Author(s): Vasiola Zhaka; Victoria Bonath; Bjørnar Sand; Andrzej Cwirzen

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Abstract: Winter navigation in the North Sea is expanding with respect to vessel size and traffic volume. Icebreakers create routes for ice-going vessels by breaking the level ice cover. Repeated vessel passages in the fairways and harbors initiate the formation of brash ice. The brash ice has the ability to refreeze quickly. In the current work, a field study was conducted on a refrozen brash ice ship channel located in Marjaniemi harbor in Bay of Bothnia. Aim of this study is to evaluate the structure and the strength of ice in the fully refrozen ship channel. Ship channel geometry, ice temperature and salinity were assessed in the field. The ice thickness was in average 45 cm covered by a snow layer with an average of 20 cm. The temperature profiles showed approximately -15ᴼC at the ice surface and close to 0ᴼC in the depths above 10 cm. Salinity varied from 0 to 1.5 ppt. Ice texture, density and compressive strength of refrozen brash ice were measured in the laboratory on 200 mm diameter cores. The behavior of refrozen brash ice with random ice texture was more ductile and stronger in uniaxial compression compared to the adjacent level ice.

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Year: 2020