PHYSICAL AND MECHANICAL-PROPERTIES OF HOBSONS-CHOICE ICE ISLAND CORES

Arctic ice islands occasionally drift into the Alaskan Beaufort Sea where because of their size, thickness and longevity, they could impose a serious ice load concern for future production facilities operating in these waters. An understanding of ice island physical properties and mechanical behavior is useful to improve ice force estimates and to develop defense measures that could reduce the forces these features exert on structures. Towards this end, vertical ice cores, the longest of which was 42 m, were retrieved from Hobson's Choice Ice Island and machined into samples for constant strain rate uniaxial compression tests. Presented herein are descriptions of the ice core retrieval and the ensuing laboratory tests as well as discussion of the results. A total of 126 tests were performed over a suite of strain rates from 10(-2) to 10(-6) s-1 and at temperatures of -15, -10, -5 and -2-degrees-C. The highest strengths were measured at a strain rate of 10(-4) s-1 whereas the lowest strengths were associated with tests conducted at 10(-6) s-1. A strong strength dependence on temperature was identified at intermediate and high strain rates where the mean strength decreased about 60% over the temperature range evaluated. When tested under the same temperature and strain rate conditions, the ice near the bottom of the ice island was stronger than that near the top.