Reduction of local scour around an oblong bridge pier by using vanes
摘要
Scour around hydraulic structures in alluvial rivers, backwaters, or estuaries leads to progressive lowering of the riverbed, often resulting in the exposure of bridge pier foundations and increased vulnerability to structural failure. This study presents a comprehensive experimental investigation into the effectiveness of sacrificial vanes placed upstream of bridge piers as a scour mitigation strategy. These vanes, termed "sacrificial" due to their own susceptibility to scouring, alter the local flow regime and weaken the formation of horseshoe vortices, thereby reducing the intensity of local scour. The efficacy of the vanes was evaluated based on key parameters, including vane angle, number of vane arrays, distance of the first array from the pier, and vane height above the bed. Preliminary tests involved vane angles ranging from 10° to 75°, with detailed analysis conducted at 10° and 15°, which yielded significant reductions in scour depth by 52% and 63%, respectively, compared to an unprotected pier. A multivariate regression model was developed using the experimental data to predict equilibrium scour depth. The model demonstrated strong agreement with observed data, indicating its potential applicability for scour prediction and bridge pier design in alluvial river environments. Importantly, the findings of this study offer valuable insights for protecting bridge foundations in sea backwater regions, where tidal currents and sediment transport can exacerbate local scour around marine piers.