Author(s): Nina Krupina; Alexey Chernov; Vladimir Likhomanov; Pavel Nickolayev; Evgeny Shakhov
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Abstract: In 2006–2007 AARI performed works according to grant RFFI № 06-08-01288 “Research on failure criteria and fracture resistance of ice at complex laboratory loading”. The experiments took place in a big ice tank of AARI capable for obtaining ice of the given properties. Tank water salinity was about 15‰. Air temperature above the ice tank was maintained at the level of –15°С. As a result, lab ice of natural freezing with thickness of 45 cm analogous to the in-situ ice was made. If accounting that temperature regime in the laboratory is rather stable and it completely lacks solar radiation and snow effect the tank-frozen ice becomes more homogenous than the in-situ ice, i. e. the ideal (pattern) conditions for experiments are created. Uniaxial compression tests were conducted on cylindrical samples of 250 mm height and 142 mm diameter taken both perpendicular and parallel to the ice surface. Transverse sizes of samples were at least one order larger than the sizes of ice crystals. The load was applied along the samples’ axis. The total amount of test samples comprised 398. During each experiment timesample force and time-sample strain dependencies were fixed. Primary processing of the test data included plotting of strain-stress diagrams for each specimen which were normalized by maximum values for each sample. The high degree of non-linearity of obtained diagrams was identified. Statistic processing showed that strain-stress diagrams for sea ice can be approximated with high accuracy by an exponential function, whereas distribution of values of power parameters follows the log-normal law. For more detailed analysis a finite element model of sample loading with account of physical and mechanical ice properties was developed. The obtained results of numerical modeling were used for comparison of the calculated model of strain-stress state and the real failure. Based on comparison an attempt to work out ice failure criteria depending on the sample loading rate and ice temperature was made.
Year: 2008