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Duong T.V.,ParisTech National School of Bridges and Roads | Trinh V.N.,ParisTech National School of Bridges and Roads | Cui Y.J.,ParisTech National School of Bridges and Roads | Tang A.M.,ParisTech National School of Bridges and Roads | Calon N.,French National Railway Company SNCF
Geotechnical Testing Journal

To study the hydraulic behavior of fouled ballast, an infiltration column 600mm high and 300mm in diameter was developed. Five time domain reflectometer (TDR) sensors and five tensiometers were installed at various levels, allowing the measurement of volumetric water content and matric suction, respectively. The material studied was fouled ballast that was formed in the railway track-bed by penetration of fine-grained soil into the ballast. This material is characterized by a high contrast of size between the largest and the smallest particles. During the test, three stages were followed: saturation, drainage, and evaporation. Based on the test results, the water-retention curve and the unsaturated hydraulic conductivity were determined. The quality of the results shows the capacity of this large-scale infiltration column in studying the unsaturated hydraulic properties of such fouled ballast.Copyright © 2012 by ASTM International. Source

Duong T.V.,ParisTech National School of Bridges and Roads | Tang A.M.,ParisTech National School of Bridges and Roads | Cui Y.-J.,ParisTech National School of Bridges and Roads | Trinh V.N.,ParisTech National School of Bridges and Roads | And 4 more authors.
Soils and Foundations

In the ancient railway sub-structure in France, after years of operation, the inter-penetration of fine particles of sub-grade and ballast has created a new layer referred to as the interlayer. As it was naturally formed, the fines content and water content of the interlayer vary considerably. In this study, the effects of the fines and water contents on the mechanical behavior of interlayer soil were investigated by carrying out large-scale monotonic and cyclic triaxial tests. The results of the monotonic triaxial tests show that adding more fines in the interlayer soil does not significantly change the shear strength in the dry condition (water content w=4% and 6%), but drastically decreases the shear strength parameters (friction angle and cohesion) in the nearly saturated condition (w=12%). The cyclic triaxial tests were performed at various deviator stress levels. By considering the permanent axial strain at the end of application of each stress level, it was found that the higher the fines content in the nearly saturated condition (w=12%), the larger the permanent axial strain. In the case of lower water content (w=4% and 6%), the opposite trend was identified: adding fines decreases the permanent axial strain. © 2013 The Japanese Geotechnical Society. Source

Bausseron T.,French National Railway Company SNCF | Baucour P.,FEMTO ST Institute | Glises R.,FEMTO ST Institute | Verschelde S.,French National Railway Company SNCF | Chamagne D.,FEMTO ST Institute
ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE)

The overheating problem of the railroad catenary at the contact with the pantograph when the train is stopped and electrically fed is responsible of many incidents. This paper describes an experimental study and a numerical model of a catenary/pantograph system used during the preconditioning of the train. Several incidents of wire breakage have highlighted the importance of the catenary/pantograph heating problem, in those incidents the contact wire had melted and broke itself. The experimental setups consists of estimating the contact's thermal resistance and area in order to calculate which part of the interface heat flux go throught the catenary's contact wire and which part go throught the pantograph's collector strip. The numerical model is based on several phenomena as heat conduction into the wires, heat exchange with ambiance through convection, Joule effects and heat flux from the interface. Copyright © 2014 by ASME. Source

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