A micromechanical analysis of the effects of particle shape and contact law on the low-strain stiffness of granular soils

Abstract

The effects of particle shape and contact law on the low-strain shear stiffness properties of granular soils were assessed using Discrete Element simulations. Soil grains of different shapes were obtained by clumping spheres having various levels of overlap. The conducted simulations showed that particle sphericity (or large-scale shape parameter) influences mostly the void radio term, F(e), in the expression of low-strain shear modulus as a function of void ratio, e, and mean confining stress σo. This parameter is also the main consequential factor affecting the coordination number term, FM(Mn), in the expression of low-strain shear modulus as a function of mechanical coordination number, Mn, and mean confining stress. In contrast, particle angularity affects mostly the confining stress exponent solely through the corresponding inter-particle contact law. A law reflecting an angular inter-particle contact (rather than the usual flat Hertzian one) was shown to be necessary to obtain the stress exponent n=0.5 commonly used with granular soils.