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Title: Riprap stability on earth embankments : tested in large-and small-scale wave tanks
Authors: Thomsen, Arvid L.
Wohlt, Paul E.
Harrison, Alfred S.
Keywords: Shore protection
Hydraulic models
Publisher: Coastal Engineering Research Center (U.S.)
Series/Report no.: Technical Memorandum (Coastal Engineering Research Center (U.S.));no. 37
Abstract: Tests of models in wave tanks were made to determine the effectiveness of several riprap designs in protecting embankment slopes from wave action. Models ranging from about 1:20 scale to almost full scale were tested with waves up to about 6 feet high. A range of wave periods were tested, embankment slopes varied from 1 on 2 to 1 on 5, and armor layers were composed of quarried stone, glacial boulders and tribars. Relationships that aefine the effect of wave height, wave period, embankment slopes and Reynolds number on size of stable armor units were experimentally determined and are given in graphs and tables. Significant conclusions are: 1. The median weight of graded armor material is a satisfactory "effective size" with respect to stability. 2. Small-scale models are less stable than larger scale models. The difference in stability is a function of Reynolds number apparently caused by viscous effects. Consequently, there is a "scale effect" that produces conservative results when the stability determined in a small model is scaled up to prototype size on the basis of Froude number alone when equivalent viscous fluids exist in both prototype and model. 3. Stability is a function of wave period. For longer periods that produced wave steepness less than 0.03, stability is little affected by period. For wave steepness greater than 0.03, stability increases withshorter period. Section VI of this report presents a detailed summary and conclusions.
Description: Technical Memorandum
Rights: Approved for public release; distribution is unlimited.
Appears in Collections:Technical Memorandum

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