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F. Lamas-Lopez^1,2, Y.J. Cui¹, T. Zhang¹, J.-C. Dupla¹, N. Calon², S. Costa D'Aguiar³, J. Canou¹ and A.-M. Tang¹

¹Ecole des Ponts ParisTech, Laboratoire Navier - CERMES, Marne-la-Vallée, France
²Direction Ingénierie & Projets, Département Ligne, Voie et Environnement, SNCF-Réseau, La Plaine Saint-Denis, France
³Direction Innovation & Recherche, SNCF, Paris, France

Keywords: track-bed materials, interlayer, cyclic loading, strain amplitude effect, train-speed impact, triaxial tests, hysteresis loop, elastic behaviour.

Summary

In order to improve the service provided by railway operators, infrastructure administrators seek to upgrade the service speeds on their conventional networks. When train speed is upgraded, an increase of the cyclic strain amplitude caused by the trains' axles is expected. The strain amplitude loading track-bed layers below ballast, as the interlayer, depends on the train speed, the rolling stock (axle load) and the mechanical state of the upper track-bed materials. The train loading, resulting in soil strain, is attenuated by ballast grains at a depth when transmitted from rail to track-bed materials. Axle loads and train speeds will play a significant role in the track-bed materials cyclic strains. An interlayer soil, fabricated in the laboratory, was tested on a large scale triaxial cell. Different cyclic solicitations, controlled by strains amplitudes, were induced to the sample. The range of vertical strain amplitudes were taken from accounts from a literature review and from in-situ measurements on conventional tracks. Moreover, different soil confining pressures were considered for the cyclic tests: from 25 kPa to 200 kPa. Cyclic loading was applied in compression and traction. Furthermore, as strain amplitudes were very small, they were measured using local strain gages able to measure strains up to 10-6 percent. These gauges were glued to the sample to determinate vertical and radial strains. Therefore, the tests results showed a decrease of soil's resilient modulus similar to when the strain amplitude is increased. The decrease rate is similar for all the tested confining pressures. This decrease of resilient modulus could involve an increase of the materials plastic deformation when the train speed is upgraded or the axle load is increased on a line.

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Front Page Browse CCP CSETS CTR IJRT Other Authors Search Purchase Guide FAQ Contact us	Civil-Comp Proceedings ISSN 1759-3433 CCP: 110 PROCEEDINGS OF THE THIRD INTERNATIONAL CONFERENCE ON RAILWAY TECHNOLOGY: RESEARCH, DEVELOPMENT AND MAINTENANCE Edited by: J. Pombo Paper 28 Cyclic Strain Amplitude Impact on the Soil Dynamic Parameters of Conventional Railway Track-Bed Materials F. Lamas-Lopez^1,2, Y.J. Cui¹, T. Zhang¹, J.-C. Dupla¹, N. Calon², S. Costa D'Aguiar³, J. Canou¹ and A.-M. Tang¹ ¹Ecole des Ponts ParisTech, Laboratoire Navier - CERMES, Marne-la-Vallée, France ²Direction Ingénierie & Projets, Département Ligne, Voie et Environnement, SNCF-Réseau, La Plaine Saint-Denis, France ³Direction Innovation & Recherche, SNCF, Paris, France doi:10.4203/ccp.110.28 purchase the full-text of this paper Full Bibliographic Reference for this paper F. Lamas-Lopez, Y.J. Cui, T. Zhang, J.-C. Dupla, N. Calon, S. Costa D'Aguiar, J. Canou, A.-M. Tang, "Cyclic Strain Amplitude Impact on the Soil Dynamic Parameters of Conventional Railway Track-Bed Materials", in J. Pombo, (Editor), "Proceedings of the Third International Conference on Railway Technology: Research, Development and Maintenance", Civil-Comp Press, Stirlingshire, UK, Paper 28, 2016. doi:10.4203/ccp.110.28 Keywords: track-bed materials, interlayer, cyclic loading, strain amplitude effect, train-speed impact, triaxial tests, hysteresis loop, elastic behaviour. Summary In order to improve the service provided by railway operators, infrastructure administrators seek to upgrade the service speeds on their conventional networks. When train speed is upgraded, an increase of the cyclic strain amplitude caused by the trains' axles is expected. The strain amplitude loading track-bed layers below ballast, as the interlayer, depends on the train speed, the rolling stock (axle load) and the mechanical state of the upper track-bed materials. The train loading, resulting in soil strain, is attenuated by ballast grains at a depth when transmitted from rail to track-bed materials. Axle loads and train speeds will play a significant role in the track-bed materials cyclic strains. An interlayer soil, fabricated in the laboratory, was tested on a large scale triaxial cell. Different cyclic solicitations, controlled by strains amplitudes, were induced to the sample. The range of vertical strain amplitudes were taken from accounts from a literature review and from in-situ measurements on conventional tracks. Moreover, different soil confining pressures were considered for the cyclic tests: from 25 kPa to 200 kPa. Cyclic loading was applied in compression and traction. Furthermore, as strain amplitudes were very small, they were measured using local strain gages able to measure strains up to 10-6 percent. These gauges were glued to the sample to determinate vertical and radial strains. Therefore, the tests results showed a decrease of soil's resilient modulus similar to when the strain amplitude is increased. The decrease rate is similar for all the tested confining pressures. This decrease of resilient modulus could involve an increase of the materials plastic deformation when the train speed is upgraded or the axle load is increased on a line. purchase the full-text of this paper (price £22) go to the previous paper go to the next paper return to the table of contents return to the book description purchase this book (price £85 +P&P)
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