Effect of Simultaneous Use of the Six-Legged Element and Rip-Rap for the Control of Scouring and Economic Comparison

Scouring control in the downstream of the ski jump spillway is one of the most important issues faced by hydraulic engineers. In this study, an experimental investigation was done to evaluate the reduction of the maximum scour volume due to the combination of six-legged concrete elements (A-Jacks) in different hydraulic conditions. These elements were placed in the downstream of the ski jump spillway. The experiments included a single size of concrete element and two sizes of riprap with five discharges and three different tail-water depths. The change in depth of tail-water resulted in the spillway having free, semi-submerged and submerged states. The results showed that as the scour depth increased, the scour rate is reduced significantly. The simultaneous presence of concrete elements and riprap amid different hydraulic conditions caused a 100% decrease to the maximum scour volume when compared to the control tests. The use of A-Jacks when equated to riprap covered structures in a 100 m2 area indicated a 10% reduction in bed protection costs ( By use of Price list ).