Samples of natural sea ice obtained from shorefast ice were loaded in compression, in the horizontal direction, both parallel and perpendicular to the C-axis, at a constant strain rate of 10−3 sec−1. The average compressive strength parallel to the C-axis was 7.23 MPa at -10 °c and 6.77 MPa at -20°C. This is in fair agreement with published values; the smaller strength at -20 °c is attributed to the formation of internal microcracks upon thawing of the sodium chloride dihydrate in the brine inclusions, and the annealing of the microcracks prior to testing at the higher temperature.
The natural ice sheet, moving against offshore structures, can fail in several modes, including compression, bending, buckling, and splitting. In most of these failures, part of the ice sheet will be in compression as the forces on the offshore structure are increasing, and it is possible that a compressive failure in the ice sheet will affect the maximum value of the force on the structure for that particular failure mode. It is therefore of interest to consider the compressive strength of ice taken from a natural sea ice sheet in the horizontal direction.
Earlier research on the compressive strength of oriented sea ice, in both vertical loading and horizontal loading (both parallel to the C-axis and perpendicular to the C-axis) has been rather extensive. The early work of Peyton (1966) was with samples of natural sea ice extracted from the natural ice sheet at Barrow, Alaska. Subsequent research by Hausler (1981), Nawwar et. al (1983), Kuehn and Schulson (1994), and others was with artificial sea ice grown in a tank in a cold laboratory. Laboratory ice has randomly-oriented horizontal C-axes in the middle and lower regions of the ice. Thus those results are based upon saline ice which was not directly comparable with the natural sea ice tested in our program. Peyton (1966).
