Note: Descriptions are shown in the official language in which they were submitted.
1119~23
Background of the Invention
1. Field of the Invention
This invention relates generally to piles, and
particularly to precast reinforced concrete screw-threaded piles.
This invention further relates to concrete piling constructed
in sections to permit variations in the length of the piles.
2. Description of the Prior ~rt
In areas such as New Orleans, Louisiana and adjacent
parishes, or in-~oft and marshy lands which ~xist in places
other than Louisiana, it is necessary to employ piles to provide
a proper foundation for buildings and similar structures. Most
commonly employed for residential and light commercial con-
struction are friction piles usually constructed of wood. These
piles may run 20 to 25 feet in length and must be driven into the
ground by special machinery of large size. Accordingly, where such
machinery is inaccessible, proper-ty owners have been unable to
undertake desired construction.
A problem encountered with the use of precast con-
crete screw-threaded piling is encountered during handling of the
piling between the manufacturing facility and site where the
piling is to be used. Further, the length requirements for the
piling varies as a function of the depth required at a particular
site. Thus, it has generally been necessary in the past to con-
stru~t such pre~cast pili~g in a great variety of leng*hs in order
to provide piling only of the length necessary for a particular
application.
~ Another~problem encountered with precast concrete
screw-threaded piling is attainment of adequate strength at the
threaded peripheral portions of the piles. This problem becomes
more acute the deeper and closer together are the threads o-f the
piles.
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f~3
It is particularly desirable in order to construct
a precast concrete screw-threaded piling which can be efficiently
threaded into the earth, and the like, even by the use of an
instal]er's hands, to have the screw-threads of the piles as
deep and as close together as possible. The problem arises, how-
ever, of providing suitable reinforcement for such deep and close-
ly spaced screw-threading.
A further problem experienced in prior art devices,
is that the tensile and torsional stresses developed during the
insertion of a concrete pile into the earth cannot be carried
by concrete. It is known in the art, that concrete has great
compressive stren`gth, but has little or no tensile strength
and little or no torsional strength. Thus, it has been a
problem with prior art devices that the piling were not
properly reinforced from the point of attachment of a suitable
torsional driving force throughout the pile. Thus, the piling
of the prior art would not be suitable for driving, because
torsional stress would cause the concrete portion of the pile
to fail.
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'w v
11198Z3
G~NERAL DISCUSSION OF THE PREC,ENT INVENTION
It is an object of the present invention to provide
a screw-threaded pile which is easier to insert and affords more
effective frictional gripping surface than prior screw-threaded
pile.
It is another object of the present invention to
provide a pile which can be installed by hand where suitable
machinery is unavailable or inaccessible.
It is yet another object of the present invention
to provide a pile which avoids problems of erosion of the pile
by electrolysis and similar electrochemical and chemical reactions.
It is another object of the present invention to
provide an extendible pile system which permits piling to be
constructed in sections for transport to a field site and for
assembly in a length appropriate to the geophysical conditions
encountered at the site.
It is another object of the present invention to
provide an efficient and simple, yet rugged and reliable, connecting
arrangement for attaching together sections of a precast concrete
screw-threaded pile.
These and other objects are achieved according to
the present invention by providing a pile having: a preferably
metallic head arranged for being rotated by suitable machine-
powered or manual driving tools; a metallic reinforcement core
- connected to the head for rotation by the head, and having a
longitudinal axis extending from the head to a tip, about which
axis the core is rotated by the head; and a body in the form of
a solid mass of concrete disposed embedding the core and
rotating therewith, the body tapering from the head to the tip
of the core and having an outer surface providing equally
spaced threads along the entire length between the head and
the tip with the screw threads facilitating insertion of
the pile in earth by rotation of the head. Torsional
and tensilestresses are transmitted from the metallic head to
the integrally connected reinforcement core, with the tensile
and torsional stresses developed throughout the pile, thereby
2~eventing failure of the concrete.
