Concrete
A concrete bearing pile may be cast in-place or
precast. A cast-in-place concrete pile may be a shell
type or a shell-less type.
A shell type of cast-in-place pile is constructed as
shown in figure 10-11. A steel core, called a mandrel,
is used to drive a hollow steel shell into the ground.
The mandrel is then withdrawn, and the shell is filled
with concrete. If the shell is strong enough, it may be
driven without a mandrel.
A shell-less cast-in-place concrete pile is made by
placing the concrete in direct contact with the earth.
The hole for the pile may be made by driving a shell
or a mandrel and shell, or it may be simply bored with
an earth auger. If a mandrel and shell are used, the
mandrel, and usually also the shell, are removed
before the concrete is poured. In one method, how-
ever, a cylindrical mandrel and shell are used, and only
the mandrel is removed before the concrete is poured.
The concrete is poured into the shell, after which the
shell is extracted. This sequence of events is shown in
figure 10-12.
Casting in place is not usually feasible for
concrete piles used in waterfront structures. Concrete
piles for waterfront structures are usually precast. The
cross section of precast concrete piles is usually either
square or octagonal (eight-sided). Square-section
Figure 10-11.-Shell type cast-in-place concrete pile.
Figure 10-12.-Procedure for cast-in-ground concrete piles.
piles run from 6 to 24 inches square. Concrete piles
more than 100 feet long can be cast, but are usually
too heavy for handling without special equipment.
Sheet
Sheet piles are special shapes of interlocking piles
made of steel, wood, or formed concrete. They are
widely used to form a continuous wall to resist
horizontal pressures resulting from earth or water
loads. Examples include retaining walls, cutoff walls,
trench sheathing, cofferdams, and bulkheads in
wharves, docks, or other waterfront structures.
Cofferdams exclude water and earth from an
excavation so that construction can proceed easily.
Cutoff walls are built beneath water-retaining
structures to retard the flow of water through the
foundation.
Sheet piles may also be used in the construction
of piers for bridges and left in place, Here, steel piles
are driven to form a square or rectangular enclosure,
The material inside is then excavated to the desired
depth and replaced with concrete.
Timber Pier Piles
Working drawings for advanced base timber
piers are contained in Facilities Planning Guide,
Volume I, NAVFAC P-437. Figure 10-13 shows
a general plan; figure 10-14, a part plan; and
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