Finite element modeling of the static behavior of an elastic-plastic soil base under the action of rolling stock

Abstract

A numerical method for studying the static behavior of the soil base in a geometrically and physically nonlinear formulation from the action of rolling stock is proposed. A mathematical model of the boundary value problem of the statics of the ballast prism and the soil base is constructed using the computational procedures of the finite element analysis program NASTRAN. Single-layer and multilayer base models in the form of a flat half-space are considered. The static action of the rolling stock is presented in the form of a concentrated force applied to the ballast prism from the weight of empty and loaded freight train cars. To describe the elastic-plastic behavior of a single-layer soil base, the Mohr-Coulomb model is used, and for a multilayer one, the Drucker-Prager model. To assess the elastic-plastic behavior of the soil base, a comparison of the results of linear and nonlinear static calculations of two models from two loads is performed. The Newton-Raphson method is used to study the static characteristics of the models in a nonlinear formulation. The influence of taking into account the elastic-plastic models of single-layer and multi-layer soil bases on their stress-strain state was assessed. Due to the physical nonlinearity of the soil in the elements of the single-layer base model under the action of the weight of an empty and loaded car, an increase in the Mises deformation was observed by 15.9% and 16.7%, respectively, while the plastic deformation was 20% and 31.4% of the total deformation, the Mises stress decreased by 53.94% and 54.02%. The results of the study of the multilayer base under the action of the weight of an empty and loaded car showed that due to the physical nonlinearity of the soils, the Mises deformation of the elements increased by 5.8% and 7.4%, respectively, while the plastic deformation was 54.1% and 54.33% of the total deformation, the Mises stress decreased by 43.45% and 43.34%. The proposed methodology allowed us to form a computational model of the ballast prism and base and to investigate the nonlinear deformation of soils taking into account their elastic-plastic properties under the static action of rolling stock.