Purpose: Determination of legitimacies of clogging, pollution for broken stone ballast, perceiving vibrodynamic load from a rolling stock, as well as of the ballast life. Methods: Theoretical and empirical research methods are used in the study. Theoretical methods are based on the analysis of known models describing broken stone degradation processes during railway track exploitation, and empirical methods — on the pursued experiments and trials. The identification of the legitimacies for pollutants and clogs accumulation in broken stone ballast was based on the results of dynamic bench tests and laboratory determination of broken stone grain composition removed from ballast layer of exploited railway track with various tonnage workout. The methods of statistical processing of test results and regression analysis were used in the study. Results: According to the statistical processing of test results and laboratory determinations of broken stone grain composition, functional dependencies were established for the accumulation in broken stone ballast of the products of own crushing, abrasive wear as well as of external pollution, depending on broken stone initial physical and mechanical properties, railway track exploitation conditions and the system of its maintenance. Mathematical model for the prediction of broken stone ballast life depending on railway track section exploitation conditions was developed in the study. Practical significance: The results of the study make it possible to prognose broken stone ballast life from the condition of its maximally acceptable pollution and clogging and also to plan reasonably railway track maintenance work.

Purpose: Mathematical model for studying the process of soil freezing given moisture migration is developed. Numerical modeling of temperature mode of railway subgrade at non-stationary pro-cess in cold climate conditions is performed. Methods: Numerical implementation of the model is performed by mathematical module processing in COMSOL Multiphysics program, which’s based on partial differential equations (PDE), with finite element method. The model reliability is con-firmed by the comparison with previous experimental data and the results of simulation by other authors. Results: Calculation results on the developed model basis show the best correlation with experimental data in comparison with the results for other models. Calculation example and calcu-lation results for subgrade temperature mode in freezing-thawing fifth cycle are presented. The analysis of soil freezing depth change and soil temperature fluctuation change by depth by fifth year are carried out. Practical significance: The developed mathematical model makes it possible to predict soil freezing depth, taking into account moisture migration, including freezing and thawing depth changes caused by climate warming. The developed model can be used both, to study the mechanism of subgrade temperature mode distribution at freezing and thawing, and to improve subgrade construction for to protect it from soil frost heaving.

Purpose: Study of strength and deformation properties of basalt broken stone ballast depending on its grain composition, the properties are necessary for further assessment of bearing capacity and deformability of railway track ballast layer. Methods: Determination of mechanical properties of broken stone ballast from basalt rock was carried out in a triaxial compression chamber which intense state close to real operating conditions was simulated. In the trial process, the dependences of axial and volumetric deformations from tension deviator were being determined. The methods of trial result statistical processing and regression analysis were used in the work. Results: According to laboratory test result statistical processing, the key characteristics of broken stone ballast strength as well as deformation modulus and Poisson’s ratio depending on the ballast grain composition were determined. Practical importance: The study results make it possible to elaborate recommendations regarding broken stone ballast grain composition, the ballast is from the basalt used in the areas of especially heavy traffic of trains.

Purpose: Experimental determination of vertical dynamic forces of wheel impact on a rail at ballastless construction of railway track RHEDA2000 upper structure with subsequent analysis of obtained data; definition of main factors affecting vertical dynamic force value; identification of dependence of change in the value of wheel vertical dynamic force impact on a rail from motion speed and rolling stock type; calculation of coefficients of vertical dynamics at ballastless construction of rail upper structure. Methods: Measurement of wheel vertical dynamic force impact on a rail was carried out by strain-gauge method (Schlumpf method). Numerical values of those, obtained in the course of experiment, were processed by mathematical statistics method, in its turn, probability level was taken equal to 0.994. Results: The values of vertical dynamic forces of wheel impact on a rail for ballastless structure of RHEDA2000 type at rolling stock different types and various ranges of motion speed have been determined. The dependence of change in the value of wheel vertical dynamic force impact on a rail from motion speed and rolling stock type has been graphically built. Comparison of vertical dynamics coefficients of ballastless construction of railway RHEDA2000 upper structure with the construction of a track on a ballast has been carried out. Practical significance: The obtained results can be used in projection, construction, reconstruction and repair of railway track where track ballastless upper composition is provided.

The objective of the research is a railway ballast layer created from new and recycled ballast particles in different ratio. In order to study the possibility of using recycled ballast grains in ballast layer, it is necessary to carry out laboratory triaxial tests of ballast crushed stone with size of the particles 25-60 mm with different grain shape. Abrasion testing machine allows to reach the effect on new ballast, which is similar to abrasion of ballast particles in the railway track. Therefore, it is possible to create ballast samples from (new) mixed and recycled ballast and estimate which proportion has the strength characteristics, which are close to the ones in ballast layer created only with new ballast particles. The result of the study shows, that it makes sense to return the recycled crushed stone in a mix with a new one in order to reduce the cost on a railway maintenance.