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Title: Pier Scour in Clear-Water Conditions With Non-Uniform Bed Materials

Description: Pier scour design in the United States is currently accomplished through application of the Colorado State University (CSU) equation. Since the Federal Highway Administration recommended the CSU equation in 2001, substantial advances have been made in the understanding of pier scour processes. This report explains a new formulation for describing scour processes and proposes a new equation for pier scour design. A critical review of selected studies is summarized. A simplified scour mechanism is proposed in terms of a pressure gradient resulting from the flowstructure, flow-sediment, and sediment-structure interactions. An equilibrium scour depth equation is proposed based on this understanding of the scour mechanism and is validated and refined by a combination of laboratory and field data. The proposed equation is primarily applicable to clear-water scour conditions with non-uniform coarse bed materials.

FHWA Publication Number: HRT-12-022

Publication Year: 2012

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Updated: 09/06/2013

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