Shock Transmission Through Ice and Snow

摘要

During the summer of 1963, twenty-six 32-pound and twenty-one 10-pound spherical TNT charges were detonated at depths varying from 9.5 feet below to 9.5 feet above the snow surface near Camp Century on the Greenland Ice Cap. Airblast pressure-time measurements were made to determine pressure loadings on the snow surface, and acceleration-time measurements were made to determine near-surface snow motion, particularly the late-arriving motion. Detonation of multiple shots on the same gage array caused compaction of the near-surface snow. The increase in snow density resulted in higher amplitude motions on succeeding shots. The shock wave generated by an explosive source at or above the snow surface attenuates very rapidly to a depth of 5 feet. Peak vertical downward accelerations from gages at a 2.0-foot depth of burial are three to four times greater than accelerations from gages at a 5.0-foot depth. Below a 5.0-foot depth the data indicate a much smaller decrease of peak vertical downward acceleration with depth. A typical acceleration-time history shows the airblast-induced motion arriving first, followed by the refracted airblast-induced shock. After passage of these waves comes a relatively long-duration (20-60 msec) downward acceleration of approximately 1 g, followed by a bottoming action or an abrupt apparent upward acceleration, i.e. the abrupt coming to rest of the accelerometer.