Laboratory Study of the Hydraulics of Flow in Gabion Stepped Weirs

In this study, different components that affect energy dissipation on flow over gabion-stepped spillways were investigated using physical models, and comparisons were made with the other studies. Flow over gabion spillway was conducted in both through flow and overflow simultaneously. The discharge is in the range of 5 to 65 liters per second.  Uniform particles with three medium diameters of 10, 25, and 40 mm were used. The height and width of the physical models were 60 and 40 cm, respectively, with 3 steps and the downstream slope of weirs was 1:1, 1:2, and 1:3 (V: H). Tow end sills including rectangular and inclined shapes were used. The results showed that the effect of end sills in gabion-stepped weirs with lower slope is more than that of weirs comprising higher slope. The effect of the end sills on the energy dissipation in the weir for d50=40 mm and S=1:2 is about 10% more than the weir with d50=10 mm and S=1:1. In weir including d50=10 mm and S=1:2 is about 30 to 35 percent more than the weir with d50=10 mm and S=1:1. Therefore, the existence of end sills in the weirs with the body of materials of d50=10 and 40 mm have the highest and the least effects on the energy dissipation. On the other hand, the effect of the rectangular end sill on the energy loss is about 3-4% more than that the effect of the triangular end sill.