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Détail de l'auteur
Auteur Poul V. Lade
Documents disponibles écrits par cet auteur
Affiner la rechercheCharacterization of Failure in Cross-Anisotropic Soils / Abelev, Andrei V. in Journal of engineering mechanics, Vol. 130 N°5 (Mai 2004)
in Journal of engineering mechanics > Vol. 130 N°5 (Mai 2004) . - 599-606 p.
Titre : Characterization of Failure in Cross-Anisotropic Soils Titre original : Caractérisation d'Echec dans les Sols Anisotropes en Travers Type de document : texte imprimé Auteurs : Abelev, Andrei V., Auteur ; Kaliakin, Victor N., Editeur scientifique ; Poul V. Lade, Auteur Article en page(s) : 599-606 p. Note générale : Génie Mécanique Langues : Anglais (eng) Mots-clés : Anisotropy Clays Sand Failures Shear strength Triaxial tests Anisotropie Argiles Sable Echecs Résistance aux cisaillements Essais à trois axes Index. décimale : 621.34/624 Résumé : Drained true triaxial tests on dense Santa Monica Beach sand deposited with a cross-anisotropic fabric have been performed to study the failure condition in the principal stress space. The failure surface was assumed to be symmetric around the vertical axis (on the octahedral plane of the principal stress space), but varying as a function of the Lode angle. Data from previously performed consolidated-undrained true triaxial tests on San Francisco Bay Mud and data from triaxial compression, triaxial extension, and plane strain tests on Toyoura sand showed similar behavior in terms of effective stresses. A three-dimensional failure criterion is proposed for characterization of failure in cross-anisotropic soils, under commonly occurring conditions when loading and depositional directions coincide and no significant rotation of principal stresses occur. This cross-anisotropic criterion is developed using a coordinate rotation of the principal stress space and utilization of an existing isotropic failure formulation. Derivation of the three required parameters is explained and illustrated. The proposed criterion is compared with various experimental results; and it is demonstrated that the failure criterion for cross-anisotropic soils captures the experimental behavior with good accuracy.
De Véritables essais à trois axes vidangés sur le sable dense de plage de Santa Monica déposé avec un tissu anisotrope en travers ont été réalisés pour étudier la condition d'échec dans l'espace principal d'effort. On a assumé que la surface d'échec est symétrique autour de l'axe vertical (sur le plan octaédrique de l'espace principal d'effort), mais autour de changer en fonction de l'angle de filon. Les données précédemment d'exécuté consolidé undrained de véritables essais à trois axes sur la boue de compartiment de San Francisco et les données de la compression à trois axes, de la prolongation à trois axes, et des essais plats de contrainte sur le sable de Toyoura ont montré le comportement semblable en termes d'efforts efficaces. Un critère tridimensionnel d'échec est proposé pour la caractérisation de l'échec dans les sols croix-anisotropes, sous se produire généralement conditionne quand le chargement et les directions dépositionnelles coïncident et aucune rotation significative de principaux efforts ne se produisent. Ce critère anisotrope en travers est développé en utilisant une rotation du même rang de l'espace principal d'effort et l'utilisation d'une formulation isotrope existante d'échec. La dérivation des trois paramètres exigés est expliquée et illustrée. Le critère proposé est comparé à de divers résultats expérimentaux ; et on le démontre que le critère d'échec pour les sols anisotropes en travers capture le comportement expérimental avec la bonne exactitude.
[article] Characterization of Failure in Cross-Anisotropic Soils = Caractérisation d'Echec dans les Sols Anisotropes en Travers [texte imprimé] / Abelev, Andrei V., Auteur ; Kaliakin, Victor N., Editeur scientifique ; Poul V. Lade, Auteur . - 599-606 p.
Génie Mécanique
Langues : Anglais (eng)
in Journal of engineering mechanics > Vol. 130 N°5 (Mai 2004) . - 599-606 p.
Mots-clés : Anisotropy Clays Sand Failures Shear strength Triaxial tests Anisotropie Argiles Sable Echecs Résistance aux cisaillements Essais à trois axes Index. décimale : 621.34/624 Résumé : Drained true triaxial tests on dense Santa Monica Beach sand deposited with a cross-anisotropic fabric have been performed to study the failure condition in the principal stress space. The failure surface was assumed to be symmetric around the vertical axis (on the octahedral plane of the principal stress space), but varying as a function of the Lode angle. Data from previously performed consolidated-undrained true triaxial tests on San Francisco Bay Mud and data from triaxial compression, triaxial extension, and plane strain tests on Toyoura sand showed similar behavior in terms of effective stresses. A three-dimensional failure criterion is proposed for characterization of failure in cross-anisotropic soils, under commonly occurring conditions when loading and depositional directions coincide and no significant rotation of principal stresses occur. This cross-anisotropic criterion is developed using a coordinate rotation of the principal stress space and utilization of an existing isotropic failure formulation. Derivation of the three required parameters is explained and illustrated. The proposed criterion is compared with various experimental results; and it is demonstrated that the failure criterion for cross-anisotropic soils captures the experimental behavior with good accuracy.
