Laboratory investigation of scour downstream of the Stepped spillway

Abstract

Abstract The most complicated problem that threatens the spillway's overall stability is local scour downstream of the spillways due to hydraulic jumps and flow disturbance. A series of experiments were conducted in the laboratory of the Water and Soil Research Center to investigate the scour downstream of the hydraulic jump formed on the stepped spillway. Experiments were conducted under different approaching flow discharges, tail-water depths and sediment sizes. The optimal design of parameters including; type, crest and slope of chute, step height and type of flow stepped spillway has been done considering the economic reasons and criteria that lead to more energy dissipation. Generally, the scour dimensions decreased as sediment sizes and tail-water depth increased or particle's Froude number (Frd) and critical depth reduced. With the reduction of Frd, the relative scour depth, the relative distance of maximum scour depth and the relative scour length decreased by 68.6%, 75.6% and 73.4%, respectively. The empirical equations of regression analysis were developed to estimate the scour parameters.