Documents disponibles écrits par cet auteur

Amplification of seismic accelerations at slope crests / A. J. Brennan in Canadian geotechnical journal, Vol. 46 N° 5 (Mai 2009) 

Public ISBD [article]  in Canadian geotechnical journal > Vol. 46 N° 5 (Mai 2009) . - pp. 585–594 Titre : Amplification of seismic accelerations at slope crests Type de document : texte imprimé Auteurs : A. J. Brennan, Auteur ; S. P.G. Madabhushi, Auteur Article en page(s) : pp. 585–594 Note générale : Sciences de la Terre Langues : Anglais (eng) Mots-clés : Centrifuge  Earthquake  Slopes  Centrifuge  Séisme  Pente Index. décimale : 550 Sciences auxiliaires de la géologie. Résumé : Earthquake accelerations can cause many problems in sloping ground. One such problem is that accelerations are greatly amplified at the crest of slopes. This topographic amplification can lead to acceleration gradients along the ground surface, which could create tensile forces in long surface structures that extend between areas of different amplifications. This paper uses centrifuge modelling to demonstrate and quantify this as a problem for a particular slope configuration. A special brittle structure has been constructed to undergo damage in the presence of large differential accelerations. The structure is seen to connect the crest to the level ground behind the crest during an earthquake, reducing the amplitude of the crest motion at the expense of structural tension. Topographic amplification is shown to be a clear function of frequency, and is especially serious for loading frequencies above the natural frequency of the soil layer. Les accélérations des séismes peut causer plusieurs problèmes sur des pentes. Un de ces problèmes est que ces accélérations sont grandement amplifiées au sommet des pentes. Cette amplification topographique peut entraîner des gradients d’accélération le long de la surface du sol, ce qui pourrait créer des forces en tension dans des structures de surfaces longues qui s’étendent entre des zones d’amplification différentes. Cette étude se sert de la modélisation centrifuge pour démontrer et quantifier ce problème pour une configuration de pente spécifique. Une structure fragile spéciale a été construite pour subir le dommage causé par la présence de grandes accélérations différentielles. La structure relie le sommet au sol derrière la pente durant un séisme, ce qui réduit l’amplitude des mouvements du sommet, au détriment des tensions dans la structure. On a aussi démontré que l’amplification topographique est directement fonction de la fréquence, et ce phénomène est particulièrement important lorsque les fréquences des charges sont au-dessus de la fréquence naturelle de la couche de sol. DEWEY : 550 ISSN : 0008-3674 En ligne : http://rparticle.web-p.cisti.nrc.ca/rparticle/AbstractTemplateServlet?calyLang=f [...] [article] Amplification of seismic accelerations at slope crests [texte imprimé] / A. J. Brennan, Auteur ; S. P.G. Madabhushi, Auteur . - pp. 585–594. Sciences de la Terre Langues : Anglais (eng) in Canadian geotechnical journal > Vol. 46 N° 5 (Mai 2009) . - pp. 585–594 Mots-clés : Centrifuge  Earthquake  Slopes  Centrifuge  Séisme  Pente Index. décimale : 550 Sciences auxiliaires de la géologie. Résumé : Earthquake accelerations can cause many problems in sloping ground. One such problem is that accelerations are greatly amplified at the crest of slopes. This topographic amplification can lead to acceleration gradients along the ground surface, which could create tensile forces in long surface structures that extend between areas of different amplifications. This paper uses centrifuge modelling to demonstrate and quantify this as a problem for a particular slope configuration. A special brittle structure has been constructed to undergo damage in the presence of large differential accelerations. The structure is seen to connect the crest to the level ground behind the crest during an earthquake, reducing the amplitude of the crest motion at the expense of structural tension. Topographic amplification is shown to be a clear function of frequency, and is especially serious for loading frequencies above the natural frequency of the soil layer. Les accélérations des séismes peut causer plusieurs problèmes sur des pentes. Un de ces problèmes est que ces accélérations sont grandement amplifiées au sommet des pentes. Cette amplification topographique peut entraîner des gradients d’accélération le long de la surface du sol, ce qui pourrait créer des forces en tension dans des structures de surfaces longues qui s’étendent entre des zones d’amplification différentes. Cette étude se sert de la modélisation centrifuge pour démontrer et quantifier ce problème pour une configuration de pente spécifique. Une structure fragile spéciale a été construite pour subir le dommage causé par la présence de grandes accélérations différentielles. La structure relie le sommet au sol derrière la pente durant un séisme, ce qui réduit l’amplitude des mouvements du sommet, au détriment des tensions dans la structure. On a aussi démontré que l’amplification topographique est directement fonction de la fréquence, et ce phénomène est particulièrement important lorsque les fréquences des charges sont au-dessus de la fréquence naturelle de la couche de sol. DEWEY : 550 ISSN : 0008-3674 En ligne : http://rparticle.web-p.cisti.nrc.ca/rparticle/AbstractTemplateServlet?calyLang=f [...]

