Neutron Moisture Meter Calibration for Minespoils Containing Coal
1986
Halvorson, Gary A.
Laboratory calibrations were used to determine the effect of coal in spoil on neutron moisture meter measurements. Calibrations were conducted on clay loam and loamy sand minespoils from western North Dakota, with and without coal added. Volumetric water contents were overestimated by 3.7% in clay loam containing 8% coal by weight, and 4.7% in loamy sand containing 9% coal by weight using a calibration curve based on similar material without coal. The equivalent water content of the coal (θc) was calculated from the H content of the coal. Correction of calibration curves containing coal by adding θc to volumetric water contents substantially accounted for differences between calibration curves with and without added coal. Due to the large variability in both concentration and size of coal fragments in minespoil, accurate calibration is difficult at best. Since the slope of the calibration curve is unaffected by the presence of coal, changes in soil-water content over time can be accurately determined from one calibration curve. At sites containing coal fragments, absolute measurements of soil-water content are difficult, and therefore, only relative differences in water content over time should be determined.
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