Documents disponibles écrits par cet auteur

Experimental behaviour of compacted marls / R. Cardoso in Géotechnique, Vol. 62 N° 11 (Novembre 2012) 

Public ISBD [article]  in Géotechnique > Vol. 62 N° 11 (Novembre 2012) . - pp. 999 –1012 Titre : Experimental behaviour of compacted marls Type de document : texte imprimé Auteurs : R. Cardoso, Auteur ; E. Maranha Des Neves, Auteur ; E. E. Alonso, Auteur Année de publication : 2012 Article en page(s) : pp. 999 –1012 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Suction  Soft  rocks  Embankments  Partial  saturation  Compaction  Fabric/structure  of  soils Résumé : Jurassic marls from Abadia, Portugal, were used in the construction of some motorway embankments. Large fragments of this evolving material remained after the construction process, and their degradation was of concern because of the expected change of the engineering properties of the compacted material. The material exhibits a very complex behaviour, which is difficult to reproduce with existing constitutive models for unsaturated structured materials. This paper focuses on understanding and providing data on the interaction between the pure marls (rock) and the aggregate behaviour. It presents the main results of tests performed to characterise the hydro-mechanical behaviour of compacted marls in specimens prepared with different grading size distributions and subjected to oedometer tests where both stress and suction changes were applied. The experimental data obtained were analysed, considering the presence of fragments and their degradation. The marl matrix was characterised to complete the existing data previously published for this material, but now with the purpose of providing a better explanation for the volumetric behaviour of the aggregate. The discussion is assisted by the explanation provided by a simple elasto-plastic model for unsaturated soils. Discrepancies with model predictions help to highlight the singularity of the marl aggregate. Compacted marls behave as materials in the transition between rockfill (when the fragments remain brittle) and a clayey soil (when the degradation accumulates). Therefore the compacted marl exhibits a dual behaviour. If it is dry, deformations are explained by the breakage of particles and rearrangement of the structure. If it is wet, the compacted marl is dominated by bond degradation of the material, the release of swelling potential and simultaneous changes in the stiffness and strength of the fragments. It appears that the transition from dry to wet can be identified by the current suction; moreover, it is rather abrupt. ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.10.P.093 [article] Experimental behaviour of compacted marls [texte imprimé] / R. Cardoso, Auteur ; E. Maranha Des Neves, Auteur ; E. E. Alonso, Auteur . - 2012 . - pp. 999 –1012. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 62 N° 11 (Novembre 2012) . - pp. 999 –1012 Mots-clés : Suction  Soft  rocks  Embankments  Partial  saturation  Compaction  Fabric/structure  of  soils Résumé : Jurassic marls from Abadia, Portugal, were used in the construction of some motorway embankments. Large fragments of this evolving material remained after the construction process, and their degradation was of concern because of the expected change of the engineering properties of the compacted material. The material exhibits a very complex behaviour, which is difficult to reproduce with existing constitutive models for unsaturated structured materials. This paper focuses on understanding and providing data on the interaction between the pure marls (rock) and the aggregate behaviour. It presents the main results of tests performed to characterise the hydro-mechanical behaviour of compacted marls in specimens prepared with different grading size distributions and subjected to oedometer tests where both stress and suction changes were applied. The experimental data obtained were analysed, considering the presence of fragments and their degradation. The marl matrix was characterised to complete the existing data previously published for this material, but now with the purpose of providing a better explanation for the volumetric behaviour of the aggregate. The discussion is assisted by the explanation provided by a simple elasto-plastic model for unsaturated soils. Discrepancies with model predictions help to highlight the singularity of the marl aggregate. Compacted marls behave as materials in the transition between rockfill (when the fragments remain brittle) and a clayey soil (when the degradation accumulates). Therefore the compacted marl exhibits a dual behaviour. If it is dry, deformations are explained by the breakage of particles and rearrangement of the structure. If it is wet, the compacted marl is dominated by bond degradation of the material, the release of swelling potential and simultaneous changes in the stiffness and strength of the fragments. It appears that the transition from dry to wet can be identified by the current suction; moreover, it is rather abrupt. ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.10.P.093

Impact of bituminous subballast on railroad track deformation considering atmospheric actions / T. Moço Ferreira in Journal of geotechnical and geoenvironmental engineering, Vol. 137 N° 3 (Mars 2011) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 137 N° 3 (Mars 2011) . - pp. 288-292 Titre : Impact of bituminous subballast on railroad track deformation considering atmospheric actions Type de document : texte imprimé Auteurs : T. Moço Ferreira, Auteur ; P. Fonseca Teixeira, Auteur ; R. Cardoso, Auteur Année de publication : 2011 Article en page(s) : pp. 288-292 Note générale : Géotechnique Langues : Anglais (eng) Mots-clés : Railroad  engineering  Ballasted  tracks  Bituminous  subballast  Unsaturated  soils Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : High-speed ballasted track design standards usually require the use of sand and gravel layers as subballast to fulfill an accurate protection of the formation layers, not only against traffic loads, but also against the effects of weather. Seasonal changes in soil water content, or suction changes, are responsible for cyclic volumetric strains on railroad trackbed layers, thus on the infrastructure. Being almost completely water-resistant when compared with granular-only layers, bituminous subballast offers a higher protection of the subgrade, consequently improving its behavior along the infrastructure life cycle. This question is investigated through the comparison of the performance of the track formation against atmospheric actions, taking into consideration the unsaturated state of the geomaterials. The method adopted consists of modeling the vertical displacements of both bituminous and granular subballast designs through a finite-element coupled thermo-hydro-mechanical (THM) analysis. The comparison of the two design solutions confirms that the adoption of a bituminous subballast layer might allow important reductions in seasonal vertical displacements. DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.org/gto/resource/1/jggefk/v137/i3/p288_s1?isAuthorized=no [article] Impact of bituminous subballast on railroad track deformation considering atmospheric actions [texte imprimé] / T. Moço Ferreira, Auteur ; P. Fonseca Teixeira, Auteur ; R. Cardoso, Auteur . - 2011 . - pp. 288-292. Géotechnique Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 137 N° 3 (Mars 2011) . - pp. 288-292 Mots-clés : Railroad  engineering  Ballasted  tracks  Bituminous  subballast  Unsaturated  soils Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : High-speed ballasted track design standards usually require the use of sand and gravel layers as subballast to fulfill an accurate protection of the formation layers, not only against traffic loads, but also against the effects of weather. Seasonal changes in soil water content, or suction changes, are responsible for cyclic volumetric strains on railroad trackbed layers, thus on the infrastructure. Being almost completely water-resistant when compared with granular-only layers, bituminous subballast offers a higher protection of the subgrade, consequently improving its behavior along the infrastructure life cycle. This question is investigated through the comparison of the performance of the track formation against atmospheric actions, taking into consideration the unsaturated state of the geomaterials. The method adopted consists of modeling the vertical displacements of both bituminous and granular subballast designs through a finite-element coupled thermo-hydro-mechanical (THM) analysis. The comparison of the two design solutions confirms that the adoption of a bituminous subballast layer might allow important reductions in seasonal vertical displacements. DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.org/gto/resource/1/jggefk/v137/i3/p288_s1?isAuthorized=no