Design of Cover Layers for Rubble-Mound Breakwaters Subjected to Nonbreaking Waves

摘要

The need for fundamental data for use in designing rubble-mound breakwaters led to a laboratory investigation to develop design criteria. The first phase of this investigation, which dealt with the design of smooth quarrystone cover layers on breakwater trunks in depths of water sufficient to prevent the breaking of waves due to depth limitation, was described in a previous report by Hudson. The present report is concerned with the design of rubble-mound breakwaters constructed of rough and smooth quarrystones, quadripods, tetrapods, hexapods, tribars, modified cubes, and truncated tetrahedrons. For the tests described herein, the layered type of construction was used for both breakwater trunks and breakwater heads. The small-scale rubble-mound breakwater sections were hand constructed in concrete flumes 119 ft long, 5 and 12.5 ft wide, and 4 ft deep and subjected to mechanically generated waves. The limit of stability of the armor units forming the protective cover layer was determined. Tests were also conducted in which damage to the cover layers was determined as a function of wave height. In these tests wave heights greater than those corresponding to incipient instability were used. When the breakwater slope was steepened, wave runup and wave rundown increased; when the wave steepness decreased, wave runup and wave rundown increased. Measurements were made to determine the average thickness and percentage of voids for all types of armor units used in this investigation. (Author)