Experimental survey of static pressure in stepped chutes with inclined and horizontal steps equipped with end sills in nappe and skimming flow regimes

A spillway is one of the most important parts of a dam for controlling floods. Among different types of spillways, stepped spillways are one of the best energy dissipaters. Due to technological advances and the satisfaction of two elements for safe and low-cost construction, the use of stepped spillways has increased widely. Due to this, more studies are focused on stepped spillways. Researchers have made some efforts and proposed different methods to improve structural efficiency to dissipate energy. Modifications on step geometry, regarding flow regime type, are one of these efforts. Flow pressure and its fluctuations on the steps of the stepped spillways is one of the main factors affecting structural design and safety. In this experimental research, reverse inclined steps combined with the end sills have been applied in four degrees [0o (horizontal), 5o, 8o, and 11o] to obtain static pressure in both the nappe flow and skimming flow regimes of stepped spillways. Static pressure obtained from reverse inclined steps with end sills have been compared to the amount in the horizontal step. Results indicate a slight increase in the energy loss rate when reverse inclined steps have been applied in the nappe flow regime of stepped spillways.