CHARACTERIZATION AND FLEXURAL STRENGTH OF ICEBERG AND GLACIER ICE

Flexural strength of iceberg and glacier ice was determined from four- point beam-bending experiments. A large quantity of glacial ice was co llected from four icebergs and one glacier, and a detailed ice-charact erization program was performed on samples from the five sources. Beam -bending experiments were conducted at four temperatures in the range -1 degrees to -16 degrees C and at strain rates of 10(-3) 10(-5) s(-1) . The flexural strength was found to increase with increasing strain r ate (based on extreme fibre strain) and decreasing temperature. The da ta suggest that air bubble inclusions play an important role in determ ining the flexural strength of glacial ice and this can explain the si gnificant differences in mean strength of the ice from the five source s. At a strain rate of 10(-3) s(-1) and temperature of -11 degrees C, the flexural strength was found to increase as the number of bubbles p er unit volume increased. Reduction of crack-initiating stresses at gr ain boundaries by ''softening'' of grains due to intragranular air-bub ble inclusions is thought to be the mechanism.