USGS Groundwater Information: Branch of Geophysics
C. Kochiss 1,2 and L. Liu 1,3
1) University of Connecticut, Department of Geology and Geophysics, 354 Mansfield Road, Storrs, CT, 06269-2045
2) U.S. Geological Survey, Branch of Geophysics, 11 Sherman Place, Unit -5015, Storrs, CT 06269-5015
3) Cold Regions Research and Engineering Laboratory, 72 Lyme Road, Hanover, NH 03755-1290
Ground-penetrating radar (GPR) is widely used for subsurface characterization in environmental contaminant remediation studies. GPR can be used to detect the extent of the contaminant plume and monitor the remediation process as contaminants are removed. Thermal remediation methods, such as steam injection, are used to mobilize non-aqueous phase liquids (NAPLs) for vapor extraction; these methods cause a temperature change in earth materials, which subsequently causes variations in GPR signal response. When using GPR to monitor a remediation process, it is critical to account for all possible factors that affect GPR signatures for better definition and delineation of contaminant flow and transport. Numerical and physical models were used to quantify the effects of temperature changes and fluid phase changes in a porous medium. The numerical modeling shows that when a porous media is heated, the GPR signal will show both a decrease in traveltime and an increase in amplitude from a reflector. A simplified numerical model of the GPR signal response to a steam injection, characteristic of some thermal remediation methods, was made by comparing GPR signal responses to a water-filled layer and an air-filled (steam) layer within the saturated porous medium. The polarity of the reflected GPR signal is opposite for the water- and air-filled layers. The results from physical experiments conducted in a laboratory-scale sand tank confirm the results obtained from the numerical models.
Final copy as submitted to the American Geophysical Union for publication as: Kochiss, C.S. and Liu, Lanbo, 2004, Numerical and physical modeling of the effects of temperature change on ground penetrating radar signals: Eos Trans. American Geophysical Union, 85(17), Jt. Assem. Suppl., Abstract NS22A-05.
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