Dynamic Deformation Characteristics of Soil in the Tasks of Seismic Micro Zoning

The article discusses a technique for determining the nonlinear characteristics of the layers of computational models of the soil profile for the equivalent linear and nonlinear modeling of its response to seismic effects. The results of studying the factors influencing the curves of the strain-dependent shear modulus G (γ) and damping ratio D (γ) are analyzed. Based on the results of the analysis, the main parameters have identified that control the shape of the curves and allow you to quickly select the corresponding curves from the existing database with acceptable accuracy for each layer of the soil profile model. For clayey rocks: this is the plasticity index PL and the depth of occurrence; for sandy rocks: particle size, percentage, and depth. The paper presents the results of studying the effect of relative errors that arise when choosing the curves G (γ) and D (γ) for the soil layers of the computational seismic-geological model on the parameters of the frequency response of the soil, calculated using the equivalent linear modeling of ground vibrations during earthquakes. It was found that errors in determining the strain characteristics of soil layers in the calculation model lead to a shift in the maxima of the amplitude-frequency characteristic, to a change in the amplification factors of oscillations, as well as to the appearance of "false" maxima at high frequencies. The methodological approach to the formation of computational seismic-geological models of soil strata, by introducing the curves G (γ) and D (γ), which reflect the nonlinear properties of the soil, makes it possible to improve the computational methods for determining the resonance properties of soils under construction sites. The most accurate values of the frequency characteristics of the soil strata under construction sites are necessary for the development of effective measures to ensure the seismic resistance of the designed and existing facilities. As a result, the validity and accuracy of determining the quantitative parameters of seismic hazard at the construction and operational sites under study are increased.