A Multi-Scale Study on the Consolidation and Freeze-Bonding of Thick Sea Ice Features in the Arctic
Over recent decades, there has been a continuing rise in commercial interest in the Arctic and its natural resources. Thick sea ice features, such as ridge keels and rafted ice, can generate some of the highest loads encountered by an offshore structure or marine vessel operating in the Arctic. Two...
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| Format: | Doctoral or Postdoctoral Thesis |
| Language: | English |
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UCL (University College London)
2021
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| Online Access: | https://discovery.ucl.ac.uk/id/eprint/10139070/1/Shortt_10139070_Thesis_redacted.pdf https://discovery.ucl.ac.uk/id/eprint/10139070/ |
| Summary: | Over recent decades, there has been a continuing rise in commercial interest in the Arctic and its natural resources. Thick sea ice features, such as ridge keels and rafted ice, can generate some of the highest loads encountered by an offshore structure or marine vessel operating in the Arctic. Two important but closely associated properties that govern their initial strength are the degree of consolidation and the ice freeze-bond strength which are highly sensitive to a number of parameters, including space and time, the physical properties of the ice, the local meteorological and oceanographic conditions, and the loading conditions encountered. This thesis has focused on developing the understanding of the thermodynamics of consolidation, and the resultant mechanical properties of the freeze-bonds that form as a function of these parameters. Experiments have been undertaken from the micro-scale up to the metre-scale under both controlled laboratory and ice tank conditions, and Arctic field conditions. Results show that sea ice undergoing consolidation in the field is strongly influenced by the presence of oceanic heat fluxes, which acts to diverge the thermodynamic behaviour away from what is observed in the laboratory and ice tank. The shear freeze-bond strength also shows strong angular dependency, and under a significant degree of misorientation will approach the strength of level ice and samples instead fail in compression. This is significant as it indicates that there may be large local variations in the strength of a ridge keel due to geometry alone. Mechanical tests on the millimetre-scale conducted in-situ under a scanning electron microscope (SEM) have revealed that both solid and freeze-bonded ice exhibit the same failure modes that are typically observed on the centimetre-scale. The strength of solid ice and freeze-bonds at this scale also appears to be similar to what has been previously observed on larger scales. |
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