Suction Removal of Sediment from between Armor Blocks. II: Waves
Publication: Journal of Hydraulic Engineering
Volume 134, Issue 10
Abstract
When a stone/armor layer on a sand bed is exposed to flow, the sand underneath will be agitated by the flow turbulence. When the flow velocity reaches a critical value, the sand will be sucked (winnowed out) from between the armor blocks. In a previous investigation, we studied suction removal of sediment in steady currents. The present study is an extension of our previous investigation to waves. The critical condition for the onset of suction is determined. It is found that the onset of suction is governed by three parameters: (1) the sediment mobility number (based on the sediment size); (2) the ratio of sediment size to stone size, ; and (3) the Keulegan-Carpenter (KC) number, based on the armor block/stone size. The variation of the critical mobility number for suction as a function of and KC is determined for the ranges of the parameters and . The case of steady current is included as a reference case. The effect of waves superimposed on current, the effect of a multilayer stone cover, and the effect of regularly placed armor blocks are investigated. Suction of the base-bottom sediment will cause sinking of the armor layer and, therefore, general lowering of the bed. The time scale of the latter process and the downward displacement of armor blocks/stones are also investigated.
Get full access to this article
View all available purchase options and get full access to this article.
Acknowledgments
This study was partially funded by the European Commission, Research-Directorate-General, Contract No. UNSPECIFIEDEVK-2000-22038, “Environmental Design of Low Crested Coastal Defence Structures” (DELOS), and by (1) the Danish Res. Coun. for Technol. and Production Sciences (FTP) under the program Exploitation and Protection of Coastal Zones (EPCOAST), and (2) the Danish Council for Strategic Research (DSF)/Energy and Environment under the program Seabed Wind Farm Interaction. Ms. Figen Hatipoglu’s stay at the Tech. Univ. of Denmark has been partially supported by two research scholarships from Turkey, (1) TUBITAK; and (2) Istanbul Tech. Univ. Res. Fund; and by EPCOAST. Mr. Andrass Z. Davidsen, MSc, did the combined wave and current experiments under the guidance of the writers.
References
Bakker, K. J., Verheij, H. J., and de Groot, M. B. (1994). “Design relationship for filters in bed protection.” J. Hydraul. Eng., 120(9), 1082–1088.
Brauns, J., Heibaum, M., and Schuler, U., eds. (1993). Filters in geotechnical engineering, Balkema, Rotterdam, The Netherlands.
Bryndum, M. B., Jacobsen, V., and Tsahalis, D. T. (1992). “Hydrodynamic forces on pipelines: Model tests.” J. Offshore Mech. Arct. Eng., 114, 231–241.
Cheng, N. S., and Chiew, Y. M. (1999). “Analysis of initiation of sediment suspension from bed load.” J. Hydraul. Eng., 125(8), 855–861.
Chiew, Y. M. (1995). “Mechanics of riprap failure at bridge piers.” J. Hydraul. Eng., 121(9), 635–643.
Chiew, Y. M. (2002). “Failure mechanisms of riprap layer around bridge piers.” Proc., First Int. Conf. on Scour of Foundations, H.-C. Chen and J.-L. Briaud, eds., Stallion Press, Singapore, Vol. I, 70–92.
Chiew, Y. M., and Lim, F.-H. (2000). “Failure behaviour of riprap layer at bridge piers under live-bed conditions.” J. Hydraul. Eng., 126(1), 43–55.
de Graauw, A. F., van der Meulen, T., and de Bye, M. R. D. (1984). “Granular filters: Design criteria.” J. Waterway, Port, Coastal, Ocean Eng., 110(1), 80–96.
Dixen, M., Hatipoglu, F., Sumer, B. M., and Fredsøe, J. (2008). “Wave boundary layer over a stone-covered bed.” Coastal Eng., 55, 1–20.
Fredsøe, J., Andersen, K. H., and Sumer, B. M. (1999). “Wave plus current over ripple-covered bed.” Coastal Eng., 38, 177–221.
Jakobsen, N. G. (2007). “Shape and dimensions of ripples.” MS thesis Coastal, Maritime, and Structural Engineering Section, Technical Univ. of Denmark, MEK.
Jensen, B. L., Sumer, B. M., and Fredsøe, J. (1989). “Turbulent oscillatory boundary layers at high Reynolds numbers.” J. Fluid Mech., 206, 265–297.
Lauchlan, C. S., and Melville, B. W. (2001). “Riprap protection at bridge piers.” J. Hydraul. Eng., 127(5), 412–418.
Melville, B., van Ballegooy, R., and van Ballegooy, S. (2006). “Flow-induced failure of cable-tied blocks.” J. Hydraul. Eng., 132(3), 324–327.
Nielsen, P. (1992). Coastal bottom boundary layers and sediment transport, World Scientific, London.
Raudkivi, A. J. (1998). Loose boundary hydraulics, Balkema, Rotterdam, The Netherlands.
Raudkivi, A. J., and Ettema, R. (1982). “Stability of armor layers in rivers.” J. Hydr. Div., 108(9), 1047–1057.
Raudkivi, A. J., and Ettema, R. (1984). “Scour at cylindrical bridge piers in armored beds.” J. Hydraul. Eng., 111(4), 713–731.
Sumer, B. M. (1986). “Recent developments on the mechanics of sediment transport.” Proc., Euromech 192, Balkema, Rotterdam, The Netherlands, 3–13.
Sumer, B. M., Cokgor, S., and Fredsøe, J. (2001). “Suction removal of sediment from between armor blocks.” J. Hydraul. Eng., 127(4), 293–306.
Sumer, B. M., and Fredsøe, J. (1997). Hydrodynamics around cylindrical structures, World Scientific, London.
Sumer, B. M., and Fredsøe, J. (2002). Mechanics of scour in the marine environment World Scientific, London.
Sumer, B. M., Jensen, B. L., and Fredsøe, J. (1991). “Effect of a plane boundary on oscillatory flow around a circular cylinder.” J. Fluid Mech., 225, 271–300.
Terzaghi, K. (1948). Theoretical soil mechanics, Wiley, New York.
Truelsen, C., Sumer, B. M., and Fredsøe, J. (2005) “Scour around spherical bodies and self-burial.” J. Waterway, Port, Coastal, Ocean Eng., 131(1), 1–13.
Vanoni, V. A., and Brooks, N. H. (1957). “Laboratory studies of the roughness and suspended load of alluvial streams.” Rep. No. E-68, California Institute of Technology, Pasadena, Calif.
Worman, A. (1989). “Riprap protection without filter layers.” J. Hydraul. Eng., 115, (12), 1615–1630.
Worman, A. (1992). “Incipient motion during static armoring.” J. Hydraul. Eng., 118(3), 496–501.
Information & Authors
Information
Published In
Journal of Hydraulic Engineering
Volume 134 • Issue 10 • October 2008
Pages: 1405 - 1420
Copyright
© 2008 ASCE.
History
Received: Jul 31, 2006
Accepted: Feb 8, 2008
Published online: Oct 1, 2008
Published in print: Oct 2008
Authors
Metrics & Citations
Metrics
Citations
Download citation
If you have the appropriate software installed, you can download article citation data to the citation manager of your choice. Simply select your manager software from the list below and click Download.