Documents disponibles écrits par cet auteur

Determination of dynamic track modulus from measurement of track velocity during train passage / J. A. Priest in Journal of geotechnical and geoenvironmental engineering, Vol. 135 N° 11 (Novembre 2009) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 135 N° 11 (Novembre 2009) . - pp. 1732–1740 Titre : Determination of dynamic track modulus from measurement of track velocity during train passage Type de document : texte imprimé Auteurs : J. A. Priest, Auteur ; W. Powrie, Auteur Année de publication : 2009 Article en page(s) : pp. 1732–1740 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Railroad  tracksStiffnessVelocityDynamic  loadsMeasurement Résumé : The measurement of track stiffness, or track modulus, is an important parameter for assessing the condition of a railway track. This paper describes a method by which the dynamic track modulus can be determined from the dynamic displacements of the track during normal train service, measured using geophones. Two techniques are described for calculating the track modulus—the inferred displacement basin test (DBT) method and a modified beam on an elastic foundation (BOEF) method. Results indicate that the viscoelastic response of the soil will influence the value of track modulus determined using the DBT method. The BOEF method was therefore used to calculate the apparent increase in axle load due to train speed. Hanging or partly supported sleepers were associated with a relatively small increase in dynamic axle loads with train speed. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29GT.1943-5606.0000130 [article] Determination of dynamic track modulus from measurement of track velocity during train passage [texte imprimé] / J. A. Priest, Auteur ; W. Powrie, Auteur . - 2009 . - pp. 1732–1740. Geotechnical and geoenvironmental engineering Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 135 N° 11 (Novembre 2009) . - pp. 1732–1740 Mots-clés : Railroad  tracksStiffnessVelocityDynamic  loadsMeasurement Résumé : The measurement of track stiffness, or track modulus, is an important parameter for assessing the condition of a railway track. This paper describes a method by which the dynamic track modulus can be determined from the dynamic displacements of the track during normal train service, measured using geophones. Two techniques are described for calculating the track modulus—the inferred displacement basin test (DBT) method and a modified beam on an elastic foundation (BOEF) method. Results indicate that the viscoelastic response of the soil will influence the value of track modulus determined using the DBT method. The BOEF method was therefore used to calculate the apparent increase in axle load due to train speed. Hanging or partly supported sleepers were associated with a relatively small increase in dynamic axle loads with train speed. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29GT.1943-5606.0000130

Dynamic stress analysis of a ballasted railway track bed during train passage / L. A. Yang in Journal of geotechnical and geoenvironmental engineering, Vol. 135 N° 5 (Mai 2009) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 135 N° 5 (Mai 2009) . - pp. 680–689 Titre : Dynamic stress analysis of a ballasted railway track bed during train passage Type de document : texte imprimé Auteurs : L. A. Yang, Auteur ; W. Powrie, Auteur ; J. A. Priest, Auteur Année de publication : 2009 Article en page(s) : pp. 680–689 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Railroad  track  Numerical  models  Numerical  analysis  Stress  analysis Résumé : Scientific design of a railway track formation requires an understanding of the subgrade behavior and the factors affecting it. These include the effective resilient stiffness during train passage, which is likely to depend on the stress history and the stress state of the ground, and the stress path followed during loading. This study investigates the last of these, by means of a two-dimensional dynamic finite-element analysis. The effects of train speed, acceleration/braking, geometric variation in rail head level, and a single unsupported sleeper are considered. Results indicate that dynamic effects start to become apparent when the train speed is greater than 10% of the Rayleigh wave speed, vc , of the subgrade. At a train speed of 0.5vc , the shear stresses will be underestimated by 30% in a static analysis, and at train speeds greater than vc the stresses due to dynamic effects increase dramatically. Train acceleration/braking may increase shear stresses and horizontal displacements in the soil, and hence the requirement for track maintenance at locations where trains routinely brake or accelerate. For heavy haul freight trains, long wavelength variations in rail head level may lead to significantly increased stresses at passing frequencies (defined as the train speed divided by the wavelength of the variation in level) greater than 15, and short wavelength variations at passing frequencies of 60–70. Stress increases adjacent to an unsupported sleeper occur in the ballast and subballast layers, but rapidly become insignificant with increasing depth. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29GT.1943-5606.0000032 [article] Dynamic stress analysis of a ballasted railway track bed during train passage [texte imprimé] / L. A. Yang, Auteur ; W. Powrie, Auteur ; J. A. Priest, Auteur . - 2009 . - pp. 680–689. Geotechnical and geoenvironmental engineering Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 135 N° 5 (Mai 2009) . - pp. 680–689 Mots-clés : Railroad  track  Numerical  models  Numerical  analysis  Stress  analysis Résumé : Scientific design of a railway track formation requires an understanding of the subgrade behavior and the factors affecting it. These include the effective resilient stiffness during train passage, which is likely to depend on the stress history and the stress state of the ground, and the stress path followed during loading. This study investigates the last of these, by means of a two-dimensional dynamic finite-element analysis. The effects of train speed, acceleration/braking, geometric variation in rail head level, and a single unsupported sleeper are considered. Results indicate that dynamic effects start to become apparent when the train speed is greater than 10% of the Rayleigh wave speed, vc , of the subgrade. At a train speed of 0.5vc , the shear stresses will be underestimated by 30% in a static analysis, and at train speeds greater than vc the stresses due to dynamic effects increase dramatically. Train acceleration/braking may increase shear stresses and horizontal displacements in the soil, and hence the requirement for track maintenance at locations where trains routinely brake or accelerate. For heavy haul freight trains, long wavelength variations in rail head level may lead to significantly increased stresses at passing frequencies (defined as the train speed divided by the wavelength of the variation in level) greater than 15, and short wavelength variations at passing frequencies of 60–70. Stress increases adjacent to an unsupported sleeper occur in the ballast and subballast layers, but rapidly become insignificant with increasing depth. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29GT.1943-5606.0000032

