Evaluation of angled splitters as scour countermeasure at circular piers

Abstract

Scour around bridge piers is local phenomenon may cause complete failure for the hydraulic structure. This study explored experimentally using splitter plates at specific angles installed upstream single circular bridge pier to improve the nearby flow field and minimize the local scour. Ninety runs were carried out considering 9 splitter models. Four splitter lengths and 3 vertex angles were used. The splitter lengths were between 0 and 1.5 times of pier diameter, each was tested for 3 vertex angles ranged between 0° and 30°. The tests were done under 9 different hydraulic conditions including 3 discharges of 75, 100, and 125 l/s and 3 tailwater depths of 12.5, 15, and 17.5 cm. The turbulent flow conditions were investigated by plotting velocity profiles at different sections. The bed configurations under clear water conditions were presented. The results of pier without splitter were used as reference. The study outcome that the local scour depth was decreased by the increase of splitter length and vertex angle. The near-bed flow velocity and the corresponding Froude No. downstream of the pier was minimized for 1.5D splitter length at 30° vertex angle and the minimum scour geometry was located. The effectiveness of splitters were remarkable by the decrease of flow discharge and increase of tailwater depth provided that the discontinuity of scour hole length in case of multi-circular piers. Regression analysis was employed to develop empirical formula for the estimation of maximum scour depth around circular pier with splitter.

Keywords

• Angled splitter
• Circular pier
• Local scour
• Velocity distribution
• Bed configurations