Accumulated Pore Pressures around Submarine Pipeline Buried in Trench Layer with Partial Backfills

The evaluation of seabed response around an offshore pipeline has been studied since the 1980s. Most previous investigations considered full backfilled conditions. However, partial backfill is normally used in engineering practice, rather than full backfill. In this study, a two-dimensional (2D) integrated numerical model (PORO-WSSI-PIPE) is proposed to investigate the wave-induced residual liquefaction in a seabed around a partially backfilled trenched pipeline. The present model is validated through the comparison with previous laboratory experiments to ensure its accuracy and effectiveness. Sensitivity analysis indicates that the thickness of backfills significantly affects the wave-induced pore pressure around a trenched pipeline, and liquefaction may occur in the underlying trench layer with shallow backfill under large waves and in shallow water. Based on the numerical examples, a simplified approximation for the design of the thickness of backfills (Hb) with given wave and soil parameters is suggested for engineering practice, in which the pipeline can be prevented from seabed liquefaction.