Huisman Equipment B.V. has developed an Arctic drilling unit, which has three main operating modes. The 'Huisman Arctic Drilling Unit' can operate in open water as a conventional semi-submersible unit and also in ice conditions afloat. In addition to floating operating modes, the unit is foreseen to be placed as Gravity-Based-Structure (GBS) in offshore arctic conditions. As a GBS the Unit is designed for drilling activities in water depths typically ranging from 12 to 30 m. Witteveen+Bos has performed a pre FEED foundation study for the GBS. The study consists of stability analysis for certain soil conditions and load combinations. The aim of the study is the identification of the ultimate capacity envelopes in terms of combined vertical, horizontal and overturning loads. The vertical foundation load is related to water depth, with some variation due to variable loads from topsides, operation and ballast weight. Horizontal loads are dominated by interaction of the structure with drifting ice.
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