Experimental method to predict scour characteristics downstream of stepped spillway equipped with V-Notch end sill

Abstract

To protect the dam body and downstream area, spillways should be built. Because the difference in water level upstream and downstream spillways is usually very big, energy dissipation facilities should be introduced. Stepped spillways were discovered to immensely enhance energy dissipation. V-notch end sills installed on stepped spillways were not investigated enough. The challenge in using this type of end sills is to know the ideal angle of the notch. The second challenge is to link the energy dissipation percent and the scour hole characteristics with the hydraulic parameters of the spillway and the soil properties. This paper aims to investigate the V-notch end sills in stepped spillways and to assess their effect on energy dissipation and scour. For this purpose, physical models of four steps were built on stepped spillways in the laboratory. V-notch end sills were installed at the end of each step of the spillway. The dimensional analysis was used to link the various parameters influencing the studied phenomena. All V-notch end sill angles used enhanced energy dissipation, reduced the relative scour depth, length, and volume. Minimizing the angle of V-notch end sills enhanced energy dissipation. Three scour equations were developed to predict scour characteristics from easy-to-record measurements.