The body advantageously is constructred from a
cementitious material such as concrete cast about the core, while
the core itself is preferably constructed from ferrous reinforcing
bar, as commonly known and conventionally used, for reinforcing
the cementitious material.
According to one preferred embodiment of the
invention, the core is a framework of longitudinally extending
reinforcing bars and longitudinally spaced collars, with the
bars tied to the collars and the diameter of the collars decreasing
from the head of the pile to the tip of the core so that the core
tapers from the portion thereof either adjacent to or forming
a portion of the head down to the tip of the core.
An alternative embodiment of a core according to
the invention provides a single longitudinally extending reinforcing
bar having tied thereto at least one, and preferably several, cross-
bars extending transversely of the longitudinal extent of the
single bar.
The upper head portion may be constructed in any one
of several preferred ways, among which are the use of a solid, I~re-
ferably metallic cast head, the use of a metal sleeve affixed directl
to the reinforcing bars of the core, and the extension of the
reinforcing bars to form a framework about which a metallic or
cementitious head may be formed. Advantageously, but not necessarily,
the head is in the form of a hexagon, similar to a conventional
111 9823
nut, in order to facilitate engagement of the head by a conventional
driving tool. Alternatively, or in addition, one or more bores
or holes may be provided in the head transversely of the
longitudinal extent of the core for receiving a driving rod which
can be used to facilitate rotation of the head of the pile.
It is desireable that the upper portion of the
pile provide a point of attachment for a suitable torsional
driving force capable of threadably driving the pile into
the desired soil. A metallic upper portion having integral
attachment with the reinforcing core is preferred, however,
a metallic head can be achieved by providing greater surface
area to the point of application of the torsional force and
~ heavily reinforcing this area adjacent the application of the
torsional driving force.
. .
These and other objects accor~ing to tne present
invention are achieved by providing additionally an extendible
pile system havin(~: a pair of pile sections;and a connector arrange-
ment associated with the pile sections for releasably attaching the
pile sections together for rotation with one another. The
connector arrangement preferably includes opposed sockets provided
in adjacent ones of the sections to be connected together, and
a key removably arranged in the sockets for locking the sections
against relative rotational movement about their longitudinal
axes.
The connector arrang~ment can also include a plurality
of opposed sockets provided in the sections to be connected
together, with these sockets having associated therewith a like
number of keys. By this arrangement, the amount of torque which
can be exerted on the pile is greatly increased.
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111~8~3
Accoraing to oné preferred embodinent of an extendible
pile system according to tne present invention, one of the sections
of the pile is provided with a projection and the other of the
sections with a recess having a bottom and arranged for receiving
the projection. The socket of one of the sections is disposed
in the projection, while the socket of the other of the sections
is disposed in the bottom of the recess which receives the
projection~ Steel plates, and the like, line the bottom of the
recess and cover the top surface of the projection of the other
of the sections, which surface abuts the bottom of the recess
when the two sections are placed together, so as to permit the pile
to be driven into the earth as well as to be screwed thereinto
by rotation.
The core of each section of a pile, according to
the invention, advantageously includes a central frame extending
along the longitudinal axis of the core, and has a spiral rein---
forcing element pitched to the pitch of the screw-threads of
the section and disposed winding around the frame in spaced
relation thereto. This reinforcing element permits deeper and
more closely spaced threads to be used so as to increase the
efficiency of the resulting pile to that where the pile can
be screwed into the earth even by manual rotation where desired.
These together with other objects and advantages
which will become subsequently apparent reside in the details of
. . --
construction and operation as more fully hereinafter described
and claimed, reference being had to the accompanying drawings
forming a part hereof, wherein like numerals refer to like
parts throughout.
^7
1119?S123
Brief Description of the Drawings
For a further understanding of the nature and objects
of the present invention, reference should be had to the follow- -
ing detailed description, taken in conjunction with the accom-
panying drawings, in which like parts are given like reference
numerals and wherein:
Figure 1 is an exploded, perspecti~e view showing a
first embodiment of a pile formed by add-on sections according
to the present invention.
