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https://nap.nationalacademies.org/catalog/27432/critical-issues-in-transportation-for-2024-and-beyond

SCOUR AT BRIDGE PIERS

The local clear-water scour at cylindrical piers in beds composed of uniform and layers of uniform sediments was investigated in an extensive experimental study coupled with a comprehensive review of published literature. The aim of the study was to improve the understanding of local scour process at bridge piers. Relationships are developed which enable the designer to estimate the maximum equilibrium depth of local scour at piers in cohesionless sediments. Once initiated, the development of a scour hole at a pier is determined by the strength of the downflow at the leading edge of the pier, and by the size of the bed particles. The development of local scour at piers in uniform, and non-uniform, sediments is described. Variations in the local scour process and the equilibrium depth of local scour, for a constant stage of particle motion on the approach bed, are related to the comparative pier and particle diameters, approach flow depths, and the particle size distribution of a sediment. A maximum equilibrium depth of local scour at a pier in a bed of either a uniform or a non-uniform sediment is defined. A major contribution of this study is the description of the compound scour that can occur at a pier placed in a bed of uniform sediment armoured by a layer of coarser sediment. The formation of a scour hole at the pier may be accompanied by a localised scour of the finer sediment which becomes exposed to the flow by the erosion of the armour layer. In order to describe the localised bed scour due to the local erosion of the armour layer, concepts are developed which delineate the stability of thin armour layers on beds of uniform sediment. The stability of a thin armour layer as a function of its thickness is described in terms of the stability of a single armour particle seated on the surface of the finer bed sediment. The experimental results showed that larger depths of clear-water scour can occur at piers placed in beds composed of a uniform sediment armoured by a layer of coarser sediment than if the pier were in a bed of uniform sediment only. (Author/TRRL)

  • Corporate Authors:

    University of Auckland

    Department of Civil Engineering, Private Bag
    Auckland 1,   New Zealand 
  • Authors:
    • Ettema, Robert
  • Publication Date: 1980-2

Media Info

  • Features: Figures; Photos; References; Tables;
  • Pagination: 527 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00348170
  • Record Type: Publication
  • Source Agency: Transport Research Laboratory
  • Report/Paper Numbers: No. 216 Monograph
  • Files: ITRD, TRIS
  • Created Date: Mar 30 1982 12:00AM