Numerical Simulation of Ice Ridge Gouging

Abstract

In coastal regions throughout the Arctic, the seabed is frequently scoured or gouged by sea ice ridges and icebergs. This presents an environmental hazard to pipelines or subsea infrastructures operating in the area and therefore a greater understanding of these processes is needed. This paper describes a three dimensional (3D), numerical model that was developed to simulate the failure behavior of a ridge keel as it interacts with the seabed. The simulation was conducted in Yade, an open-source code, which uses the Discrete Element Method (DEM) to model particle motions. The ice blocks in the ridge keel are modeled as spheres, which are initially bonded to contacting blocks via freeze-bonds. A Cohesive Frictional Model (CFM) which has cohesive bonds in tension and shear was used to simulate the freeze-bonds between ice blocks. In addition to normal and shear bonds, the model features springs which resist compression, shear, bending and torsion. Once the bonds are broken the material is assumed to behave like a Mohr-Coulomb material with a constant friction angle. Since the main focus of this paper is the failure behavior of the keel, the seabed is simplified as being rigid. Numerical simulation is compared with data collected from the Pipeline Ice risk Assessment and Mitigation (PIRAM) test program.