Structuration in natural clays, dredged sediments, and oil sands tailings

ABSTRACT: Though creep in clays has received considerable attention in the literature, with several mature semi-empirical models available to practitioners, structuration (or restructuration) has received less attention. Structuration refers to the increase in apparent pre-consolidation pressure in clays that occurs over time without the application of mechanical load, and is often reversible through shearing and recoverable over time. While the difference in structured intact clays and remoulded clays is widely studied, the rate of structuration (or restructuration) less so. From a conventional geotechnical prospective, this makes sense as practitioners are usually faced with predicting settlement in intact undisturbed clays, and how or at what rate the clays achieved their in-situ properties is less important. By contrast, however, in the oil sands industry, where deep deposits of clay dominated tailings are being contemplated, and the performance of such deposits depends on their consolidation, the rate of structuration, if such a phenomenon exists, may substantially affect magnitudes of expected strength gain and settlement. This paper reports on ongoing experiment and numerical studies of structuration in Leda clay and in-line flocculated oil sands tailings, and proposes a preliminary model to describe the rate of structuration in these materials.