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

Effects of high permeability lenses on efficiency of wellpoint dewatering / W. Powrie in Géotechnique, Vol. 39 N°3 (Septembre 1989) 

Public ISBD [article]  in Géotechnique > Vol. 39 N°3 (Septembre 1989) . - pp. 543 –547 Titre : Effects of high permeability lenses on efficiency of wellpoint dewatering Type de document : texte imprimé Auteurs : W. Powrie, Auteur ; T. O. L. Roberts, Auteur ; H. E. D. Moghazy, Auteur Année de publication : 2007 Article en page(s) : pp. 543 –547 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Finite  elements  Groundwater  Permeability  Seepage  Water  flow Note de contenu : Technical Note ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.1989.39.3.543 [article] Effects of high permeability lenses on efficiency of wellpoint dewatering [texte imprimé] / W. Powrie, Auteur ; T. O. L. Roberts, Auteur ; H. E. D. Moghazy, Auteur . - 2007 . - pp. 543 –547. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 39 N°3 (Septembre 1989) . - pp. 543 –547 Mots-clés : Finite  elements  Groundwater  Permeability  Seepage  Water  flow Note de contenu : Technical Note ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.1989.39.3.543

Factors controlling the seasonal variation in soil water content and pore water pressures within a lightly vegetated clay slope / J.A. Smethurst in Géotechnique, Vol. 62 N° 5 (Mai 2012) 

Public ISBD [article]  in Géotechnique > Vol. 62 N° 5 (Mai 2012) . - pp. 429 –446 Titre : Factors controlling the seasonal variation in soil water content and pore water pressures within a lightly vegetated clay slope Type de document : texte imprimé Auteurs : J.A. Smethurst, Auteur ; D. Clarke, Auteur ; W. Powrie, Auteur Année de publication : 2012 Article en page(s) : pp. 429 –446 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Suction  Slopes  Clays  Monitoring  Pore  pressures  Vegetation Résumé : Seasonal cycles of soil water content cause shrinking and swelling in clay soils, which can in turn contribute to strain-softening and progressive slope failure. This paper presents and analyses six years of field measurements of soil water content and pore water pressures in the upper layers of a lightly vegetated London Clay slope near Newbury, UK, and shows how they can be related quantitatively to the climate using a water balance model. The field observations are set in the context of a 40-year run of rainfall data for the site. Moderately extreme rainfall and drought events were experienced over the period 2003–2008, allowing almost the full variation in likely pore water pressures to be characterised. Pore water pressures were found to return to near hydrostatic during most winters. Variations in summer rainfall, particularly during June–August, are shown to have a large influence on the magnitude of the cycles of pore water pressure and effective stress. The 40-year rainfall dataset is used to calculate approximate return periods for the observed soil conditions, and provides a benchmark for calculating the impacts of expected climate change on similar sites. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.10.P.097 [article] Factors controlling the seasonal variation in soil water content and pore water pressures within a lightly vegetated clay slope [texte imprimé] / J.A. Smethurst, Auteur ; D. Clarke, Auteur ; W. Powrie, Auteur . - 2012 . - pp. 429 –446. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 62 N° 5 (Mai 2012) . - pp. 429 –446 Mots-clés : Suction  Slopes  Clays  Monitoring  Pore  pressures  Vegetation Résumé : Seasonal cycles of soil water content cause shrinking and swelling in clay soils, which can in turn contribute to strain-softening and progressive slope failure. This paper presents and analyses six years of field measurements of soil water content and pore water pressures in the upper layers of a lightly vegetated London Clay slope near Newbury, UK, and shows how they can be related quantitatively to the climate using a water balance model. The field observations are set in the context of a 40-year run of rainfall data for the site. Moderately extreme rainfall and drought events were experienced over the period 2003–2008, allowing almost the full variation in likely pore water pressures to be characterised. Pore water pressures were found to return to near hydrostatic during most winters. Variations in summer rainfall, particularly during June–August, are shown to have a large influence on the magnitude of the cycles of pore water pressure and effective stress. The 40-year rainfall dataset is used to calculate approximate return periods for the observed soil conditions, and provides a benchmark for calculating the impacts of expected climate change on similar sites. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.10.P.097

Influence of large-scale inhomogeneities on a construction dewatering system in chalk / M. A. Bevan in Géotechnique, Vol. 60 N° 8 (Août 2010) 

Public ISBD [article]  in Géotechnique > Vol. 60 N° 8 (Août 2010) . - pp. 635–649 Titre : Influence of large-scale inhomogeneities on a construction dewatering system in chalk Type de document : texte imprimé Auteurs : M. A. Bevan, Auteur ; W. Powrie, Auteur ; T. O. L. Roberts, Auteur Année de publication : 2011 Article en page(s) : pp. 635–649 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Numerical  modelling  Excavation  Permeability  Geology  Groundwater Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : Large-scale anisotropy and inhomogeneities resulting from the presence of fissures, fractures and high-permeability zones can have a major impact on local groundwater flows, and affect significantly the performance of a construction dewatering system. A groundwater model for the HS1 Channel tunnel rail link Thames tunnel southern approach excavation is used to show that the observed performance of the construction dewatering system cannot adequately be explained unless such features are incorporated. While experience suggested that such features were likely to be present in this geological setting, at the design stage there was significant uncertainty regarding their scale. Groundwater flow modelling enabled the location and extent of the inhomogeneities present to be deduced in some detail. Features such as highly permeable zones might be identified by more thorough site investigation, including the more widespread use of pumping tests. However, the influence of anisotropy is harder to establish, primarily because its effect is most significant once a horizontal flow barrier (for example, a retaining wall) is in place, which is generally not the case during site investigation. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.9.p.010 [article] Influence of large-scale inhomogeneities on a construction dewatering system in chalk [texte imprimé] / M. A. Bevan, Auteur ; W. Powrie, Auteur ; T. O. L. Roberts, Auteur . - 2011 . - pp. 635–649. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 60 N° 8 (Août 2010) . - pp. 635–649 Mots-clés : Numerical  modelling  Excavation  Permeability  Geology  Groundwater Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : Large-scale anisotropy and inhomogeneities resulting from the presence of fissures, fractures and high-permeability zones can have a major impact on local groundwater flows, and affect significantly the performance of a construction dewatering system. A groundwater model for the HS1 Channel tunnel rail link Thames tunnel southern approach excavation is used to show that the observed performance of the construction dewatering system cannot adequately be explained unless such features are incorporated. While experience suggested that such features were likely to be present in this geological setting, at the design stage there was significant uncertainty regarding their scale. Groundwater flow modelling enabled the location and extent of the inhomogeneities present to be deduced in some detail. Features such as highly permeable zones might be identified by more thorough site investigation, including the more widespread use of pumping tests. However, the influence of anisotropy is harder to establish, primarily because its effect is most significant once a horizontal flow barrier (for example, a retaining wall) is in place, which is generally not the case during site investigation. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.9.p.010

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

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