28 July 2005
Diaphragm. This type consists of two series of circular arcs
connected together by diaphragms perpendicular to the axis of the
cellular structure. The width of cells may be widened by increasing
the length of the diaphragms without raising interlock stress, which
is a function of the radius of the arc portion of the cell. Cells must
be filled in stages so that the heights of fill in adjoining cells are
maintained at equal levels to avoid distortion of the diaphragm
walls. Diaphragm type cells present a flatter faced wall than
circular cells and are considered more desirable for marine
Cloverleaf. This type is a modification of the circular cell type and
is generally used in deep water where the diameter required for
stability would result in excessively high interlock stress if
diaphragms were not added.
d. Reinforced Concrete Caisson. See Figure 2-12. In this type of
construction, concrete caissons are cast in the dry, launched, and floated
to the construction site where they are sunk on a prepared foundation.
The caisson is filled with gravel or rock and a cast-in-place retaining wall is
placed from the top of the caisson to the finished grade. This type of
construction is prevalent in countries outside the United States.
e. Precast Concrete Blocks. See Figure 2-12. This form of solid wharf is
a gravity type wall made up of large precast concrete blocks resting on a
prepared bed on the harbor bottom. A select fill of granular material is
usually placed in the back of the wall to reduce lateral earth pressures.
This type of construction is popular outside the United States.
Construction of the floating type usually requires a flood basin, graving dock, or
drydock. The units are essentially constructed in the dry and floated out and
transported (on their own or on barges) to the site. Availability of such a facility
and transportation of the floating units through open ocean waters and restricted
inland waters for deployment at the site are serious considerations. In this
respect, the floating type has a significant advantage over others in that the bulk
of construction activity can be shifted to other parts of the country where labor,
economic, and environmental conditions are more favorable. Other concepts of
construction such as barge-mounted construction and floating-form construction
are described in UG-0007.
The soil drawn up by the suction head of a dredge, pumped with water through a
pipe, and deposited in an area being filled or reclaimed is referred to as
"hydraulic fill." At port and terminal facilities, where land is not available onshore