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Non-destructive Measurement of Soil Liquefaction Density Change by Crosshole Radar Tomography, Treasure Island, California

Robert E. Kayen1, Walter A. Barnhardt1, Scott Ashford2 and Kyle Rollins3

1 USGS, 345 Middlefield Road, Menlo Park, CA 94025
2 UCSD, La Jolla, CA
3 Brigham Young University, Provo, Utah.

Reprinted from:

Computer Simulation of Earthquake Effects
Proceedings of the sessions of Geo-Denver 2000
American Society of Civil Engineers
Held August 5-8, 2000, Denver, Colorado

This abstract is reproduced by permission of the publisher, ASCE

ABSTRACT

A ground penetrating radar (GPR) experiment at the Treasure Island Test Site [TILT] was performed to non-destructively image the soil column for changes in density prior to, and following, a liquefaction event. The intervening liquefaction was achieved by controlled blasting. A geotechnical borehole radar technique was used to acquire high-resolution 2-D radar velocity data. This method of nondestructive site characterization uses radar trans-illumination surveys through the soil column and tomographic data manipulation techniques to construct radar velocity tomograms, from which averaged void ratios can be derived at 0.25 - 0.5m pixel footprints. Tomograms of void ratio were constructed through the relation between soil porosity and dielectric constant. Both pre- and post-blast tomograms were collected and indicate that liquefaction related densification occurred at the site. Volumetric strains estimated from the tomograms correlate well with the observed settlement at the site. The 2-D imagery of void ratio can serve as high-resolution data layers for numerical site response analysis.

For more information about this paper or to view the entire article please contact Robert Kayen. To purchase the article please visit the ASCE Publications site.


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