Influence of particle size on the small-strain stiffness in granular soils: experimental observations and micromechanical interpretation

The aim of the current study is to provide evidence regarding the influence of particle size on the dynamic properties in granular materials. Experiments using a resonant column (RC) device were conducted on glass beads having similar coefficient of uniformity, but four different mean grain sizes to describe the tendencies in the magnitude of G max and E max . It can be clearly seen that for similar particle gradation the influence of particle size is significant, in particular for larger mean grain sizes d 50 exceeding 1·5 mm. The experimental data were fitted using existing empirical relationships with corresponding fitting parameters. The fitting parameters describing the void ratio and pressure dependence to estimate maximum stiffness were found to depend on grain size to a certain extent. This influence was diminished for the materials with a d 50 < 1·5 mm. It was therefore possible to use a unique set of fitting parameters for these materials with a satisfying degree of accuracy. The results were compared with some previous studies to highlight the size dependency of G max and E max for materials with mean size greater than 2 mm, but also the relatively small influence on materials with lower mean particle sizes (d 50 < 2 mm) is acknowledged. The results are furthermore discussed through a micromechanical interpretation highlighting why larger grain sizes influence stiffness values.