Investigations on wagon–track interaction and running safety with unsupported sleepers

Abstract

Unsupported sleeper defects are not rare for the ballasted track. Based on the status quo of the railway in Kosovo, this paper presents a study on the wagon–track interaction and running safety risk with unsupported sleepers. A three-dimensional wagon–track dynamic model is first developed and validated through a full-scale field experiment. The dynamic response features of wagon and track components are respectively presented and analysed under the sleeper hanging condition. Parameter studies and safety analysis are then conducted with different wagon speeds, including gap height, unsupported quantity, wagon load, and asymmetric effects of the unsupported sleeper. The results indicate that unsupported sleepers will induce wheel–rail impact and significantly exacerbate the vibrations of the wagon and track. The wavelength corresponding to the dominant frequency for the wagon vertical acceleration (ACC) is equal to the wheelbase. Moreover, adjacent ballasts of the unsupported zone exhibit maximal displacements and ACCs, which could be the compelling evidence to explain the extension of the unsupported zone. The derailment risk is typically higher when the unsupported sleepers are asymmetrically distributed compared to the scenarios with symmetrically unsupported sleepers. Additionally, the combined effects of unsupported sleepers and wheel flat will further deteriorate the wagon running safety. The presented results can provide a significant reference for the wagon speed increase and track maintenance in Kosovo and other countries with deficient railway infrastructure.