Development of New Design Guidelines for Protection Against Erosion at Bridge Abutments and Embankments - Phase I

Over the last two decades, the US Midwest has experienced increasingly catastrophic flood events. Severe erosion problems occurred even though the erosion protection design measures for the bridge piers, bridge abutments and their embankments followed the existing guidelines (e.g., as outlined in Hydraulic Engineering Circular HEC-23 2001 and following updates - 2009). We suspect this is because the methodology proposed to estimate design variables in scour protection measure formulas (e.g., size of rip rap stone) at such sites is oversimplified and the calibration of these formulas is based on a limited series of laboratory experiments conducted for a limited range of the relevant geometrical and flow parameters that control erosion at such bridge sites.<br/>Main tasks: Check performance of existing guidelines for rip-rap sizing at spill-through (e.g., Figure 1a) and wing-wall abutments adopted by HEC-23 and the Set Back Ratio method for estimating abutment velocity for design equations as described in NCRHRP 24-23 and 24-18. The simulations will cover the relevant range of the main geometrical and flow parameters (e.g., Reynolds numbers covering lab and field scale conditions, abutment length, distance between the abutment toe and the main channel bank, flow depth over the floodplain, slope of the abutment face) needed for estimating the performance of the design formulas recommended by HEC-23. Propose a correction coefficient to account for turbulence effects to be incorporated in the design formula, similar to the approach used in HEC-23 for pier design. Check if design formulae for rip-rap sizing at spill-through and wing-wall abutments are conservative enough, once these formulas are used for conditions outside their calibration range. If such cases are identified, make recommendations in terms of extension of rip-rap protected region and/or increase of the mean diameter of rip-rap stone.

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Final Data: http://doi.org/10.13014/K2C24TN4