The density and stress state significantly impact on the sand stiffness. Many of hardening soil models used for geotechnical computation are based on Duncan-Chang model and do not consider the influence of density on the soil stiffness. In course of triaxial compression of very dense or loose sands

the shear strains rise induces significant changes in density. In order to evaluate the effects of grain size distribution

density

and stress state on stiffness

the results of 962 isotropic triaxial tests on soil samples from 15 Moscow and Minsk construction sites were processed using statistical and regression analysis. As a result

empirical equations enabling evaluation of the effects of density and stress state on stiffness of sands with different particle size distribution were proposed. Comparative analysis of tests performed on alluvial and continental soils from Europe

India

and the United States sites showed that the sand stiffness is in the same range as sands from Moscow and Minsk sites. Proposed equations can be applied for preliminary estimation of the stiffness parameters for finite element method calculation and also can be used in geotechnical models that allow variability

horizontal and vertical distribution of stiffness to be taken into account. Additionally

the semi-empirical relationship based on the Duncan-Chang model

is proposed. The relationship provides more realistic results for loose and extra dense sands affected by large deformations and/or complex loading paths

when the changes in density influence soil stiffness. Generally

geotechnical engineers may utilize the obtained results to apply them to design of complex soil models.