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Title: Erosion control of scour during construction. Report 4, Stability of underlayer material placed in advance of construction to prevent scour : hydraulic model investigation
Authors: Coastal Engineering Research Center (U.S.)
Hales, Lyndell Z.
Houston, James R. (James Robert), 1947-
Keywords: Coastal structures
Hydraulic structures
Erosion control
Hydraulic models
Water waves
Sediment transport
Construction projects
Publisher: Hydraulics Laboratory (U.S.)
Engineer Research and Development Center (U.S.)
Series/Report no.: Technical report (U.S. Army Engineer Waterways Experiment Station) ; HL-80-3 rept. 4.
Description: Technical Report
Partial Abstract: When major rubble-mound stone structures such as breakwaters, jetties, or groins are constructed in the coastal zone, they alter the existing current and wave conditions that normally exist at a particular location. Waves breaking on such structures under construction may cause bottom material to be suspended and transported from the region, resulting in scour holes that must be filled with construction material. This may result in substantial cost overruns. To minimize potential cost increases due to scour during nearshore construction, a foundation blanket of underlayer material can be placed some distance ahead of the construction of the upper portions of the structure. The stability of such an underlayer material section will depend on the size of the material used in the layer, the extent of the section, and the incoming wave climate. The purpose of this study was to determine the stability during construction of such an underlayer material section, which also serves as the foundation blanket for rubble-mound structures constructed on a movable bottom. A simple beach profile consisting of straight, uniform contours parallel with the shoreline was physically modeled on a 1V-on-25H slope in a 6-ft-wide wave flume. A major stone structure was assumed to be under construction perpendicular to the shoreline and thus perpendicular to the uniform parallel contours. A two-dimensional section of this stone structure was modeled (16-to-1 linear scale ratio) along the major axis of the structure. The waves which produced the most severe movement of the underlayer section (scour) were those with characterist ics that caused breaking with plunging to occur directly at the toe of the rubble-mound structure. Seven uniform material sizes were used to construct three different lengths of underlayer material sections (3-, 5-, and 7-ft model dimensions; 48- , 80-, and 112-ft prototype dimensions, respectively). These 21 different underlayer sections were subjected to breaking waves with periods of 2-, 3-, 4-, and 5-sec model time (8-, 12- , 16-, and 20-sec prototype time, respectively). These 168 total tests were performed with an underlayer material section thickness of 2.0 ft prototype, which is a typically representative value presently being utilized under prototype conditions. NOTE: The rest of the abstract contains equations the character set of this system cannot render. See the file of the report for the full abstract.
Rights: Approved for public release; distribution is unlimited.
Appears in Collections:Technical Report

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