Optimal model for particle size distribution of granular soil

In this study an attempt is made to develop an optimal parametric model to represent the particle size distribution (PSD) curves of granular soils based on experimental data. Four unimodal models and one bimodal model are studied to determine which model performs best. As it is very difficult to determine the model parameter values without the assistance of a computer, because of the equations’ complexity, a software package has been developed based on the Matlab platform. A database of 21 soil specimens with pre-fitted PSD curves and 13 soil specimens with a number of experimental data are studied to evaluate the performance of these models. The results indicate that most of the gap-graded soil PSD curves can be correctly represented using the Fredlund bimodal parametric (FBP) model, while all the well-graded soil PSD curves can be represented using both the FBP and Fredlund 4 parametric (F4P) models.