Simple Design Criterion for Residual Energy on Embankment Dam Stepped Spillways

Abstract

The stepped spillway design is associated with significant flow resistance and associated energy dissipation on the steps, yielding smaller, more economical downstream dissipation structures. A number of design guidelines were developed for steep stepped spillways typical of concrete gravity dams. The focus of this study is on embankment stepped spillways. A large set of air-water flow data is compared with reanalyzed data sets to provide a simple unifying design approach for the residual energy at the stepped chute’s downstream end and to highlight the uncertainties involved. The results provided some simple design criteria in terms of the dimensionless residual energy of stepped chutes with flat steps. It is believed that a stepped design with a 1V:2.5H slope (θ=21.8°) might be optimum in terms of energy dissipation performances. The Darcy-Weisbach friction factors were close for all stepped data ranging between 0.1≤fe≤0.4.