Evaluation of dynamic image analysis for characterizing granular soils

This study investigates the efficacy of dynamic image analysis (DIA) for determining particle size and shape distribution. The method employs a high-frame-rate camera to image individual particles of sand that have been transported and separated using a stream of pressurized air. DIA can generate both particle size and shape information and provides a quantitative statistical description of the grain size and shape distribution within the specimen. The feasibility, repeatability, and accuracy of DIA for routine analysis of particle size and shape distribution was investigated using 16 granular soils spanning a number of common sizes and shapes. Several particle shape descriptors were evaluated, including aspect ratio, convexity, and sphericity. The effect of a variety of test parameters including moisture content, sample weight, primary air pressure, and test duration were explored to determine the optimal specimen weight and equipment settings for DIA. Finally, the efficacy of DIA in resolving mixtures of fine and coarse sands was also explored. The method proved to be feasible, repeatable, and accurate for providing particle size distributions spanning four orders of magnitude, in terms of particle size. DIA offers a number of advantages; the method is quick, requires small specimen sizes, and provides quantitative information on approximately 3-4 % of the particles in the specimen.