SUBSTANTIATION OF THE REGULARITIES OF THE SUBGRADE STRESS-STRAIN STATE AFTER THE IMPLEMENTATION OF THE EUROPEAN TRACK

Purpose. The implementation of the European track (1435 mm) on the existing subgrade, built on the territory of Ukraine, is a factor that leads to a change in the stress-strain state. The purpose of the article is to substantiate the regularities of the stress-strain state of the subgrade based on the results of numerical analysis of finite-element models. Methodology. For numerical analysis based on the finite element method, a 6 m high subgrade model for the combined track was developed. The developed model reproduces all the real geometric characteristics of the subgrade, the upper structure of the track, as well as the sleeper for the combined track. The developed model allows to vary the application of the train load with the setting of a couple of forces on the rails, which have the Ukrainian value of the track gauge (1520 mm), as well as the European one. The model also simulates the reinforcement of the subgrade for four options (without pile, with pile length of 2.0, 4.0 and 6.0 m). Findings. The results of the numerical analysis made it possible to obtain the values of horizontal and vertical stresses, as well as to obtain the regularities of the stress-strain state of the subgrade before the introduction of the European track. Qualitative analysis of the train position shows that the reduction of the track gauge and its asymmetric location on the sleeper increases vertical deformations. The biggest problem is precisely the asymmetric distribution of vertical displacements. It was found that the increase in the length of the vertical reinforcement element provides a reduction in displacements by 1.1 … 1.2 times. It was found that the patterns of changes in the displacements of the subgrade, when the length of the vertical reinforcement element is varied, are linear for the horizontal component and polynomial of the second degree for the vertical component. Originality. For the first time, based on the regularities of the stress-strain state of the subgrade, a picture of the stresses formation and the distribution of deformations before and after the implementation of the European track was obtained. Practical value. Based on the results of the numerical analysis, it was found that increasing the length of the vertical reinforcement element by 2.0 m provides a reduction in displacements by 10 … 20 %. This data makes it possible to create a methodology for the initial selection of the reinforcement element parameters.