Mechanism of Sleeper–Ballast Dynamic Impact and Residual Settlements Accumulation in Zones with Unsupported Sleepers
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Date
2021
Journal Title
Journal ISSN
Volume Title
Publisher
MDPI
Abstract
EN: Unsupported sleepers or void zones in ballasted tracks are one of the most recent and
frequent track failures. The void failures have the property of intensive development that, without
timely maintenance measures, can cause the appearance of cost-expensive local instabilities such
as subgrade damages. The reason for the intensive void development lies in the mechanics of the
sleeper and ballast bed interaction. The particularity of the interaction is a dynamic impact that occurs
due to void closure. Additionally, void zones cause inhomogeneous ballast pressure distribution
between the void zone and fully supported neighbour zones. The present paper is devoted to
studying the mechanism of the sleeper–ballast dynamic impact in the void zone. The results of
experimental in situ measurements of rail deflections showed the significant impact accelerations
in the zone even for lightweight slow vehicles. A simple three-beam numerical model of track and
rolling stock interaction has shown dynamic interaction similar to the experimental measurements.
Moreover, the model shows that the sleeper accelerations are more than 3 times higher than the
corresponding wheel accelerations and the impact point appears before the wheel enters the impact
point. The analysis of ballast loadings shows the specific impact behaviour in combination with the
quasistatic part that is different for void and neighbour zones, which are characterised by high ballast
pre-stressed conditions. The analysis of void size influence demonstrates that the maximal impact
loadings and maximal wheel and sleeper accelerations appear at a certain void depth, after which the
values decrease. The ballast quasistatic loading analysis indicates an increase of more than 2 times
in the ballast loading in neighbour zones for long voids and almost full quasistatic unloading for
short-length voids. However, the used imitation model cannot explain the nature of the dynamic
impact. The mechanism of the void impact is clearly explained by the analytic solution using a
simple clamped beam. A simplified analytical expression of the void impact velocity shows that it is
linearly related to the wheel speed and loading. The comparison to the numerically simulated impact
velocities shows a good agreement and the existence of the void depth with the maximal impact. An
estimation of the long-term influences for the cases of normal sleeper loading, high ballast pre-stress
and quasistatic loading in the neighbour zones and high impact inside the void is performed.
Description
M. Sysyn: ORCID 0000-0001-6893--0018; O. Nabochenko: ORCID 0000-0001-6048-2556
Keywords
ballasted track, unsupported sleepers, sleeper–ballast dynamic impact, dynamic simulation, analytic solution, discrete element modelling, КРС (ЛФ)
Citation
Sysyn M., Przybylowicz M., Nabochenko O., Liu J. Mechanism of Sleeper–Ballast Dynamic Impact and Residual Settlements Accumulation in Zones with Unsupported Sleepers. Sustainability. 2021 Vol. 13, Iss. 14. DOI: 10.3390/su13147740.