Determining the Density and Unit Weight of Soil in Place by Nuclear Methods (Shallow Depth) - Soil Properties: Testing, Measurement, and Evaluation - page 228

Figure 16-1 Nuclear Moisture-Density Apparatus (Courtesy of Troxler Electronic
Laboratories, Inc., North Carolina).

This method for determining in situ unit weight is known as “density
of soil and soil-aggregate in-place by nuclear methods (shallow depth)”
and is designated as ASTM D 2922.
There are several modes for measuring soil (wet) density by nuclear
methods. One is the direct transmission method, where the gamma
radiation source is placed at a known depth up to 12 in. (300 mm) while
the detector or detectors remain on the surface (see Figure 16-2).
Another mode is the backscatter method, in which both source and
detector(s) remain on the surface (see Figure 16-2).

APPARATUS
AND SUPPLIES

Nuclear gage containing a sealed source of high-energy gamma
radiation and a gamma detector (see Figure 16-1)
Reference standard
Site-preparation device (a plate, straightedge, or other leveling tool)
Drive pin and drive pin extractor
Slide hammer