The deep-mixing is nowadays world-wide accepted method as a ground treatment technology to improve the permeability, strength and deformation properties of soils. Binders, such as lime or cement are mixed in-situ with the soil by rotating mixing tools. The method is undergoing rapid development, particularly with regard to its range of applicability, cost effectiveness and environmental advantages. The paper describes the results of laboratory tests on chalky silt samples mixed with cement of different content. The influence of the different mixing parameters on the unconfined compression strength and deformation modulus is shown and evaluated. Typical results of the laboratory tests were used in numerical modeling with PLAXIS 3D as input parameters to study the behavior of a 4 m high embankment constructed on this soil improved by deep mixed columns with different spacing and diameters. The parameters of the soil improvement technique were analyzed to study their influence on the settlement and the stability of the embankment. The trends of the calculation outputs are shown and evaluated.