DEVELOPMENT AND FIELD EVALUATION OF PROTOTYPE SOIL MOISTURE SENSORS
This paper discusses a study where moisture determinations from nuclear magnetic resonance (NMR) and dielectric sensors were compared with moisture measurements obtained by nuclear depth probes and gravimetric analysis of soil borings. The following are general observations and conclusions of the field evaluation phase of the study: some operational problems were encountered with several sensors of each type; with suitable calibration, both sensors are capable of determining in situ moisture content with an estimated accuracy of 2 percent; although the actual moisture levels encountered in the field were only in the 20 to 30 percent range, on the base of the results of laboratory tests, the actual operating range of the sensors is estimated to be 0 to 50 percent; best results are obtained by calibrating the sensors using the soils of interest; special installation procedures devised for the sensors produce minimal disturbance of the subgrade soil; laboratory studies of temperature effects showed that the dielectric sensor can be used to determine with a high degree of certainty when freezing of pore fluid occurs; and on the basis of current fabrication costs, the price to the user for production quantities is estimated to be $125 per sensor, $1,000 for the dielectric readout, and $5,000 for the NMR readout. The results of this research indicate that both the dielectric and the NMR measurement systems can be potentially useful for in situ determination of moisture in pavement subgrades; and with proper calibration, the accuracy of moisture measurement with these sensors can be at least comparable to existing in situ sensor types such as moisture blocks.
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Washington, DC United States 20001
- Matzlamom, G A
- Selig, E T
- Wobschall, D C
- Publication Date: 1980-6
- Media Type: Digital/other
- Pagination: 3 p.
- NCHRP Research Results Digest
- Issue Number: 121
- Publisher: Transportation Research Board
Open Access (libre)
- TRT Terms: Freezing; Measurement; Moisture content; Prototype tests; Sensors; Soils; Subgrade (Pavements)
- Subject Areas: Geotechnology; Highways; Materials; I42: Soil Mechanics;
- Accession Number: 00319182
- Record Type: Publication
- Files: TRIS, TRB
- Created Date: Dec 30 1980 12:00AM