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Copyright of Canadian Journal of Civil Engineering is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Civil Engineering is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Civil Engineering is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Civil Engineering is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Civil Engineering is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Civil Engineering is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Civil Engineering is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper reports on a laboratory study that examines the effectiveness of submerged vanes for the control of erosion in strongly curved narrow channel bends. All previous researches on submerged vanes were performed in either straight or weakly curved channels that were hydraulically owideo. Submerged vanes are thin rectangular-shaped low-profile foils, typically set at small angles to the main current and arranged in either single or multiple parallel arrays in the longitudinal direction. When installed in a channel bend they induce a helicoidal vortex that interacts with and weakens the centrifugally induced secondary current. The latter effect leads to reduced local erosion near the bend's outer bank. Physical model testing was performed to determine the effects of several parameters affecting submerged vane performance, including submerged vane height H, length L, angle to main flow direction α, vane streamwise spacing δ[subs], vane transverse spacing from outer bank δ[subn] , and bend angle φ. Submerged vanes effectively stabilize channel bend erosion by reducing the scour depth at the outer bank, generating positive transverse bed slope at the outer bank, and by reducing the net sediment loss through the channel. In general, an increase in vane height tends to shift the thalweg away from the outer bank; an increase in vane length tends to reduce the general erosion through the channel. [ABSTRACT FROM AUTHOR]

Various coefficients in sediment transport models must be accounted for. Models based on depth-averaged equations and sediment carrying capacity formula contain some coefficients: α, k, and m. At the present, no widely acceptable method has been developed for determining the values of these coefficients. The focus of this paper is in the development of semi-theoretical formulas for estimating these coefficients such that, in practical applications, the uncertainty involved in selecting coefficients is minimized. Model verification shows that the coefficients obtained from the proposed formulas give a good simulation of the channel bed deformation. In addition, Rouse's equation for sediment concentration distribution will become solvable because the reference concentration can be determined from the derived expression for α. The simulated concentration profiles obtained by solving the Rouse's equation and α formula agree reasonably well with the measured data.Key words: depth-averaged model, sediment transport, sediment-carrying capacity.Plusieurs coefficients doivent être considérés dans les modèles de transport des sédiments. De façon similaire, les modèles basés sur les équations avec profondeurs moyennes et la formule de capacité de transport contiennent quelques coefficients: α, k et m. Pour le moment, aucune méthode acceptable en général n'a été développée pour la détermination de leurs valeurs. Le but de cet article est le développement de plusieurs formules semi-théoriques afin d'estimer ces coefficients de sorte que, dans les applications pratiques, l'incertitude inhérente à la sélection de ces coefficients est minimisée. La vérification avec un modèle montre que les coefficients obtenus par les formules proposées produisent une bonne simulation de la déformation du lit d'un canal. En plus, l'équation de Rouse pour la distribution de la concentration en sédiments va pouvoir être résolue, car la concentration de référence peut être déterminée par le biais de l'expression pour le coefficient α. Les profils de concentration simulés par la résolution de l'équation de Rouse et la formule pour α concordent raisonnablement avec les données mesurées.Mots clés : modèle avec profondeurs moyennes, transport de sédiments, capacité de transport de sédiments.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

The validity of dam failure studies is based on the appropriateness of the expected failure mode. Failures of earth-fill structures show the importance of the choice of breach parameters for failure evaluation and consequences. This paper summarizes the state of the possibilities for forecasting the breach and the resulting hydrograph in the downstream valley. It describes the most current methods, applies them on a failure case observed in the Saguenay region, Province of Québec, and compares the results. Considering the large uncertainty margin on the results, the paper allows one to understand why breach forecasting must not, in the current state of knowledge, be part of the safety study process, and that it is preferable to stay with a definition for breach based on a rule intelligently applied with respect to the case, the structure, and its composition.Key words: dam failure, dam breach, erosion, forecasting, flood of failure, earth-fill dam.[Journal translation]La validité des études de rupture de barrage repose sur la fiabilité du mode de rupture appréhendé. Les ruptures d'ouvrage en terre et enrochement montrent l'importance du choix des paramètres de brèche dans l'évaluation et les conséquences de rupture. Ce présent article résume l'état des possibilités de prévision de la brèche et de l'hydrogramme transmis dans la vallée en aval. Il décrit les méthodes les plus courantes, les applique à un cas de rupture observé au Saguenay en juillet 1996 et compare les résultats. À la lumière de la grande marge d'incertitude observée dans les résultats, il permet de comprendre pourquoi la prévision de la brèche ne doit pas dans l'état des connaissances actuelles faire partie de la démarche des études de sécurité et qu'il vaut mieux s'en tenir à une définition de celle-ci basée sur une norme appliquée intelligemment en fonction du cas, de l'ouvrage et de sa composition.Mots clés : rupture de barrage, brèche de barrage, érosion, prévision, crue de rupture, barrage en terre. [ABSTRACT FROM AUTHOR]