Centrifuge modeling of rock-fill embankments on deep loose saturated sand deposits subjected to earthquakes / L. M. N. Peiris in Journal of geotechnical and geoenvironmental engineering, Vol. 134 n°9 (Septembre 2008) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 134 n°9 (Septembre 2008) . - pp. 1364–1374 Titre : Centrifuge modeling of rock-fill embankments on deep loose saturated sand deposits subjected to earthquakes Type de document : texte imprimé Auteurs : L. M. N. Peiris, Auteur ; S. P.G. Madabhushi, Auteur ; A. N. Schofield, Auteur Année de publication : 2008 Article en page(s) : pp. 1364–1374 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Centrifuge  models  Earthquakes  Failures  Liquefaction  Rock  Fills  Embankments  Sand Résumé : Rockfill is commonly used for construction of artificial islands, breakwaters, jetties, quay walls, coastal defenses, protective barriers for reclaimed land, and even as ship impact protection structures around bridge piers. The economic construction method often involves rock dumping onto loose or liquefiable sediments with little or no ground improvement. Hence in a seismic environment, these rock-fill or rubble mound structures are potentially vulnerable to failure due to pore pressure generation effects of the underlying deposits. This paper presents experimental investigation carried out using dynamic centrifuge modeling to study the seismic performance of rock-fill or rubble mound embankment structures on liquefiable sand deposits. The centrifuge test results indicate that the rock-fill embankments suffer substantial settlement owing to rock-fill penetration into the founding sand deposit assisted by the pore pressure generation effects. This mechanism of failure was not, however, observed for a sand embankment where the particle size distribution is comparable to the foundation. This result has important implications in the design methodologies adopted for rock-fill or rubble mound structures. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A9%2813 [...] [article] Centrifuge modeling of rock-fill embankments on deep loose saturated sand deposits subjected to earthquakes [texte imprimé] / L. M. N. Peiris, Auteur ; S. P.G. Madabhushi, Auteur ; A. N. Schofield, Auteur . - 2008 . - pp. 1364–1374. Geotechnical and geoenvironmental engineering Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 134 n°9 (Septembre 2008) . - pp. 1364–1374 Mots-clés : Centrifuge  models  Earthquakes  Failures  Liquefaction  Rock  Fills  Embankments  Sand Résumé : Rockfill is commonly used for construction of artificial islands, breakwaters, jetties, quay walls, coastal defenses, protective barriers for reclaimed land, and even as ship impact protection structures around bridge piers. The economic construction method often involves rock dumping onto loose or liquefiable sediments with little or no ground improvement. Hence in a seismic environment, these rock-fill or rubble mound structures are potentially vulnerable to failure due to pore pressure generation effects of the underlying deposits. This paper presents experimental investigation carried out using dynamic centrifuge modeling to study the seismic performance of rock-fill or rubble mound embankment structures on liquefiable sand deposits. The centrifuge test results indicate that the rock-fill embankments suffer substantial settlement owing to rock-fill penetration into the founding sand deposit assisted by the pore pressure generation effects. This mechanism of failure was not, however, observed for a sand embankment where the particle size distribution is comparable to the foundation. This result has important implications in the design methodologies adopted for rock-fill or rubble mound structures. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A9%2813 [...]

