Evaluation of Bridge-Scour Research: Abutment and Contraction Scour Processes and Prediction (2011) / Chapter Skim
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83 APPENDIX A Table A-1. A selection of abutment scour formulas (revised and extended from Melville and Coleman 2000)
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84 Reference Formula Notes Lim ( ) L s L s d L YL Y d Χ +++Χ + = + 3/2 1 3/4 1 1tan1 /2.11 2 1 φ Applies to live-bed scour −=Χ 2 1*
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85 APPENDIX B Table B-1. A selection of contraction scour formulas (B1 = approach flow channel width; B2 = contracted channel width; Y1 = approach flow channel depth; Y2 = contracted channel depth after scour)
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86 Reference Formula Notes Dey and Raikar (2005) 26.1 2 1 19.0 1 5055.0 1 1 368.0 = − B B Y d Y d e s F Clear-Water Scour (0.9 |
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87 APPENDIX C RESEARCH PROBLEM STATEMENTS C.1 INTRODUCTION This appendix provides brief problem statements for the research needs and associated designrelated research tasks listed in Tables 8-1, 8-2, and 8-3 of Chapter 8. The problem statements comprise short outlines indicating the purpose of the research needed.
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88 b. Geotechnical stability of embankments exposed to abutment scour Most cases of abutment failure attributable to scour show a geotechnical failure of the earthfill embankment associated with the abutment.
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89 Research Need L2: Overtopping of embankments and abutment scour under pressure scour conditions Within the context of climate change and more commonly occurring pressure scour and overtopping events, experimental research is needed on abutment scour for these flow conditions with realistic compound channel geometry and erodible embankments. Even with riprap protection, the abutment is subject to catastrophic failure under this combination of flow types, especially for moderate to small setback distances from the main channel.
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90 Research Need N2: Education of engineers concerning limitations of 1D abutment scour estimation formulas and the potential and applicability of 2D and 3D numerical modeling in combination with physical modeling Implementation of advanced numerical models requires commensurate education of modelers. Because turbulence is inherently three-dimensional, engineers require basic instruction in the structure of turbulence and how it is modeled in 3D numerical models followed by an introduction to the simplifications concomitant with 2D and 1D numerical models.
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91 relationship would provide a useful check on scour depth estimated using hydraulics-based methods for scour-depth estimation.
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92 The inclusion of a countermeasure such as an apron or skirt alters abutment form. As such countermeasures often are recommended for use in abutment design, the scour-estimation methods mentioned for research topics E1 and F1 should be adjusted for abutment forms that include them.
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93 I1-b. Instrumentation for monitoring embankment soil condition.
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