The complex phenomenological model for prediction of inhomogeneous deformations of railway ballast layer after tamping works

Abstract

The given article considers the method of calculating the track geometry deformation with respect to uneven accumulation of residual deformations along the track. The technique proposes two significant changes in existing approaches to calculating the efficiency of the ballast layer. The transition from the approach of allowable stresses design in the ballast layer to the deformative approach of accumulations of track geometry deformations allows us to draw conclusions regarding the intervals of track tamping and the duration of ballast layer life cycle. The transition from the determinative to probabilistic approaches makes it possible to draw conclusions not only from the average unevenness, but also with regard to all possible facts of unevenness. The method is based on the mechanism of sudden and gradual deformations occurrence, which depends on a number of key factors: dynamic stresses on the ballast, non-uniformity of track elasticity, performance of current maintenance work. Based on the experimental studies results, the dependencies of sudden deformations and the intensity of gradual deformations on the level of stress on the ballast layer were established. The experimental results of the influence of the sub-ballast base elasticity on the intensity of accumulation of residual deformations are shown. On the basis of the developed method, the prediction of track geometry deterioration for a given structure of the track, the rolling stock and the permissible level of geometric deviations for track maintenance is presented.

Railroad Ballast Particle Breakage with Unique Laboratory Test Method

“…);  deterioration effect accelerated by substructure or superstructure defect;  effects of other dynamic loadings (e.g. welts, rail joints, turnout frogs [27,28,29,30,31,32]);  effects of track geometry and its degradation [33].…”

“…Other additional dynamic loading effect can't be neglected in sophisticated methods, e.g. surroundings of rail welts, rail joints, as well as switch frogs where higher ballast breakage should be expected [27,28,29,30,31,32]. Rubber coated and bitumen stabilised ballast particles hinder the geometric deterioration of railway track and ballast breakage [43,44,45], in detailed analysis it can be considered.…”

Stiffness and strength of structural layers from cohesionless material

“…The dynamic elastic modulus is usually around a factor of 1.2 to 2.5 above the static deformation modulus . From a coefficient comparison of (18) and (19), it follows that the safety factor of the condition expressed by equation (19) is 1.4 to 2.9. It should again be noted that the strength according to (18) or the permissible load according to (19), in contrast to solids is not a constant, but depends on the compression, so the size of the existing horizontal support stress.…”

Specific Evaluation Methodology of Railway Ballast Particles’ Degradation

“…The degradated ballasted track cause significant geometric changes that cause structural, stability and drainage problems. These problems could shorten the lifetime of the track even in a short term [1,50,51,52].…”