Scour protection around bridge pier and two-piers-in-tandem arrangement
Vikas Garg, Baldev Setia, Vijay P. Singh, Anil Kumar
Abstract
In the present study, experiments were carried out on circular model bridge piers individually as well as with two-piers-in-tandem arrangement under clear water scour conditions predominantly caused by formation of horseshoe vortex. Independent collar plates around bridge piers and a continuous collar plate covering both the piers were installed as countermeasures against scouring. In case of two piers, efficacy of scour-protection devices for front and rear piers was checked for the overall stability. Performance potential was noted to be about 67% and 100% for continuous collar plates of sizes 2.5D and 3.0D around two piers at average bed level with spacing of 2.0D; where D is the diameter of the pier. During degradation of general bed level, a group of three continuous collar plates was employed around both the piers to ensure considerable reduction of scour. A group of three collar plates of sizes 2.5D and 3.0D having an inter-plate spacing Cs equal to D/4 with the middle plate placed at the average bed level reduced scour by 79 and 82%, respectively, in comparison to the scour depth for an unprotected pier. A mathematical model was developed by multivariate regression analysis to prediction the scour depth for both the pier arrangements.