The Federal Highway Administration and its contractors, in cooperation with the State Highway Commission of Kansas (now the Kansas Department of Transportation), completed a field program in Kansas during 1971 to evaluate field geophysical systems for detecting subsurface cavities. The geophysical systems included passive microwave radiometers, an impulse radar profiling instrument, and direct-current electrical resistivity. Verification borings were completed in 1972 after analysis of the field data. Field data and test borings are presented for 1 traverse line in Galena, Kansas, to characterize the research findings. Passive microwave radiometers are sensitive to soil moisture and often record the effects of surface drainage, groundwater seepage, and subtle topography. The penetration of microwaves into soils, however, is limited, and the microwave radiometers are not well suited for detecting subsurface cavities. The impulse radar profiling system produced a graphical output that closely approximated the subsurface soil, rock, water, and void interfaces. The depth of radar penetration was limited to 8 ft (2.4 m) because of the presence of moist, clay-rich soils. Electrical resistivity proved to be the most useful technique for delineating subsurface materials. Geoelectrical soundings are well suited for locating conductive and insulative layers, but, because of the principle of equivalence, they may be unable to distinguish a water-filled cavity from another conductive subsurface zone.

Media Info

  • Media Type: Print
  • Features: Figures; Photos; References;
  • Pagination: pp 31-41
  • Monograph Title: Innovations in subsurface exploration of soils
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00141420
  • Record Type: Publication
  • ISBN: 0309024951
  • Report/Paper Numbers: Conf Paper
  • Files: TRIS, TRB
  • Created Date: Nov 3 1976 12:00AM