EFFECTS OF GRADATION AND COHESION ON BRIDGE SCOUR. VOLUME 2: EXPERIMENTAL STUDY OF SEDIMENT GRADATION AND FLOW HYDROGRAPH EFFECTS ON CLEAR WATER SCOUR AROUND CIRCULAR PIERS
In the first part of this experimental study effects of sediment size gradation on clear-water pier scour was studied using four sand mixtures with median sediment sizes (D sub 50) of 0.76 mm, 1.8 mm, and 1.87 mm and with different gradation coefficients. Experiments were conducted in the two-foot-wide by sixty-foot-long experimental flume at the Engineering Research Center, Colorado State University, using 2 in., 2.50 in., and 2.75 in. diameter (51, 64, and 70 mm) circular piers. A regression equation was derived to fit the experimental data specific to the particular pier and flow conditions used in the experiments. This equation shows that gradation effects are not constant through the entire range of flow conditions but vary with flow intensity. In the second part of the experimental study, effects of flow hydrograph is investigated by subjecting circular piers used in the first part to bursts of discharges of varying duration and rate of increase. It is found that up to 60% of the ultimate scour could be attained in short duration events for rapidly increasing flow conditions. Results are expressed in the form of a regression expression using one of the test cases as the normalizing event.
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- The other volumes in this six volume series are: Volume 1, FHWA-RD-99-183; 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
- Noshi, H M
- Publication Date: 1999-12
- Pagination: 89 p.
- TRT Terms: Bridge piers; Hydrographs; Laboratory studies; Regression analysis; Sand; Scour
- Uncontrolled Terms: Flow conditions; 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: 00795282
- Record Type: Publication
- Source Agency: Federal Highway Administration
- Report/Paper Numbers: FHWA-RD-99-184,, NCP 3D3C1-582,, Laboratory Final Report
- Contract Numbers: DTFH61-91-C-00004
- Files: NTL, TRIS, USDOT
- Created Date: Jul 13 2000 12:00AM