Seismic Analysis as a Tool in the Design of Two Earth Dams

Two dynamic analysis studies of embankment dams are described. One dam is 43m high on alluvium, the other is 140m high on a rock foundation in a highly seismic area. The main emphasis is on the practical nature of the analytical methods and their value as design tools. The earthquake design features of both projects are described and the closing paragraphs attempt to draw attention to the main points to be considered when running an earthquake analysis of earth dams

Safety of existing arch-dams

International audienceThere are about a hundred arch dams in France, essentially built between 1935 and 1980. These elegant, often majestic, structures testify to the knowledge of a generation of brilliant engineers. These engineers dared to draw pure and thin lines by optimizing the material placement to reconcile the structures safety with the projects costs.The mechanical operating mode ideally depends on the transmission of the efforts to their foundation by mobilizing arch effects. So it seems safe provided that the rock supports resist. In practice the behavior of these structures iscomplex, especially for geometries which are far from the standard design: arch dams settled in wide or expanded flat-bottom valleys, unfavorable slopes of banks.Due to the number of projects becoming scarce (set apart in some countries), it is essential to assess the safety of existing dams taking into account incidents and accidents analysis of these structures, as well as experiences gained through their behavior analysis carried out for more than 50 years.These experimental lessons allow identifying the main failure modes, by distinguishing what come from a normal adaptation of the structure, from located cracks due to structure hyperstatic design, or from more global mechanisms.The present development of risk analyses and the regulatory requirements to take into account low frequency events require the search for analysis methods and if necessary for solutions (monitoring, remedial works) adapted to possible failure kinematics.In this context, a working group of the French Committee of Dams and Reservoirs, consisting of experts coming from consulting firms, operational groups and monitoring department, has introduced an approach centered on the analysis of the existing arch dams portfolio. This article presents the first results in terms of recommendations of behavior analyses, failure modes, performance criteria and adapted monitoring.In addition, Coyne and Bellier / Tractebel and Artelia, two French engineeringconsulting firms present their innovative practices on two specific topics,respectively:- concrete abutments behavior and modeling through three examples ;- dam modeling taking into account the loading history on structures by “cyclic calculations”.La France possède un parc d'une centaine de barrages-voûtes, construites essentiellement entre 1935 et 1980. Ouvrages élégants, souvent majestueux, ils témoignent du savoir-faire d'une génération d'ingénieurs brillants qui ont osé dessiner des lignes pures et minces en optimisant le placement de la matière pour concilier la sûreté des structures avec l'économie des projets.Le mode de fonctionnement mécanique des voûtes, reposant idéalement sur la transmission des efforts à leur fondation par la mobilisation des effets d'arcs,apparaît sûr à condition que les appuis rocheux résistent. Dans la pratique le comportement de ces ouvrages est complexe, surtout pour des géométries qui s'éloignent du dimensionnement standard : voûtes implantées dans des vallées larges ou à fond plat étendu, inclinaisons défavorables des rives.Le nombre de projets se raréfiant (mis à part quelques pays), il est primordial d'appuyer l'appréciation de la sûreté des barrages existants sur l'incidentologie et l'accidentologie de ces ouvrages, ainsi que sur l'analyse comportementalepratiquée depuis plus de 50 ans.Cet enseignement expérimental permet d'identifier les principaux mécanismes de défaillance, en distinguant ce qui relève d'une adaptation normale de l'ouvrage, de processus de rupture localisée liés à l'hyperstaticité des structures, ou de mécanismes plus globaux. Le développement actuel des analyses de risques, et l'évolution des réglementations visant à prendre en compte des évènements d'occurrence très faibles, imposent la recherche de méthodes d'analyse et le cas échéant de solutions (surveillance, confortements) adaptées aux cinématiquesde ruptures possibles.La démarche initiée par un groupe de travail du Comité Français des Barrages et Réservoirs composé d'experts de l'ingénierie, de l'exploitation et du contrôle des voûtes, centrée sur l’analyse du parc existant de voûtes, s'inscritdans ce cadre. L'article présente les premiers résultats en termes de recommandations d'analyses comportementales, de scénarii de défaillances, de critères de performance, de surveillance adaptée.En plus de la présentation des travaux du groupe de travail, Coyne et Bellier/Tractebel et Artelia, deux bureaux d’études français présentent leurs pratiques innovantes sur deux sujets particuliers, respectivement :- une méthode de modélisation des culées au travers de trois exemples ;- une modélisation tenant compte de l’historique de chargements des ouvrages par des « calculs cycliques »

