A Comparison of Time-Induced Stability Differences Between a Framework-Supported and a Matrix-Supported Gravel:Sand Mixture

Heather Haynes, Anne Ockelford

Research output: Chapter in Book/Conference proceeding with ISSN or ISBNConference contribution with ISSN or ISBN

Abstract

It is well established that the critical threshold of entrainment decreases rapidly with sand content over the transition from a framework-supported bed to a matrix-supported bed in gravel-sand bed rivers. Also, it is recognized that the proportion of fines in the bed surface may be related to flood history. Seeking to combine this knowledge, recent ‘stress history' experiments have shown that graded beds increase in stability when subjected to prolonged periods of sub-threshold flow durations. Flume experiments are presented that compare fine and coarse grain size distributions response to exposure to two flow phases: (i) an antecedent period of 0, 10, 20, 40 and 60 minutes duration using an applied sub-threshold bed shear stress of magnitude 50% that of the critical entrainment of the D50; (ii) a stability test in which flow was increased to establish the new critical entrainment threshold of the bed. As expected, results indicate that the critical shear stress for the fine distribution was up to 39.8% lower than that of the coarse. However, the fine bed was up to 3.5 times more responsive to stability induced during the flow history period. Discussion focuses on explaining these stress history effects with reference to recent literature. Keywords: Graded, Sediment, Entrainment, Bedload, Stability, Stress History
Original languageEnglish
Title of host publication33rd IAHR World Congress Water Engineering for a Sustainable Future
Place of Publicationproceedings
Pages0-0
Number of pages1
Publication statusPublished - 10 Aug 2009
Event33rd IAHR World Congress Water Engineering for a Sustainable Future - Vancouver, Canada 9th-14th August 2009
Duration: 10 Aug 2009 → …

Conference

Conference33rd IAHR World Congress Water Engineering for a Sustainable Future
Period10/08/09 → …

Fingerprint

gravel
entrainment
matrix
sand
history
shear stress
flume experiment
bottom stress
two phase flow
river bed
bedload
grain size
comparison
sediment
experiment

Keywords

  • Graded
  • Sediment
  • Entrainment
  • Bedload
  • Stability
  • Stress History

Cite this

Haynes, H., & Ockelford, A. (2009). A Comparison of Time-Induced Stability Differences Between a Framework-Supported and a Matrix-Supported Gravel:Sand Mixture. In 33rd IAHR World Congress Water Engineering for a Sustainable Future (pp. 0-0). proceedings.
Haynes, Heather ; Ockelford, Anne. / A Comparison of Time-Induced Stability Differences Between a Framework-Supported and a Matrix-Supported Gravel:Sand Mixture. 33rd IAHR World Congress Water Engineering for a Sustainable Future. proceedings, 2009. pp. 0-0
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Haynes, H & Ockelford, A 2009, A Comparison of Time-Induced Stability Differences Between a Framework-Supported and a Matrix-Supported Gravel:Sand Mixture. in 33rd IAHR World Congress Water Engineering for a Sustainable Future. proceedings, pp. 0-0, 33rd IAHR World Congress Water Engineering for a Sustainable Future, 10/08/09.

A Comparison of Time-Induced Stability Differences Between a Framework-Supported and a Matrix-Supported Gravel:Sand Mixture. / Haynes, Heather; Ockelford, Anne.

33rd IAHR World Congress Water Engineering for a Sustainable Future. proceedings, 2009. p. 0-0.

Research output: Chapter in Book/Conference proceeding with ISSN or ISBNConference contribution with ISSN or ISBN

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Haynes H, Ockelford A. A Comparison of Time-Induced Stability Differences Between a Framework-Supported and a Matrix-Supported Gravel:Sand Mixture. In 33rd IAHR World Congress Water Engineering for a Sustainable Future. proceedings. 2009. p. 0-0