Seabed Response Around a Partially Buried Pipeline Subjected to the Combined Ocean Waves and Currents Loads in a Trench Layer

Abstract The widespread co-existence of the wave and ocean currents is a common phenomenon in coastal environment, nevertheless, the relevant work for seabed response was primarily restricted to either wave-alone or waves and a following/opposing co-directional current conditions. Unlike the previous studies, the oblique currents, ranging from perpendicular incidence to parallel incidence, are considered in the present study for fluid-pipeline-seabed interactions, which might be claimed that a two-dimension simulation was no longer applicable. An integrated model is proposed to examine the soil behavior from a three dimension prospective, in which the RANS equation is applied to govern the fluid domain, while the Biot’s poro-elastic theory is employed for the solid domain description. Results show that a fully/partially-backfilled pipeline in a trench layer has a remarkable resistance to the seabed momentary liquefaction in comparison with one positioned on the seabed surface. Under the presence of the counter-current waves, the transient pore pressure would be strengthened, whereas the co-current waves would weaken the pore pressure oscillation. The momentary liquefaction depth surrounding the undersea pipeline increases with the declination in the obliquity between the waves and current. Moreover, as the backfill thickness reduce and trench gradient decline, the instantaneous instability of the subsea pipeline and its underlying seabed would be compromised.