Documents disponibles écrits par cet auteur

Analysis of the stability of I-walls with gaps between the I-wall and the levee fill / Thomas L. Brandon in Journal of geotechnical and geoenvironmental engineering, Vol. 134 N°5 (Mai 2008) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 134 N°5 (Mai 2008) . - pp. 692–700 Titre : Analysis of the stability of I-walls with gaps between the I-wall and the levee fill Type de document : texte imprimé Auteurs : Thomas L. Brandon, Auteur ; Stephen G. Wright, Auteur ; J. Michael Duncan, Auteur Année de publication : 2008 Article en page(s) : pp. 692–700 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Hurricanes  Louisiana  Walls  Levees  Fills Résumé : Following Hurricane Katrina an extensive investigation of the performance of floodwalls in the New Orleans area was undertaken by the U. S. Army Corps of Engineers and others. This investigation included detailed study of failures of cantilevered sheet pile “I-walls” during the hurricane. An important lesson from this investigation was that gaps can form on the canal side of I-walls as the water rises in the canal and causes the I-wall to deflect. Once formed, these gaps filled with water, resulting in significantly higher loads on the walls. Gap formation was a key factor in several I-wall failures, and modeling such gaps correctly is clearly an important aspect of analyzing I-wall stability. This paper describes simple procedures for estimating the depths of gaps behind I-walls, for calculating the loads to which they are subjected, and for including them in stability analyses. The effects of gaps on the stability of the 17th Canal and the London Avenue Canal I-walls are discussed. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A5%2869 [...] [article] Analysis of the stability of I-walls with gaps between the I-wall and the levee fill [texte imprimé] / Thomas L. Brandon, Auteur ; Stephen G. Wright, Auteur ; J. Michael Duncan, Auteur . - 2008 . - pp. 692–700. Geotechnical and geoenvironmental engineering Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 134 N°5 (Mai 2008) . - pp. 692–700 Mots-clés : Hurricanes  Louisiana  Walls  Levees  Fills Résumé : Following Hurricane Katrina an extensive investigation of the performance of floodwalls in the New Orleans area was undertaken by the U. S. Army Corps of Engineers and others. This investigation included detailed study of failures of cantilevered sheet pile “I-walls” during the hurricane. An important lesson from this investigation was that gaps can form on the canal side of I-walls as the water rises in the canal and causes the I-wall to deflect. Once formed, these gaps filled with water, resulting in significantly higher loads on the walls. Gap formation was a key factor in several I-wall failures, and modeling such gaps correctly is clearly an important aspect of analyzing I-wall stability. This paper describes simple procedures for estimating the depths of gaps behind I-walls, for calculating the loads to which they are subjected, and for including them in stability analyses. The effects of gaps on the stability of the 17th Canal and the London Avenue Canal I-walls are discussed. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A5%2869 [...]

Deformation and cracking of seepage barriers in dams due to changes in the pore pressure regime / John D. Rice in Journal of geotechnical and geoenvironmental engineering, Vol. 136 N° 1 (Janvier 2010) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 136 N° 1 (Janvier 2010) . - pp. 16-25 Titre : Deformation and cracking of seepage barriers in dams due to changes in the pore pressure regime Type de document : texte imprimé Auteurs : John D. Rice, Auteur ; J. Michael Duncan, Auteur Article en page(s) : pp. 16-25 Note générale : Géotechnique Langues : Anglais (eng) Mots-clés : Seepage  barrier  Cutoff  Seepage  Deformation  Dam  Finite  element Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : A procedure is presented for analyzing postconstruction deformation of seepage barriers due to changes in the pore pressure regime after seepage barrier construction. The procedure uses the changes in pore pressures calculated by finite-element seepage analyses to calculate changes in buoyancy and seepage forces that occur as a result of seepage barrier construction. When the buoyancy and seepage forces are applied to a finite-element soil-structure interaction model, the result is an effective-stress analysis that rigorously models seepage effects. This paper discusses application of the procedure to five dams to calculate postconstruction deformation and stresses in seepage barriers. The results of the analyses indicate that deformation due to pore pressure regime changes is a likely mechanism causing cracking in rigid seepage barriers. DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.aip.org/vsearch/servlet/VerityServlet?KEY=JGGEFK&smode=strres [...] [article] Deformation and cracking of seepage barriers in dams due to changes in the pore pressure regime [texte imprimé] / John D. Rice, Auteur ; J. Michael Duncan, Auteur . - pp. 16-25. Géotechnique Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 136 N° 1 (Janvier 2010) . - pp. 16-25 Mots-clés : Seepage  barrier  Cutoff  Seepage  Deformation  Dam  Finite  element Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : A procedure is presented for analyzing postconstruction deformation of seepage barriers due to changes in the pore pressure regime after seepage barrier construction. The procedure uses the changes in pore pressures calculated by finite-element seepage analyses to calculate changes in buoyancy and seepage forces that occur as a result of seepage barrier construction. When the buoyancy and seepage forces are applied to a finite-element soil-structure interaction model, the result is an effective-stress analysis that rigorously models seepage effects. This paper discusses application of the procedure to five dams to calculate postconstruction deformation and stresses in seepage barriers. The results of the analyses indicate that deformation due to pore pressure regime changes is a likely mechanism causing cracking in rigid seepage barriers. DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.aip.org/vsearch/servlet/VerityServlet?KEY=JGGEFK&smode=strres [...]

Dynamic centrifuge testing of slickensided shear surfaces / Christopher L. Meehan in Journal of geotechnical and geoenvironmental engineering, Vol. 134 n°8 (Août 2008) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 134 n°8 (Août 2008) . - pp. 1086–1096 Titre : Dynamic centrifuge testing of slickensided shear surfaces Type de document : texte imprimé Auteurs : Christopher L. Meehan, Auteur ; Ross W. Boulanger, Auteur ; J. Michael Duncan, Auteur Année de publication : 2008 Article en page(s) : pp. 1086–1096 Note générale : Geotechnical and geotechnical engineering Langues : Anglais (eng) Mots-clés : Dynamic  stability  Clays  Residual  strength  Slope  stability  Earthquakes  Soil  deformation  Shear  strength  Overconsolidated  soils  Centrifuge Résumé : Movement along preexisting slickensided rupture surfaces in overconsolidated clay and clay shale slopes can represent a critical sliding mechanism during earthquakes. The seismic behavior of preexisting slickensided surfaces in overconsolidated clay was examined by performing dynamic centrifuge model tests of two slickensided sliding block models constructed using Rancho Solano lean clay. Dynamic shear displacements were concentrated along the preformed slickensided surfaces. The peak shear resistances mobilized along the slickensided surfaces during dynamic loading were 90–120% higher than the drained residual strength measured prior to shaking. To accurately predict the displacements of the sliding blocks using Newmark’s method, it was necessary to use dynamic strengths that were 37–64% larger than the drained residual strength of the soil. Dynamic loading caused a positive pore pressure response in the soil surrounding the slickensided planes. The postshaking shear strengths were 17–31% higher than those measured prior to shaking. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A8%2810 [...] [article] Dynamic centrifuge testing of slickensided shear surfaces [texte imprimé] / Christopher L. Meehan, Auteur ; Ross W. Boulanger, Auteur ; J. Michael Duncan, Auteur . - 2008 . - pp. 1086–1096. Geotechnical and geotechnical engineering Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 134 n°8 (Août 2008) . - pp. 1086–1096 Mots-clés : Dynamic  stability  Clays  Residual  strength  Slope  stability  Earthquakes  Soil  deformation  Shear  strength  Overconsolidated  soils  Centrifuge Résumé : Movement along preexisting slickensided rupture surfaces in overconsolidated clay and clay shale slopes can represent a critical sliding mechanism during earthquakes. The seismic behavior of preexisting slickensided surfaces in overconsolidated clay was examined by performing dynamic centrifuge model tests of two slickensided sliding block models constructed using Rancho Solano lean clay. Dynamic shear displacements were concentrated along the preformed slickensided surfaces. The peak shear resistances mobilized along the slickensided surfaces during dynamic loading were 90–120% higher than the drained residual strength measured prior to shaking. To accurately predict the displacements of the sliding blocks using Newmark’s method, it was necessary to use dynamic strengths that were 37–64% larger than the drained residual strength of the soil. Dynamic loading caused a positive pore pressure response in the soil surrounding the slickensided planes. The postshaking shear strengths were 17–31% higher than those measured prior to shaking. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A8%2810 [...]