Measurements of transient ground movements below a ballasted railway line / J. A. Priest in Géotechnique, Vol. 60 N° 9 (Septembre 2010) 

Public ISBD [article]  in Géotechnique > Vol. 60 N° 9 (Septembre 2010) . - pp. 667–677 Titre : Measurements of transient ground movements below a ballasted railway line Type de document : texte imprimé Auteurs : J. A. Priest, Auteur ; W. Powrie, Auteur ; L. Yang, Auteur Année de publication : 2011 Article en page(s) : pp. 667–677 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : In  situ  testing  Dynamics  Field  instrumentation  Deformation  Monitoring  Numerical  modelling Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : This paper presents the results of a detailed investigation into the ground deformations that occur under a railway line during the passage of a train. Four horizontal boreholes were installed at different depths below a ballasted railway track. Ground deformations were measured using geophones at set distances from the centreline of the track within each borehole. The results show vertical displacements reducing with depth, from a maximum at the sleeper. Sleeper displacements are dominated by pairs of bogies at the ends of adjacent wagons (which have a frequency of loading 1 Hz), although the effects of individual bogies (2 Hz) and axles (6 Hz) are also apparent. Higher loading frequencies attenuate with depth so that at a depth of 0·780 m below the sleeper soffit no axles are visible within the displacement data and by a depth of 1·98 m only the combined effect of pairs of adjacent bogies is apparent. In contrast, longitudinal horizontal motion is greatest at a depth of 0·78 m below the sleeper soffit, and the longitudinal horizontal displacements at the sleeper and at a depth of 0·78 m are dominated by the individual axles (∼6 Hz). By a depth of 1·98 m, the longitudinal horizontal motion is dominated by the bogie pairs. A dynamic linear-elastic two-dimensional finite element model was developed and validated using the measured displacements. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.7.00172 [article] Measurements of transient ground movements below a ballasted railway line [texte imprimé] / J. A. Priest, Auteur ; W. Powrie, Auteur ; L. Yang, Auteur . - 2011 . - pp. 667–677. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 60 N° 9 (Septembre 2010) . - pp. 667–677 Mots-clés : In  situ  testing  Dynamics  Field  instrumentation  Deformation  Monitoring  Numerical  modelling Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : This paper presents the results of a detailed investigation into the ground deformations that occur under a railway line during the passage of a train. Four horizontal boreholes were installed at different depths below a ballasted railway track. Ground deformations were measured using geophones at set distances from the centreline of the track within each borehole. The results show vertical displacements reducing with depth, from a maximum at the sleeper. Sleeper displacements are dominated by pairs of bogies at the ends of adjacent wagons (which have a frequency of loading 1 Hz), although the effects of individual bogies (2 Hz) and axles (6 Hz) are also apparent. Higher loading frequencies attenuate with depth so that at a depth of 0·780 m below the sleeper soffit no axles are visible within the displacement data and by a depth of 1·98 m only the combined effect of pairs of adjacent bogies is apparent. In contrast, longitudinal horizontal motion is greatest at a depth of 0·78 m below the sleeper soffit, and the longitudinal horizontal displacements at the sleeper and at a depth of 0·78 m are dominated by the individual axles (∼6 Hz). By a depth of 1·98 m, the longitudinal horizontal motion is dominated by the bogie pairs. A dynamic linear-elastic two-dimensional finite element model was developed and validated using the measured displacements. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.7.00172