Pile Design and Construction Practice, Fifth edition

50 Types of pile
2.3 Driven and cast-in-place displacement piles
2.3.1 General
Driven and cast-in-place piles are installed by driving to the desired penetration a heavy-section
steel tube with its end temporarily closed. A reinforcing cage is next placed in a tube which
is filled with concrete. The tube is withdrawn while placing the concrete or after it has been
placed. In other types of pile, thin steel shells or precast concrete shells are driven by means of
an internal mandrel, and concrete, with or without reinforcement, is placed in the permanent
shells after withdrawing the mandrel.
Driven and cast-in-place piles have the principal advantage of being readily adjustable in
length to suit the desired depth of penetration. Thus in the withdrawable-tube types the tube
is driven only to the depth required by the ground conditions. In the shell types, the length
of the pile can be easily adjusted by adding or taking away the short units which make up
the complete shell. In conditions favourable for their employment, where the required penetration
depth is within the capability of the piling rig to pull out the tube, and there are no
restrictions on ground heave or vibrations, withdrawable tube piles can be installed more
cheaply than any other type of driven or bored pile for comparable capacities. They also have
the advantage, which is not enjoyed by all types of shell pile, of allowing an enlarged base
to be formed at the toe. However, some codes of practice, notably that of New York City,
forbid the use of a wholly uncased shaft for all forms of driven and cast-in-place pile, where
these are installed in soft to firm clays or in loose to medium-dense sands and materials such
as uncompacted fill. These restrictions are the result of unfortunate experiences resulting
from lifting of the concrete while pulling out the driving tube, and of squeezing (‘waisting’)
the unset concrete in the pile shaft where this is formed in soft clays or peat. The firms that
install these proprietary types of pile have adopted various techniques for avoiding these
troubles, such as inserting permanent light-gauge steel shells before placing the concrete.
However, such expedients increase the cost of the withdrawable-tube piles to the extent that
their advantage in price over shell piles may be wholly or partially lost. The soundness of
the uncased type of pile depends on the skill and integrity of the operatives manning the
piling rig.
Piling rigs have not yet been developed to install driven and cast-in-place piles of the very
large diameters which are possible with driven thick-walled steel tubes or bored and castin-place
piles. Thus the working loads are limited to the light to medium range. Also the
withdrawable-tube or thin-shell types are unsuitable for marine structures, but they can be
employed in marine situations if they are extended above the sea bed as columns or piers in
steel or precast concrete.
Problems associated with ground heave when installing driven and cast-in-place piles in
groups are discussed in Section 5.7.
2.3.2 Withdrawable-tube types
Descriptions of the various types of driven and cast-in-place piles are given in CIRIA report
A Review of bearing pile types (2.13) . The methods of installing these piles are essentially the
same. A piling rig consisting of a mast, leaders and winch on a track or roller-mounted
frame (see Section 3.1) is used to support and guide the withdrawable tube. The original
Franki pile is now mainly available in Australia and Southeast Asia, for pile working loads