Safety of existing arch-dams [La sûreté des barrages-Voûtes existants]

cited By 0; Conference of 26th International Congress on Large Dams, 2018 ; Conference Date: 4 July 2018 Through 6 July 2018; Conference Code:220729International audienceThere are about a hundred arch dams in France, essentially built between 1935 and 1980. These elegant, often majestic, structures testify to the knowledge of a generation of brilliant engineers. These engineers dared to draw pure and thin lines by optimizing the material placement to reconcile the structures safety with the projects costs. The mechanical operating mode ideally depends on the transmission of the efforts to their foundation by mobilizing arch effects. So it seems safe provided that the rock supports resist. In practice the behavior of these structures is complex, especially for geometries which are far from the standard design: arch dams settled in wide or expanded flat-bottom valleys, unfavorable slopes of banks. Due to the number of projects becoming scarce (set apart in some countries), it is essential to assess the safety of existing dams taking into account incidents and accidents analysis of these structures, as well as experiences gained through their behavior analysis carried out for more than 50 years. These experimental lessons allow identifying the main failure modes, by distinguishing what come from a normal adaptation of the structure, from located cracks due to structure hyperstatic design, or from more global mechanisms. The present development of risk analyses and the regulatory requirements to take into account low frequency events require the search for analysis methods and if necessary for solutions (monitoring, remedial works) adapted to possible failure kinematics. In this context, a working group of the French Committee of Dams and Reservoirs, consisting of experts coming from consulting firms, operational groups and monitoring department, has introduced an approach centered on the analysis of the existing arch dams portfolio. This article presents the first results in terms of recommendations of behavior analyses, failure modes, performance criteria and adapted monitoring. In addition, Coyne and Bellier / Tractebel and Artelia, two French engineering consulting firms present their innovative practices on two specific topics, respectively: - concrete abutments behavior and modeling through three examples; - dam modeling taking into account the loading history on structures by “cyclic calculations”. The full text of this article is available in English: http://barrages-cfbg.eu/IMG/pdf/gtvoute_vienne2018.pdf. © 2018 ICOLD/CIGB, Paris, France

Safety of existing arch-dams [La sûreté des barrages-Voûtes existants]

cited By 0; Conference of 26th International Congress on Large Dams, 2018 ; Conference Date: 4 July 2018 Through 6 July 2018; Conference Code:220729International audienceThere are about a hundred arch dams in France, essentially built between 1935 and 1980. These elegant, often majestic, structures testify to the knowledge of a generation of brilliant engineers. These engineers dared to draw pure and thin lines by optimizing the material placement to reconcile the structures safety with the projects costs. The mechanical operating mode ideally depends on the transmission of the efforts to their foundation by mobilizing arch effects. So it seems safe provided that the rock supports resist. In practice the behavior of these structures is complex, especially for geometries which are far from the standard design: arch dams settled in wide or expanded flat-bottom valleys, unfavorable slopes of banks. Due to the number of projects becoming scarce (set apart in some countries), it is essential to assess the safety of existing dams taking into account incidents and accidents analysis of these structures, as well as experiences gained through their behavior analysis carried out for more than 50 years. These experimental lessons allow identifying the main failure modes, by distinguishing what come from a normal adaptation of the structure, from located cracks due to structure hyperstatic design, or from more global mechanisms. The present development of risk analyses and the regulatory requirements to take into account low frequency events require the search for analysis methods and if necessary for solutions (monitoring, remedial works) adapted to possible failure kinematics. In this context, a working group of the French Committee of Dams and Reservoirs, consisting of experts coming from consulting firms, operational groups and monitoring department, has introduced an approach centered on the analysis of the existing arch dams portfolio. This article presents the first results in terms of recommendations of behavior analyses, failure modes, performance criteria and adapted monitoring. In addition, Coyne and Bellier / Tractebel and Artelia, two French engineering consulting firms present their innovative practices on two specific topics, respectively: - concrete abutments behavior and modeling through three examples; - dam modeling taking into account the loading history on structures by “cyclic calculations”. The full text of this article is available in English: http://barrages-cfbg.eu/IMG/pdf/gtvoute_vienne2018.pdf. © 2018 ICOLD/CIGB, Paris, France

