Anisotropy of Sea Ice Strength Characteristics In the Okhotsk Sea

Sea ice is characterized by strength anisotropy as a function of load application mode which may be normal (┴) or parallel (||) to the freezing plane. This problem was addressed in a number of papers (Frederking and Timco, 1984). Anisotropy coefficient, k_R introduced by the Moscow Construction Engineering Institute (MISI) is obtained as: where R= is the mean value of ultimate uniaxial compressive strength of ice when load direction is normal to the freezing plane and R': is that when load direction is parallel to the freezing plane (MISI Report, 1992). Note that the introduction of anisotropy coefficient involves a number of issues opened to argument. It is known from the law of probability that the ratio of mean values is not the mean value in itself (as opposed to the production of mean values), i.e. k_R may be a measure of the mean value but the error of the measure will be unknown. Furthermore, the mean value depends substantially on the number of tests, which is not taken into account in the expression (I). However, anisotropy coefficient was used by MISI and estimated based on a number of data used by some authors involved in anisotropy studies. It varied from 1.04–2.0 (MISI Report, 1992). Anisotropy coefficient was estimated as k_R =1.39 during the expedition on the icebreaker "Yermak" in the sea of Okhotsk in 1982 (Report on Expedition... 1982). Institute "SakhalinNIPImorneft" performed ice studies in the Chayvo Bay also using anisotropy coefficient (Polomoshnov, 1990; Polomoshnov et al, 1992). However, no reliable results were obtained: anisotropy coefficient was either over or below 1. Note that the majority of ice strength tests were performed on samples cut out normal to the freezing plane, therefore, knowledge of ice strength anisotropy is required adequate evaluation of the results obtained and substantiation