Author(s): Anthony J. . Gow
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Keywords: No Keywords
Abstract: Standard petrographic techniques were used for studying microstructure in thin sections of urea ice sheets now being used extensively in the CRREL Test Basin for modeling sea ice. Depending mainly on the seeding techniques employed and partly on the thermal condition in the column of urea-doped water two kinds of ice with radically different structural and mechanical properties have been identified. In the one exhibiting vertical c-axis structure minimal urea is incorporated into the ice crystals, and ice sheets with this kind of structure tend to remain "strong" even after the temperature of the ice is raised close to its melting point. Ice of the second type is characterized by a preponderance of crystals exhibiting horizontal c-axes. This kind of ice, which is only produced when the test basin is seeded prior to freezing, also contains abundant inclusions of urea systematically incorporated into the crystals; the overall columnar structure of this ice closely resembles that of ordinary sea ice and optimum test conditions for modeling purposes are usually obtained with warm isothermal ice sheets of the latter type.
Year: 1984