Effect of Transversal Bed Slope on the Equilibrium Scour Depth at Bridge Piers

Abstract

This study focused on the effect of the transversal bed slope on scouring at bridge piers. Twenty-four experiments were conducted, half of them being on a horizontal bed and the other half on inclined beds. Three inclination angles, three flow intensities, and three pier diameters were combined within the degrees of freedom of the available experimental setup. Velocity measurements were performed to characterize the velocity field at triangular cross sections. Contrary to intuition, it was concluded that the equilibrium scour depth around cylindrical piers inserted in an erodible inclined bed decreases with the inclination angle for angles between approximately 11° and 25°, which suggests that practitioners can safely use scour depth predictors derived for horizontal beds to calculate the scour depth at inclined beds, provided that they properly assess the approach flow velocity and the critical velocity for the beginning of sediment motion on inclines. Within the range of nondimensional values covered by this study, practitioners can also use a new scour depth predictor.