EFFECTS OF GRADATION AND COHESION ON BRIDGE SCOUR. VOLUME 5: EFFECT OF COHESION ON BRIDGE ABUTMENT SCOUR
The effects of cohesion on abutment scour was investigated experimentally using four-foot-wide and eight-foot-wide test flumes at the Engineering Research Center, Colorado State University. In the first part of the experiments, clayey-sand mixtures with varying amounts of clay were subjected to different approach flow conditions. The abutment scour resulting from these experiments was normalized with pure sand scour experiments. For Montmorillonitic clay mixtures, experimental results show that for sandy clays, increasing the clay content up to 30% may reduce scour by up to 40%. For Kaolinitic clay mixtures the results are more dramatic, for scour reduction is up to 80% of that observed in pure sands. Beyond a certain percentage of clay content (30-40% for the present mixture) parameters such as compaction, initial water content, degree of saturation, shear strength, etc., dominate the abutment scour. In the second part of the experiments, these effects were investigated for flow conditions with Froude numbers ranging from 0.2 to 0.8. Regression equations relating flow and selected cohesive soil parameters to abutment scour were developed for the particular abutment and flow conditions that were used in the experiments. These experiments showed that abutment scour in cohesion material can be expressed in terms of cohesive soil parameters which can be determined in the field. The equations derived from this study do not attempt to relate effects due to abutment geometry, flow depth, gradation of sand in clay-sand mixtures, etc., and therefore are not intended for general application. These relationships are derived to explain the variability of abutment scour with cohesion properties.
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- The other volumes in this six volume series are: Volume 1, FHWA-RD-99-183; Volume 2, FHWA-RD-99-184; Volume 3, FHWA-RD-99-185; Volume 4, FHWA-RD-99-186; 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
- Relad, N Y
- Publication Date: 1999-12
- Pagination: 250 p.
- TRT Terms: Bridge abutments; Cohesion; Cohesive soils; Froude number; Kaolinite; Laboratory studies; Montmorillonite; Regression analysis; Sandy clays; Scour
- Uncontrolled Terms: Flow conditions
- Subject Areas: Bridges and other structures; Data and Information Technology; Design; Highways; Hydraulics and Hydrology; I24: Design of Bridges and Retaining Walls;
- Accession Number: 00795285
- Record Type: Publication
- Source Agency: Federal Highway Administration
- Report/Paper Numbers: FHWA-RD-99-187,, NCP 3D3C1-582,, Laboratory Final Report
- Contract Numbers: DTFH61-91-C-00004
- Files: NTL, TRIS, USDOT
- Created Date: Jul 13 2000 12:00AM