A dislocation-based analysis of the creep of granular ice: Preliminary experiments and modeling

Abstract

The nature f fal-off at lower stress from power law behavior to a lower-order stress dependency is of particular interest in glacier and ice-sheet modeling Preliminary experiments show that the stress level of which the fall-off occurs is a function of the specimens dislocation density. The analysis employs a dislocation anelasticity that provvides a quantitative relationship between the effective dislocation density and the area of hysteresis loops observe in cyclic loading experiments. Combining the technique with a stage creep experiments makes it possible to calculate the dislocation density as a function of strain, therby supporting a quantitative dislocation associated with power-law behavior increased as a result of prior straining power-law behavior emerged when the effective dislocation density increased measurably during deformation and approximately linear behavior was evident when the dislocatin density remained relatively constant. Those findings motivated the experiments on fresh-water ice presented here. The preliminary experiments show that pre-straining increases the stress associated with the fall-off from power law behavior, and their results are interpreted in the context of a dislocation-based constitutive model develop for sea ice. © International Glaciological Society.