Ice-structure interaction in shallow water - A study based on laboratory-scale experiments and discrete element simulations

• Published in: Cold Regions Science and Technology
• Main Author: Lemström, Ida
• Other Authors: Tuhkuri, Jukka, Prof., Aalto University, Finland, Insinööritieteiden korkeakoulu, School of Engineering, Konetekniikan laitos, Department of Mechanical Engineering, Polojärvi, Arttu, Asst. prof., Aalto University, Department of Mechanical Engineering, Finland, Solid Mechanics, Aalto-yliopisto, Aalto University
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: Aalto University 2022
• Subjects: Marine engineering; Mechanical engineering; ice-structure interaction; ice mechanics; offshore structures; model-scale experiments; finite-discrete element method; ice loads; ice load distribution; jää-rakenne vuorovaikutus; jäämekaniikka; arktiset merirakenteet; jäämallikokeet; diskreettielementtimenetelmä; jääkuormat; painejakauma; Arctic; Arktis*; Global warming; Ice Sheet; Sea ice
• Online Access: https://aaltodoc.aalto.fi/handle/123456789/113089

The global warming and retreating sea ice cover open up new transportation routes and offer new opportunities for exploratory activities in the Arctic regions. The increasing levels of marine activities in these regions constantly increase the demand for offshore structures in ice-covered sea areas. Optimizing the design of offshore structures still requires new engineering insight on ice-induced loads and the mechanics of ice-structure interaction. During an ice-structure interaction process, ice is drifting against a structure and failing into ice blocks, which form an ice rubble pile. This process may subject the structure to high ice loads. Many offshore structures operate in shallow water, meaning that the rubble pile may ground, which affects the further ice loading process. This thesis studies the ice-structure interaction against a wide, sloping structure in shallow water. The work consists of model-scale experiments and full-scale numerical simulations. The model-scale experiments were performed in the Aalto Ice Tank by pushing an ice sheet against a ten-meter-wide, inclined, structure in shallow water. The structure consisted of ten identical segments and the loads measured on the structure were analysed in different resolutions. The experiments were conducted in three tests series with varying ice strength. The novelty within the experiments was in the very wide structure and the segmentation of the structure. The ice loading process in the experiments showed two distinct phases: the load on the structure (1) first increased linearly with a rate of increase depending on the ice mass above waterline, after which (2) a steady-state phase with an approximately constant load level was reached. The experiments also showed that the magnitude of ice loads was not directly proportional to the ice strength, as the weakest ice yielded higher loads than the ice having twice its strength. The loads on the individual segments correlated strongly on the level of the entire interaction process, suggesting that the ...