Microcracking and shear fracture in ice

Abstract

The relationship between microcracking and ice Strength has been examined using triaxial apparatus in which track damage can be inhibited by the imposition of confining pressure. Shear fracture in ice is observed to be a rapid, unstable process with no apparent indication of tensile crack localisation or interaction prior to failure and no accompanying large-scale volumetric changes, at least to within 1 ms of the occurrence of macroscopic failure. Shear fracture strength displays little or no dependence on confinement at moderate pressures (P = 5–20MPa), and there is no evidence of significant crack sliding before macroscopic fracture under these conditions. Where flow with distributed microcracking occurs, yield strength can also remain remarkably unaffected by confining pressure, despite reduced crack damage. Particularly under conditions where microcracks are induced by predominantly elastic strains, they may remain stable and non-interacting even at high volumetric densities.