Local scour around bridge piers

TLDR

The study experimentally investigated local scour around cylindrical bridge piers in uniform, cohesionless sediment and defined adjustment factors for sediment size and flow depth effects. Empirical functions linking equilibrium scour depth to approach velocity, sediment size, and flow depth were derived, showing that scour depth first decreases just above threshold velocity, reaches a minimum at about twice threshold, then rises to a maximum at transition flat bed before declining at higher velocities due to antidune formation, with sediment size and flow depth effects independent of bed motion stage and velocity.

Abstract

Local scour around cylindrical bridge piers in uniform, cohesionless sediment was investigated experimentally. Three empirical functions which relate equilibrium scour depth with approach velocity, sediment size and How depth were obtained. The variations of equilibrium scour depth with approach velocity show that the depth of scour decreases at velocities just above the threshold until it reaches a minimum at about twice the threshold velocity. Thereafter, it increases again until a maximum is reached at the transition flat bed condition. At still higher velocity, the equilibrium scour depth decreases due to the formation of antidunes. Both the effects of sediment size and flow depth were found to be independent of the stage of bed particle motion and the approach velocity. Adjustment factors, for the effects of sediment size and flow depth were defined and evaluated.