Tutorial on the fragmentation of the railway ballast particles and calibration methods in discrete element modelling

Juhász, Erika; Fischer, Szabolcs

doi:10.14513/actatechjaur.00569

Cited by 8 publications

(4 citation statements)

References 31 publications

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“…The intensity is defined as the linear accumulation of the vertical residual deformations per million loading cycles. The DEM is widely used to study ballasted railway tracks [50][51][52][53][54][55][56]. Jing et al [57] used the DEM to simulate the hanging sleeper dynamic characteristics of the ballast bed, and the ballast particle breakage under dynamic cyclic loads was investigated.…”

Section: Estimation Of Residual Settlement Intensity Of the Ballast L...mentioning

confidence: 99%

Mechanism of Sleeper–Ballast Dynamic Impact and Residual Settlements Accumulation in Zones with Unsupported Sleepers

et al. 2021

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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.

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Section: Estimation Of Residual Settlement Intensity Of the Ballast L...mentioning

confidence: 99%

Mechanism of Sleeper–Ballast Dynamic Impact and Residual Settlements Accumulation in Zones with Unsupported Sleepers

et al. 2021

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“…The ballast layer consolidation was investigated by several researchers using different methods (Sysyn et al, 2018;Sysyn et al, 2019;Juhász & Fischer, 2021). These methods are related to laboratory tests, field tests, numerical modeling, finite element, as well as discrete element modeling, etc.…”

Section: Reports In Mechanical Engineeringmentioning

confidence: 99%

Investigation of deformations of ballasted railway track during collapse using the Digital Image Correlation Method (DICM)

Szalai¹,

Eller²,

Juhász³

et al. 2022

Rep. Mech. Eng.

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This paper summarizes the results of laboratory tests in which the authors investigated the effects of extremely high vertical load to a railway track segment. The segment consisted of a cut concrete sleeper (contact area: 290×390 mm) with a pair of direct-elastic rail fasteners; the sleeper pieces had a standard, full height; the structure had a typical 350 mm depth railway ballast, underneath approx. 200 mm sandy gravel supplementary layer. The whole assembly was built in a 2.00×2.20 m area wooden rack. The deformations due to the approx. 150 kN static concentrated vertical force were measured and recorded by Digital Image Correlation Method (DICM), ensuring the GOM ATOS technology. The 150 kN peak load meant 1326 kPa vertical stress at the sleeper-ballast interface. The 3D geometry was scanned before the loading and after the collapse. In this way, the comparison was able to be executed. The maximum vertical deformation was 115 mm. The DICM technique is a relatively new methodology in civil engineering; however, it has been applied for more than ten years in mechanical engineering. Therefore, the authors investigated the applicability of DICM in this field. As a result, the pre and the post-states were determined in 3D. The displacement of the ballast particles was able to be defined with the possibility of drawing the displacement trajectories of given points. The DICM can be a valuable methodology in railway engineering, e.g., laboratory tests and field test applications.

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“…A brief literature review according to the fracture of the railway ballast particles was introduced by Juhász and Fischer [32]. Providing better understanding of the international achievements was the goal of this work.…”

Section: Figure 12 Local Substructure Failure [32]mentioning

confidence: 99%

Special reinforcement solutions of railway permanent ways’ soil substructures

Habashneh

2021

Acta Tech. Jaurinensis

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This mini review aims to summarize relevant international publications. Thus, based on this, giving a comprehensive review about the reinforcement solutions of permanent ways' soil substructure. Generally, the core weakness of soil is its inadequacy to resist tensile stresses. The main target of strengthening the soil is to enhance the engineering characteristics of the soil to build up specific parameters such as shear strength, compressibility, density, and hydraulic conductivity. In addition, special reinforcement techniques of railway permanent ways' soil substructures will be considered in this paper due to the increasing demand of improving railways and rehabilitation process. The main findings of this study that there are a lot of special reinforcement techniques which can be considered as effective solution for soil stabilization such as geosynthetic reinforcement.

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Tutorial on the fragmentation of the railway ballast particles and calibration methods in discrete element modelling

Cited by 8 publications

References 31 publications

Mechanism of Sleeper–Ballast Dynamic Impact and Residual Settlements Accumulation in Zones with Unsupported Sleepers

Mechanism of Sleeper–Ballast Dynamic Impact and Residual Settlements Accumulation in Zones with Unsupported Sleepers

Investigation of deformations of ballasted railway track during collapse using the Digital Image Correlation Method (DICM)

Special reinforcement solutions of railway permanent ways’ soil substructures

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