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.

  • Record URL:
  • Supplemental Notes:
    • 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.
  • 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
    • Relad, N Y
  • Publication Date: 1999-12


  • English

Media Info

  • Pagination: 250 p.

Subject/Index Terms

Filing Info

  • 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