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Proceedings Paper

Field study of GPR attenuation rates in natural and contaminated silt
Author(s): Steven A. Arcone; Allan J. Delaney
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Paper Abstract

GPR is considered ineffectual in penetrating silty soils. Capillary tension appears to move the interstitial water dielectric relaxation frequency near the GPR range. If hydrocarbons relieve the tension, then GPR attenuation rates should decrease. We profiled these rates across a partly contaminated quartz silt diamicton at an inactive fuel terminal in Haines, Alaska. We calculated the rates from the signal amplitude decay within a series of 400-MHz moveout surveys recorded along a single transect. We sampled the hydrocarbon content along the transect and on the wall of a trench we excavated beside it, along with water content, density and resistivity. The silt was saturated and generally at 50—80 ohm-m. The ground impedance loading brought the antenna pulse center frequency down to near 200 MHz. The rates ranged from 5 to 8 dB/m in the contaminated zone and about 10 to 15 dB/m in the uncontaminated zone. The resistivities account for the contamination rates, but a dielectric relaxation centered near 1—2 GHz, using a simple mixing model, is required to account for those in the uncontaminated zone. Hydrocarbon soil analysis suggests that the threshold level for the attenuation effect is not higher than about 1000 ppm. We suggest GPR offset surveys for assessing contamination zones.

Paper Details

Date Published: 12 April 2002
PDF: 6 pages
Proc. SPIE 4758, Ninth International Conference on Ground Penetrating Radar, (12 April 2002); doi: 10.1117/12.462306
Show Author Affiliations
Steven A. Arcone, U.S. Army Cold Regions Research and Engeering Lab. (United States)
Allan J. Delaney, U.S. Army Cold Regions Research and Engineering Lab. (United States)

Published in SPIE Proceedings Vol. 4758:
Ninth International Conference on Ground Penetrating Radar
Steven Koppenjan; Hua Lee, Editor(s)

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