Investigation of impact forces on pipeline by submarine landslide using material point method

Quantitative assessment of impact forces by submarine landslide is significant for the safe operation of pipelines that must cross potential runout paths. In this paper, the transient process of a submarine landslide impacting a pipeline is modelled using the material point method (MPM) with an enhanced contact algorithm. For simplicity, the partially-embedded pipeline is assumed to be fixed in space. The Herschel-Bulkley rheological model is incorporated to reflect the dependence of the undrained shear strength of the sliding mass on the shear strain rate. The behaviour of the mass flowing over the pipe was reproduced by allowing separation between the pipe and the sliding mass. The horizontal impact forces predicted by the MPM are verified by comparison with those estimated using a computational fluid dynamics approach. The impact forces are interpreted with a hybrid model considering the combined effects due to the soil's inertia, its shear strength, and also the asymmetric static pressure of the sliding material. The coefficients for the three terms are retrieved by a best-fit to the results of an extensive parametric study. The effect of the projected height of the pipe above the seabed is also investigated.