THE FAILURE OF FRESH-WATER GRANULAR-ICE UNDER MULTIAXIAL COMPRESSIVE LOADING

The failure of fresh-water granular ice under multiaxial compressive l oading was investigated at -10, -20 and -40 degrees C at 10(-3) s(-1), using a true multiaxial servo-hydraulic testing system. The tests wer e carried out on cubic samples proportionately loaded under different confinement ratios R = sigma(3)/sigma(1) = sigma(2)/sigma(1). Two regi mes were revealed at all three temperatures. Under lower confinement t he failure stress, sigma(1f), increases sharply with R, whereas at hig her confinement sigma(1f) is roughly constant. Both brittle and pseudo -ductile behavior were observed under lower confinement, depending upo n the confining stress and the temperature, while the behavior was bri ttle under higher confinement. An analysis of the brittle to pseudo-du ctile transition within the lower confinement regime was performed in terms of the frictional crack sliding/wing-crack mechanism. The high-c onfinement regime is characterized by intense intergranular damage. Th e final failure, however, is caused not by the linking of the uniforml y distributed microcracking, but by damage localized at the ice/platen interface. The saturation in the failure stress with increasing confi nement is attributed to a mechanism specific to the boundary condition s and not to the ice per se.