Pile driving

A screw-on splicer for use in driving composite pipe-shell piles and a screw-on tip for shell piles. Each has an outer diameter at least about 2 inches greater than the O.D. of the shell. An enlarged tip for shell piles, comprises a mass of concrete encased in a non-tapered corrugated shell and having a corrugated shell socket for receiving the shell stem.

One aspect of this invention relates to the driving of composite pipe-shell 
piles. Such composite piles comprise: (a) a lower stem portion of pipe (of 
substantially uniform diameter along its length) capable of receiving and 
transmitting pile-driving blows, (b) an upper stem portion of corrugated 
shell (also of substantially uniform diameter along its lenth) incapable 
of withstanding such blows, and (c) a splicer joining the two stems. The 
corrugated shell is typically made of steel having a wall thickness of 
about 1/32 inch to 1/16 inch (such as 14, 16 or 18 U.S. Standard gage) 
which is helically corrugated. Typically the valleys of the corrugations 
are about 1/2 inch deep and the corrugations are about 2 inches wide 
(measured from one peak to the next) with a helical pitch of about 3/4 
turn per foot of axial length. The shell is thus susceptible to expansion 
and concentration both radially and axially. 
Usually there is a suitable closure element such as a "boot" at the bottom 
of the pipe stem portion of the pile; this prevents the soil and/or water 
from entering the pipe stem during driving. The boot may, for example, be 
a flat plate, welded to the bottom of the pipe, or a fabricated point. 
These composite pipe-shell piles are used, for example, when the pile must 
be driven to such a great depth that the use of a long shell stem is 
impracticable. Many pile driving rigs are not capable of driving shell 
stems over 60 feet long, using correspondingly long mandrels; furthermore 
longer mandrels are less rigid and their use can result in damage during 
handling and driving. Current practice is to drive a lower, pipe, portion 
of the stem in the usual manner (by blows applied to the top of the pile) 
until the top of the pipe is at or near ground level and then to fit, onto 
the top of the pipe, a splicer (described below) to which the bottom of 
the upper, shell portion of the stem has been welded. The welding may be 
done at the pile driving site or in a fabricating shop. 
Composite pipe-shell piles are also used in cases where the pile does not 
have to be driven to great depth, when the ground contains obstructions 
which could damage a shell stem. Here the use of the heavy-wall pipe as 
the lower portion of the stem will often overcome the obstructions with 
little or no damage to the stem; once the pile has been driven past the 
obstructions, a shell stem may be used safely for the rest of the length 
of the pile.

