This paper concerns evaluation of initial stiffness in natural cohesive soils. Initial stiffness is here represented by the small strain shear modulus (G₀ ), which was measured for the variety of the confining pressures and the mean effective stresses. The researches were conducted in laboratory, using the resonant column (RC) technique. The soil was isotropically consolidated and subsequently stiffness parameter was determined for each effective stress level. Different values of G₀ were evaluated, depending on the test conditions, then summarized on the general graphs. This study demonstrates as well conclusively high non-linear stress – strain behaviour of an examined material. The principal motivation of the article was improvement of our understanding of the stiffness property of natural soils at small strains.

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