La France, ainsi que d'autres regions du monde, sont frequemment l'objet d'episodes de crues devastatrices. Les degâts humains et materiels sont amplifies en cas de rupture d'un ouvrage de protection. Malheureusement, ces structures a longs lineaires sont des ouvrages le plus souvent mal entretenus et ayant montre des signes de fragilite a de nombreuses reprises. Aussi, la gestion des digues fluviales souleve plusieurs problemes considerables pour les decideurs charges de garantir une securite maximale a la population pour un cout de gestion acceptable. Le projet Digsure a pour vocation de proposer aux gestionnaires des methodes scientifiques ainsi que des outils techniques de gestion des digues. Ces outils d'aide au diagnostic permettront d'evaluer la performance des digues tout le long du lineaire.
In France, levees remain most of the time badly maintained; these long linear structures show signs of weaknesses on numerous occasions. Only incomplete information is usually available. The general lack of data describing the behavior of the infrastructure during unwanted events led to estimate their safety mainly from expert judgment. Thus the ability of the expert to predict the level of functioning of an infrastructure for a type of hazard and its intensity is crucial. An error of judgment can have very serious consequences and the production of reliable information requires the ability of the expert to report accurately the uncertainties in its estimations, as well as associated confidence. In order to meet this need, our research within Incertu project (French Ministry of Ecology funding) aims to produce relevant scientific approaches and tools for the collection and processing reliable experts' statements or combined with a confidence level in the context of uncertain information and input data.
This paper proposes a methodology to take into account of the dependence between hydraulic loading and shear strength in a probability-based procedure for assessing the gravity dam structural safety. This is a major point in a probability-based approach where extreme loadings are a determining factor of dam reliability. The proposed approach uses a parabolic formulation of concrete shear strength. It aims at providing a better representation of the intrinsic curve for normal stress lower levels that might develop in the dam upstream area under extreme hydrostatic loading conditions. Based on the FORM method and on Monte Carlo simulations, a case study shows how relevant the proposed method is and the impact thereof on the results of a reliability analysis completed for an existing gravity dam.
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No abstract is provided for this article.
Les retenues d'altitude sont des ouvrages hydrauliques implantes dans les stations de loisirs de montagne destines a creer une reserve d’eau pour la production de neige de culture, d’eau potable, pour l’irrigation, etc. En raison de l’implantation de ces retenues, les difficultes techniques, reglementaires, environnementales et liees a la securite publique sont nombreuses et specifiques. Ce livre, veritable manuel integre, etablit les regles en matiere de conception, de realisation et de surveillance. Il repond aux questions d’evaluation des sites, d’analyse des aleas naturels et technologiques et d’etude d’onde de submersion. Enfin, il propose des elements d’aide a la decision pour les maitres d’ouvrage et leurs bureaux conseils quant a l’organisation d’un tel projet.
Levees are large alignment civil engineering works with a performance that is assessed with great difficulty due to its longitudinal variability. We hereby suggest that a decision-making support procedure should be identified, built and implemented so as to split levee alignments into homogeneous sections and identify them according to their performance level. Our work is focused on defining actions for the purpose of solving the decision-making problem with regard to large alignment works. In order to select a suitable decision-making method, we suggest a formulation and a comparison between two types of multi-criteria methods: the ELECTRE TRI outranking method and a unicriterion method. The relevance of building a unicriterion for the purpose of our study is investigated considering the existing operational interconnections between the levee evaluation criteria. Les digues sont des ouvrages de génie civil à grand linéaire dont la performance est difficile à évauler parce que très variable longitudinalement. Dans cet article, nous proposons l’identification, la construction et la mise en œuvre d’une démarche d’aide à la décision permettant le découpage des linéaires de digues en tronçons homogènes, et leur identification par niveau de performance. Notre travail examine avec attention la question de la définition des actions objets de l’aide à la décision pour des ouvrages à grands linéaires. Pour le choix d’une méthode d’aide à la décision, nous proposons une formulation et une comparaison de deux types de méthodes multicritères : la méthode surclassement ELECTRE TRI et une méthode du critère unique de synthèse. Nous examinons l’intérêt de la construction d’un critère unique de synthèse pour notre recherche du fait des liens fonctionnels existants entre les critères d’évaluation des digues.
No abstract is provided for this article.
reservoirs are hydraulic structures in ski resorts in the mountains, used to store water in general for snowmaking. There are more than one hundred of them in France, most of them less than 10 years of age. Despite their modest volumes (5,000 to 400,000 m3) and dam heights of between 5 and 20m, these structures do induce potentially high risks for people and property situated downstream from them. They are located at altitudes between 1,200 and 2,700m, and often face difficult topographical, geological and geotechnical conditions, mountain-specific hazards, a very limited period for construction in the year, considerable pressure from ice and intense cold, the difficulty of surveillance in winter, etc. A survey conducted on about 70 of these mountain reservoirs provided considerable information, particularly on the behaviour and pathologies of these small dams at high altitudes. These reservoirs are generally entirely sealed by geomembranes (85% of cases). This feedback on experience served as a basis for writing a set of guidelines on studying, designing, constructing, monitoring and rehabilitating these mountain reservoirs [4]. This guideline has been supported by the French ministry of environment and it has been prepared by a working group lead by the Cemagref and with the contribution of EDF and ISL. The article presents, through the guideline Mountain reservoirs, a summary of the feedback on the behaviour and pathology of mountain reservoirs. It gives a general description of the guideline [4], and emphasis on the main key themes: environmental impacts, risks specific to the mountain, design of embankments and drainage system, monitoring and operation, and those aspects of the underlying layer, drainage and cover layer of the GSS that appear to be essential for the system to behave correctly.
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