A comparison using two numerical approaches for modelling the impact of submarine landslides on suspended pipelines

ABSTRACT: Submarine landslides could pose a significant threat to as-laid offshore pipelines. In the present study, numerical modelling is performed to study the impact of a clay block, which could be originated from a submarine landslide, on suspended pipelines in deep water environments. Two numerical approaches are used. In the coupled Eulerian–Lagrangian (CEL) approach in Abaqus FE software, the soil is modelled using the undrained shear strength of clay (su). In the computational fluid dynamics (CFD) approach of ANSYS CFX, the soft clay debris is modelled as a non-Newtonian fluid. In both approaches, the ‘free water’ (different from pore water) is modelled explicitly. Analyses are also performed without modelling the free water. It is shown that the free water in the cavity that forms behind the pipe during the flow of soil around it plays a significant role in the drag force. The developed numerical approaches in CEL and CFX can model the process of landslide impact; however, the CFX modelling is computationally efficient compared to the simulations with Abaqus CEL.