image: Track bed cumulative dynamic effect prediction framework.
Credit: Liu Pan, Tatsuya Ishikawa, Lei Xu, Bin Yan
The combined effects of cyclic train loading, track irregularities, and the longitudinal non-uniformity of ballasted tracks induce uneven ballast settlement. Concurrently, the deterioration of dynamic performance accelerates the progression of ballast settlement. In particular, the dynamic cumulative effect (DCE) of ballast settlement poses major challenges to the operation, maintenance, and scientific management of ballasted tracks.
In a new study published in the Journal of Railway Science and Technology, a team of researchers proposed a model consisting of three main components: the train-ballasted track (TBT) system dynamic model, the University of Illinois at Urbana-Champaign (UIUC) empirical model, and an improved Newton iteration method that accounts for sleeper voids.
"We analyzed the evolution of ballast settlement and the dynamic performance of the TBT system under varying moisture contents and degrees of aging," shares lead author Liu Pan. "Focus was placed on the influence of dynamic cumulative effects and sleeper voiding on the development pattern of ballast settlement."
Numerical results indicate that the DCE of ballast settlement exacerbates the deterioration of both ballast settlement and the dynamic performance of the TBT system.
"Specifically, this effect becomes more pronounced with higher ballast moisture content and prolonged operation time," says Pan. "For ballasts in better condition than AB L30, the influence of ballast settlement and DCE on the dynamic performance of the TBT system can be disregarded."
Conversely, for ballasts in poorer condition than AB L30, the dynamic response of the ballasted track increases by 30%, and the wheel load reduction rate more than doubles. "Therefore, it is crucial to prioritize monitoring areas with significant dynamic responses within the TBT system such as rail welds, bridge-subgrade transition sections," adds Pan.
According to corresponding author Tatsuya Ishikawa, it is worth noting that incorporating DCE requires iterative solutions of the TBT system, which significantly increases the computational cost. "When ballast settlement is minimal, the DCE can be neglected to reduce computational expenses, allowing the UIUC model to be used directly for predicting ballast settlement," says Ishikawa.
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Contact the author:
Tatsuya Ishikawa
Faculty of Civil Engineering, Hokkaido University, Sapporo 060-8628, Japan
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Article Title
Dynamic Cumulative Effect of Ballast Settlement Considering Sleeper Void using a 3D Train–Ballasted Track
COI Statement
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.