— When heavy repetitive train load acts on the ballast its particles are crushed Crushed fine particles enter into the void spaces of the ballast This reduces the porosity of the ballast and affects its drainage properties Recycled ballast has less angularity number as their sharp corners might have been broken due to past train load
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— It is important to have consistent ballast testing methods that provide results reflecting the performance of different ballast materials in the railway trackbed Extensive laboratory tests have been conducted to investigate the correlation between simple ballast index tests and box tests simulating ballast field loading conditions in a
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— Railway ballast is an angular and coarse material which demands careful DEM modelling and validation Particle shape is often modelled in high accuracy thus leading to computational expensive DEM models Whether this effort will increase the DEM model s overall prediction quality will also vitally depend on the used contact law and the
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— Railway ballast is a layer of coarse stones located beneath the track and around the sleepers Its primary function is to provide drainage support the track vertically and to provide lateral
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— Ballast is coarse aggregate with particle size normally ranging from 10 mm to 65 mm Upon repeated train loading ballast deteriorates in the form of either continuous abrasion of sharp corners or size degradation which have been reported as the fundamental cause for the instability of railway tracks In this study the splitting behavior
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— Railway ballast layer is an indispensable component of railway transport when AR and Φ are both constant for different type of ballast the porosity distributions are same for parameters AR
— The porosity of railway ballast is an important maintenance quality evaluation index during tamping process In this paper based on the discrete characteristics of railway ballast the discrete
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— Values of flow resistivity porosity viscous characteristic length and tortuosity either measured non acoustically or deduced from impedance tube data for railway ballast and porous concrete have
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— In this study a numerical simulation of fluid flow through railway ballast in the time domain is presented providing a model for unsteady state flow It is demonstrated that the position of the free surface with respect to time can also be used to solve the steady flow case The effect of ballast fouling is included in the model to capture the realistic
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— The porosity of railway ballast is an important maintenance quality evaluation index during tamping process In this paper based on the discrete characteristics of railway ballast the discrete element analysis model of railway ballast is created using the discrete element method numerical simulations are performed to study the evolution of
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— We investigated the dynamic behavior of a railway ballast layer during tamping operation by 3D Discrete Element simulations The ballast layer was prepared with ballast grains that had a realistic shape and was measured by a laser scanner and modeled by clumped spheres using the dynamic optimization technique
— The porosity of railway ballast is an important maintenance quality evaluation index during tamping process In this paper based on the discrete characteristics of railway ballast the discrete
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— The method is then extended to realistic railway ballast including the effects of ballast fouling It is shown that when the flow begins to overtop the ballast the free surface shifts to greatly increase the chance of ballast scouring Before beginning our comparison we must determine the porosity of the ballast from the reported
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— 1 Introduction Today mainly in the last decades railroad transportation will have a significant role in development and civilization In the 1800s and 1900s more and more railway lines were constructed worldwide [1] There were main tasks that had to be solved developing the hauling force of the railway engines; continuously changeover
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— When the railway in desert areas adopts ballasted track structure due to the voids between ballast in the ballast bed [7] [8] the sand will invade and sink continuously under the coupling action of wind and train load which will gradually reduce the ballast voids increase the the particle arrangement of the ballast bed and the
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— Introduction Ballast layer is the crucial component for the ballasted track [1] Ballast layer differential deformation very likely results in track irregularity [2] [3] Under the train cyclic loadings after long service time the ballast layer differential deformation possibility gradually increases and meanwhile the ballast layer gradually loses its
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— The flow resistivity and porosity of this ballast sample have been measured These have been used in a local reaction model based on the Johnson Allard formulation to predict the ballast absorption showing good agreement with measurements of the absorption coefficient Due to the gaps between the stones the railway ballast behaves
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— We characterize an industrial process currently used on railway track tamping operation This process is employed in order to restore the geometry of railway track distorted by train traffics The main goal is to compact the granular material under the sleepers supporting the railroad squeezing and vibrations
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— As was expected by decreasing the ballast porosity making a more compacted layer of higher density the lateral resistance of the track increased Behavior of fresh and fouled railway ballast subjected to direct shear testing discrete element simulation Geomechanics 14 2014 pp 34 44 View in Scopus Google Scholar
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— Measurement of the porosity of ballast The porosity is the other important and fundamental parameter required to describe the acoustic property of porous materials This is defined as the ratio of the voids to the total volume of the sample A measurement method has been devised to determine the porosity of the 1 5 scale ballast
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