Analysis and Design of Buried Pipelines for Ice Gouging Hazard: A Probabilistic Approach

Abstract

In cold environments, marine pipelines may be at risk from ice keels that gouge the seabed. Large quantities of material are displaced and soil deformations beneath a gouge may be substantial. To meet safety criteria, excessive strains are avoided by burying pipelines to a sufficient depth. In this paper, a probabilistic approach for the analysis and design of buried pipelines is outlined. Environmental actions are applied through distributions of gouge width, gouge depth, subgouge soil deformations, and bearing pressure. Three-dimensional pipe/soil interaction problem is modeled using nonlinear soil springs and special beam elements using the finite element method to estimate pipe response for statistically possible ranges of gouge depths, gouge widths, and burial depths. Relevant failure mechanisms have been considered, including local buckling and a variety of strain and stress based criteria. The methodology presented in the paper was developed and successfully used for several pipeline and electrical cable projects in ice gouge environments. Significantly reduced burial depth requirements have been demonstrated through the application of the probabilistic approach and through the use of strain-based design criteria. Because ice actions are applied through displacements of the soil, more ductile pipes are often necessary to meet reliability targets.