Finite Element Modeling of the Dynamic Response of Critical Zones in a Ballasted Railway Track

Abstract

The critical zones are the discontinuities along a railway line that are highly susceptible to differential settlement, due to an abrupt variation in the support conditions over a short span. Consequently, these zones require frequent maintenance to ensure adequate levels of passenger safety and comfort. A proper understanding of the behavior of railway tracks at critical zones is imperative to enhance their performance and reduce the frequency of costly maintenance operations. This paper investigates the dynamic behavior of the critical zone along a bridge-open track transition under moving train loads using two-dimensional finite element approach. The influence of different subgrade types on the track behavior is studied. The effectiveness of using geogrids, wedge-shaped engineered backfill and zone with reduced sleeper spacing in improving the performance of the critical zone is evaluated. The numerical model is successfully validated against the field data reported in the literature. The results indicate that the subgrade soil significantly influences the track response on the softer side of the critical zone. The difference in vertical displacement between the stiffer and the softer side of a track transition decreases significantly with an increase in the strength and stiffness of the subgrade soil. The subgrade layer also influences the contribution of the granular layers (ballast and subballast) to the overall track response. As the subgrade becomes stiffer and stronger, the contribution of the granular layers to the overall track displacement increases. The mitigation techniques that improve the stiffness or strength of granular layers may prove more effective for critical zones with stiff subgrade than critical zones with soft subgrade. Among all the mitigation techniques investigated, the wedge-shaped engineered backfill significantly improved the performance of the critical zone by gradually increasing the track stiffness.

Response Analysis of a Ballasted Rail Track Constructed on Soft Soil by 3D Modeling

“…Te subgrades for the other two cases also show a similar increase in force per unit area compared to their respective subballasts. Tis signifes that the subgrade carries greater loads than the ballast or subballast when subjected to wheel loads [61] also showed that subgrade reactions to wheel loads are larger than subballast and ballast reactions.…”

Numerical Investigation of Deformation Behavior of Ballast Reinforced with Polyurethane Under a Moving Wheel Load

“…Sonlu elemanlar yönteminin demiryolu hatlarının yük altındaki davranışını analiz etmedeki etkinliği literatürde kanıtlanmıştır [24]. Demiryolu hatlarının davranışı geoteknik mühendisleri tarafından yaygın olarak kullanılan PLAXIS sonlu elemanlar programı ile iki ve üç boyutlu olarak araştırılmıştır [24,[28][29][30][31]. İki boyutlu analizler ile kıyaslandığında, üç boyutlu analizler daha fazla hesaplama süresine ihtiyaç duymaktadır.…”

“…Önceki çalışmalara uygun olarak, ray ve traversin modellenmesinde lineer elastik (LE) model kullanırken taban zemini ve alt balastın davranışının modellenmesinde Mohr-Coulomb (MC) model kullanılmıştır [24,28]. Ray, travers, alt balast ve taban zeminin malzeme özellikleri ise Jiang ve Nimbalkar [24] Lokomotif kısmında bulunan dingillerin her birinin yükü yaklaşık 170 kN, uç bojilerdeki dingil yükleri yaklaşık 120 kN ve bar vagonlarındaki dingil yükleri de yaklaşık 155 kN'dir.…”

The effect of soil improvement and auxiliary rails at railway track transition zones

“…A suitable FEM approach depends on the required precision and the complexity of the problem [5]. 2D models can consider the discontinuities of track structure in either horizontal or longitudinal planes [23][24][25][26]. However, the real field geometries of track transition zones can be more complex and non-typical in both directions; for example, the embankment bridge approaches with the auxiliary rails representing the discontinuities in longitudinal and horizontal direction [27].…”