In situ thermal profiles and laboratory impact experiments on iceberg ice

A series of 40 impact tests was conducted on large right-circular cylinders (68.5 cm diameter and 25.7 cm thickness) of iceberg ice collected from an iceberg in Labrador. Temperature profiles were also obtained for the iceberg and the profiles exhibited differences associated with the probe location. Temperatures as low as -15 degrees C were measured at penetration depths of about 8 In. The impact specimens were confined at the perimeter and base by a rigid metallic ring and prate. A spherically terminated impactor, with center-mounted pressure transducer, was dropped on to the flat top surface of specimens from various heights and with various added masses. Impact velocity varied from 1.8 to 3.9 m s(-1); impactor mass varied from 155 to 510 kg and the ice-specimen temperature varied from -0.5 degrees to -14.5 degrees C. Peak center pressures averaged from about 25 MPa at the highest temperature to about 41 MPa at the lowest temperature, with the highest recorded pressure being 50 MPa. Crater volume increased with increasing impact energy, as expected; however, the specific energy of the ejected material was found to decrease as the energy of impact and crater volume increased. A mechanism for this observed behaviour is proposed.