Reduction of local scour around bridge piers: Combined system of aerofoil and slot

Abstract

Local scouring is one of the main causes of bridge damage or collapse in river crossings. Bridge failure can cause severe damage and can result in serious injury or death. Hence, study on the control of scouring at bridge piers plays an important role in bridge design. The aim of this study was to evaluate the effectiveness of a slotted aerofoil shaped pier in reducing local scour, as compared to a circular shaped and aerofoil shaped pier. The piers were tested under clear-water conditions for a uration of 3 hours and the resulting scour holes were scanned using a ScanStation 2. Further to this, velocity measurements were recorded at key points around the piers using an acoustic Doppler velocimeter. The results showed that the slotted aerofoil shaped pier reduces local scour. The reduction of the scour hole volume was about 85% when compared to the circular pier. Measured velocities assisted in the understanding of the resultant scour holes for the three piers and showed that for the case of the slotted aerofoil pier, the wake vortex shedding had been significantly reduced, as had the intensity of the downflow and horseshoe vortex at the nose of the pier. These results showed that the combination of a slot and aerofoil shape may be a very effective countermeasure against local scouring at bridge piers