Scale Modelling of the RCC Dam with Stepped Spillway

Abstract

Design of an RCC (roller-compacted concrete) dam had been verified using a scale model. The scale of the model was 1:40 and hydraulic parameters were scaled using Froude similarity. The aim of investigations were flood mitigation structures – a standard Creager profiled spillway crest (with five bays), a converging stepped chute and a stilling basin. The main problem of the initial design was selecting the optimal shape of stepped chute side walls. As the converging chutes generate standing waves, this results in significant increase of the water level in the zones in the vicinity of the walls. The final shape of the side walls had been selected through trial-and-error procedure, provideing the most favorable flow conditions. As a consequence, improving the flow conditions in the chute resulted in better flow conditions inside the stilling basin as well, so the proposed energy dissipation baffle blocks could be removed. For the final design, measurements of the hydraulic parameters (water levels, depths, velocities, pressures) on the scale model verified the implemented improvements (compared to the initial design).