A series of laboratory experiments was conducted in a confined channel to study the effect of armor layer on the scour formation induced by a deeply submerged circular turbulent wall jet. A wide range of particle sizes was utilized to form an armor layer and the local erosion downstream of a circular wall jet was measured. The time evolution of scour dimensions was recorded and the scour profiles of the mixed bed were compared with the scour profiles of a relatively uniform sand bed with the same average particle size. Three regimes were identified as the initial stage (Regime I), the quasi-steady state (Regime II), and the steady state (Regime III). The characteristic lengths of the scour showed rapid growth at the early stage of scour development and the growth rate decreased until the scour reached the steady-state condition. The effect of armor layer on scour dimensions was pronounced, which significantly reduced the maximum scour depth due to formation of an armor layer. The characteristic parameters affecting the maximum scour depth and width were identified and empirical correlations were introduced for the prediction of scour dimensions. The scour profiles in the mixed bed showed two consecutive scour depths. It was found that the area occupied by the armor layer increased by increasing the Froude number of the jet. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Civil Engineering is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Civil Engineering is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Civil Engineering is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Civil Engineering is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Civil Engineering is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Civil Engineering is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Civil Engineering is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Civil Engineering is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Civil Engineering is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Civil Engineering is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Civil Engineering is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Civil Engineering is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Civil Engineering is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Investigates the mechanism of erosion and the factors influencing erosion rates of clay banks of the Saint Lawrence River along the Montréal to Lac Saint Pierre n Quebec. Literature review; Details on the experiments; Results of the study; Conclusions.

A macro-roughness lining system for the protection of earth embankment dams during overflow is presented. It consists of precast concrete elements placed on a drainage-separation layer. The main difference between this system and other existing concrete element systems is the stability concept, based on the self-weight of the blocks. Several types of elements were developed and tested in a physical model for a typical dam slope of 1V:3H. Failure conditions were identified after submitting the elements to increasing flow discharges. Furthermore, different foundation drainage and shear conditions between the elements and their foundation and different joint alignments were studied. Flow characteristics were observed and measured for quasi-uniform flow conditions. Based on the experimental results, a stability model was developed to compute the design safety factor. The model is based on the governing overturning equation (predominant failure mechanism) and on assumptions concerning the acting hydrodynamic forces, the hydrostatic uplift, and the concentration of air in the flow. Synoptic design charts were derived for 1V:3H dam slopes, allowing the rapid estimate of the lining characteristics as dimensions and weight for a certain withstood design unit discharge, for various margins of safety. The developed macro-roughness lining system is envisaged for the spillway rehabilitation of existing dams, but also for the design and construction of spillways of low dams (up to 30 m in height) and for the protection of overflow cofferdams.Key words: overflow dams, erosion protection, linings, macro-roughness, stability, drainage and spillways.Un système de macro-rugosités pour la protection superficielle de barrages en remblais est présenté. Ce système est composé de blocs préfabriqués en béton posés sur une couche de drainage, dont la stabilité est assurée par leur poids propre. Plusieurs géométries d'éléments ont été développées et testées dans un modèle physique du parement d'un barrage avec une pente de 1V:3H. Les conditions de rupture ont été identifiées après avoir soumis les blocs à des débits croissants. Pour la fondation des blocs, différentes conditions de drainage et de frottement ont été testées, ainsi que différents alignements des joints longitudinaux. Les caractéristiques de l'écoulement ont été observées et mesurées en conditions quasi-uniformes. Basé sur l'étude expérimentale, un modèle de stabilité a été développé pour le calcul des coefficients de sécurité. Ce modèle est basé sur la stabilité au renversement (mécanisme de rupture dominant) et des hypothèses concernant les forces hydrodynamiques, la pression hydrostatique et la concentration d'air dans l'écoulement. Des diagrammes de dimensionnement ont été élaborés pour parements de pente 1V:3H, permettant une estimation rapide des caractéristiques du système de protection, comme les dimensions et le poids des blocs, résistant à un certain débit spécifique, pour plusieurs marges de sécurité. Le système développé est envisagé pour la réhabilitation d'évacuateurs de crues de barrages existants, ainsi que pour le dimensionnement et la construction d'ouvrages d'évacuation pour des barrages allant jusqu'à 30 m de hauteur et pour la protection des batardeaux submersibles. Mots clés : barrages submersibles, protection contre l'érosion, recouvrement du parement, macro-rugosités, stabilité, drainage et évacuateurs de crues. [ABSTRACT FROM AUTHOR]

