. Coastal scour problems and methods for prediction of maximum scour. Scour (Hydraulic engineering); Sea-walls; Underwater pipelines; Rubble mound breakwaters. 33. Recently, laboratory scaled model studies were conducted by Markle (1989) to address the sizing of toe berra and toe buttressing stone in breaking wave environments. These tests resulted in the most recent guidance for sizing toe berm armor stone and toe buttressing stone. Basically, guidance is given in terms of the stability number Ns defined by N„ = 1/3 Hr (Sr - 1) (44) with W50, the median weight of individual berm stone in lbf,
. Coastal scour problems and methods for prediction of maximum scour. Scour (Hydraulic engineering); Sea-walls; Underwater pipelines; Rubble mound breakwaters. 33. Recently, laboratory scaled model studies were conducted by Markle (1989) to address the sizing of toe berra and toe buttressing stone in breaking wave environments. These tests resulted in the most recent guidance for sizing toe berm armor stone and toe buttressing stone. Basically, guidance is given in terms of the stability number Ns defined by N„ = 1/3 Hr (Sr - 1) (44) with W50, the median weight of individual berm stone in lbf, as defined previously in Equation 39. In addition, 7rb = specific weight of berm stone, lbf/ft3 Sr = specific gravity of berm stone relative to the water in which the structure resides, , Sr = 7rb/7 HD = design wave height, ft 7 = specific weight of water in which structure resides, lbf/ft3 Basically, the guidance for toe berm stone states that "unless site-specific model tests are conducted to justify higher values of Ns, stability number should be selected based on the lower limit curve presented in Figures 11 and 12, and the individual toe berm armor stone weights should range from a maximum of W50 to a mimimum of ; For toe buttressing stone, limited 2-D stability tests for toe buttressing a one-layer uniformly placed tri-bar structure, a stability number Ns equal to should be used in a wave-breaking environment. Ns3 VS dl/da ALL TESTS TESTS: 5- & FUUUES 08UQUE WAVES ON TRUNKS 90 OECREE WAVES OH TRUNK! 06UOUE WAVES OH MEADS 90 OECREE WAVES OH HEAOS I TESTS: T-SHAPED WAVE BASW. RELATIVE BERM DEPTH, dl/da Figure 11. Stability number cubed versus relative berm depth from Markle (1989). (See Figure 12 for definition of dx and ds) 31. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the
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