Impact of Upstream Bridge Pier on the Scouring Around Adjacent Downstream Bridge Pier

Abstract

The study aspires to investigate a relative scour condition around three-pier group. It identifies the upstream downstream scour geometries when two tandem piers are placed inline and third pier is placed eccentrically in middle of tandem piers. Laboratory scale experiments were physically performed by gradually varying the intermediate longitudinal spacing in between tandem piers. After each experimental run, the scour formation around the pier group and the dune formation downstream of the pier group are investigated. The main aim here is to experimentally identify and highlight the nature and location of scour formed around and also to identify the location of the dune formed downstream of this pier group due to combined interference of flow. The spacing between the inline piers were varied to identify which relative spacing produces the maximum scour. A detailed investigation shows significant effect of inline pier spacing on scour parameters. It was observed that for such three pier combinations, the scour so formed near staggered piers was found maximum and around tandem downstream pier was found minimum. It confirms the shifting of sediment load away from this pier group and is deposited downstream, drifting more towards the staggered pier that is towards channel sidewall. Equations are proposed with respect to the pier spacing between tandem piers to evaluate the scour depth around individual pier of the pier group combination.