EI 02C097
01 Jul 97
(1) Timber piles. These are generally used for
comparatively light axial and lateral loads where foundation
conditions indicate that piles will not be damaged by driving or
exposed to marine borers. Overdriving is the greatest cause of
damage to timber piles. Pile driving is often decided by a
judgment that depends on the pile, soil condition, and driving
equipment. Overdriving typically occurs when the dynamic
stresses on the pile head exceed the ultimate strength of the
pile. Timber piles can broom at the pile tip or head, split, or
break when overdriven. Such piles have an indefinite life
when constantly submerged or where cut off below the
groundwater level. Some factors that might affect the
performance of timber piles are the following:
(a) Splicing of timber piles is expensive and time-
consuming and should be avoided. The full bending resistance
of timber pile splices may be obtained by a concrete cover
(Figure 1-1a) (Pile Buck Inc. 1992). Other transition splicers
are available to connect timber with cast concrete or pipe piles.
(b) Tips of timber piles can be protected by a metal boot
(Figure 1-1b).
(c) Timber piles are normally treated with creosote to
prevent decay and environmental attack.
(d) American Society for Testing and Materials
(ASTM) D 25 provides physical specifications of round timber
piles. Refer to Federal Specifications TT-W-00571J, "Wood
Preservation: Treating Practices," for other details.
(2) Precast concrete piles. These piles include
conventionally reinforced concrete piles and prestressed
Figure 1-1. Timber pile splice and boot
concrete piles. Reinforced concrete piles are constructed with
an internal reinforcement cage consisting of several
longitudinal bars and lateral ties, individual hoops, or a spiral.
Prestressed concrete piles are constructed using steel rods or
(b) Special steel points can be attached to precast precast
wire strands under tension as reinforcement. Since the
piles during casting of the piles and include steel H-pile tips or
concrete is under continuous compression, transverse cracks
cast steel shoes (Figure 1-2).
tend to remain closed; thus, prestressed piles are usually more
durable than conventionally reinforced piles. Influential
(3) Raymond step-tapered piles. These consist of a
factors for precast concrete piles include splices and steel
corrugated steel shell driven into the ground using a mandrel.
points.
The shell consists of sections with variable diameters that
increase from the tip to the pile head. A mandrel is a heavy,
(a) Various splices are available to connect concrete
rigid steel tube shaped to fit inside the shell. The mandrel is
piles. The splice will provide the tensile strength required
withdrawn after the shell is driven and the shell filled with
during driving when the resistance to driving is low. Figure 1-
concrete. Raymond step-tapered piles are predecessors of
2a illustrates the cement-dowel splice. Refer to "Foundations"
drilled shafts and are still popular in the southern United
(Pile Buck Inc. 1992) for additional splices.
States.
(4) Steel piles. These are generally H-piles and pipe piles.
Pipe piles may be driven either "open-end" or "closed-end."
Steel piles are vulnerable to corrosion, particularly in
saltwater; however, experience indicates they are not
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