ABSTRACT
Stiffness parameters are defined as the ratio of stress to strain and depend on many factors, e.g. on soil type, stress conditions, stress history. The stress–strain behaviour of soil is highly non-linear. Therefore, the moduli - i.e. parameters characterizing soil stiffness - are not constant and, in addition to the previously mentioned factors, also depend on the deformation level. The initial soil stiffness is assumed as moduli values for strains smaller than approximate 1x10-4%. It can be determined on the basis of shear wave velocity measurement or tests in a resonant column. It is assumed that these are non-destructive tests, carried out in the range of very small soil strains. Resonant column test allows to determine the shear modulus in the range of shear strains 10-4÷10-1%. As the deformation increases, the soil stiffness decreases. The change in stiffness occurs faster for less cohesive soils than for very cohesive soils. The paper presents the analysis of resonant column test results in terms of soil stiffness reduction along with deformation for different soils. The authors of the paper proposed a relationship between shear modulus and values of shear strains based on the initial stiffness and basic soil index properties.
