EVALUATION OF NUCLEAR METHODS OF DETERMINING SURFACE IN SITU SOIL WATER CONTENT AND DENSITY
ARMY ENGINEER WATERWAYS EXPERIMENT STATION VICKSBURG MS
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Laboratory tests were conducted to evaluate the accuracy and reliability of measuring surface in situ soil water content and density by the backscatter and direct transmission nuclear methods using a single nuclear device and scaler. The nuclear device functioned as a surface backscatter moisture and density meter or as a direct transmission density probe. To determine the accuracy of the nuclear measurements, it was necessary to know the actual density and water content of the test soil. Boxes were fabricated to exact dimensions, filled with uniformly compacted soil, and weighed, and actual average soil density values were calculated. Five soil types were tested to approximate a full range of possible construction materials. Each soil type was tested at eight different densities and water contents. To obtain comparative results, soil densities of each sample were determined by two accepted conventional methods sand-cone and water-balloon for determining density in the field. Test results indicated that in situ densities determined by the direct transmission nuclear method using the factory calibration curve furnished with the device were as accurate as densities obtained by the sand-cone and water-balloon methods. The direct transmission nuclear method using a WES-developed calibration curve provided slightly more accurate density measurements than either conventional method. A test procedure for determining surface layer density and water content of soil by nuclear methods is presented in Appendix A.
- Hydrology, Limnology and Potamology
- Soil Mechanics