IN-SITU THERMAL PROFILES AND LABORATORY IMPACT EXPERIMENTS ON ICEBERGICE

A series of 40 impact tests was conducted on large right-circular cyli nders (68.5 cm diameter and 25.7 cm thickness) of iceberg ice collecte d from an iceberg in Labrador. Temperature profiles were also obtained for the iceberg and the profiles exhibited differences associated wit h the probe location. Temperatures as low as -15 degrees C were measur ed at penetration depths of about 8 In. The impact specimens were conf ined at the perimeter and base by a rigid metallic ring and prate. A s pherically terminated impactor, with center-mounted pressure transduce r, was dropped on to the flat top surface of specimens from various he ights and with various added masses. Impact velocity varied from 1.8 t o 3.9 m s(-1); impactor mass varied from 155 to 510 kg and the ice-spe cimen temperature varied from -0.5 degrees to -14.5 degrees C. Peak ce nter pressures averaged from about 25 MPa at the highest temperature t o about 41 MPa at the lowest temperature, with the highest recorded pr essure being 50 MPa. Crater volume increased with increasing impact en ergy, as expected; however, the specific energy of the ejected materia l was found to decrease as the energy of impact and crater volume incr eased. A mechanism for this observed behaviour is proposed.