Two types of moisture sensors for long term in situ monitoring of moisture in highway subgrade soils have been developed and field tested. One sensor is based on the relationship between the soil moisture and the dielectric constant of the soil which affects the capacitance as sensed by a pair of embedded electrodes. The other sensor is based on the nuclear magnetic resonance of hydrogen of the water molecules in the soil. Results of the evaluation program show that the tested sensors are capable of determining soil moisture content in the range of 20% to 30% with an accuracy in the field of plus or minus 2% over dray moisture content and a precision of plus or minus 2% oven dry moisture content. The sensors were evaluated in the field for over a year under in-service highways in Arizona and Pennsylvania, and under a test road at the U.S. Army Cold Regions Research Laboratory in New Hampshire. Periodic comparisons were made among the sensor readings and results of other moisture measurements including nuclear probe and gravimetric analysis of borings. Although some discrepancies were observed among the field results, and the field tests were not conclusive, the data obtained with the newly developed sensors appear to be consistent with the indicated moisture conditions. (Author)

  • Supplemental Notes:
    • This work was sponsored by the American Association of State Highway and Transportation Officials, in cooperation with the Federal Highway Administration, conducted by the National Cooperative Highway Research Program.
  • Corporate Authors:

    Southwest Research Institute

    6220 Culebra Road, P.O. Drawer 28510
    San Antonio, TX  United States  78228-0510
  • Authors:
    • Matzkanin, G A
    • Selig, E T
    • Wobschall, D C
  • Publication Date: 1979-12

Media Info

  • Features: Appendices; Figures; Tables;
  • Pagination: v.p.

Subject/Index Terms

Filing Info

  • Accession Number: 00319183
  • Record Type: Publication
  • Report/Paper Numbers: SwRI Proj No. 154063Final Rpt.
  • Files: TRIS
  • Created Date: Dec 30 1980 12:00AM