Numerical Study on Wave-induced Oscillatory Soil Liquefaction around a Partially Buried Pipeline

To examine the oscillatory soil response around a partially buried pipeline under wave load, a numerical model for wave-seabed-pipeline interactions was proposed using the finite element method, in which the momentum source function was added to the Reynolds-averaged Navier-Stokes (RANS) equation to generate waves, and the Level Set Method was used to track the water free surface. The wave pressure calculated from the wave model was applied to be the seabed model boundary condition to determine the wave-induced soil response. Based on the proposed model, a set of analyses regarding the effects of backfill thickness and wave characteristics on the oscillatory soil response was carried out. Numerical results indicate that wave characteristics can significantly affect the wave-induced oscillatory soil response, and that the liquefaction depth increases with the increment of wave height and period. The liquefaction depth at the bottom of the pipeline can reach 0.92 m when the wave height is 3 m and the wave period is 10 s. Moreover, the soil at the bottom of the pipeline can be prevented from being liquefied when the backfill thickness is greater than the critical backfill thickness under a certain soil condition. In other words, the soil at the bottom of the pipeline can be protected by increasing the backfill thickness.