This report is a summary of a six-volume series describing detailed laboratory experiments conducted at Colorado State University for the Federal Highway Administration as part of a study entitled "Effects of Sediment Gradation and Cohesion on Bridge Scour." This report will be of interest to hydraulic engineers and bridge engineers involved in bridge scour evaluations. It will be of special interest to other researchers conducting studies of the very complex problem of estimating scour in cohesive bed materials and to those involved in preparing guidelines for bridge scour evaluations. The six-volume series has been distributed to National Technical Information Service (NTIS) and to the National Transportation Library, but it will not be printed by FHWA. This summary report, which describes the key results from the six-volume series, will be published by FHWA.
T. Paul Teng, P.E.
Director, Office of Infrastructure
Research and Development
This document is disseminated under the sponsorship of the U.S. Department of Transportation in the interest of information exchange. The U.S. Government assumes no liability for the contents or use thereof. This report does not constitute a standard, specification, or regulation.
The U.S. Government does not endorse products or manufacturers. Trade and manufacturers' names appear in this report only because they are considered essential to the object of the document.
1. Report No.
FHWA-RD-03-083 |
2. Government Accession No. |
3. Recipient's Catalog No. |
4. Title and Subtitle
BRIDGE SCOUR IN NONUNIFORM SEDIMENT MIXTURES AND IN COHESIVE MATERIALS: SYNTHESIS REPORT |
5. Report Date June 2003 |
6. Performing Organization Code |
7. Author(s) Albert Molinas |
8. Performing Organization Report No. |
9. Performance Organization Name and Address
Colorado State University
Engineering Research Center
Fort Collins, CO |
10. Work Unit No. (TRAIS)
NCP# 3D3C1-582
n |
11. Contract or Grant No.
DTFH61-91-C-00004 |
13. Type of Report and Period Covered
Laboratory Final Report
Jan 1991 - Jan 1996 |
12. Sponsoring Agency and Address
Office of Infrastructure Research and Development
Federal Highway Administration
6300 Georgetown Pike
McLean, VA 22101 |
14. Sponsoring Agency Code |
15. Supplementary Notes
Contracting Officer's Technical Representative: J. Sterling Jones HRDI-07 |
16. Abstract
This report presents the summary and synthesis of the various components of the experimental study entitled "Effects of Gradation and Cohesion on Bridge Scour" conducted at Colorado State University between the dates 1991 through 1996.
As a result of this effort, in excess of 250 new pier scour data was collected and a new equation was developed expressing pier scour in terms of the dimensionless excess velocity factor, flow depth, pier diameter and a correction factor for the coarse fractions present in mixtures was derived. The new method was tested with available data from previous research. This equation shows that gradation effects are not constant through the entire range of flow conditions but vary with flow intensity. Additionally, a new method to adjust FHWA's Colorado State University pier scour equation for initiation of motion and sediment size was developed.
Abutment scour experiments resulted in over 384 new points and 2 new abutment scour equations. The first equation was derived from a 0.1 mm uniform sand mixture and defines an envelop relationship. The second equation applies to mixtures with coarse fractions. A coarse size fraction compensation factor Wg is presented to account for the presence of varying amounts of coarse material in sediment mixtures under different dimensionless flow intensities. These new equations represented the experimental data accurately but have not been tested with field data.
Effects of cohesion on pier and abutment scour was studied systematically, and in excess of 200 new data points were collected covering a range of flow and cohesive parameter values. Relationships were developed to explain the variability of bridge scour in cohesive materials for various cohesive material properties.
This report summarizes results from the following six-volume series, which was not printed but was distributed to the National Technical Information Service and the National Transportation Library:
- FHWA-RD-99-183 Volume 1. Effect of Sediment Gradation and Coarse Material Fraction on Clear-Water Scour Around Bridge Piers.
- FHWA-RD-99-184 Volume 2. Experimental Study of Sediment Gradation and Flow Hydrograph Effects on Clear Water Scour Around Circular Piers.
-
FHWA-RD-99-185 Volume 3. Abutment Scour for Nonuniform Mixtures.
-
FHWA-RD-99-186 Volume 4. Experimental Study of Scour Around Circular Piers in Cohesive Soils.
-
FHWA-RD-99-187 Volume 5. Effect of Cohesion on Bridge Abutment Scour.
-
FHWA-RD-99-188 Volume 6. Abutment Scour in Uniform and Stratified Sand Mixtures.
|
17. Key Words:
Bridge scour, Pier scour, Abutment scour, Local scour, Sand Mixtures, Gravel scour, Gradation, Cohesion, Clay, Montmorillonite, Kaolinite, Clear-water, Experimental study |
18. Distribution Statement
No restrictions. This document is available to the public through the National Technical Information Service, Springfield, VA 22161 |
19. Security Classif. (of this report)
Unclassified |
20. Security Classif. (of this page)
Unclassified |
21. No. of Pages
121 |
22. Price |