DISPERSE SOILS DILATANCY STUDIES AND THE METHODS OF ITS QUANTITATIVE ASSESSMENT

The phenomenon of dilatancy is a unique property of dispersed media, and in the case of soils can have a significant impact on the shear resistance and the stress-strain state change during loading. In the conditions of free boundaries dilatancy leads to volume increase, and in the presence of volume expansion restrictions to the growth of average stresses. Thus, dilatancy leads to an increase in shear resistance, which makes it possible to increase the degree of use of the bearing capacity of the base. Many modern mechanical models of soil allow dilatancy calculation, most often on the basis of the Rowe’s theory, according to which the angle of internal friction changes during loading, and to calculate the base taking into account its hardening. In addition, the introduction of the plastic potential into the strength conditions allows the calculation of the final plastic strains. This is very important in case of complex loading trajectories, often implemented in soil foundations. The article provides an overview of dilatancy phenomenon studies in our country and abroad with main analytical dependencies given. Four main methods for determining the dilatancy angle are considered: the method of direct simple shear (DSS) and multiplane direct shear (MDS), triaxial compression and torsion shear, their main advantages and disadvantages are highlighted in a form of a table. It is shown that determination of the dilatancy angle does not present significant difficulties and does not require specialized equipment, at the same time, the effective use of this parameter in the design leads to economic effect, primarily in the case of sandy and coarse soils.