The influence of pipeline-backfill-trench interaction on pipeline response to ice gouging: a numerical investigation

Ice gouging is a destructive incident to subsea pipelines in Arctic regions. Trenching and backfilling is a cost-effective solution to physically protect the pipeline against ice gouging. Ice gouging imposes a complex combination of stresses and strains through the soil medium, the pipeline, and the interface. Remolded backfill materials with considerably less stiffness than native soil result in more complexity in soil failure mechanisms and pipe trajectories. However, this critical aspect is less explored in the literature on ice gouges. This paper investigated the influences of pipeline-backfill-trench interaction on the soil failure mechanisms and the pipeline responses by coupled Eulerian-Lagrangian method. Two model configurations (shallowly buried and deeply buried pipeline) were set up to investigate the influence of trenching/backfilling, as well as pipe burial depth. Incorporation of the strain rate dependency and strain-softening effects in the soil constitutive model involved the development of a user-defined subroutine and incremental update of the undrained shear strength within the Abaqus software. The research findings indicate that the conventional approach of assuming uniform seabed soil for trenched and backfilled pipelines may not accurately capture the pipeline behavior and soil failure mechanisms.