Changing soil strength and stiffness during pipe-soil interaction at the touch down zone

Steel catenary risers (SCRs) are pipelines widely used for transporting hydrocarbons from subsea fields to hosting vessels. The long-term fatigue life assessment of SCRs at the touchdown zone, where complex soil-fluid-structure interaction occurs, remains a significant challenge for designers. A key question generating considerable debate relates to the evolution of the cyclic soil stiffness and the associated competing effects of remoulding with those of consolidation. Centrifuge tests were performed to reveal the soil stiffness evolution under different loading regimes in overconsolidated sediments, which typically occurs in strong crusts of Gulf of Guinea, Gulf of Mexico, and North West Shelf.