Experimental Comparison of Sacrificial Piles and Submerged Vanes as Scour Countermeasures around Bridge Pier

Abstract

An experimental study has been conducted on the effectiveness of two types of flow-altering countermeasures placed around a cylindrical pier under clear water condition, which consists of sacrificial piles and submerged vanes. Their arrangements follow the optimal configurations recommended in the published articles with some modification. The temporal evolution of maximum scour depth and its equilibrium amount around the pile without and with two scour countermeasures were recorded; scour depth reduction rates and changes in bed topography were then computed. It can be concluded that pursuant to the result which has been earned from the experiments of this study, submerged vanes had better performances compare with the sacrificial piles in all of investigated aspects. By applying submerged vanes 75% of the scour only occurred in first 5 minute. Presence of submerged vanes played more efficient role in reducing scour depth as subjected scour depth reduction was 17% more than one subjected to sacrificial piles. The length of changes downstream the pier (L) were 12, 13.2 and 6 times of pier diameter (D) corresponding to pier with no protection, sacrificial piles and submerged vanes respectively, which revealed the effectiveness of submerged vanes in reducing the area affected by pier scour. Also the maximum changes of bed level were -6.9 cm to 3.9 cm in unprotected pier test, -4.4 to 3.5 cm in protection by sacrificial piles test and -3 to 3.2 cm in protection by submerged vanes.