Detailed velocity and erosion measurements in the near wake of a flat plate with a gap between the plate and the channel bed in an open channel are presented. A "wall jet" like flow (confined to the wall region) is observed to interact with the wake flow behind the body. Two axial stations downstream of the body were chosen to obtain the velocity profiles in the near wake region. The span-wise velocity profiles across the wake at two distances from the channel bottom were also obtained. This yielded information in the development of the "wall jet" like flow and also provided some sense of the velocity components in the near wake. At mid-section of the gap, the streamwise mean velocity attains its peak value at one body width. The velocity measurements across the wake exhibit the cause of erosion. Erosion measurements were simulated on an erodible sand bed of D[sub 50] = 0.59 mm grain size. The erosion patterns obtained show symmetry about the centerline of the plate. A ripple-like pattern was observed with deeper scour holes generated towards the edge of the wake. Flow separations from the lower corners and the sides of the plate account for this typical nature of the erosion pattern.Key words: velocity profile, local scour, wake flow, wall jet flow.Des mesures détaillées de la vélocité et de l'érosion dans le sillage proche d'une plaque plate avec un espace libre entre la plaque et le lit du canal sont présentées. Un écoulement de parois (confiné dans la région des parois) est observé d'avoir une interaction avec le sillage laissé derrière le corps. Deux stations axiales en aval du corps ont été choisies afin d'obtenir les profils verticaux de vélocité dans la région près du sillage. Les profils de vélocité dans la section transversale à travers le sillage ont aussi été obtenus pour deux profondeurs à partir du lit du canal. Ceci a amené de l'information dans le développement de l'écoulement de parois et a aussi donné du sens aux composantes de vélocité dans la région près du sillage. Au centre de la section de l'ouverture, la vélocité moyenne en direction de l'écoulement atteint sa valeur maximale à une hauteur équivalent à la largeur du corps. Les mesures de la vélocité à travers le sillage montre la cause de l'érosion. Les mesures d'érosion ont été simulées sur un lit de sable érosif ayant un diamètre de grains D[sub 50] = 0,59 mm. Les motifs d'érosion se montrent symmétriques par rapport au centre de la plaque. Un motif ondulatoire a été observé, avec des trous d'érosion plus profonds générés vers la fin du sillage. Les séparations d'écoulement venant des coins inférieurs et des côtés de la plaque expliquent la nature typique du motif d'érosion.Mots clés : profil de vélocité, érosion locale, sillage, écoulement de parois.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

In this study, the effect of grain size on the dynamics of local scour processes is discussed in the context of the erosion that takes place downstream from a submerged sluice gate. Four gradations of non-cohesive bed material were used to study the scour process for various tailwater depth and flow rate conditions. The sand gradations included three sizes of uniformly graded sand and a fourth size, which was obtained by mixing the three uniform sands in equal proportions by weight. A total of 36 tests was carried out, each for a period of 24 h. An equilibrium scour condition was not attained over this time period for any of the tests, although a sense of similarity in the bed profiles is observed in the region close to the sluice gate. The present results indicate that the depth and the area of scour are highly dependent on the bed grain size, both increasing as the grain size is reduced. As well, it was found that the tests with a mixed (i.e., graded) sand bed resulted in less scour relative to those in which a uniformly graded sand of similar grain size was used. Moreover, the maximum scour depth increases with increases in the discharge and the tailwater depth. Finally, it was found that the location of the point of maximum scour depth, as measured from the upstream end of the erodible sand bed, moved downstream with an increase in either the discharge or tailwater depth and upstream with an increase in the grain size.Key words: grain size, grain size distribution, local scour, scour dynamics, sluice gate, tailwater depth, video image data acquisition.Dans cette étude, l'effet de la taille des grains sur la dynamique des processus d'érosion locale est discuté dans le contexte où celle-ci prend place en aval d'une vanne submergée. Quatre gradations de matériaux de fond non cohésif ont été employées pour l'étude du processus d'érosion sous différentes conditions de profondeur d'écoulement et de débit. Les gradations de sable comprennent 3 types de sable de grade uniforme et un quatrième type, qui a été obtenu par le mélange des trois types de sable uniformes dans des proportions de poids identiques. Un total de 36 tests a été entrepris, chacun sur une période de 24 heures. Un équilibre de la condition d'érosion n'a pas été atteint durant cette période de temps pour tous les tests, bien qu'un genre de similarité dans les profils du lit est observé dans la région proche de la vanne. Les présents résultats indiquent que la profondeur et l'aire d'érosion sont hautement dépendantes de la taille des grains du lit, les deux augmentant à mesure que la taille du grain est réduite. Aussi, il a été trouvé que les tests avec un lit de sable de grades mixtes ont résulté en une érosion moindre comparée à celles dans lesquels un sable de grade uniforme, avec taille de grain similaire, a été employé. De plus, la profondeur maximale d'érosion s'accroît à mesure que s'accroît le débit et la profondeur d'écoulement. Finalement, il a été trouvé que la position du point de profondeur maximale d'érosion, telle que mesurée à partir de l'extrémité amont du lit de sable qui peut s'éroder, se déplace vers l'aval lorsque que le débit ou la profondeur d'écoulement augmentent et vers l'amont lorsque la taille de grain s'accroît.Mots clés : taille des grains, distribution de la taille des grains, érosion locale, dynamique d'érosion, vanne, profondeur d'écoulement, acquisition de données par image vidéo.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]