Étude quantitative de l'érosion en aval des dissipateurs d'énergie type auge

Abstract

Scour tests on downstream roller bucket energy dissipators have shown that, at the equilibrium, bed characteristics are mainly influenced by the discharge and by the height of the bucket lip. The discharge affects scour characteristics, without however modifying the shape of the bed. On the other hand, the height of the bucket lip simultaneously affects scour characteristics and the shape of the bed mainly in the vicinity of the structure. In the latter area, for larger values of the height of the bucket lip, one observes a deposition with a small depression on the top and, on the contrary, when the height of the bucket lip is small, one observes an erosion. Both the depth of scour and the thickness of the deposit increase proportionally to the height of the bucket lip. Values of the other bed characteristics decrease slightly with the height of the bucket lip to reach a minimum, then they increase for higher values of the height of the bucket lip. Comparison of bed characteristics at the equilibrium with the literature shows that theory overestimates the depth of the scour measured in the laboratory by an average of 68% for the three values of discharge, underestimates the impact distance by about 6% for low discharges, and overestimates it by 10% for the highest discharge.Key words: hydraulic energy dissipation, roller bucket, scour mecanism, scour, small-scale model.