Effects of axial load and slope arrangement on pile group response in laterally spreading soils / J. A. Knappett in Journal of geotechnical and geoenvironmental engineering, Vol. 138 N° 7 (Juillet 2012) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 138 N° 7 (Juillet 2012) . - pp. 799–809 Titre : Effects of axial load and slope arrangement on pile group response in laterally spreading soils Type de document : texte imprimé Auteurs : J. A. Knappett, Auteur ; S. P.G. Madabhushi, Auteur Année de publication : 2012 Article en page(s) : pp. 799–809 Note générale : Géotechnique Langues : Anglais (eng) Mots-clés : Earthquake  engineering  Soil  liquefaction  Layered  soils  Pile  groups  Centrifuge  model Résumé : This paper presents the results of a series of dynamic centrifuge tests that were conducted for 2×2 pile groups in a three-layer laterally spreading soil profile consisting of a nonliquefiable cohesive crust overlying loose, liquefiable sand, overlying dense sand. Two main variables are considered, both of which received little attention in previous work on piles in laterally spreading soils, namely (1) the axial load carried by the foundation, and (2) whether the slope boundary conditions are infinite or finite. The data show that the presence of axial load reduces the lateral stiffness of the foundation resulting from P-Δ effects and reduces their capacity to resist lateral kinematic loads from spreading soil. This degradation in lateral response (bending) may be accompanied by substantial settlement of the foundation as a competing failure mode that must also be considered in design. Furthermore, the mechanical response of the liquefied soil appears to vary greatly with the slope boundary condition. This is particularly true at the interface between the liquefied sand and the cohesive crust, where the downslope displacement of the crust for infinite slopes is much greater than the underlying sand, with the reverse being true for finite slopes. The data also suggest an alternative mechanism to the water film concept that has been used previously to account for the large downslope movements of low permeability crustal layers. This fundamental difference in mechanical response provides insight that may lead to the improvement of simplified empirical methods for estimating surficial displacements caused by lateral spreading. ISSN : 1090-0241 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29GT.1943-5606.0000654 [article] Effects of axial load and slope arrangement on pile group response in laterally spreading soils [texte imprimé] / J. A. Knappett, Auteur ; S. P.G. Madabhushi, Auteur . - 2012 . - pp. 799–809. Géotechnique Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 138 N° 7 (Juillet 2012) . - pp. 799–809 Mots-clés : Earthquake  engineering  Soil  liquefaction  Layered  soils  Pile  groups  Centrifuge  model Résumé : This paper presents the results of a series of dynamic centrifuge tests that were conducted for 2×2 pile groups in a three-layer laterally spreading soil profile consisting of a nonliquefiable cohesive crust overlying loose, liquefiable sand, overlying dense sand. Two main variables are considered, both of which received little attention in previous work on piles in laterally spreading soils, namely (1) the axial load carried by the foundation, and (2) whether the slope boundary conditions are infinite or finite. The data show that the presence of axial load reduces the lateral stiffness of the foundation resulting from P-Δ effects and reduces their capacity to resist lateral kinematic loads from spreading soil. This degradation in lateral response (bending) may be accompanied by substantial settlement of the foundation as a competing failure mode that must also be considered in design. Furthermore, the mechanical response of the liquefied soil appears to vary greatly with the slope boundary condition. This is particularly true at the interface between the liquefied sand and the cohesive crust, where the downslope displacement of the crust for infinite slopes is much greater than the underlying sand, with the reverse being true for finite slopes. The data also suggest an alternative mechanism to the water film concept that has been used previously to account for the large downslope movements of low permeability crustal layers. This fundamental difference in mechanical response provides insight that may lead to the improvement of simplified empirical methods for estimating surficial displacements caused by lateral spreading. ISSN : 1090-0241 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29GT.1943-5606.0000654

On the behaviour of flexible retaining walls under seismic actions / R. Conti in Géotechnique, Vol. 62 N° 12 (Décembre 2012) 

Public ISBD [article]  in Géotechnique > Vol. 62 N° 12 (Décembre 2012) . - pp. 1081 –1094 Titre : On the behaviour of flexible retaining walls under seismic actions Type de document : texte imprimé Auteurs : R. Conti, Auteur ; S. P.G. Madabhushi, Auteur ; Viggiani, G. M. B., Auteur Année de publication : 2012 Article en page(s) : pp. 1081 –1094 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Diaphragm  and  in  situ  walls  Dynamics  Centrifuge  modelling  Soil/structure  interaction Résumé : This paper describes an experimental investigation of the behaviour of embedded retaining walls under seismic actions. Nine centrifuge tests were carried out on reduced-scale models of pairs of retaining walls in dry sand, either cantilevered or with one level of props near the top. The experimental data indicate that, for maximum accelerations that are smaller than the critical limit equilibrium value, the retaining walls experience significant permanent displacements under increasing structural loads, whereas for larger accelerations the walls rotate under constant internal forces. The critical acceleration at which the walls start to rotate increases with increasing maximum acceleration. No significant displacements are measured if the current earthquake is less severe than earthquakes previously experienced by the wall. The increase of critical acceleration is explained in terms of redistribution of earth pressures and progressive mobilisation of the passive strength in front of the wall. The experimental data for cantilevered retaining walls indicate that the permanent displacements of the wall can be reasonably predicted adopting a Newmark-type calculation with a critical acceleration that is a fraction of the limit equilibrium value. ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.11.P.029 [article] On the behaviour of flexible retaining walls under seismic actions [texte imprimé] / R. Conti, Auteur ; S. P.G. Madabhushi, Auteur ; Viggiani, G. M. B., Auteur . - 2012 . - pp. 1081 –1094. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 62 N° 12 (Décembre 2012) . - pp. 1081 –1094 Mots-clés : Diaphragm  and  in  situ  walls  Dynamics  Centrifuge  modelling  Soil/structure  interaction Résumé : This paper describes an experimental investigation of the behaviour of embedded retaining walls under seismic actions. Nine centrifuge tests were carried out on reduced-scale models of pairs of retaining walls in dry sand, either cantilevered or with one level of props near the top. The experimental data indicate that, for maximum accelerations that are smaller than the critical limit equilibrium value, the retaining walls experience significant permanent displacements under increasing structural loads, whereas for larger accelerations the walls rotate under constant internal forces. The critical acceleration at which the walls start to rotate increases with increasing maximum acceleration. No significant displacements are measured if the current earthquake is less severe than earthquakes previously experienced by the wall. The increase of critical acceleration is explained in terms of redistribution of earth pressures and progressive mobilisation of the passive strength in front of the wall. The experimental data for cantilevered retaining walls indicate that the permanent displacements of the wall can be reasonably predicted adopting a Newmark-type calculation with a critical acceleration that is a fraction of the limit equilibrium value. ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.11.P.029