Measurement of Density of Soil in place by Nuclear Density Gauge

Purpose

This is a quick method of determining the in-situ density of soil which is based on the radiation.

Equipment

For this test special equipment which measures in place density using gamma radiation is used. Gauge usually contains a small gamma source (about 10 mCi) such as Cesium – 137 on the end of a retractable rod.

Procedure

1. Make the surface even by using a guide plate or any other suitable equipment.
2. Make a hole by pounding a steel rod with a similar diameter to that of gauges retractable rod. The hole should be at least 50mm deeper than the intended depth of measurement.
3. Nuclear Density Gauges normally operate in two modes.
   1. Direct Transmission
   2. Back Scatter
4. For measuring the density of soil, set the equipment to ‘Direct Transmission Mode’.
5. Lower the source rod into the hole. Set the handle to the depth position required.
6. Read the detector count on the panel. Use the calibration chart provided by the manufacturer to obtain density of material.
7. It may be noted that the detector count is inversely proportional to the density of the surrounding material.

Note

The Nuclear Density Gauges are calibrated at the factory. Since the source material undergoes decay, it needs to be calibrated from time to time in accordance with the procedure given by the manufacturer.