Figure 2 is an enlarged, fragmentary, sectional view
taken generally along the line 2-2 of Figure 1, with the
connecting key displaced from the position shown in Figure 1.
Figure 3 is a sectional view taken generally along
the line 3-3 of Figure 2.
Figure 4 is a topplan view showing the bottom section
of a pile constructed according to a second embodiment of
the present invention.
Figure 5 is an enlarged, fragmentary, sectional view
- taken generally along the line 5-5 of Figure 4.
Figure 6 is a top plan view showing a bottom section
of a third embodiment of a pile according to the present
invention.
Figure 7 is a perspective VieW showing a modified
connector key for use with any of the embodiment of add-on
pile section, according to the invention.
~; Figure 8 is a perspective view showing the general
; configuration of a pile according to the present invention,
with one preferred embodiment of a head for the pile.
Figure 9 is a fragmentary, enlarged, sectional view
taken generally along the line 9-9 of Figure 8.
Figure 10 i9 a fragmentary, sectional view, similar
to Figure 9, hut showing a modified embodiment of a head for a
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823
pile according to the invention.
Figure 11 is a perspective view showing one embodiment
of a core for a pile accordlng to the present invention.
Figure 12 is a perspective view, partly cut away
and in section, showing yet another embodiment of a pile
according to the present invention.
Figure 13 is a partial schematic view of the lowermost
tip portionof the preferred embodiment of the apparatus of
the present invention illustrating the force experienced by
the tip during insertion of the pile.
Figure 14 i9 a partial schematic view of a thread
portion of the preferred embodiment of the apparatus of the
present invention illustrating the compressi~e lateral movement
of a single thread against the "soil-socket" during insertion
of the pile.
Figure 15 ls a partial schematic view of a plurality
of threads on a portion of the preferred embodiment of the
apparatuq of the present invention.
Description of the Preferred Embodiments
Figures 1-7 show various exemplary embodiments of a
multi-section pile system including an initial pile with one
or more "add-on" section; while Flgures 8~12 show various
exemplary embodiments of a single pile which is similar in
structure to the initial or lowermost ~ection of the pile
systems of Figures 1-7. Accordingly, for a beginning under-
standing of the subject matt~r of the present invention, the
embodiments of Figure~ 8-12 will be described first.
Referring now to Figures 8 and 9 o~ the drawings,
a screw-threaded pile 110 includes a head 112 constructed from
a piece of solid material, such as a suitable steel, and
having a substantially hexagonal shape for receiving a conven-
tional driving socket tool (not shown), or the like, in order
_ g _
~i9823
to rotate the head 112 when pile 110 is being installed. The
lower portion of head 112 terminates in a flared skirt 114
whlich comes down over the main portion of the pile 110 so as
to form a transition. A core 116 i~ connected to head 112 in
a suitable manner for rotation by head 112, and has longitudinal
axis extending from the head 112 to a tip 118 of pile 110,
about which axis core 116 is rotated by the head 112.
A body 120 in the form of a solid mass constructed
from a cementitious material cast about the core 116 is dis-
posed embedding the core 116 and rotates with the core 116
during installation of pile 110. ~n other words, head 112,
core 116, and body 120 form an integral unit. Body 120 has
an outer surface 122 which tapers continuously along the entire
length of core 116 from head 112 to tip 118, and is provided
with spiral screw threads 124 along the entire length of
body 120 for facilitating insertion of pile 110 in earth (not
shown) by rotation of head 112.
Threads 124 will preferably be supplied at a minimumthread pitch, or a minimum number of threads per foot which
would be sufficient to give mechanical advantage that would
allow piling 110 to be inserted easily into any desired soil
medium. The insertion of the pile into the soil should be
achieved with minimal torsional stresses generated, so as not
to cause the pile or adjacent soil to fail. (The mechanics
of insertion of the pile into the soil will be discussed more
fully hereinafter, and particularly with reference to Figure
13, 14 and lS). This in combination with the appropriate
reinforcing cage 136 and the appropriate attachment of the
reinforcing cage 136 to the head which is provided for applica-
tion of a torsional force will achieve the desired result.
