RADAR PROFILING OF BURIED REFLECTORS AND THE GROUNDWATER TABLE

Abstract

Investigations of ground radar performance over thawed and seasonally frozen silts, and sands and gravels containing artificial and natural reflectors were carried out in Alaska. The radar emitted 5-10 ns pulses, the center frequency of which was approximately 150 MHz. The artificial reflectors were metal sheets and discs and the natural reflectors were the groundwater table and interfaces between frozen and thawed material. The water table was profiled at three sites where the subsurface material was coarse-grained alluvium. Dielectric constants of 16 to 18 were measured for the thawed silts, 6 to 7 for the frozen silts and 3 to 9 for the sands and gravels. Signal penetration in the thawed high moisture content silts may be achieved only by use of a lower frequency radar, whereas in the sands and gravels greater depths may be detected with more sophisticated signal processing.