Author(s): Knut V. Hoyland
Linked Author(s): Knut Hoyland
Keywords: No Keywords
Abstract: Ice ridges are vital ice features and have important implications for engineering activities in icy waters. The forces at play when an ice ridge hits a ship, a moored or fixed structure often give the design quasi-static environmental action, and a realistic estimation of these forces is important to make safe and sound solutions. Before any design can be decided, the ice ridges in an area need to be characterized in a sufficiently accurate manner, and the first important distinction is that between first-year- and old ridges. Old ridges are believed to be completely consolidated and considerably stronger so they are assumed to give higher forces. The ridge geometry is important input and the most important parameter is the keel depth. Keel depths up to 50 m have been measured in the central Arctic, but a 100 year ridge in the Fram Strait has been estimated to 37to 41 m. For first-year ridges the thickness of the consolidated layer is essential and a good conservative estimate is 2-2.5 times the level ice thickness. The mechanical properties of the solid parts of ice ridges (the consolidated layer and old ridges) are assumed to be close to those of level ice (though no measurements have been done deep down in old ridges). One may use simple analytical models, advanced discretized numerical models or scale-model experiments to estimate the ridge action on structures. All three methods have weaknesses and a designer should not rely on only one of these.
Year: 2014