Reduction of Scour Around a Bridge Pier by Multiple Collar Plates

Abstract

Scour around a bridge pier is one of the major possible causes of the hydraulic failures of a bridge. A typical sediment-water-structure interaction at the upstream junction of the bridge pier initiates a vortex system, the primary vortex of which is responsible for local scour around the pier. The growth of the primary vortex can be arrested by retaining it on a rigid surface as on a collar plate. A number of experiments covering various sizes of collar plates were carried out in an effort to minimize scour around a bridge pier. A collar plate of size three times the diameter of the circular pier, 0 or larger when placed at the average bed level assures I 00% scour reduction while a collar plate of size 20 placed 0.10 below the bed does not allow scour depth to go beyond it. Anticipating degradation of general bed level, a group of multiple collar plates of smaller size were employed at the laboratory scale to reduce the scour considerably. A group ofthree collar plates of size 1.50 having an inter-plate spacing C, of0/6 with the middle plate placed at the average bed level reduces scour by 83% in comparison to the scour depth of an unprotected pier. The composite device, apart from being axis symmetric, is highly suited to degrading river beds.

Impact Assessment of Pier Shape and Modifications on Scouring around Bridge Pier

“…The pier modification countermeasures include the provision of collars, cables, opening slots, hooked collars, etc. Collars of different shapes and varying thicknesses are practiced by many researchers around the bridge piers as protective plates against sediment removal [11,26,[29][30][31][32][33]. According to Alabi [34], a collar that is thinner than 5 mm has no adverse effect on scour development.…”

Reduction of scour around circular piers using collars

“…The scour hole around bridge elements typically occurs due to the primary vortex, which is caused by hydrodynamic lift and drag forces on sediments and carry them downstream of the structure (Choufu et al, 2019; Ghaderi and Abbasi, 2019; Hoffmans and Verhiej, 1997; Melville, 1997; Melville and Coleman, 2000; Pandey, Chen, et al, 2019; Pandey, Lam, et al, 2019). The scour mechanism, estimation, and prevention techniques at bridge elements have been widely studied by (Chiew, 1992; Choufu et al, 2019; Garg et al, 2005; Gaudio et al, 2012; Hoffmans and Verhiej, 1997; Kumar et al, 1999; Kothyari et al, 2002, 2007; Melville, 1997; Melville and Coleman, 2000; Pandey et al, 2018; Panici et al, 2018; Sheppard et al 2014). The scour depth is high in front of the pier, with the main scour hole size develops along the pier (Kothyari & Rangaraju, 2001; Pandey et al, 2018).…”

“…They suggested the performance of the collar decreases with an increase in the angle of attacks. Garg et al (2005) studied the influence of three different collars with a diameter of 1.5 b , b is the pier diameter. For the same flow conditions, this approach reduced the maximum scour depth by approximately 80% as compared to a non‐protected pier.…”

Optimum Design for Controlling the Scouring on Bridge Piers

“…Keshavarzi et al (2018) made experimental investigation of interaction of two piers (L/D) from zero to twelve where L spacing between two piers from center to center and D the diameter of the pier with different flow intensities, it was found that the scour depth when the spacing 1< L/D< 2.5 increases, in the same meaning when the spacing increases the scour depth at upstream of the front pier increases [20]. Vikas et al investigated experimentally of using a collar plate at bed level of different sizes, the larger size was three times the diameter of pier and gave zero scour depth, also it was studied the using of triple collar with different spacing between them, it was found when the spacing between collar (D/6) reduces the scour by 84 % comparing with the pier without any protection [21].…”