Maximum and minimum void ratios for sand-silt mixtures

• An analytical model for minimum and maximum void ratios of sand-silt mixtures is proposed and verified with experimental results.
• The packing microstructures are distinctly different for low fines content and high fines content for sand-silt mixtures.
• An explicit linear relationship between minimum and maximum void ratios is derived and verified by experimental results.

Minimum and maximum void ratios provide a general basis for comparative evaluation of material properties for soils with various densities. Either the minimum or the maximum void ratio is dependent considerably upon the fines content of soil. There are a few mathematical models in the literature for predicting the variation of minimum void ratio with respect to fines content. However, mathematical models for predicting maximum void ratio with respect to fines content are very limited in the field of geotechnical engineering. This study shows that the variation of maximum void ratio with respect to fines content of a sand-silt mixture is caused by the same mechanisms that influence the variation of minimum void ratio. Consequently, the mathematical model previously proposed by the authors for predicting minimum void ratios of sand-silt mixtures is extended to be capable of predicting the maximum void ratios of sand-silt mixtures due to the influence of fines content. The applicability of this extended mathematical model is verified by data from 24 sand-silt mixtures with various fines contents. Furthermore, based on the extended mathematical model, the relationship between the maximum and the minimum void ratios of a sand-silt mixture can be derived. The derived relationship is found to be linear and is a function of fines content. The validity of the derived linear relationship between the maximum and the minimum void ratios of a sand-silt mixture is also verified by the measured results from experiments.