A Moored Arctic Floater in First-Year Sea Ice Ridges

Abstract

First-year sea ice ridges are a major concern for structures operating in the Arctic offshore and will in many cases give the design mooring load. In this paper, the response of a moored conical floater, somewhat similar to the well-known Kulluk, is studied in first-year ridges. The study is based on model tests performed at Hamburg Ship Model Basin (HSVA) in several ridges with different properties. Mooring forces and floater response, resulting from interaction with different ridges, were compared with respect to ridge properties, ridge behavior, and simulated ice management. Clearance of accumulated rubble upstream the structure was the dominating physical process in the ridge–structure interaction. Accumulation of rubble caused large mooring forces. The amount of accumulated rubble depended on the ridge cross-sectional area, thus the mooring forces increased with ridge cross-sectional area. Large mooring forces were also experienced after the ridge was passed by the structure due to difficulties with clearing of accumulated rubble.

Development of environmental contours for first-year ice ridge statistics

“…A ship can break through sea ice ridges either continuously or by ramming, which depends on the ridge breaking energy, propulsive energy and kinetic energy of the vessel. Additionally, model tests performed at HSVA for a moored slope structure have confirmed the common knowledge that ice loads due to ice ridges are significantly higher than loads caused by the surrounding level ice (Dalane et al, 2015). Furthermore, field experiments performed on ships (or slope structures)…”

On Characteristics of Ice Ridges and Icebergs for Design of Ship Hulls in Polar Regions Based on Environmental Design Contours

“…The type of interaction depends on the ridge breaking energy, and the propulsive and the kinetic energy of the ship. Model tests that were carried out at HSVA for a moored floater having a sloping surface have confirmed that ridge ice loads are significantly higher than the loads due to the adjacent level ice [35]. Field experiments related to ship hulls interacting with first-year ridges have also been reported, e.g., [36][37][38].…”

Morphology, internal structure and formation of ice ridges in the sea around Svalbard

“…Regarding the variations in keel shape, the keel area could provide better information on the keel size (Obert and Brown, 2011), rather than only considering ridge heights. Dalane et al (2015) showed in a series of ice-tank measurements on ridge-structure interaction that forces from unmanaged ridges increased almost linearly with increased ridge cross-sectional area, giving that ridge parameter a major importance. The present ridge areas are listed in Table 2 for both, sail, keel and consolidated part.…”