Method for determining the foundation stiffness coefficient based on its physical and mechanical characteristics and the theory of a linear-elastic half-space

The reliability and durability of building structures largely depend on the proper consideration of their interaction with the soil foundation. Determining foundation deformations is a key stage in design, as it defines the structural behavior under load. Both analytical methods and numerical approaches are used for calculations, among which the finite element method (FEM) is the most widely applied. Numerical modeling based on FEM allows for the simulation of the soil foundation as a finite bounded domain, using various mathematical soil models and appropriate boundary conditions. An alternative approach is to model a flexible foundation as a slab on an elastic Winkler foundation, where a critical step is determining the stiffness coefficients (coefficient of foundation subgrade reaction): C1 (subgrade reaction coefficient) and C2 (shear coefficient). However, regulatory documents do not provide clear recommendations for their determination. The authors propose a method for calculating the bed coefficient C1, which eliminates the need for settlement calculations and relies solely on the average soil deformation modulus, the compressed layer depth parameter, and special coefficients that account for the decrease in stress intensity with depth according to the theory of a linear-elastic half-space. These coefficients are provided in an easy-to-use tabular format and can also be applied for analytical assessment of settlement magnitudes using the derived formulas.