Shear faulting and localized heating in ice: The influence of confinement

摘要

Systematic experiments on laboratory-grown polycrystalline granular ice and columnar S2 ice loaded triaxially at -10 ℃ at a strainrate ε_(11)= 2.2 × 10~(-2)s~(-1)under increasing levels of confinement have established two distinct modes of brittle-like shear faulting. Onemode, termed Coulombic (C) or frictional faulting, develops under lower degrees of confinement and is characterized by macroscopicfaults, comprising a narrow band of microcracks, oriented ～30° from the direction of maximum shortening; and by pressure hardening,grain-size-dependent strength, localized heat production and the creation of fault gouge. The second mode of faulting, termed plastic (P) or non-frictional faulting, develops under higher degrees of confinement and is characterized by macroscopic faults, comprising a fineband of recrystallized grains, oriented ～45° to the direction of maximum shortening; and by pressure and grain-size-independentstrength and localized heat production. The transition from C-faulting to P-faulting corresponds to the level of confinement requiredto suppress frictional sliding.