MEASURING THE SMALL-STRAIN ELASTIC MODULUS OF GAP-GRADED SOILS USING AN EFFECTIVE-MEDIUM MODEL AND THE RESONANT COLUMN APPARATUS

ABSTRACT: Much of our soil mechanics knowledge relates to testing results from uniformly graded materials, but many natural soils are composed of a wide range of different sized particles. Many soils such as sandy silts, sandy clays, (with the fine particles acting as the soil matrix and sand being the floating particles acting as inclusions) can be considered to be a combination of two poorly graded soils with different grain size distributions. These types of soils are usually known as “gap-graded soils”. Although there is a lack of mechanical knowledge of gap-graded soil mechanics in the literature, some work has been conducted on binary mixtures, which provide a reasonable representation of this type of soil. The main focus of this work was to investigate the elastic properties of binary mixtures through the application of an effective-medium model used in rock mechanics. Results from resonant column test experiments on sand-glass bead mixtures were used in this study. Amongst the findings, it was possible to determine a threshold value where the mixture properties abruptly changes and how the elastic moduli of the binary mixtures is affected by this sudden change.