Head 112 is provided with a transverse through bore126 arranged for receiving a driving, or leverage, bar (not
-- 10 --
:lliS~8~3
shown) to impart rotational torque to head 112 in order to
cause rotation of pile 110 as it is being installed.
Referring now to Figure 10 of the drawing, a head is
shown similar in configuration to head 112, but constructed
as a, for example, steel sleeve 128 ending in a dependin~
flared skirt 130 and provided with a transverse bore 132
similar to bore 126 for receiving a leverage rod. Sleeve 123,
possibly at the skirt 130 thereof, is fastened to the reinforc-
ing bars of a core 134 in a conventional manner, such as by
welding, prior to the casting of a body about the core 134.
It will be appreciated that core 116 of pile 110 will also be
appropriately attached to head 112, such as by welding, prior
to the casting of body 120 about the core 116. Since such
attaching and casting techniques are well known in the particu-
lar arts, ~hese techniques will not be described in detail
herein. The connection between core 116 and head 112 will be
an integral connection so that the torsional stresses generated
in head 112 when a suitable driving force is attached thereto
will be developed through core 116 into the entire pile 110.
It should be understood, that it is desirable to develope the
tensile and torsional forces generated during insertion through
the reinforcement members of core 136. Thus, head 130 is
preferably metal and integrally connected to core 136 by weld-
ing or the like. However, a substantially similar effect could
be achieved by providing a heavily reinforced socket or head
having a large concrete area..to which a suitable torsional
force is attached. In the latter structure, although the
surface would be in fact concrete, the head, if heavily rein-
forced (the reinforcement attached to core 136), would perform
as satisfactorily as metallic head 112 and the term "metallic
head" or upper portion is intended to include such equivalent
structures.
~9823
Figure 11 of the drawings shows one preferred construc-
tion of a core ~or a pile according to the invention, wherein
the core is a framework 136 of longltudinaily extending rein-
forcing barR 138 and longitudinally spaced collars 140, 142,
14~, 146, and 148. The bars are tied to the aforementioned
collars in the conventional manner, with the diameter of the
collars beginning with collar 142 decreasing from the head area
150 toward the tip 152 of the core so as to create a continuous-
ly tapering, or linear slopel to the core. While collar 140 is
illustrated as being of substantially the same diameter as
collar 142, it is possible to construct collar 140 of slightly
smaller diameter than collar 142 so as to use the portion of
framework 136 between collars 140 and 142 as a cage for being
a head associated with the core. For example, the portion of
framework 136 whlch extends between collars 140 and 142 may be
inserted into the sleeve 128 (Figure 10) in a manner not shown,
or the portion of framework 136 between the collars 140 and 142
may be surrounded by a straight steel sleeve welded to the
reinforcing bars and cast into an outer head portion as in the
embodiment shown in Figure 12 of the drawing.
Referring now more particularly to Figure 12 of the
drawing, a core 154 is shown which includes a single longitud-
inally extending reinforcing bar 156 havinq tied thereto at
least one, and preferably the illustrated plurality of cross-bars
158, 160, 162, 164 and 166 such that the aforementioned cross-
bars extend transversely of the longitudinal extent of bar 156.
Core 154 is illustrated in Figure 12 as being affixed
to a head 168 constructed as a framework forming a generally
cylindrical open cage 170 embedded in a mass 172 of a cementi-
tious or other suitable casting material. Provided within thismass 172, and disposed extending transversely to the longitud-
inal extent of bar 156, is at least one hole disposed for
- 12 -
23
receiving a leverage bar (not shown). In Figure 5 a pair ofsuch cross-holes or bores are illustrated as formed by a pair
of intersecting tubes 174 and 176 extending completely through
the mass 172 which embeds cage 170. These tubes 174 and 176
may be attached to the reinforcing bars forming cage 170 in a
suitable manner, such aq by welding or by the use of tie-wire,
with the use of the pair of intersecting holes as formed by
tubes 174 and 176 permitting an installer to make quarter turns,
as for an installation of a pile next to a building or other
object where a 360 turn is impossible.
