Influence of voids on density measurements of granular materials using gamma radiation techniques

Abstract

This paper presents the results of laboratory gamma-ray density measurements on 100-mm-diameter specimens with an adapted twin-probe transmission-type density gage originally developed for field use. Primary factors affecting density calibration for soils include soil composition and soil porosity. To appreciate the soil composition factor, 100-mm-diameter specimens of solid materials similar to the soil minerals were tested, and from the data a linear ln (COUNT) versus DENSITY calibration line for solid materials was obtained. Next, aluminium cylindrical specimens with concentric holes of various diameters representing various porosities from 0 to 90% were tested. When compared to the solid material calibration line, it is clear that the bulk density calculated based on the gamma-ray path geometry gives the same calibration as the solid specimens. Subsequently, cylindrical specimens of dry sands and gravels were also made and tested.