Analysis of the Dynamic Wheel Loads in Railway Transition Zones Considering the Moisture Condition of the Ballast and Subballast

Abstract

Transition zones in railway tracks are the locations with considerable changes in vertical support structures, e.g., near bridges. Due to possible water flow constrictions in transition zone structures, there is frequently an increased moisture level in the ballast/subballast layers, which is a potential source of track degradation. This paper presents results of the moisture condition measured in three transition zones using ground penetrating radar, where the ballast/subballast are analyzed. The relationship between the moisture condition and track degradation in the transition zones is studied by comparing it to the longitudinal track level that is measured by the track inspection coaches. A strong connection is found between the high moisture condition and track degradation in the transition zones. The dynamic behavior of the transition zones with high moisture condition is analyzed using the Finite Element method. Differential stiffness and settlement are taken into consideration in the transition zone model, which is also coupled with a vehicle. The ballast/subballast layers are modelled as solid elements. Increased moisture conditions are considered as a reduction of elastic modulus, according to laboratory findings. Results show that high moisture leads to an increase of dynamic wheel loads in the transition zone, which explains the connection and confirms that the high moisture condition is a source of transition zone problems.

Advancement and Application of the Bezgin Method to Estimate Effects of Stiffness Variations along Railways on Wheel Forces

“…Comparison of Equations 15 and 27 shows that the impact forces generated because of a transition along a track relate to whether k 1 increases n-fold to k 2 or reduces 1/n th to k 2 . Existing work based on advanced finite element analysis (FEA) also supports this finding (5).The next section provides an application of the two presented equations.…”

“…Changes related to environmental conditions such as freeze–thaw and variations of moisture content of the track supporting layers may contribute to variation of track stiffness. Water flow constrictions in transition zones can result in increased moisture content that can lead to reduced track stiffness ( 5 ). Use of micropiles and other foundation elements or treatments to the supporting layers can change the track stiffness as well ( 6 ).…”

Dynamic Behavior in Transition Zones and Long-Term Railway Track Performance

“…While many authors have studied the transient train-track interaction at transition zones using tri-dimensional numerical approaches (Wang et al, 2017;Paixão et al, 2018;Ngamkhanong et al, 2020), others have proposed 3D FEM models with true tridimensional plastic deformation formulations to simulate the development of settlements, but mostly focusing on aspects other than transition zones. For example, Li et al (2016) and Shih et al (2019) presented implementations in commercial FEM software, but limited the analysis to very short sections of track and considered the static loading only (no vehicle-track interaction).…”

Effect of Track Irregularities on the Response of Two-Way Railway Tracks

“…This assumption is not useful while considering track irregularities. Furthermore, a lot of FEM based parametric studies have been carried out to investigate the effect of moving load under different track and ground conditions [16][17][18][19][20][21][22].…”