Assessing the Microcontact Strength of Particles in Dense Sandy Soils

The objective of this study is to establish the force range of applicability of the Hertz's contact theory in the mechanics of dense sandy soils by developing and testing a methodology for calculating the microcontact strength of mineral particles. A force analysis of the elastic contact of soil particles within a unit cell modeled by microspheres with a diameter equal to the average diameter of particles of the fractional composition under consideration was performed. The particle packing in the unit cell was assumed to be a body-centered cube. The frictional interaction between the particles was described by the Amontons-Coulomb friction law. Contact interaction parameters were determined using Hertz formulas, taking into account the difference in the mechanical properties of the surface layer from similar indicators of standard samples. A model for converting loads in a single cell to the nominal pressure on the soil mass is proposed. The calculated force acting on a particle was determined as the product of the nominal pressure in the particle mass and the cross-sectional area of the unit cell. Analytical relationships are provided for calculating the forces arising in the particle contact zone, as well as the maximum pressures at the contact areas. An assessment was made of the external pressures on the soil mass at which the equivalent microcontact pressures, calculated using the second theory of strength, reach the compressive strength limit of the material of the surface layer of mineral particles. It is proposed to consider these pressures as a limitation on the applicability of Hertz’s theory to solving contact problems in sandy soils. The research results can be used in educational programs for training specialists in construction and chemical engineering specialties, as well as in scientific research practice.