Page - 1081 - in Book of Full Papers - Symposium Hydro Engineering

REMOVAL OF OVERFLOW PIERS AT THE SPILLWAY INTAKE The existing design of the overflow piers (Fig. 2) does not ensure stable spiral inflow to the vertical shaft and sufficient air supply even at low flow rates of 1 in 2 years return period. The inflow into the vertical shaft is strongly affected by the piers and the pressure pulsations were observed. These pulsations generate an unwanted load on the spillway and the shaft structure. Fig. 2 Model of the original design with 4 overflow piers In order to improve the hydraulic performance of the existing spillway the overflow piers were removed (Fig. 3). 1081