De Véritables essais à trois axes vidangés sur le sable dense de plage de Santa Monica déposé avec un tissu anisotrope en travers ont été réalisés pour étudier la condition d'échec dans l'espace principal d'effort. On a assumé que la surface d'échec est symétrique autour de l'axe vertical (sur le plan octaédrique de l'espace principal d'effort), mais autour de changer en fonction de l'angle de filon. Les données précédemment d'exécuté consolidé undrained de véritables essais à trois axes sur la boue de compartiment de San Francisco et les données de la compression à trois axes, de la prolongation à trois axes, et des essais plats de contrainte sur le sable de Toyoura ont montré le comportement semblable en termes d'efforts efficaces. Un critère tridimensionnel d'échec est proposé pour la caractérisation de l'échec dans les sols croix-anisotropes, sous se produire généralement conditionne quand le chargement et les directions dépositionnelles coïncident et aucune rotation significative de principaux efforts ne se produisent. Ce critère anisotrope en travers est développé en utilisant une rotation du même rang de l'espace principal d'effort et l'utilisation d'une formulation isotrope existante d'échec. La dérivation des trois paramètres exigés est expliquée et illustrée. Le critère proposé est comparé à de divers résultats expérimentaux ; et on le démontre que le critère d'échec pour les sols anisotropes en travers capture le comportement expérimental avec la bonne exactitude.
in Journal of geotechnical and geoenvironmental engineering > Vol. 137 N° 12 (Décembre 2011) . - pp. 1169-1178
Titre : Effect of strain rate on the stress-strain behavior of sand Type de document : texte imprimé Auteurs : Jerry A. Yamamuro, Auteur ; Antonio E. Abrantes, Auteur ; Poul V. Lade, Auteur Année de publication : 2012 Article en page(s) : pp. 1169-1178 Note générale : Géotechnique Langues : Anglais (eng) Mots-clés : Global strain Image analysis Local strain Photography Sand Strain Strain rate Stress strain Transient testing Triaxial tests Résumé : Drained triaxial compression tests on crushed coral sand were performed from near-static strain rates to very high strain rates (up to approximately 1,800%/s). Experiments were performed on dry, vacuum-confined axisymmetric specimens at two different confining pressures (98 and 350 kPa) and two different densities (Dr approximately 36 and 60%). A gravity drop weight loading system was used to generate high strain rates. High-speed film photographs of the specimen were taken through the flat sides of a square triaxial cell. By using digital image analysis techniques, strains were locally measured near the center of the specimen to obtain the most uniform assessment. Stress-strain relationships are presented. The following effects were observed with increasing strain rates: the elastoplastic stiffness increased significantly; the failure shear strength increased moderately; the axial strain at peak stress decreased significantly; and volumetric strains became more dilatant. Unusual behavior was observed at very high strain rates. Examples include the peak stress was not always associated with the maximum dilatancy rate and shear band inclination angle was noticeably reduced. DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.org/gto/resource/1/jggefk/v137/i12/p1169_s1?isAuthorized=no [article] Effect of strain rate on the stress-strain behavior of sand [texte imprimé] / Jerry A. Yamamuro, Auteur ; Antonio E. Abrantes, Auteur ; Poul V. Lade, Auteur . - 2012 . - pp. 1169-1178.
