On the physical meaning of equivalent skeleton void ratio for granular soil with fines

Abstract

Recent research on the behavior of silty sand usually involves the use of equivalent skeleton void ratio to characterize its packing density state. The equivalent skeleton void ratio is a modified void ratio by the introduction of a parameter b to account for the participation of fines in the force chains. However, the parameter b is poorly understood. This paper presents an investigation into the physical meaning of the equivalent skeleton void ratio by conducting a series of discrete element method (DEM) simulations on biaxial tests of assemblies of coarse and fine particles. The simulation results reveal that the parameter b is a state variable dependent on confining pressure, packing density and particle gradation and it varies during shearing. It should not be treated as a constant as reported in the literature. It is also found that the distribution pattern of fine particles in the skeleton of the assembly plays a crucial role in the overall macroscopic response. Contraction is principally induced by the movement of fine particles out of the force chains and dilation is generally involved with the migration of fine particles into forces chains. Furthermore, a new expression of the equivalent skeleton void ratio is put forward with the introduction of the parameter d to take into account the absence of large particles from force chains, along with comparisons between this new definition for the equivalent skeleton void ratio and the existing one. © 2013 AIP Publishing LLC