Findings of case histories on the long-term performance of seepage barriers in dams / John D. Rice in Journal of geotechnical and geoenvironmental engineering, Vol. 136 N° 1 (Janvier 2010) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 136 N° 1 (Janvier 2010) . - pp. 2-15 Titre : Findings of case histories on the long-term performance of seepage barriers in dams Type de document : texte imprimé Auteurs : John D. Rice, Auteur ; J. Michael Duncan, Auteur Article en page(s) : pp. 2-15 Note générale : Géotechnique Langues : Anglais (eng) Mots-clés : Seepage  barrier  Cutoff  wall  Seepage  Case  history  Long-term  performance Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : In a vast majority of cases, seepage barriers increase the reliability of dams. However, it is important to recognize that seepage barriers often drastically increase hydraulic gradients around the boundaries of the barrier, and through any windows or defects in the barrier. The result is increased water pressures and hydraulic gradients behind and around the barrier. These increased pressures and gradients have potential to provide the catalyst for initiation of several modes of internal erosion that were either unlikely or less likely without the seepage barrier. As a consequence, seepage barriers give rise to the potential for additional mechanisms of internal erosion and piping in the dam and the foundation. A compendium of 30 case histories of dams that have had seepage barriers in place for over 10 years has been assembled, and observations and insights garnered from these case studies were compiled. Finite-element seepage and deformation analyses have been performed to provide better understanding of the performance of seepage barriers and the mechanisms that affect their performance. This paper presents a summary of our findings from the case histories and the analyses performed. DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.aip.org/vsearch/servlet/VerityServlet?KEY=JGGEFK&smode=strres [...] [article] Findings of case histories on the long-term performance of seepage barriers in dams [texte imprimé] / John D. Rice, Auteur ; J. Michael Duncan, Auteur . - pp. 2-15. Géotechnique Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 136 N° 1 (Janvier 2010) . - pp. 2-15 Mots-clés : Seepage  barrier  Cutoff  wall  Seepage  Case  history  Long-term  performance Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : In a vast majority of cases, seepage barriers increase the reliability of dams. However, it is important to recognize that seepage barriers often drastically increase hydraulic gradients around the boundaries of the barrier, and through any windows or defects in the barrier. The result is increased water pressures and hydraulic gradients behind and around the barrier. These increased pressures and gradients have potential to provide the catalyst for initiation of several modes of internal erosion that were either unlikely or less likely without the seepage barrier. As a consequence, seepage barriers give rise to the potential for additional mechanisms of internal erosion and piping in the dam and the foundation. A compendium of 30 case histories of dams that have had seepage barriers in place for over 10 years has been assembled, and observations and insights garnered from these case studies were compiled. Finite-element seepage and deformation analyses have been performed to provide better understanding of the performance of seepage barriers and the mechanisms that affect their performance. This paper presents a summary of our findings from the case histories and the analyses performed. DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.aip.org/vsearch/servlet/VerityServlet?KEY=JGGEFK&smode=strres [...]

