Aged Undrained Shear Strength of Remolded Clays

Installation of offshore foundations and anchors in soft fine-grained soils often results in disturbance and full or partial remoulding of the soil. Design for rapid undrained loading often relies on the undrained shear strength which is appropriately the aged reconsolidated undrained shear strength; the aging period being defined as the time between foundation/anchor installation and loading. The gain in strength over time at constant water content is often termed thixotropy and is a complex mechanism. In the past, thixotropic strength gain in clays has been related to plasticity index however there is considerable scatter and plasticity alone does not accurately describe the thixotropic behavior. Results of laboratory tests conducted on several remolded soft clays using the fall cone are used to illustrate the influence of composition (mineralogy, clay content, CEC, SSA, plasticity) and soil state (liquidity index) on thixotropic behavior.