Pier Scour in Clear-Water Conditions with Non-Uniform Bed Materials

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 flow-structure, 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.

[1]  O. Barndorff-Nielsen.  Exponentially decreasing distributions for the logarithm of particle size , 1977, Proceedings of the Royal Society of London. A. Mathematical and Physical Sciences.

[2]  Emmett M. Laursen,et al.  An Analysis of Relief Bridge Scour , 1963 .

[3]  A Molinas,et al.  BRIDGE SCOUR IN NONUNIFORM SEDIMENT MIXTURES AND IN COHESIVE MATERIALS: SYNTHESIS REPORT , 2004 .

[4]  B. Melville.  PIER AND ABUTMENT SCOUR: INTEGRATED APPROACH , 1997 .

[5]  Bruce W. Melville,et al.  Maximum local scour depth at bridge piers and abutments , 1998 .

[6]  T. N. Stevenson,et al.  Fluid Mechanics , 2021, Nature.

[7]  Willi H. Hager,et al.  Further Results to Time-Dependent Local Scour at Bridge Elements , 2005 .

[8]  Ali Tafarojnoruz,et al.  Vortex scouring process around bridge pier with a caisson , 2012 .

[9]  B. Sumer,et al.  Numerical and experimental investigation of flow and scour around a circular pile , 2005, Journal of Fluid Mechanics.

[10]  Emmett M. Laursen,et al.  Closure of "An Analysis of Relief Bridge Scour" , 1964 .

[11]  Robert Ettema,et al.  Coherent Structures in the Flow Field around a Circular Cylinder with Scour Hole , 2008 .

[12]  W. Hager,et al.  Temporal Evolution of Clear-Water Pier and Abutment Scour , 2002 .

[13]  Willi H. Hager,et al.  Down-flow and horseshoe vortex characteristics of sediment embedded bridge piers , 2006 .

[14]  T. Milligan,et al.  Grain‐size characteristics of fine‐grained unflocculated sediments II:‘multi‐round’ distributions , 1996 .

[15]  H W Shen,et al.  MECHANICS OF LOCAL SCOUR , 1966 .

[16]  Stephen R. Holnbeck,et al.  Investigation of Pier Scour in Coarse-Bed Streams in Montana, 2001 through 2007 , 2011 .

[17]  Robert Ettema,et al.  SCOUR AT BRIDGE PIERS , 1980 .

[18]  B. Sumer.  Mathematical modelling of scour: A review , 2007 .

[19]  George Constantinescu,et al.  Evaluation of Bridge Scour Research: Pier Scour Processes and Predictions , 2011 .

[20]  Bruce W. Melville,et al.  Scour at Wide Piers and Long Skewed Piers , 2011 .

[21]  D. S. Mueller,et al.  CHANNEL SCOUR AT BRIDGES IN THE UNITED STATES , 1996 .

[22]  Emmett M. Laursen,et al.  Scour at Bridge Crossings , 1960 .

[23]  Wei Zhao,et al.  Large-Eddy Simulation of Three-Dimensional Turbulent Flow Around a Circular Pier , 2006 .

[24]  William Miller,et al.  Live-Bed Local Pier Scour Experiments , 2006 .

[25]  Stephen R. Holnbeck,et al.  Evaluation of pier-scour equations for coarse-bed streams , 2004 .

[26]  L. W. Zevenbergen,et al.  Evaluating Scour at Bridges, Fifth Edition , 2012 .

[27]  Willi H. Hager,et al.  Generalized Approach for Clear-Water Scour at Bridge Foundation Elements , 2007 .

[28]  D. Mohrig,et al.  Statistical Characterization of Grain-Size Distributions in Sandy Fluvial Systems , 2010 .

[29]  Bijan Dargahi,et al.  Controlling Mechanism of Local Scouring , 1990 .

[30]  Subhasish Dey,et al.  Characteristics of Horseshoe Vortex in Developing Scour Holes at Piers , 2007 .

[31]  B. Purkait.  Patterns of Grain-Size Distribution in Some Point Bars of the Usri River, India , 2002 .

[32]  Ali Tafarojnoruz,et al.  Flow-altering countermeasures against scour at bridge piers: a review , 2010 .

[33]  B. Dargahi.  The turbulent flow field around a circular cylinder , 1989 .

[34]  C R Neill,et al.  Guide to bridge hydraulics , 1973 .

[35]  N. Fieller,et al.  Statistics of Particle Size Data , 1992 .

[36]  B. Melville,et al.  TIME SCALE FOR LOCAL SCOUR AT BRIDGE PIERS , 2000 .

[37]  Willi H. Hager,et al.  Shields' Entrainment Criterion in Bridge Hydraulics , 2002 .

[38]  T. Papanastasiou,et al.  Viscous Fluid Flow , 1999 .

[39]  George Constantinescu,et al.  Detached Eddy Simulation Investigation of Turbulence at a Circular Pier with Scour Hole , 2009 .

[40]  N. Fieller,et al.  The statistical analysis of ‘mixed’ grain size distributions from aeolian sands in the Libyan Pre-Desert using log skew Laplace models , 1987, Geological Society, London, Special Publications.