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GROUTED REVETMENTS: Smith and Chapman also reported that grouting
the armor units by filling the voids with concrete has not
enhanced the structure stability.
On the contrary, grouted
revetment reduces the permeability thus, increases magnitudes of
wave runup and overtopping that lead to extensive early soil
erosion at the back of revetment.
This erosion initiates toe
scour which causes settlement of the toe units, and leaves the
mass of grouted armor units in suspension.
The grouted revetment
collapses eventually in a single shattering event.
-OP A-D TO- PROTECTIONS:
T
N
E
It was observed that the stability of
top and toe units are critical to overall structural integrity.
Dislocation of these armor units would result in structure
failure.
The initiation of toe failure is always followed by
"beach fluidization" at toe area when the wave trough passes
there.
Large toe units, particularly with low specific surface,
easily sink into the fluidized beach.
It is recommended that
proper design should be accomplished by extending the toe units
deep into a stable layer inside the beach profile.
The design
guidance for rubble toe protection, provided in EM 1110-Z-1614
(U.S. Army Corps of Engineers, 1985) and in Chapter 7 of the SPM
(1984), should be followed to minimize the chance of toe failure,
The top armor unit has no gravity surcharge and has the least
interlocking with its neighboring units.
Therefore, it is the
unit most susceptible to wave uprush and backwash actions.
Dislocation of the top units could result in back erosion which
further lead to toe scouring.
Smith and Chapman (1982) recommend
the use of the largest high aspect armor units laid flat at the
top of'the revetment with their smallest face exposed seaward.
ADDITIONAL INFORMATION:
For additional information contact Dr.
Yen-hsi Chu at (601) 634-2067 of the Coastal Engineering Research
Center.
REFERENCE:
Smith, A. W., and Chapman, D. M.
1982.
"The Behavior of
Prototype Boulder Revetment Walls", Proceedings of 18th Coastal
Engineering Conference, Cape Town, South Africa.
Shore Protection Manual.
1984.
4th ed., 2 vols, US Army
Engineer Waterways Experiment Station, Coastal Engineering
Research Center, US Government Printing Office, Washington, DC.
US Army Corps of Engineers.
1985.
"Design of Coastal
Revetments, Seawalls, and Bulkheads", EM 1110-2-1614.
Washington, DC.
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