SIIBED: Development of Numerical Models for Ice Loads on a Subsea Pipeline

Abstract

When designing subsea pipelines, flowlines or cables to traverse shallow offshore regions with icebergs, iceberg keel interactions may be of concern. Given sufficiently low contact rates, the possibility of laying the pipe or cable on the seabed without burial may be an option. Consideration is then needed regarding possible denting, buckling, or lateral forces which can result in high axial tensions. In previous analyses of keel interactions, the ice keels have been treated as rigid, under the assumption that the ice strength is significantly higher than the soil strength. Recent studies have shown that under rapid loading, soil resistance can be significantly higher than previously considered, while conservatisms in estimates of ice strength have been reduced over time. As a result, ice-pipe-soil interactions are being reassessed as part of a study "SIIBED: Subsea Ice Interaction Barriers to Energy Development" (Ralph et al., 2023). This paper discusses background and progress on one component of that study, the development of improved ice strength inputs for an overall ice-pipe-soil finite element model (Barrett et al., 2023). The paper includes a review of relevant literature and describes the use of different finite-element (FEA) techniques to better understand relevant ice failure processes. Calibration of the models is largely based on the results of a medium-scale test program using a novel test frame, RHITA (Rapid-High-capacity-Impact-Testing-Apparatus), which was designed and built especially for the project.