Prediction of Particle Size Distribution in Clay Using Electrical Conductivity Measurement

The mechanical and hydraulic behavior of most soils is often directly reflected in the particle size distribution of the soil. For fine grained soils, the distribution of particle sizes smaller than 0.075 mm is determined by a sedimentation process, using the hydrometer analysis. The hydrometer analysis measures the change in specific gravity of a soil-water solution with time and relates that change with the distribution of various particle sizes. The change in specific gravity of a solution also results in a change in the electrical conductivity of a soil-water solution. This paper presents the development of a generalized model to predict the particle size distribution of fine grained soils from the changes in electrical conductivity measurements of a soil-water solution with time. The developed model included several fitting parameters, which were found to be dependent upon soil type. To enhance applicability of the developed model, the fitting parameters were formulated based on electrical conductivity measurements corresponding to Atterberg Limits of soils. This approach made it possible to predict the entire particle size distribution, smaller than 0.075 mm, without needing to conduct conventional hydrometer test.