Stainless and galvanized steel cable, polypropylene, nylon, Poly-D, and Kevlar rope, galvanized
and raw steel chain, and rubber conveyor belt edging have been used as fastening materials. Of these, the
conveyor belt edging has proven most satisfactory. The others failed because of corrosion in seawater,
abrasion by the tires, fatigue, or deterioration from other factors. Steel cables sawing through the tires
have caused some devices to fail. Rubber belt edging, a scrap material derived from manufacture of
conveyor belts, is available from several rubber companies in a wide range of widths and thicknesses.
For tire breakwater construction, the belting should be at least 2 inches wide and 0.375 inches thick.
Secure anchorage is necessary to prevent displacement. Danforth, screw anchors and large
concrete blocks have been used with mixed results. They are satisfactory for seasonal use in mild
waves, but they tend to creep over long periods in soft bottoms and are not always desirable for
permanent installations. In these cases, driven piling is the best means of stable anchorage over long
periods. Pile driving, of course, adds considerably to total installation costs.
Other Materials
Bundles of logs can be chained together or other barriers can be fabricated from treated timber.
Modules of lightweight concrete filled with flotation foam have also been successful. The proportioning
and design factors presented for rubber tire breakwaters also apply to these.
FIXED BREAKWATERS
The most important feature of a fixed breakwater is its height, which determines how much wave
energy is dissipated. In building a fixed breakwater or sill, some settlement should be anticipated in the
structure's design height. The amount depends on the type of soil, the structure's weight, and type of
foundation. Uniform settlement does not necessarily adversely affect performance, but if one portion of
breakwater sinks significantly below the others, there will be increased wave transmission over the low
section.
Longard Tubes
Wave Height Range: Below five feet.
The same advantages and disadvantages mentioned for Longard tube bulkheads (APPENDIX A)
apply when they are used as breakwaters. An added disadvantage is that the protective epoxy coating
cannot be applied to wet tubes so that damages are more like Therefore, they should not be used at
locations where the tube exposed to vandalism or water-borne debris. Figure C- 2 shows before and after
views of a Longard tube slashed by vandals. Damage eventually caused the entire tube to deflate. Where
69-inch tube cannot provide sufficient height; an alternate breakwater system should be used.
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