ANALYSIS OF VISUAL DATA FROM MEDIUM-SCALE INDENTATION EXPERIMENTS AT HOBSONS-CHOICE ICE ISLAND

Medium scale ice indentation experiments were performed at Hobson's Ch oice Ice Island using an indentor outfitted with a window and video ca mera so that the ice behavior could be observed in situ. The video ima ges revealed high pressure zones of relatively intact ice, surrounded by crushed ice, that bore most of the load. The load data exhibited a sawtooth pattern which the video records showed was due to spalling of ice away from the contact area. This determined the shape of the high pressure zones. All damage to the ice, and actual movement of the ind entor into the ice, occurred during the sharp drops in the sawtooth lo ad data. Pressures in the high pressure zones, determined from the vis ual records and load data, agreed with the highest pressures measured by sensors on the indentor face (40 to 60 MPa range). (C) 1998 Elsevie r Science B.V. All rights reserved.