Referring now more particularly to Figures 1 through 3
of the drawings, a first embodiment of an extendible pile
according to the present invention is shown as including a head
section 10 and a tip section 12 attached together for rotation
with one another by a connector arrangement 14. While only a
palr of sections 10 and 12 have been ~hown, it will be appre-
ciated that middle sections (not shown), in any number desired,
similar to section 10, but without the head 16, can be inserted
between sections 10 and 12 to make the length of the resulting
pile that desired for a particular application. In addition,
the bottom or tip section 12 can be employed itself as a pile,
if desired, by attaching a suitable turning handle or device,
neither of which is shown, to the key receiving socket in the
uppermost portion of section 12 as is to be described below.
In addition to head 16, the pile formed by sections 10
and 12 also includes a tip 18 disposed at the lower portion of
the tapered tip section 12. Note Figure 13, where an enlarged
partial view of a preferred tip 18 is provided. This tip 18
may take the form of the illustrated cutter 20, if desired,
although a conventional point (Figure 13) may also be used.
Each of the sections 10 and 12 also includes a frame
22, 24, respectively, formed of longitudinally extending
- 13 -
ill98~3
re:inforcing bars 26, 28,and longitudinally spaced collars 30,
32, and 34, 36. It will be appreciated that other collars
similar to those shown will be spaced out along the longitud-
inal extent of the sections 10 and 12. The bars 26 and 28 are
tied to the aforementioned collars 30, 32, and 34, 36, as well
as the other collars not shown, in the conventional manner of
attaching such reinforcing elements, with the diameter of the
collars in the tapered section 12 decreasing from the portion
of section 12 adjacent section 10 toward the tip 18 of section
12 so as to create a continuous tapering or linear slope, to
the core formed by frame 24. Each of the sections 10 and 12
also includes a respective body 38, 40 in the form of a solid
mass constructed from a cementitlous material cast about the
associated frame 22, 24. Each respective body 38, 40 embeds
the core formed by the assoclated frame 22, 24 and rotates
with the core during installation of the pile. In other words,
the frame 22, 24 and body 38, 40 of the sections 10, 12, co-
operate to form an integral unit. Each body 38, 40 also has an
outer surface provided with screw-threads 42, 44 along the
entire length of each sectlon 10, 12. ~hese threads 42, 44
facilitate insertion of the pile in earth (not shown) by
rotation of head 16.
Head 16 may be connected to the frame 12 of section 10
in a manner as shown in Figures 9 and 10, the connection being
sufficient to develop torsional stresses from head 116 to
frame 22.
In additio~ to the cen~ral frame 22 extending along
the longitudinal axis of the core of the associated sections 10,
12, each of the sections 10, ~2 further includes a spiral
reinforcing element 46, 48 having a pitch similar to the pitch
of the associated screw-threads 42, 44 and disposed winding
around the respective frames 22, 24 ln spaced relationship
- 14 -
~119823
therewith. Tie bars 50, 52 connect the elements 46, 48 to the
frame 22, 24 such that the entire set of reinforcing elements
are connected together, but the spacing of the element 46, 48
from the associated frame 22, 24 permits the element 46, 48 to
be dlsposed at the base of, or even within, the associated
thread 42, 46 for reinforcing the thread 42, 44 even when the
same is very deep in configuration.
While the number of threads 42, 44 per foot of axial
length of sections 10, 12 can vary in accordance with particu-
lar conditions expected to be encountered, in general thenumber of threads for a class 9 residential piling with an 8"
butt and a 5" tip should be at least 6 to the foot, with 1-3/4"
depth per thread, along the longitudinal extent of the cores
of the sections 10, 12 in order to achieve the desired effi-
ciency of insertion of the resulting plle into the ground which
is to anchor the pile.
