Liquefaction around a Buried Pipeline in a Backfilled Trench

Pipelines buried in the seabed have been used as one of the basic infrastructures in the oil and gas industry for many years. However, these infrastructures may face challenging hydro-geotechnical engineering problems, such as soil liquefaction, under cyclic loads caused by earthquakes or waves, especially when buried in loose and fine seabed soil. In this study, wave-induced residual liquefaction around a buried cylindrical structure (pipelines) in a backfilled trench is studied by means of a numerical model developed on the OpenFOAM (foam-extend 4.1) platform. First, the model is validated against experimental data from flume tests. Then, the model is used to parametrically study the effect of backfilled trench on liquefaction susceptibility of the seabed around the pipelines. The results, among others, show that the risk of wave-induced liquefaction around cylindrical structures increases significantly if loosely backfilled and low-permeability soil is used. The findings indicate that, for the backfill soil, a permeability greater than O(10^-5) m/s, combined with a medium-dense to dense state, significantly enhances resistance to wave-induced liquefaction around the pipeline.