BRITTLE FAILURE OF COLUMNAR SALINE ICE UNDER TRIAXIAL COMPRESSION

The brittle compressive failure of cubes of columnar saline ice was st udied under triaxial (proportional) loading where the ratio of normal stresses (sigma(11):sigma(22):sigma(33)) was varied in a systematic ma nner using a true multiaxial loading system. The strain rate in the di rection of the greatest applied compressive stress was 6 x 10(-3) s(-1 ) and the temperature was -10 degrees C. The failure surface is facete d and reveals three regimes: (1) of lower across-column confinement wh ere the along-column confinement has no significant effect on the majo r across-column stress at failure, but where the minor across-column s tress raises the strength; (2) of higher across-column confinement whe re along-column confinement now raises the major across-column stress at failure; and (3) of predominantly along-column loading where the al ong-column failure stress increases in proportion to the smaller of th e two across-column confining stresses. Each regime shows a high sensi tivity of strength to the appropriate confining stress. The behavior i s explained in terms of the frictional crack sliding-wing crack mechan ism of brittle compressive failure.