Safety of existing arch-dams

International audienceThere are about a hundred arch dams in France, essentially built between 1935 and 1980. These elegant, often majestic, structures testify to the knowledge of a generation of brilliant engineers. These engineers dared to draw pure and thin lines by optimizing the material placement to reconcile the structures safety with the projects costs.The mechanical operating mode ideally depends on the transmission of the efforts to their foundation by mobilizing arch effects. So it seems safe provided that the rock supports resist. In practice the behavior of these structures iscomplex, especially for geometries which are far from the standard design: arch dams settled in wide or expanded flat-bottom valleys, unfavorable slopes of banks.Due to the number of projects becoming scarce (set apart in some countries), it is essential to assess the safety of existing dams taking into account incidents and accidents analysis of these structures, as well as experiences gained through their behavior analysis carried out for more than 50 years.These experimental lessons allow identifying the main failure modes, by distinguishing what come from a normal adaptation of the structure, from located cracks due to structure hyperstatic design, or from more global mechanisms.The present development of risk analyses and the regulatory requirements to take into account low frequency events require the search for analysis methods and if necessary for solutions (monitoring, remedial works) adapted to possible failure kinematics.In this context, a working group of the French Committee of Dams and Reservoirs, consisting of experts coming from consulting firms, operational groups and monitoring department, has introduced an approach centered on the analysis of the existing arch dams portfolio. This article presents the first results in terms of recommendations of behavior analyses, failure modes, performance criteria and adapted monitoring.In addition, Coyne and Bellier / Tractebel and Artelia, two French engineeringconsulting firms present their innovative practices on two specific topics,respectively:- concrete abutments behavior and modeling through three examples ;- dam modeling taking into account the loading history on structures by “cyclic calculations”.La France possède un parc d'une centaine de barrages-voûtes, construites essentiellement entre 1935 et 1980. Ouvrages élégants, souvent majestueux, ils témoignent du savoir-faire d'une génération d'ingénieurs brillants qui ont osé dessiner des lignes pures et minces en optimisant le placement de la matière pour concilier la sûreté des structures avec l'économie des projets.Le mode de fonctionnement mécanique des voûtes, reposant idéalement sur la transmission des efforts à leur fondation par la mobilisation des effets d'arcs,apparaît sûr à condition que les appuis rocheux résistent. Dans la pratique le comportement de ces ouvrages est complexe, surtout pour des géométries qui s'éloignent du dimensionnement standard : voûtes implantées dans des vallées larges ou à fond plat étendu, inclinaisons défavorables des rives.Le nombre de projets se raréfiant (mis à part quelques pays), il est primordial d'appuyer l'appréciation de la sûreté des barrages existants sur l'incidentologie et l'accidentologie de ces ouvrages, ainsi que sur l'analyse comportementalepratiquée depuis plus de 50 ans.Cet enseignement expérimental permet d'identifier les principaux mécanismes de défaillance, en distinguant ce qui relève d'une adaptation normale de l'ouvrage, de processus de rupture localisée liés à l'hyperstaticité des structures, ou de mécanismes plus globaux. Le développement actuel des analyses de risques, et l'évolution des réglementations visant à prendre en compte des évènements d'occurrence très faibles, imposent la recherche de méthodes d'analyse et le cas échéant de solutions (surveillance, confortements) adaptées aux cinématiquesde ruptures possibles.La démarche initiée par un groupe de travail du Comité Français des Barrages et Réservoirs composé d'experts de l'ingénierie, de l'exploitation et du contrôle des voûtes, centrée sur l’analyse du parc existant de voûtes, s'inscritdans ce cadre. L'article présente les premiers résultats en termes de recommandations d'analyses comportementales, de scénarii de défaillances, de critères de performance, de surveillance adaptée.En plus de la présentation des travaux du groupe de travail, Coyne et Bellier/Tractebel et Artelia, deux bureaux d’études français présentent leurs pratiques innovantes sur deux sujets particuliers, respectivement :- une méthode de modélisation des culées au travers de trois exemples ;- une modélisation tenant compte de l’historique de chargements des ouvrages par des « calculs cycliques »