Dynamic response of pipelines buried in clay-over-sand sloping seabed under wave loading

Pipelines are frequently embedded in layered sloping liquefiable seabed. This study proposed a dynamic effective stress numerical model for buried pipelines in the clay-over-sand sloping seabed under wave loading. The u-p formulation of Biot's theory was used to describe the porous saturated seabed. The elastoplasticity of clay was determined by Mohr-Coulomb yield criterion. The liquefaction characteristics of sands was modeled by a bounding surface plasticity constitutive model. The proposed model was validated through a wave flume model test and can capture the influence of pipelines on the excess pore water pressure (EPWP) in the liquefiable seabed. The pipeline-soil interaction can significantly increase the EPWP ratio at the bottom of the pipeline under wave action. The rate of increase in the EPWP ratio at the bottom of pipelines increased as the thickness (h_c) of upper clay layer increased. Increasing h_c caused a significant increase in the settlement of pipelines in the flat seabed and the horizontal displacement of pipelines in the sloping seabed. The study also highlights the significance of considering the slope angle, the relative density of sands, and the specific gravity of pipelines.