Correlation between gradational parameters and compaction characteristics of sandy soils

This study is an attempt to develop a predictive model between gradational parameters, compaction energy (CE), and compaction characteristics, i.e. maximum dry unit weight (γdmax) and optimum moisture content (OMC) of sandy soils. For this purpose, 110 sandy soil samples, representing a wide range of grain size distribution (GSD), were selected. Besides the classification tests, standard and modified Proctor compaction tests were performed on selected samples. Based on the test results, the soils used in the study are classified into various groups of medium to fine sand with gravel content not exceeding 5% and nonplastic fines within 45%. Multiple regression analyses were carried out on the experimental data and a predictive model was developed to express compaction parameters (γdmax and OMC) in terms of two variables, namely, uniformity coefficient (Cᵤ) and CE. Following the development of predictive correlations based on the 110 samples, a new set of 40 sandy soil samples were selected and their compaction results were used to validate the proposed two predictive equations. The results showed that variation between experimental and predicted values of maximum dry unit weight (γdmax) is within the ±5% confidence interval and that of the OMC (%) is within ±3.0%. The two equations are also presented graphically for standard and modified Proctor compaction energies that are used commonly in compaction tests. The proposed correlations and the predictive curves would be very useful in geotechnical engineering for quick estimation of cdmax and OMC without performing the laboratory compaction tests