Hydraulic Performance of a Moderately Sloped Stepped Spillway with 45-Degree Beveled Steps

Spillways and overtopping protection of the downstream face of embankment dams have often used roller compacted concrete overlays, which commonly feature a beveled step to reduce the use of expensive formworks. This study experimentally investigated the hydraulic performance of a stepped spillway with and without bevels for step heights of 0.1 and 0.2 m and spillway slope of 18.43 degrees (3H:1V). Specific discharges from 0.14 to 0.565 m2/s were studied with respect to flow features due to the cavity shape; distance to inception point region; time-averaged air concentrations, flow depths, and interfacial velocities; flow resistance; energy dissipation; and chute wall heights. Beveled step data were compared to vertical step data (the classical case). Findings demonstrated that the change in step geometry from a vertical step to the beveled step altered the recirculation cavity and thus influenced flow features and shifted the location of the inception point upstream. Additionally, it was observed that the beveled steps provided slightly higher energy dissipation and increased flow depths within the chute. Furthermore, the relative extent of splash and spray was reduced with beveled steps. Consequently, a beveled stepped chute may be advantageous over vertical steps in terms of hydraulic performance when considering spillway economy and construction techniques for embankment dam rehabilitation or new constructions.