Analytical Evaluation of Ballasted Track Substructure Response under Repeated Train Loads

Punetha, Piyush; Nimbalkar, Sanjay; Khabbaz, Hadi

doi:10.1061/(asce)gm.1943-5622.0001729

Cited by 19 publications

(10 citation statements)

References 51 publications

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“…In the theoretical approach, the track modulus is evaluated by dividing the system support stiffness 39 with the sleeper spacing. The system support stiffness ( k t ) is evaluated as the series equivalent of the stiffness of the rail pad ( k p ), ballast ( k b ), subballast ( k s ) and subgrade ( k g ) layers 34

\frac{1}{k_{t}} = (\frac{1}{k_{p}} + \frac{1}{k_{b}} + \frac{1}{k_{s}} + \frac{1}{k_{g}})

…”

Section: Model Descriptionmentioning

confidence: 99%

“…To evaluate the vibrating mass and stiffness of the substructure layers, pyramidal distribution of vertical load from the sleeper bottom to the track substructure layers is assumed, which incorporates the overlapping of the load distribution pyramids along both longitudinal (i.e., the direction of train movement) and transverse directions 34 . Figure 4 illustrates the effective region of the load distribution pyramids beneath each sleeper position.…”

Section: Model Descriptionmentioning

confidence: 99%

“…Representing the track layers as an equivalent spring may simulate the overall track behaviour; however, this approach disregards the interaction among the substructure layers. Some researchers addressed this issue by modelling the substructure layers as lumped masses connected using visco‐elastic elements, such as springs and dashpots 31–34 . A few studies have also considered the substructure layers as an assemblage of discrete particles.…”

Section: Introductionmentioning

confidence: 99%

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Simplified geotechnical rheological model for simulating viscoelasto‐plastic response of ballasted railway substructure

Punetha

Nimbalkar

Khabbaz

2021

Num Anal Meth Geomechanics

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A proper understanding of the mechanical behaviour of the substructure layers is crucial for optimising the design and performance of a ballasted railway track. The recent advent of high‐speed trains and heavy haul freight wagons has heightened this need more than ever. The accurate prediction of the long‐term performance of the railway tracks under increased speed and loads still remains an intriguing challenge for researchers and design engineers. In this context, the present paper proposes a simplified geotechnical rheological model to evaluate the viscoelasto‐plastic response of the track substructure layers. The proposed approach combines plastic slider, elastic springs and viscous dampers to predict the transient response during a train passage, and the irrecoverable deformation accumulated in the track substructure over an operational period. The model simulates tri‐layered substructure (ballast, subballast, and subgrade) in comparison with existing rheological approaches employing either single or dual‐layered substructure. The model is validated against the field data published in the literature. An acceptable agreement between the predicted results and the field data verifies the accuracy of the model. Parametric investigations are conducted to study the influence of train and track parameters on the cumulative track deformation. The results demonstrate the enhanced capability of the rheological model to adequately capture the crucial effects of axle load, train speed and thickness of granular layers on the accumulation of track settlement. The proposed method can provide an effective tool for the practising engineers for quick prediction of changes to the geometry of railway tracks over their operational periods.

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\frac{1}{k_{t}} = (\frac{1}{k_{p}} + \frac{1}{k_{b}} + \frac{1}{k_{s}} + \frac{1}{k_{g}})

…”

Section: Model Descriptionmentioning

confidence: 99%

Section: Model Descriptionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Simplified geotechnical rheological model for simulating viscoelasto‐plastic response of ballasted railway substructure

Punetha

Nimbalkar

Khabbaz

2021

Num Anal Meth Geomechanics

Self Cite

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“…The displacements of the granular layers (ballast or subballast) also depend on the underlying subgrade type. Punetha et al (2020a) observed that the deformations in the ballast and the subballast layers in an open track are much higher when the subgrade soil is stiff compared to the case when the subgrade soil is soft. However, the influence of subgrade soil properties on the performance of the transition zones is not yet fully perceived.…”

Section: Introductionmentioning

confidence: 96%

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

Punetha

Maharjan

Nimbalkar

2021

Front. Built Environ.

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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.

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“…Most studies addressing track settlements at transition zones considering the train-track interaction have used simplified 1D Winkler type models coupled with empirical settlement formulas, as in (Mauer, 1995;Hunt, 1997;Kempfert and Hu, 1999;Varandas et al, 2014a). However, because 1D Winkler models require extensive calibration of material parameters and other modeling aspects, such as equivalent springs and dampers (Punetha et al, 2020), its application to real scenarios or to perform parametric studies has been somewhat limited.…”

Section: Introductionmentioning

confidence: 99%

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

Paixão

Varandas

Fortunato

2021

Front. Built Environ.

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Transition zones between embankments and bridges or tunnels are examples of critical assets of the railway infrastructure. These locations often exhibit higher degradations rates, mostly due to the development of differential settlements, which amplify the dynamic train-track interaction, thus further accelerating the development of settlements and deteriorating track components and vehicles. Despite the technical and scientific interest in predicting the long-term behavior of transition zones, few studies have been able to develop a robust approach that could accurately simulate this complex structural response. To address this topic, this work presents a three-dimensional finite element (3D FEM) approach to simulate the long-term behavior of railway tracks at transition zones. The approach considers both plastic deformation of the ballast layer using a high-cycle strain accumulation model and the non-linearity of the dynamic vehicle-track interaction that results from the evolution of the deformed states of the track itself. The results shed some light into the behavior of transition zones and evidence the complex long-term response of this structures and its interdependency with the transient response of the train-track interaction. Aspects that are critical when assessing the performance of these systems are analyzed in detail, which might be of relevance for researchers and practitioners in the design, construction, and maintenance processes.

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Analytical Evaluation of Ballasted Track Substructure Response under Repeated Train Loads

Cited by 19 publications

References 51 publications

Simplified geotechnical rheological model for simulating viscoelasto‐plastic response of ballasted railway substructure

Simplified geotechnical rheological model for simulating viscoelasto‐plastic response of ballasted railway substructure

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

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

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