MODEL STUDY OF A ROLLER COMPACTED CONCRETE STEPPED SPILLWAY

Studies were conducted with a two-dimensional 1:20 scale model of a ro ller compacted concrete stepped spillway to evaluate the flow transiti on from the level spillway crest to the sloping steps, the energy diss ipation of the steps, and performance of the proposed stilling basin. The steps were effective in dissipating energy. At maximum discharge, 14.5 m(3)/s/m (156 ft(3)/s/ft), the energy dissipation with the steps was 48% compared with an energy dissipation of 20% for the spillway wi th a smooth chute surface. At 5.81 m(3)/s/m (62.5 ft(3)/s/ft), the ene rgy dissipation with the steps was 71% compared with 25% with a smooth chute surface. The energy dissipation caused by the steps significant ly reduces the size of stilling basin required at the toe of the spill way compared to a conventional chute spillway.