Scour protection test for submarine pipelines under alternating tidal current

Many oil and gas pipelines have to be laid on the seabed during the deep development of marine oil and gas resources, but the submarine pipeline suspension due to souring under marine hydrodynamic conditions is the important factor that leads to the vortex-induced vibration failure of pipelines. In terms of the poor adaptability of the existing sour protection measures to the submarine pipelines in strong tidal area, a scale physical model test was performed with a bidirectional water channel based on a submarine pipeline in the strong tidal area of Hangzhou Bay. Meanwhile, research was conducted on the sour protection effect of artificial grass for submarine pipelines under alternating tidal current conditions. The test results indicate that the local scour depth of submarine pipelines decreases with the increasing of the density and coverage width of artificial grass. When the coverage width increases to the critical value, the sour depth is reduced to be zero. By fitting the experimental data with the multiple regression fitting method, the relational expression of the density and critical width of artificial grass can be obtained. The research results could provide reference for the design and implementation of sour protection measures for submarine pipelines in strong tidal area.