Section 12 is provided with a projection 54, while
section 10 is provided with a recess 56 having a bottom surface
and arranged for receiving the projection 54. As can be
readily seen from Figure 2, projection 54 is capped with a steel
: plate 58, and the like, whlle the recess 56, including the
bottom surface thereof, is entirely defined by cooperating steel
plates such that the bottom surface of the recess 56 and the
top of projection 54 will be steel plated in order to permit
the pile to be driven into the ground as opposed to being screw-
ed therein. A socket 60, which may also be formed from a steel
casing, and the like, is provided extendlng inwardly of section
10 along the axial extent thereof from the bottom surface of
recess 56, while a mating socket 62 is provided in projection 56,
so as to communicate with an openlng suitably provided in the
plate 58. In the sockets 60 and 62 is inserted a connecting
key 64 which cooperates with the projection 54 in mating
- 15 -
111~8~23
recess 56 to cause the sections 10 and 12 to resist torque and
rotate to one another even when the sect~ons are being rotated
into the ground. It will be appreciated that suitable rein-
forcing members connect the recess 56, and its associated
socket 60, as well as the socket 62 to the remainder of the
integral reinforcing elemen~ network of the respective sections
10 and 12.
It should be appreciated that the welding or like
attachment of reinforcement members 30, 32 to recess 56 and
the simllar connection of reinforcement members 34, 36, to
socket 62 provides integral connections which will develop the
torsional stresses created at the ~oint into the reinforcing
steel and throughout the pile. Thus, no failure of the con-
crete will result at the connection because of the application
of torsional or tensile stresses applied directly to the con-
crete.
Note in Figure 2 that threads 42, 44 "feather" at the
end portions of sections 38, 40 near the joint. ~ith such a
"feathering" structure, a continuous, even pitch thread 42, 44
will be maintained.
` Referring now more particularly to Figures 4 and 5 of
the drawings, sections 66 and 68 are illustrated which are
similar to sections 10 and 12, except that the projection 54
and recess 56 are omitted. Rather, these sections 66 and 68
are provided with respective socket 70 and 72 fashioned and
arranged in a manner similar to the sockets 60 and 62 and
having associated therewith plates 74 and 76 across the abut-
ting surfaces of the sections 56 and 68. These plates 74 and
76 serve a similar purpose as the bottom surface of recess 56
and the plate 58 of the sections 10 and 12. Otherwise, sec-
tions 16 and 68 are constructed in essentially the same manner
as sections 10 and 12.
- 16 -
. ~
It should be understood that the reinforcement shown
in Figure 5 is integrally connected to the socket 70 by welding
or the like so that torsional stress is applied to socket 70
through the connection will be transmitted to the reinforcing
~rame provided in the pile. In each of the embodiments of the
connections shown, the corresponding recesses and projections
are provided with steel plates which transmit torsional stresses
directly to reinforcement which is in each case integrally
welded to or a similar connection formed with the reinforcing
steel. Thus, a development o~ torsional stresses is seen
through the steel, that is the steel in the connection and the
reinforcing steel in the concrete. No torsional or tensile
stresses needs be carried by the concrete.
Figure 6 shows another embodiment of the present
invention wherein the connector arrangement includes a plurality
of sets of sockets and keys. More specifically, a section 78
is illustrated which is provided with three sockets 80 equally
spaced on a substantially planar end face 82 of the section.
This face 82 may constitute a plate similar to plates 74 and 76,
while it will be understood that a key, such as key 64, may be
inserted in each of the sockets 80 and into some cooperating
sockets which will be opposed to the sockets 80 in a section
(not illustrated) having an end surface essentially the same as
face 82 of section 78.
