The main objective of this paper is to investigate the wave-induced dynamic response of seabed around a pipeline in a multi-layered porous seabed. Biot's poro-elastic theory is employed to describe the phenomenon of wave-seabed-pipeline interaction in a layered porous seabed. To explore the mechanism of the pipeline instability, the partly dynamic model, u-p model is adopted, where the soil displacement (u) and the pore pressure (p) are the primary variables and it is capable of considering the acceleration of soil skeleton. A parametric study is carried out to examine the influences of various representative seabed and wave parameters. The influence of pipeline buried depth on seabed response is also investigated. The results show that the pore pressure decreases when permeability decreases. The pore pressure concentration reduces as the buried depth e increases, while the vertical stress on the pipeline surface increases as the buried depth increases.
The evaluation of wave-induced seabed response is one of the important factors in the design of offshore pipeline. When water waves propagate over a porous seabed, the dynamic wave pressure acting on the seabed surface will further induce excess pore pressure and effective stresses. When the pore pressure increases with accompanying decrease in effective stress, part of the seabed may become unstable or even liquefied. Then, the seabed around pipeline will become unstable and further cause the instability of the structure. Thus, it is important to accurately predict the dynamics and stability of such pipelines during the design phase. Many researchers have focused particularly on understanding the instability of an offshore pipeline subjected to wave loadings. However, this problem has not been fully understood because of the complicated soil behavior. There have been extensive studies on the modeling and analysis of the vibrations of pipeline systems over the past half-century.