Keywords: Rheology; parallel plate rheometer; soil structure; effective stress; osmotic potential. Rheology is a science dealing with the mechanical behavior of fluids and plastic bodies when subjected to external stresses. Hooke's law for a perfect elastic body, Newton's law for ideal fluids, and finally, Bingham's yielding represent terms, on which rheology is based. However, its technical application has been more conventional in chemical industry e.g. food science, polymer research, but uncommon in soil mechanics, yet. A parallel plate rheometer MCR 300 (Modular Compact Rheometer, Anton Paar, Germany) has been used to conduct oscillatory tests on mineral suspensions and soils, consolidated as viscoelastic material according to the Maxwell and Kelvin/Voigt models. From the stress-strain relationship in oscillation (f = 0.5 to 1.0 Hz), with preset deformation g, specific parameters such as the storage modulus G¢ (elastic part) and loss modulus G² (viscous part), viscosity h, yield stress t_y and the linear viscoelastic deformation (LVE) range including a deformation limiting value g_L were determined and calculated, respectively. In this work especially salt effects are considered. The diffuse double layer theory of Derjaguin-Landau-Verwey-Overbeek (DLVO) proved, that no physical contact between clay particles needed to take up charges, but is carried by pore fluid between the platelets. Hence, the osmotic pressure between the particles is the actual effective stress s' in a Na-montmorillonite soil. This effect might be quantifiable due to the relation of salt concentration, respectively salt characters e.g. bonding forces, at corresponding electrical conductivities and defined water content. Investigation with NaCl show that it has an influence on the net work stability of clay platelets and the menisci forces between single particles. In order to quantify the strengthening effects, the link between Terzaghi's equation for effective stress and the salt concentration (osmotic pressure) has to be established. Considering mechanical behavior of single particles in general, the friction of inner angle remains high in silty and sandy soils (20 to 25 degrees) even at high deformation: the residual friction angle equals the critical state friction angle. Montmorillonitic clay soils are prone to have a high friction angle of approximately 20 degrees initially, the particles are stochastically orientated, decreasing with a gradient shear deformation, before stabilising in the range of 2 to 10 degrees, depending on the composition of the clay soil and (cat)ions occurring in the pore water. A rotund particle shape is commonly given for sand and silt, which leads to turbulent shear behaviour and a high residual shear strength f_R of 25 to 30 degrees. Platy clay particles may show both, either a turbulent or a sliding behavior. However, only a low friction angle is always given between the clay plates. In the case of montmorillonitic clay soils a sliding shear mode can be observed due to a low residual shear strength f_R of 5 to 15 degrees. An approximation of quantifying and/or defining turbulent or sliding shear behaviour can be made by comparing elastic and viscous parts of different substrates, including their texture, chemical aspects (salt) and water content. By executing amplitude sweep tests the applicability of a parallel plate rheometer in soil mechanics shall be proved. Results from conducted tests on a Na-bentonite (active clay, Ibeco Seal-80), a Vertisol (Brazil, 60% clay), a clayey Oxisol (Brazil, 75% clay) and loess material (Israel, 65% silt) will be presented. Preliminary results show that rheometry is a potential method of investigating (micro)structural characteristics on a single particle scale of mineral suspensions and clay or silt rich soils.