Model Study of Local Scour Downstream Bridge Piers

by Laila Abed, Hydraulics and Sediment Research, Inst, Cairo, Egypt,
M. M. Gasser, Hydraulics and Sediment Research, Inst, Cairo, Egypt,



Document Type: Proceeding Paper

Part of: Hydraulic Engineering

Abstract:

A deep scour hole downstream of a large circular pier has been developed at Imbaba bridge, which is considered one of the major bridges across the Nile River in Cairo, Egypt. At that location the Nile River is considered almost clear water river with fine sand bed. An undistorted mobile bed model, with a scale 1:60, was constructed at the Hydraulics and Sediment Research Institute (HSRI), Cairo. A series of clear water scour tests were performed to investigate the causes of the local scour downstream the circular pier. It was found that the large scour hole downstream the circular pier was produced by the conflicting velocity fields at the intersection of the wake vortex streams from adjacent piers, and increased by the confluence flow. Based upon the results of this investigation, an empirical formula was developed to predict the wake and confluence maximum local scour depth downstream of a circular pier for a clear water condition.

Subject Headings: Scour | Piers | Hydraulic models | Bridges | Rivers and streams | Vortices | Sediment | Nile River | Egypt | Africa | Middle East

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