Les vagues dans les retenues d’altitudes : analyse et méthodes pour la prévention

Édifiées dans les stations de loisirs de montagne pour la production de neige de culture, les retenues d'altitude, comme tout ouvrage hydraulique, sont soumises aux aléas météorologiques qui peuvent générer des risques pour la sécurité publique. Les auteurs s'intéressent ici aux conséquences des vagues provoquées par le vent et les mouvements gravitaires rapides sur de tels ouvrages et étudient les moyens de protection à mettre en place

Déversoirs sur digues fluviales

International audienceLevees are built on many rivers and mountain torrents to protect populations against floods. During medium floods, a well-constructed levee offers sufficient protection without requiring additional hydraulic structures. But this same levee represents a source of danger during high floods, since there is a risk of overtopping. Water that spills over a levee may create a breach that could potentially provoke flash flooding in the area it was supposed to protect, endangering human lives and infrastructure.It is therefore advisable to equip levee systems with spillways, which are common appurtenant structures on dams. Yet spillways on levees play a far more complex role than those on dams, from securing protected areas to flood control. These structures can function as safety spillways or diversion spillways, or both (especially the older ones).This technical handbook, first published in French in 2012, covers different types of spillways on river levees, including their function, hydraulics, river morphology, civil engineering, and flood management. Written by a working group led by INRAE, it is intended for levee managers, control authorities, engineering firms, and hydraulics or civil engineering students. Given increasing international interest in levees and flood protection systems, particularly following ICOLD’s creation of a Technical Committee on Levees, INRAE decided to update and translate this guide into English to share the French experienc

Spillways on river levees

Levees are built on many rivers and mountain torrents to protect populations against floods. During medium floods, a well-constructed levee offers sufficient protection without requiring additional hydraulic structures. But this same levee represents a source of danger during high floods, since there is a risk of overtopping. Water that spills over a levee may create a breach that could potentially provoke flash flooding in the area it was supposed to protect, endangering human lives and infrastructure. It is therefore advisable to equip levee systems with spillways, which are common appurtenant structures on dams. Yet spillways on levees play a far more complex role than those on dams, from securing protected areas to flood control. These structures can function as safety spillways or diversion spillways, or both (especially the older ones). This technical handbook, first published in French in 2012, covers different types of spillways on river levees, including their function, hydraulics, river morphology, civil engineering, and flood management. Written by a working group led by INRAE, it is intended for levee managers, control authorities, engineering firms, and hydraulics or civil engineering students. Given increasing international interest in levees and flood protection systems, particularly following ICOLD’s creation of a Technical Committee on Levees, INRAE decided to update and translate this guide into English to share the French experience

Études de dangers des systèmes de protection contre les inondations : une méthode d'analyse de la défaillance

La défaillance est l'incapacité d'atteindre un seuil de performance défini pour une fonction donnée, ici la protection contre les inondations. L'analyse des modes de défaillance permet d'analyser, identifier et représenter les scénarios de défaillance afin de mieux évaluer la sécurité des digues et d'estimer le risque. Elle peut être basée sur une analyse fonctionnelle qui décrit le système de digues en termes de fonctions. La défaillance d'un système d'endiguement est l'inondation non souhaitée ou non maîtrisée de la zone protégée et peut se produire entre autres par entrée d'eau avant l'atteinte du niveau de protection prévu, ou par une brèche dans le système. L'article expose une méthodologie d'analyse de la défaillance des systèmes d'endiguement visant à identifier les scénarios de défaillance hydraulique et les scénarios de défaillance structurelle, afin de pouvoir estimer le risque d'inondation associé à ces défaillances. Il détaille les différentes phases de cette méthodologie : définition des fonctions hydrauliques et structurelles des composants du système de protection 

Chapter 5. Civil engineering design for levee spillways

International audienceThis guide represents a complete overview of the design and protection issues for structures built on dikes, such as spillways. This chapter presents the civil engineering of these constructions. It introduces successively the safety criteria of spillways on dikes, the principle of a fusible or mobile raise, the shape in plan of spillways on dikes, the types of rectilinear sills and constituent materials, fusible or mobile raises, the continuity of maintenance tracks, a return on erosion by overflow on earthen dikes

Les vagues dans les retenues d’altitudes : analyse et méthodes pour la prévention Water waves in mountainous lakes: analysis and methods for prevention

