Ice crystallographic and strain rate changes with strain in compression and extension

Abstract

Uniaxial compression tests were performed on a series of laboratory-prepared ice samples. The samples initially consisted of randomly-oriented crystals. Each test was carried out under, as near as practicable, the same experimental conditions. The temperature for all tests was −3.0°C and the octahedral shear stress was 2.0 bar. Tests were stopped after different amounts of total strain, thin sections cut, and the ensuing crystal fabric examined. It was found that, between 0.8% and 8% octahedral shear strain, a small circle girdle fabric developed around the compression axis, and that the “strength” of the fabric increased along with a decrease in the girdle half-angle, until a total octahedral shear strain of 32.5%. In extension however, it was found that the girdle half-angle increased with increasing strain. Crystal sizes through the experiments were also monitored and were found to change systematically. The octahedral shear strain rate, after attaining a minimum of approximately 2 × 10 −8 s −1 at 0.8% octahedral shear strain, had increased to approximately 6 × 10 −8 s −1 by 8% strain, and maintained this value thereafter.