Evaluation of particles shape and uniformity effects of grain soil on porosity

One of important goals in projects of road and soil dams is to compact whatever more of soil. Compaction of soil with reducing in void ratio causes to improve technical properties such as resistance and permeability. Minimum void ratio depends on soil properties and compaction energy. The most important properties of a soil in this regard are soil particles shape and coefficient of uniformity. Now days, presentation of exact experimental equations in geotechnical engineering have special importance. Therefore in this study it is tried to propose an equation between void ratio and the effective parameters. There are a lot of papers in this field; but the results of those previous studies were not comprehensive. In this paper, an exactly equation for calculation of minimum void ratio was recommended for poorly graded soils. In this study, 42 soil samples with different shapes, coefficient of uniformity and size were prepared; then, using instruments and preparation chart, sphericity and roundness of samples were measured; next minimum void ratio of the samples were measured. At last, using 70 percent of data, an equation for calculating of minimum void ratio based on sphericity, roundness and coefficient of uniformity was presented. Also, using other results, validation of the equation was presented. The results were completely logical.