The Peak Impact Force of Landslide-Induced Turbidity Current on Pipelines Above the Seabed

Abstract Submarine landslides pose significant risks to undersea pipelines and cables due to the intense impact forces generated by gravity-driven currents. This study examines the forces exerted by non-Boussinesq gravity currents generated by the sudden release of mudflow with a large density difference from its ambient to simulate the typical landslide conditions. Large-eddy simulations (LES) are performed for various landslide scenarios. The gravity current is produced by the sudden removal of a dam of height H and reservoir length L. The simulations determine the transient variations of the drag, lift, and total force coefficients on a cylinder above the seabed for reservoir length-to-height ratios L/H ranging from 0.125 to 5.93 and a density difference of (ρs - ρa)/ρa = 0.5 and 1. The results show the advancing front is a gravity current head connecting to the body of the current through a neck region where the velocity is greater than the frontal velocity. The impact force rises sharply upon the arrival of the gravity-current head, with a secondary peak observed in certain scenarios due to the passage of the greater velocity through the neck. For the release from a small reservoir, the peak impact force depends critically on the cylinder position associated with the maximum current through the neck. Conversely, with a sufficiently large volume of release, the impact force becomes insensitive to the cylinder’s position. We have determined the peak drag and lift coefficients, normalizing the forces by the gravity-driven pressure and correlated the coefficients’ values with the volume of the releases. These correlations of the impact force to the gravity-driven pressure and the size of the submarine landslide have provided a more precise evaluation of the landslides’ impact on the design and safety assessment of undersea pipelines and cables exposed to the gravity current.