Géotechnique
Langues : Anglais (eng)
in Journal of geotechnical and geoenvironmental engineering > Vol. 137 N° 12 (Décembre 2011) . - pp. 1169-1178
Mots-clés : Global strain Image analysis Local strain Photography Sand Strain Strain rate Stress strain Transient testing Triaxial tests Résumé : Drained triaxial compression tests on crushed coral sand were performed from near-static strain rates to very high strain rates (up to approximately 1,800%/s). Experiments were performed on dry, vacuum-confined axisymmetric specimens at two different confining pressures (98 and 350 kPa) and two different densities (Dr approximately 36 and 60%). A gravity drop weight loading system was used to generate high strain rates. High-speed film photographs of the specimen were taken through the flat sides of a square triaxial cell. By using digital image analysis techniques, strains were locally measured near the center of the specimen to obtain the most uniform assessment. Stress-strain relationships are presented. The following effects were observed with increasing strain rates: the elastoplastic stiffness increased significantly; the failure shear strength increased moderately; the axial strain at peak stress decreased significantly; and volumetric strains became more dilatant. Unusual behavior was observed at very high strain rates. Examples include the peak stress was not always associated with the maximum dilatancy rate and shear band inclination angle was noticeably reduced. DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.org/gto/resource/1/jggefk/v137/i12/p1169_s1?isAuthorized=no
in Journal of geotechnical and geoenvironmental engineering > Vol. 136 N° 3 (Mars 2010) . - pp. 500-509
Titre : Effects of particle crushing in stress drop-relaxation experiments on crushed coral sand Type de document : texte imprimé Auteurs : Poul V. Lade, Auteur ; Jungman Nam, Auteur ; Carl D. Liggio Jr., Auteur Article en page(s) : pp. 500-509 Note générale : Géotechnique Langues : Anglais (eng) Mots-clés : Creep Granular materials Sand Soil properties Stress relaxation Time dependence Triaxial tests Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : Stress relaxation and stress drop-relaxation tests have been performed to complement a test series performed to study strain rate, creep, and stress drop-creep effects on crushed coral sand. Drained experiments with constant effective confining pressure of 200 kPa were performed in which triaxial specimens of crushed coral sand were loaded to initial stress differences of 500, 700, and 900 kPa, followed by stress drops of 0, 100, 200, 300, and 400 kPa at which points the axial strains were kept constant while the axial stress relaxation and the volumetric strains were observed. The stress drops produced delays in initiation of stress relaxation that were proportional with the magnitudes of the stress drops. The experiments show that sands do not exhibit classic viscous effects, and their behavior is indicated as “nonisotach,” while the typical viscous behavior of clay is termed “isotach.” Thus, there are significant differences in the time-dependent behavior patterns of sands and clay. A mechanistic picture of time effects in sands is proposed.
DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.aip.org/vsearch/servlet/VerityServlet?KEY=JGGEFK&smode=strres [...] [article] Effects of particle crushing in stress drop-relaxation experiments on crushed coral sand [texte imprimé] / Poul V. Lade, Auteur ; Jungman Nam, Auteur ; Carl D. Liggio Jr., Auteur . - pp. 500-509.
Géotechnique
Langues : Anglais (eng)
in Journal of geotechnical and geoenvironmental engineering > Vol. 136 N° 3 (Mars 2010) . - pp. 500-509
Mots-clés : Creep Granular materials Sand Soil properties Stress relaxation Time dependence Triaxial tests Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : Stress relaxation and stress drop-relaxation tests have been performed to complement a test series performed to study strain rate, creep, and stress drop-creep effects on crushed coral sand. Drained experiments with constant effective confining pressure of 200 kPa were performed in which triaxial specimens of crushed coral sand were loaded to initial stress differences of 500, 700, and 900 kPa, followed by stress drops of 0, 100, 200, 300, and 400 kPa at which points the axial strains were kept constant while the axial stress relaxation and the volumetric strains were observed. The stress drops produced delays in initiation of stress relaxation that were proportional with the magnitudes of the stress drops. The experiments show that sands do not exhibit classic viscous effects, and their behavior is indicated as “nonisotach,” while the typical viscous behavior of clay is termed “isotach.” Thus, there are significant differences in the time-dependent behavior patterns of sands and clay. A mechanistic picture of time effects in sands is proposed.
DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.aip.org/vsearch/servlet/VerityServlet?KEY=JGGEFK&smode=strres [...]
in Journal of geotechnical and geoenvironmental engineering > Vol. 134 N°1 (Janvier 2008) . - pp. 117–124
Titre : Failure criterion for cross-anisotropic soils Type de document : texte imprimé Auteurs : Poul V. Lade, Auteur Année de publication : 2008 Article en page(s) : pp. 117–124 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Anisotropy Failures Shear strength Shear tests Triaxial tests Résumé : Experimental evidence and analyses of results of three-dimensional (3D) tests show that the shape of the failure surface for soils is influenced by the intermediate principal stress, shear banding, and cross anisotropy. Presented here is a formulation of a general 3D failure criterion for cross-anisotropic soils for both nonrotating and rotating stresses. The formulation relates the loading direction to the principal directions of the cross-anisotropic microstructure of the soil. The criterion is based on a function of stress, previously used as the 3D failure criterion for isotropic frictional materials, which is set equal to a scalar that varies over a sphere. The formulation is specialized for true triaxial tests and torsion shear tests and determination of material parameters is demonstrated. The failure criterion for cross-anisotropic soils is compared with experimental results from the literature to show that it is able to capture the conditions obtained in true triaxial tests without stress rotations as well as the conditions in torsion shear tests performed to study effects of stress rotation. Sets of data from some classic true triaxial tests are reinterpreted to show their true cross-anisotropic behavior. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A1%2811 [...] [article] Failure criterion for cross-anisotropic soils [texte imprimé] / Poul V. Lade, Auteur . - 2008 . - pp. 117–124.
