The response of layered seabed to ice gouging: Sand over clay

Abstract

Travelling icebergs may threaten the structural integrity of the offshore pipelines in any territories they can reach. Arctic offshore pipelines are usually buried for physical protection against ice gouging. The safe and cost-effective burial depth of these pipelines needs to be determined by accurately assessing the subgouge soil deformation and the ice keel-seabed contact forces. Layered seabed soil strata found in many geographical locations add to the complexity of assessing the ice keel-seabed interaction process. The currently used design codes have been developed for uniform soil strata-an assumption that may affect the accuracy and cost-effectiveness of the design. In this study, the significance of layered sand over clay seabed in the ice gouging process was investigated by performing large deformation finite element (LDFE) analysis using Coupled Eulerian-Lagrangian (CEL) approach. A comprehensive parametric study was conducted to assess the influence of ice gouging characteristics and soil properties on the subgouge soil deformation, the developed plastic shear strains, and the resultant ice keel reaction forces. The results showed that the seabed response to ice gouging largely depends on the soil strata, where the layers’ interaction effects can alter the usual response expected from a uniform seabed.