Interpretation and modelling of deformation characteristics of a stiff North Sea clay

An investigation into the behaviour of North Sea glaciomarine clays was carried out in which triaxial tests were conducted on both natural and reconstituted samples to assess the effects of structure. Although the tests were conventional CID tests, high quality instrumentation was used. The tests were also technically difficult both because of the very long test durations and because some of the samples were swelled back to very low effective stresses so that the effect of swelling on the influence of structure on the soil behaviour could be assessed. A "Class A" prediction of the behaviour in these tests was carried out using the BRICK model. Although the model is not designed to account for the influence of structure, it was found that its effects could be simulated by allowing the soil to have artificially high overconsolidation ratios (OCRs) so that the high undrained shear strengths resulting from structure could be modelled. Making the simple assumption that the decay of stiffness could be scaled from that of London Clay, reasonable predictions of the behaviour were made. The discrepancies between the predictions and the measured behaviour became significant only at the lowest stresses, where structure dominates the behaviour of the natural soil. © 2006 NRC Canada.