EFFECTS OF GRADATION AND COHESION ON BRIDGE SCOUR. VOLUME 1: EFFECT OF SEDIMENT GRADATION AND COARSE MATERIAL FRACTION ON CLEAR WATER SCOUR AROUND BRIDGE PIERS
The effects of gradation and coarse bed material fraction on pier scour were investigated experimentally in the eight-foot-wide by two-hundred-foot-long tilting flume at the Engineering Research Center, Colorado State University. Six different sand mixtures with the same median diameter (D sub 50) of 0.75 mm, but with gradation coefficients ranging from 1.38 to 3.4 were used in the experiments. To study the coarse material fraction effects, mixtures with the same median diameter and gradation coefficient, but with varying D sub 90 and D sub 95 sizes were subjected to the same scour conditions. The experiments were limited to clear water scour around a circular pier with a diameter of 7.0 in. (178 mm). Flow intensities starting with incipient conditions were increased in the experiments until live-bed conditions were encountered. Extensive bed material samples from the scour hole and the approach were obtained and analyzed. A regression equation was derived to fit the experimental data specific to the particular pier and flow conditions that were used in the experiments and is not intended for general application. Experiments reveal that the coarse material fraction, rather than the gradation coefficient, is the controlling sediment property factor in pier scour.
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- The other volumes in this six volume series are: Volume 2, FHWA-RD-99-184; Volume 3, FHWA-RD-99-185; Volume 4, FHWA-RD-99-186; Volume 5, FHWA-RD-99-187; and Volume 6, FHWA-RD-99-188.
Colorado State University, Fort CollinsEngineering Research Center
Fort Collins, CO United States 80523
Federal Highway AdministrationTurner-Fairbank Highway Research Center, 6300 Georgetown Pike
McLean, VA United States 22101
- Molinas, A
- Abdou, M I
- Publication Date: 1999-12
- Pagination: 199 p.
- TRT Terms: Bridge piers; Laboratory studies; Regression analysis; Sand; Scour
- Uncontrolled Terms: Coarse sediment; Median diameter; Sediment gradation
- Subject Areas: Bridges and other structures; Data and Information Technology; Design; Highways; Hydraulics and Hydrology; I24: Design of Bridges and Retaining Walls;
- Accession Number: 00795281
- Record Type: Publication
- Source Agency: Federal Highway Administration
- Report/Paper Numbers: FHWA-RD-99-183,, NCP 3D3C1-582,, Laboratory Final Report
- Contract Numbers: DTFH61-91-C-00004
- Files: NTL, TRIS, USDOT
- Created Date: Jul 13 2000 12:00AM