Geotechnical and geoenvironmental engineering
Langues : Anglais (eng)
in Journal of geotechnical and geoenvironmental engineering > Vol. 134 N°1 (Janvier 2008) . - pp. 117–124
Mots-clés : Anisotropy Failures Shear strength Shear tests Triaxial tests Résumé : Experimental evidence and analyses of results of three-dimensional (3D) tests show that the shape of the failure surface for soils is influenced by the intermediate principal stress, shear banding, and cross anisotropy. Presented here is a formulation of a general 3D failure criterion for cross-anisotropic soils for both nonrotating and rotating stresses. The formulation relates the loading direction to the principal directions of the cross-anisotropic microstructure of the soil. The criterion is based on a function of stress, previously used as the 3D failure criterion for isotropic frictional materials, which is set equal to a scalar that varies over a sphere. The formulation is specialized for true triaxial tests and torsion shear tests and determination of material parameters is demonstrated. The failure criterion for cross-anisotropic soils is compared with experimental results from the literature to show that it is able to capture the conditions obtained in true triaxial tests without stress rotations as well as the conditions in torsion shear tests performed to study effects of stress rotation. Sets of data from some classic true triaxial tests are reinterpreted to show their true cross-anisotropic behavior. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A1%2811 [...]
in Journal of engineering mechanics > Vol. 133 N°8 (Août 2007) . - pp.919–932.
Titre : Modeling cross anisotropy in granular materials Type de document : texte imprimé Auteurs : Abelev, Andrei V., Auteur ; Suresh K. Gutta, Auteur ; Poul V. Lade, Auteur Année de publication : 2007 Article en page(s) : pp.919–932. Note générale : Applied mechanics Langues : Anglais (eng) Mots-clés : Granular materials Anisotropy Isotropic materials Compression tests Triaxial tests Models Résumé : A constitutive model has been developed to capture the behavior of cross-anisotropic frictional materials. The elastoplastic, single hardening model for isotropic materials serves as the basic framework. Based on the experimental results of cross-anisotropic sands in isotropic compression tests, the principal stress coordinate system is rotated such that the model operates isotropically within the rotated framework. Experimental plastic work contours on the octahedral plane are plotted for a series of true triaxial tests on dense Santa Monica Beach sand to study the effects of cross anisotropy on the evolution of yield surfaces. The amount of rotation of the yield and plastic potential surfaces decreases to zero (isotropic state) with loading. The model is constructed for cases where the principal stress and material symmetry axes are collinear and no significant rotation of principal stresses occur. The model incorporates fourteen parameters that can be determined from simple experiments, such as isotropic compression, drained triaxial compression, and triaxial extension tests. A series of true triaxial and isotropic compression tests on dense Santa Monica Beach sand are used as a basis for verification of the capabilities of the proposed model. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282007%29133%3A8%2891 [...] [article] Modeling cross anisotropy in granular materials [texte imprimé] / Abelev, Andrei V., Auteur ; Suresh K. Gutta, Auteur ; Poul V. Lade, Auteur . - 2007 . - pp.919–932.
Applied mechanics
Langues : Anglais (eng)
in Journal of engineering mechanics > Vol. 133 N°8 (Août 2007) . - pp.919–932.
Mots-clés : Granular materials Anisotropy Isotropic materials Compression tests Triaxial tests Models Résumé : A constitutive model has been developed to capture the behavior of cross-anisotropic frictional materials. The elastoplastic, single hardening model for isotropic materials serves as the basic framework. Based on the experimental results of cross-anisotropic sands in isotropic compression tests, the principal stress coordinate system is rotated such that the model operates isotropically within the rotated framework. Experimental plastic work contours on the octahedral plane are plotted for a series of true triaxial tests on dense Santa Monica Beach sand to study the effects of cross anisotropy on the evolution of yield surfaces. The amount of rotation of the yield and plastic potential surfaces decreases to zero (isotropic state) with loading. The model is constructed for cases where the principal stress and material symmetry axes are collinear and no significant rotation of principal stresses occur. The model incorporates fourteen parameters that can be determined from simple experiments, such as isotropic compression, drained triaxial compression, and triaxial extension tests. A series of true triaxial and isotropic compression tests on dense Santa Monica Beach sand are used as a basis for verification of the capabilities of the proposed model. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282007%29133%3A8%2891 [...]
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