Reduction of scour around circular piers using collars

Abstract

River dynamics and sediment transport play an important role in river bed morphology. Building a bridge pier along the river alters the cross-section of the river and causes the change in flow processes. These changes are mainly responsible for pier scour. In this paper, the usage of collars to reduce scour around circular piers has been investigated. The collars with different diameters and depth positions have been studied using previous data and additional data collected in the present study to assess their effectiveness in reducing scour. Using a wide range of measured data, an empirical equation to compute the maximum scour depth around the circular piers in the presence of collars has been proposed. The proposed equation has been validated and proven to be applicable to a wide range of pier layouts. It has been found that the maximum efficiency can be achieved by fixing the collar at bed level and adopting a collar diameter 1.5–2.5 times of pier diameter.