Air Entrainment and Energy Dissipation on Gabion Stepped Weirs

In the last three decades the design of stepped spillways regained some interest because of their suitability with new construction methods including gabion placement. In this study, the hydraulic performances of gabion stepped weirs were investigated experimentally in terms of the air-water flow properties and energy dissipation rate. A physical study was performed in a relatively large size facility with a 26.6° slope (1V:2H) and 0.10 m step height. For both gabion and impervious stepped weirs, a detailed comparison of the air-water flow properties was performed. The visual observations highlighted the seepage flow through the gabions, including a modification of the cavity flow dynamics, especially in the skimming flow regime. In skimming flows, higher velocities were measured at the downstream end of the gabion stepped chute, associated with lesser energy dissipation rates.