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116 Barry’s Advanced Construction of Buildings
Concrete placed in
tubes and compacted
by air pressure
Air line Pressure cap Starter
bars
Steel tube
driven in
1
2
Tubes driven in as shell
takes out granular soil
Air pressure
lifts tubes
and
compacts
concrete
Concrete
fills
weak
pockets
of
subsoil
3
At required depth, reinforcing cage
is lowered into tubes
Tube
Boring
tube
Concrete compacted
4 5
in pile boring
Enlarged
toe
Steel boring tubes
are screwed
together
Cutting
tube
Cast iron
clack plate
opens up
Lead shoe with
cutting edge
Shell ring
Clay
cutter Steel cutting shoe
screwed to cutting tube
Boring tube and lead shoe
Figure 3.49 Bored cast-in-place concrete pile.
Clay
cutter
Shell cutter for
granular soil
the concrete is cast under pressure, it extends beyond the circumference of the original
drilling to fill and compact weak strata and pockets in the subsoil, as illustrated in Figure
3.49. Because of the irregular shape of the surface of the finished pile, it acts mainly as a
friction pile to form what is sometimes called a floating foundation. As the pile continues
to settle into the soil, the friction forces surrounding the pile increase.