The effect of confinement on the brittle compressive fracture of ice

Granular, fresh-water ice was deformed at −40°C at 10 −3 s −1 under confinement. Loading was applied such that confining stress, σ 2 and σ 3 , were equal to each other and proportional to the highest stress, σ 1 ; i.e. σ 2 = σ 3 = R σ1 . Two regimes were evident. At lower confinement, the fracture stress, σ 1f , increases markedly as R increases. At higher confinement, σ 1f increases less sharply. The transition occurs at about R = 0.15. Wing cracks were seen in the ice fractured within the low- R regime. The data are analyzed in terms of the frictional crack sliding-wing crack mechanism of brittle compressive fracture.