The cross-sectional shape of the key employed with a
connector arrangement according to the invention can assume
different shapes from the square section of key 64, such as
the round section of key 84 which may be formed from a rod 86
provided with a plurality of longitudinally, or axially extend-
ing splines 88. It will be appreciated that the sockets asso-
ciated with key 84 must be suitably configured in order to
receive the splines 88.
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lil98~3
PILE OPERATION - SOIL MECHANICS
Figures 13-15 illustrates schematically the operation
of the pile 10 of the present invention.
In Figure 13, there is a schematic illustration of the
tip portion 18 of pile 10 showing forces acting upon the tip 18
and the proximatel threads 24 while the pile is being driven
into the earth. Note force arrows 18a, which indicate upward
pressure bearing on the tip 18 as lt is descending into the
soil. During this lnsertion, the upper surface of each thread
24 will be pushing upwardly on the soil which contacts it on
the upper surface. Note force arrows 13 which schematically
illustrate this downwardly directed force of soil against thread
24. Thus, when the pile 10 is going down into the soil, there
is an upward and generally outward force on the soil by the
upper edge of the nearly flat projecting thread face 24b.
Figure 15 further illustrates this force which is
downwardly bearing on the upper face 24b of thread 24. Note
in Figure 15, a plurality of force arrows 15. These force
arrows 15 are generally inward and upwardly bearing against the
bottom face 24a of each thread 24. These force arrows ill-
ustrate the bearing of proximately located soil against the
lowermost face 24a of each thread when the pile is taking the
required dead and live loads of the building or like structure
which may be erected at the surface of the soil which structure
is being supported by pile 10, at least in part. When the pile
10 is taking this required dead and live load, the load on the
soil is downward and thrusting out, with the load being trans-
mitted through the lower face 24a of thread 24. Force arrow 15
indicate the force which opposes and supports pile 10 by the
soil which bears against the face 24a thus supporting the pile.
As can be seen and as has been more fully discussed
above, the thread vertical spacing is constant. This vertical
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823
spacing is illustrated by the arrow indicated by P in Figure 15.Th]ead spacing P is constant, so that there will be no distur-
bance of the female thread socket which is created by the
threads 24 as the pile is inserted into the soil by rotational
force. Thus, each point on the outer periphery of the thread
will pass through the same path and contact substantially the
same soil as the thread before it. This mechanical action is
highly desirable, and compacts the soil adjacent the pile as
it is threaded into the soil. It should be appreciated, that
the pile has a taper, and each successive thread pushes the
soil further from the pile, as the pile is driven down, since
the "thickening" pile as a whole occupies more and more space
at any given depth as the pile is driven further down. This
thickening of the pile is seen in Figure 14, where a single
thread 24 is seen moving from a first position 25 to a second
position 27. In Figure 14, the distance of lateral movement
outwardly of the thread and thus the lateral pushing of the
soil is indicated by the letter L. The substantially vertical
lines 25, 27 are adjacent the base of thread 24 when it moves
from a first position 25 to a second position 27. The force
arrows 24c illustrate the bearing force of the thread 24 against
the soil, which force gradually outwardly compacts the soil
adjacent the thread.
This overall operation of outward movement of the
thread can be, for example, on the order of about one and one
half inches. This outward movement would be of course the
difference in diameter of the pile measured from the center of
the~pile to the tip of the thread at any given point as con-
trasted with the diameter of the plle measured from the center
to the tip of the thread member 24 adjacent tip 18. In a ten
foot pile, it will be appreciated that the outward movement of
the thread of one and one half inches takes place in the ten
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823
feet of pile penetration, or in about eighty feet of overall
thread passage. Thus, a gradual thickening and compacting of
the adjacent soil is seen by the tapered pile of the present
invention a~ it is gradually inserted into the soil. An im-
proved soil condition is seen adjacent the pile once it is in
place. The screw-threaded pile 10 has gradually compacted the
soil adjacent the pile as it is being threadably driven into
the soil. The volume of soil compacted and displaced will be
equal to that of the pile itself. An increased effective pile
diameter is seen as a result of this mechanical action. In
Figure 15, arrow D illustrates the increased effective diameter
of pile 10. The radius of the piling lO shaft 23 is indicated
by arrow S. The thread projection is indicated by arrow T in
Figure 15.