The conventional splicer 1 (FIG. 1) comprises a plate 2 to the bottom of 
which there is welded (as at 3) a drive sleeve 4 having an internal 
circumferential shoulder 6 adapted to abut against the upper end of the 
pipe 7, and a depending body portion 8 to fit around the pipe, with a 
drive fit. 
Conventionally the shell stem 9 is, as previously indicated, welded to the 
top of the plate 2 and the sleeve 4 is fitted onto the partially driven 
pipe stem 7. Then an expanding mandrel 11 is inserted into the shell stem 
so that the bottom of the mandrel rests on the plate and the sides of the 
mandrel engage the inside of the shell; the mandrel is preferably of the 
type described in U.S. Pat. No. 3,984,992. The pile driving hammer 12 
applies its blows to the mandrel which transmits the driving force to the 
plate and thus to the pipe stem. 
After the pile has been fully driven, the pile stems are filled with 
concrete poured from above. The plate 2 has a central hole 13 to permit 
the concrete to flow from the shell stem into the pipe stem. 
The pipe stem, plate, sleeve and shell stem are circular in horizontal 
cross-section, and the outside diameter (O.D.) of the shell stem is 
usually substantially equal to or somewhat larger than, the O.D. of the 
pipe stem. The body portion 8 of the sleeve is about one half inch to one 
inch thick. The O.D. of the plate is about 1/2 to one inch larger than the 
O.D. of the shell stem. 
One aspect of the invention employs a splicer which is made up of a drive 
sleeve 4 of conventional type (such as described above), a plate 14 
secured (as by welding) to the top of the drive sleeve, and, secured to 
the top of the plate (as by welding), a shell stub 16 which is a short 
length of corrugated shell. The internal diameter of the stub 16 is 
slightly larger (e.g. about 1/8 inch larger) than the external diameter of 
the shell stem 17 which is to be used for the pile. The length of the stub 
16 is up to about 3 feet. To use this splicer, the shell stem is merely 
screwed into the stub. This is preferably done before the splicer is 
fitted over the top of the partially driven pipe stem, but it may also be 
carried out while the splicer is on the partially driven pipe stem. Then a 
pipe mandrel 18 is inserted into the shell stem with the bottom of the 
mandrel resting on the plate. Preferably the mandrel is of the type shown 
in U.S. Pat. No. 4,462,716. 
The diameter of the plate 14 used in this invention is at least about 2 
inches greater than the O.D. of the shell stub and correspondingly greater 
than the O.D., of the shell stem. When this plate is driven through the 
ground by the blows from the mandrel it forms a hole (in the ground) whose 
diameter is sufficiently larger than the shell O.D. that friction between 
the ground and the shell stem (during the driving of the latter) is 
greatly reduced or substantially eliminated, thus reducing the possibility 
of damage to the shell stem during the driving and making it feasible to 
use a pipe mandrel instead of an expanding mandrel. The resulting annular 
space around the shell stem may fill more loosely with earth thereafter as 
a result of caving in of the surrounding soil (particularly, in granular 
soils, e.g., fine sand to gravel), naturally and as augmented by the 
vibration associated with the driving of this and subsequent piles. In 
cohesive soils such as slits and clays there may be little or no such 
caving in of the soil, depending on its stiffness. Any annular space 
remaining at completion of the driving may be filed directly by the 
placement of soil from above. 
Examples of dimensions of composite piles according to this invention are: 
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Pile A 
Pile B Pile C Pile D 
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Pipe stem O.D. (inches) 
85/8 103/4 123/4 14 
Pipe wall thickness (inches) 
0.25 0.365 0.375 0.50 
Pipe stem length (feet) 
20-60 20-60 20-80 20-80 
Plate O.D. (inches) 
12 15 20 24 
Stub length (inches) 
12 16 20 24 
Shell stem O.D. (inches) 
10 12 16 19 
Shell stem length (feet) 
10,15 10,15 10,15 10,15 
or 20 or 20 or 20 or 20 
to 40 to 60 to 60 to 60 
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Another aspect of this invention relates to the driving of shell piles, 
particularly relatively short shell piles (e.g. about 10 to 30 feet in 
length), driven by means of a pipe mandrel impinging on a boot at the base 
of the shell stem (which is of substantially uniform diameter along its 
length. Conventionally, the boot is a flat steel plate and is welded to 
the bottom of the shell. In accordance with this aspect of the invention 
the boot is a steel plate 21 having welded thereto (e.g. in a fabricating 
shop) a short corrugated shell stub 22 whose internal diameter is slightly 
larger (e.g., about 1/2 inch larger) than the external diameter of the 
shell stem 23 so that the lower end of the corrugated shell stem can be 
readily screwed into the correspondingly corrugated stub. In use, long 
corrugated shells (which are conventionally supplied in lengths of up to 
60 feet) may be cut to the requisite stem length and then quickly fitted 
to the stub of the boot at the site, thus reducing costs for shell waste 
and for welding at the pile driving site. 
The plate 21 has a diameter somewhat larger than that of the stub (e.g. 2, 
3 or 4 inches or more greater that the stub diameter) to reduce frictional 
effects on the stem during driving and to increase the bearing area at the 
base of the pile. 
Examples of dimensions of piles of this aspect of the invention are: 
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Pile E 
Pile F Pile G Pile H 
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Shell O.D. (inches) 
8 10 12 16 
Stub length (inches) 
12 12 18 18 
Plate diameter (inches) 
12 14 16 21 
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Another aspect of the invention relates to a corrugated shell pile having 
an enlarged tip. The tip comprises a piece of large diameter untapered 
corrugated shell 26 having a ratio of diameter ("d" FIG. 5) to height ("h" 
in FIG. 5) of about 1:1 to 1:2, filled with concrete 27 except for a 
central socket formed by a relatively short length, or stub, of corrugated 
shell 28 suitably closed at its bottom (as by means of a plate 29) 
positioned in the upper central portion of the larger diameter piece. The 
large shell 26 is of substantially uniform diameter along its height, as 
is the stub 28. The concrete should contain suitable reinforcement; this 
is preferably fibrous reinforcement such as more or less uniformly 
distributed high tensile strength fibers, e.g. steel fibers of say 1/100 
inch diameter, 1 to 2 inches long, occupying a small proportion (such as 
about 2%) of the total volume of the concrete. When this prefabricated tip 
is moved to the construction site, the stub serves as a socket into which 
a shell stem may be screwed. The pile may then be driven in the manner 
described in U.S. Pat. Nos. 3,913,337, 4,462,716, 3,984,992 or 4,293,242. 
This tip is particularly useful for driving of piles that penetrate 
through cohesive soils (e.g. clay) but it may also be employed in granular 
soils. 
Examples of dimensions of tips according to this aspect of the invention 
are: 
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Tip 1 
Tip 2 Tip 3 Tip 4 
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O.D. of outer shell (inches) 
14 14 16 19 
Height of outer shell (inches) 
14 18 18 24 
O.D. of stub (inches) 
8 10 10 12 
Depth of socket (inches) 
7 9 6 12 
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It will be understood that in each of the described embodiments the shell 
stem and shell stub and the large diameter piece of shell are of helically 
corrugated shell as described earlier and that each of the shell stems is 
filled with concrete after it has been driven to the desired depth. 
It is understood that the foregoing detailed description is given merely by 
way of illustration and that variations may be made therein without 
departing from the spirit of the invention.