Ice keel-seabed-pipeline interaction simulation: Ice Pipe IIP extracts

摘要

Ice gouging or iceberg grounding is a major subsea pipeline safety concern in the Arctic regions. Iceberg (keel) grounding can cause large soil movements around a buried pipeline inducing high stresses and strains from excessive deformation and severely affecting pipeline integrity. Current industry knowledge of the ice-seabed-pipeline interactions during gouging is limited. Primary reason for this lack is the modelling difficulty of the severe soil deformation associated with any ice-gouging event by conventional numerical techniques. While the Arctic subsea pipelines are buried in the seabed to avoid direct contact with the gouging ice, insufficient burial depth can cause unacceptable levels of deformation transfer to the pipeline from the surrounding subgouge soil movements while,on the other hand,the burial depth can be over-conservatively deep.Therefore, an accurate simulation of subgouge soil displacements below the mudline is critical for appropriate burial design that is safe and also economic. Coupled Eulerian-Lagrangian (CEL) finite-element analysis (FEA) demonstrates great potential for realistic ice-gouging simulations with its ability to model severe material deformations without the routine convergence issues resulting from mesh distortions in the more traditional Lagrange-based numerical techniques. This article presents extracts from a study performed by J P Kenny and MCS Kenny within a subtask of the recently completed Ice Pipe joint-industry project steered by the DNV (and also presented in the first Arctic international conference [I]).The goal of the study was to investigate and verify the capabilities of the CEL technique in ABAQUS / Explicit [2] in simulating ice-gouging events vis-a-vis other available numerical techniques, such asAEL (Adaptive Eulerian-Lagrangian, used by other JIP participants).A number of ice-gouging events with preselected values for the various governing gouging parameters were simulated using ABAQUS CEL-FEA.