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.

  • Record URL:
  • Supplemental Notes:
    • 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.
  • Corporate Authors:

    Colorado State University, Fort Collins

    Engineering Research Center
    Fort Collins, CO  United States  80523

    Federal Highway Administration

    Turner-Fairbank Highway Research Center, 6300 Georgetown Pike
    McLean, VA  United States  22101
  • Authors:
    • Molinas, A
    • Noshi, H M
  • Publication Date: 1999-12

Language

  • English

Media Info

  • Pagination: 89 p.

Subject/Index Terms

Filing Info

  • 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