Édifiées dans les stations de loisirs de montagne pour la production de neige de culture, les retenues d'altitude, comme tout ouvrage hydraulique, sont soumises aux aléas météorologiques qui peuvent générer des risques pour la sécurité publique. Les auteurs s'intéressent ici aux conséquences des vagues provoquées par le vent et les mouvements gravitaires rapides sur de tels ouvrages et étudient les moyens de protection à mettre en place.<br>The load of the wind and the impact of rapid mass movements in a reservoir generate waves whose nature and properties depend on the magnitude of the load and the water depth in the reservoir. In this paper we summarized the main existing scaling laws allowing assessing the resulting hydrodynamic effects, focusing not only on the amplitude of the waves, but also on its nature. The wind and the slow movements produce sinusoidal waves while rapid mass movements produce steeper water waves such as tsunamis. Given the limited extension of the mountain lakes, the produced water waves rapidly meet the shores or the dam on which they generate a run-up whose amplitude depends on the characteristics of the incident wave and the slope of the shore. We have undertaken a theoretical analysis and collected several experimental data in order to show the similarities and the differences between the sinusoidal waves and the solitary waves in terms of run-up. We finally, choose simple formulas and produced a chart enabling any engineer to make a first diagnosis

Cotes et crues de protection, de sûreté et de danger de rupture

Cette communication présente une synthèse des différentes cotes et crues de référence habituellement utilisées pour l’évaluation de la sécurité d’un ouvrage hydraulique, y compris dans le cas d’un barrage écrêteur de crues ou d’une digue de protection contre les inondations. Les discussions au sein du groupe de travail du CFBR consacré à la justification de la stabilité des barrages et les travaux de recherche menés au Cemagref dans le domaine de l’analyse de risques appliquée aux ouvrages hydrauliques montrent les limites de ces définitions et ouvrent de nouvelles perspectives. Des propositions sont donc faites pour clarifier la terminologie. Cela aboutit à privilégier la détermination des cotes atteintes dans la retenue pour différents scénarios de crues. Au final, il apparaît possible d’associer des probabilités d’occurrence au dépassement de la cote de sûreté ou de la cote de danger de rupture, et parallèlement de proposer des valeurs minimales cibles pour ces probabilités, en fonction des types d’ouvrages et de leur classe

Food restriction, performance, biochemical, psychological, and endocrine changes in judo athletes

In order to test the hypothesis that dietary restriction may have a negative influence on physiological and psychological adaptation to a judo competition, we examined the effects of weight loss induced by restricting energy and fluid intake on the physiology, psychology, and physical performance of judo athletes. Twenty male judoka were randomly assigned to one of two groups (Group A: called diet, n = 10; height 174.8 +/- 1.9 cm, body weight 75.9 +/- 3.1 kg; they were asked to lose approximately 5 % of their body weight through self-determined means during the week before the competition; Group B: called control, n = 10; height 176.4 +/- 1.1 cm, body weight 73.3 +/- 6.3 kg maintained their body weight during the week before the competition). A battery of tests was performed during a baseline period (T1), on the morning of a simulated competition (T2) and 10 min after the end of the competition (T3). The test battery included assessment for body composition, performance tests, evaluation of mood, determination of metabolic and hormonal responses. Dietary data were collected using a 7-day diet record. The nutrient analysis indicated that all the athletes followed a low carbohydrate diet whatever the period of the investigation. For the Group A, the food restriction (- 4 MJ per day) resulted in significant decreases of the body weight and altered the mood by increasing Fatigue, Tension and decreasing Vigour. Dietary restriction had also a significant influence on metabolic and endocrine parameters and was associated with poor performance. After the competition, significant decreases of the levels in testosterone, T/C ratio, alkali reserve, and free fatty acid were observed in both groups, whereas the plasma concentrations in insulin, ammonia, urea, and uric acid were increased. In conclusion, our results suggest that the combination of energy restriction and intense exercise training, which causes weight reduction before a competition, adversely affects the physiology and psychology of judo athletes and impairs physical performance before the competition. Our data are the first to demonstrate that a competition including five 5-min bouts induced the same changes of physiological and psychological variables and performance whatever the dietary intake (dietary restriction or not) during the seven days before the competition