The qualitative performance of the track facility in Ukraine depends upon the technical state of rail track structure, which is determined by correspondence of the characteristics to the current Regulations for laying and maintenance the track on railways of Ukraine. And the parameters indicating the rail track stability directly depend on the carrying capacity of the rail base and the stress-strain behavior. The main indicators of the state of the continuous welded rail (in particular, the parameters of the track geometry), deviations from the normative position of the track rails in the profile and in the plan directly depend on the carrying capacity of the under sleeper base, that is, on its deformative properties. In this study, the under sleeper base deformability refers to the ability of the superstructure to operate under conditions of limitation to a certain level of pace (speed) accumulation of the track failures. Determining the level of the dynamic load on the railway track, its effect on the performance of its elements, and the under sleeper base deformability of the continuous welded rail will make it possible to quantify the dynamic effects on the railway track construction and its impact on the under sleeper base deformability.

The permanent way components are of key importance for safe operation of a rail way. The country regulations, in particular in Ukraine, specify the operational life limits for the permanent way but they do not define any tool or method to predict deterioration of the permanent way condition over time. The study is aimed to develop a method for assessing failure risk of the permanent way components in operation. There was a method offered to evaluate risk of failure of the permanent way components of the welded tracks, which considers accumulated freight load on a rail section. Each element of the permanent way, such as rails, fasteners, sleepers, ballast layer, accumulates defects and deformations. The accumulation rate is different for the above components and depends on freight traffic. There was probability of failure-free operation calculated for each component for the first time and an integral fatigue index of the construction has been offered which considers freight traffic accumulated load. There was a mathematical failure forecast model developed which allows planning of track maintenance. The model allows to take into account operating conditions of a railway section. The results of simulation are presented in various diagrams.

The qualitative performance of the track facility in Ukraine depends upon the technical state of rail track structure, which is determined by correspondence of the characteristics to the current Regulations for laying and maintenance the track on railways of Ukraine. And the parameters indicating the rail track stability directly depend on the carrying capacity of the rail base and the stress-strain behavior. The rail base consists of elements of various physical and mechanical properties, with its own deformation behavior and stressed state under force loading. Therefore, the stress-strain behavior of the rail base must be evaluated with an appropriate mathematic model showing a flow of forces from one element to another. The rail track structure operates under the power loading from a train. This load considerably influences operation of the rail track structure and conditions the changes in the technical state in operation. In operation the technical state of the rail track structure is getting worse because the residual deformations accumulated in it, which lead to lower train traffic safety. Nowadays requirements for operational safety of the rail track structure are high, and the problem of evaluation of the stress-strain behavior of the rail base is of great importance.