Pile 10 can be constructed of any suitable structural
concrete, such as four thousand pound per square inch reinforced
concrete. Preferably, pea gravel would be used as a suitable
aggregate, because of the smallness of threads 24 in some
residential class piling. The reinforcing steel could be any
suitable structural reinforcing bar such as A36 steel.
As can be readily understood from the above description
and from the drawings, a pile according to the invention pro-
vides a simple and efficient, yet rugged and reliable, manner
of providing a suitable anchor or piling where needed remote
from a manufacturing facility, and even in crowded conditions
where heavy machinery cannot be taken.
In the method of driving pile of the present invention,
it is important to utilize a plle of constant thread pitch.
This will prevent cross-threading which destroys the desirable
interface created between the pile and the surrounding soil.
Preliminary tests have indicated that an area spread of at
least one and one half times the original area of the threaded
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pile diameter is achieved ~hen the pile structure 10 of thepresent invention i5 properly installed. It is desirable to
provide a pile having a pltch of about six or more threads per
foot. Thi~ desirable pitch of threads per foot is necessary
in order that compatibility with differing soils be achieved.
It is desirable that the piling be threadably inserted into
the soll so that the soil is merely displaced and compacted
forming a "soil-soc~et" which forms a female thread in fact
for the pile itself as it is inserted. The tip of the pile
can be provided with driving and cutting force if necessary.
In fact, a jetting type arrangement can be provided at the tip
in order to facilitate driving. Further, there can be provided
the addition of water or other suitable lubricant to the pile's
surface as it is inserted into the ground. Such a lubricant
can be added to the soil socket into which the pile is thread-
ably rotated, which socket iR in fact created as the pile is
driven. By pouring water on the threads of the pile as it
enters the ground, a lubrication of the pile will be seen which
will lessen the friction of the thread surfaces 24a, 24b with
the surrounding soil.
When using a ~ointed pile, only the first section need
be tapered, since the thread socket will have been properly
formed once the largest thread diameter of the uppermost end
of pile section 12 (see ~igure 1) passes into the soil. There-
after, as many sectional constant diameter piles 10 as is
desirable can be added to the original pile or piles as is
desired. Each additional pile section 10 would of course be
provided with feathering at the junction which will connect
with the previous installed pil~. Thus, once the pile connec-
tion is perfected as is illustrated by Figures 2 and 5 forexample, a constant pitch smooth thread will be seen.
The means for applyln~ torsion to the pile at its
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l~l9~Z3
uppermost point can be any suitable tor~ional force. Thus, for
example, a leverage bar can be inserted into opening 12~ and the
lever pushed on by a suitable force. In such a case, the pile
could be hand-installed by manual labour. A low horsepower
motor supplied with proper gearing could be utilized to provide
such a torsional force. Additionally, a rope could be wrapped
around the upper surface of the pile and pulled on to apply the
necessary force in instances where a great deal of force was
not required.
A pile according to the invention can be manufactured
in any size or length, although ~iling in a length of 10 feet
to 12 feet has been found suitable. The use of the tapered
body of the pile and the provision of screw-threads along the
entire length of the body provides a pile which has a fri~tion
capability of a conventional wood pile twice the length of
the pile according to the present invention. Further, a pile
according to the invention can be screwed into earth without
a pilot hole under aertain soil conditions, with only a steel
leverage bar and capable personnel.
The foregoing is considered as illustrative only of
the principles of the invention. Further, since numerous modi-
fications and changes will readily occur to those skilled in
the art, it is not desired to limit the invention to the exact
construction and operation shown and described, and accordingly
all suitable modifications and equivalents may be resorted to,
- falling within the scope of the invention.
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