In my experience in industrial shoreline settings in major ports and also in residential beach settings in Long Island, there are basically 2 types of seawalls in common use, steel sheet piling and composite sheet piling. Sometimes composite can be fortified with timber piles. Steel is required for wall heights greater than 15 to 20 ft. Below that, composite starts to become economical. Composite is also corrosion-proof which is a big plus. The wall heights you describe may well be within composite territory, especially if the subsurface is not too hard. Note that the additional wall height that might be required due to sea level rise or storm surge is imposing a lateral force in the opposite direction as the soil. So that additional height is not additive for determining internal stresses.
There are various types of composite sheet pile materials including vinyl, polyethylene, fiberglass, and more. One firm that comes to mind, called CMI, has a line of such sheet piling products. I have no affiliation with them. There are many others as well. Skyline Steel is a big supplier of steel sheet piling in the US. There are a few others. Again, I have no affiliations.
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John Francescon P.E., M.ASCE
Hatch
New York NY
(646)
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Original Message:
Sent: 02-09-2017 10:51
From: Alexis Sommers
Subject: Design of effective seawalls for south Florida Intracoastal Waterway locations
As a retired professor, I am currently VP of the Hollywood Lakes Civic Association which is starting to collect info on sea level rise and is experiencing periodic tidal flooding of streets and property. Current seawalls are nonuniform, some in disrepair, and not in all flood-prone areas.
Would like to start to obtain references and information on effective sea wall designs for our muck-and -mangrove environment to begin a grassroots assessment effort and civic education. Input would be useful in speeding up our activities. An allied issue is that South Florida is subject to periodic tropical storms and resultant storm surge which can reach six feet, hence seawalls should also provide some protection for this surge while protecting against monthly tidal surge. Our current minimum seawall height of 3.5ft above MHT is generally viewed as inadequate given a sea level rise of about an inch a year. References would be appreciated.
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Alexis Sommers Ph.D., A.M.ASCE
Professor Emeritus
University of New Haven
Hollywood FL
(754)816-5648
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