensitive marine clays to have measurable effects on undisturbed behaviour, they must be concentrated at points of contact between silicate minerals. Their influence on remoulded behaviour must be the result of their decreasing the electrostatic repulsion between particles, thereby increasing the probability of flocculation. The imperfect mimicking of the natural processes complicates the interpretation of experiments in which oxide minerals are added and problems with the selectivity of chemical extractants complicate the interpretation of experiments in which oxide minerals are removed.