Scour at Vertical Piles in Sand-Clay Mixtures under Waves
Publication: Journal of Waterway, Port, Coastal, and Ocean Engineering
Volume 137, Issue 6
Abstract
Marine sediments often contain sand-clay mixtures in widely varying proportions. This study presents the results of equilibrium scour and time variation of scour depths at circular piles embedded vertically in clay alone and sand-clay mixed beds under waves. Experiments were conducted in a wave flume with different proportions of sand-clay mixtures as bed sediments. Test results for the cases of steady current and sand alone under waves are used as references. The equilibrium scour depth reduces with an increase in clay proportion (by weight) in a sand-clay mixture. Interestingly, the scour depth reductions for and 1 are almost equal, suggesting that when the clay proportion in a sand-clay mixture becomes 0.3, the sand-clay mixture behaves as if it were a clay-alone mixture, in relation to scour depths. The dependency of equilibrium scour depth on the Keulegan-Carpenter number for different -values can be expressed by an exponential law, using different coefficients and exponents. For time variation of scour, the nondimensional timescale increases with an increase in Keulegan-Carpenter number and clay proportion. However, unlike the near-equal scour depths, timescales are quite different for and 1.
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Acknowledgments
This study was funded by the Danish Council for Strategic Research through the research program Seabed and Wind Farm Interaction. The first author is thankful to the Department of Mechanical Engineering (MEK), Technical University of Denmark for providing visiting faculty position to visit the DTU during the course of this study.
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© 2011 American Society of Civil Engineers.
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Received: Sep 1, 2010
Accepted: Mar 30, 2011
Published online: Mar 31, 2011
Published in print: Nov 1, 2011
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