Stability of I-walls in New Orleans during Hurricane Katrina / J. Michael Duncan in Journal of geotechnical and geoenvironmental engineering, Vol. 134 N°5 (Mai 2008) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 134 N°5 (Mai 2008) . - pp. 681–691 Titre : Stability of I-walls in New Orleans during Hurricane Katrina Type de document : texte imprimé Auteurs : J. Michael Duncan, Auteur ; Thomas L. Brandon, Auteur ; Stephen G. Wright, Auteur Année de publication : 2008 Article en page(s) : pp. 681–691 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Walls  Louisiana  Hurricanes  Failures  Levees  Floods Résumé : Failures of I-walls during Hurricane Katrina were responsible for many breaches in the flood protection system in New Orleans. Six breaches were examined in detail by Task Group 7 of the Interagency Performance Evaluation Taskforce. Four of these failures and breaches, which occurred before the water levels reached the top of the wall, were not caused by overtopping erosion. The failure of the I-wall at the 17th Street Canal resulted from shear through the weak foundation clay. The south failure of the London Avenue I-wall was caused by subsurface erosion, which carried massive amounts of sand inland, and removed support for the wall, leading to catastrophic instability. At the north breach on London Avenue, the failure was caused by high pore pressures, combined with a lower friction angle in the loose sand, which resulted in gross instability of the I-wall under the water pressure load from the storm surge. Looking back, with the benefit of 20-20 hindsight, these stability and erosion failures can be explained in terms of modern soil mechanics, exploration techniques, laboratory test procedures, and analysis methods. An important factor in all of the cases investigated was development of a gap behind the wall as the water rose against the wall and caused it to deflect. Formation of the gap increased the load on the wall, because the water pressures in the gap were higher than the earth pressures that had acted on the wall before the gap formed. Where the foundation soil was clay, formation of a gap eliminated the shearing resistance of the soil on the flood side of the wall, because the slip surface stopped at the gap. Where the foundation soil was sand, formation of the gap opened a direct hydraulic connection between the water in the canal and the sand beneath the levee. This hydraulic short circuit made seepage conditions worse, and erosion due to underseepage more likely. It also increased the uplift pressures on the base of the levee and marsh layer landward of the levee, reducing stability. Because gap formation has such important effects on I-wall stability, and because gaps behind I-walls were found in many locations after the storm surge receded, the presence of the gap should always be assumed in I-wall design studies. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A5%2868 [...] [article] Stability of I-walls in New Orleans during Hurricane Katrina [texte imprimé] / J. Michael Duncan, Auteur ; Thomas L. Brandon, Auteur ; Stephen G. Wright, Auteur . - 2008 . - pp. 681–691. Geotechnical and geoenvironmental engineering Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 134 N°5 (Mai 2008) . - pp. 681–691 Mots-clés : Walls  Louisiana  Hurricanes  Failures  Levees  Floods Résumé : Failures of I-walls during Hurricane Katrina were responsible for many breaches in the flood protection system in New Orleans. Six breaches were examined in detail by Task Group 7 of the Interagency Performance Evaluation Taskforce. Four of these failures and breaches, which occurred before the water levels reached the top of the wall, were not caused by overtopping erosion. The failure of the I-wall at the 17th Street Canal resulted from shear through the weak foundation clay. The south failure of the London Avenue I-wall was caused by subsurface erosion, which carried massive amounts of sand inland, and removed support for the wall, leading to catastrophic instability. At the north breach on London Avenue, the failure was caused by high pore pressures, combined with a lower friction angle in the loose sand, which resulted in gross instability of the I-wall under the water pressure load from the storm surge. Looking back, with the benefit of 20-20 hindsight, these stability and erosion failures can be explained in terms of modern soil mechanics, exploration techniques, laboratory test procedures, and analysis methods. An important factor in all of the cases investigated was development of a gap behind the wall as the water rose against the wall and caused it to deflect. Formation of the gap increased the load on the wall, because the water pressures in the gap were higher than the earth pressures that had acted on the wall before the gap formed. Where the foundation soil was clay, formation of a gap eliminated the shearing resistance of the soil on the flood side of the wall, because the slip surface stopped at the gap. Where the foundation soil was sand, formation of the gap opened a direct hydraulic connection between the water in the canal and the sand beneath the levee. This hydraulic short circuit made seepage conditions worse, and erosion due to underseepage more likely. It also increased the uplift pressures on the base of the levee and marsh layer landward of the levee, reducing stability. Because gap formation has such important effects on I-wall stability, and because gaps behind I-walls were found in many locations after the storm surge receded, the presence of the gap should always be assumed in I-wall design studies. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A5%2868 [...]