GB1595432A

GB1595432A - Precast concrete piling

Info

Publication number: GB1595432A
Application number: GB45629/77A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1976-11-02
Filing date: 1977-11-02
Publication date: 1981-08-12
Also published as: MX146733A; DE2749039A1; AU511414B2; ES464036A1; NL7712013A; CA1119823A; AU3023877A

Description

(54) PRECAST CONCRETE PILING (71) I, WILLIAM FRANCIS GILLEN, of 6518 Lamb Road, New Orleans Louisiana 70126, United States of America, a citizen of the United States of America, do hereby declare the invention, for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates generally to piles, and particularly to precast reinforced concrete screw-threaded piles. This invention particularly relates to concrete piling constructed in sections to permit variations in the length of the piles.

My Co-pending application No. 80-21498 (Serial No. 1595433) also relates to such concrete piling but is directed to unitary piles of predetermined fixed length.

In many areas soft and marshy soils and lands exist in which areas it is necessary to employ piles to provide a proper foundation for buildings and similar structures. Most commonly employed for residential and light commercial construction 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, property owners have been unable to undertake desired construction. Typically such soil conditions occur in many parts of the State of Lousiana.

A problem encountered with the use of precast concrete 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 construct such precast piling in a great variety of lengths 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 adquate strength at the threaded peripheral portions of the piles. This problem becomes more acute the deeper and closer together are the threads of the piles.

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 installer's hands, to have the screw-threads of the piles as deep and as close together as possible. The problem arises, however, of providing suitable reinforcement for such deep and closely 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 strength, 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.

The present invention seeks to provide a screw-threaded pile which is easier to insert and affords more effective frictional gripping surface than prior screw-threaded pile.

The present invention also seeks to provide a pile which can be installed by hand where suitable machinery is unavailable or inaccessible and which avoids problems of erosion of the pile by electrolysis and similar electrochemical and chemical reactions.

The present invention is particularly concerned 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, while also providing an efficient and simple, yet rugged and reliable, connecting arrangement' for attaching together sections of a precast concrete screw-threaded pile.

According to the invention there is provided an extendible reinforced concrete pile system comprising: (a) at least two screw-threaded pile sections placeable and connectable in line to gether, each of said pile sections being substantially threaded along its entire length with threads of at least substantially the same pitch as that of the adjacent section; (b) a reinforcement core provided in each pile section, each of said cores comprising at least one longitudinally extending reinforcement bar and at least one laterally extending member. each of said members being integrally connected to said longitudinal bar; (c) a cementation body cast about said core, said body having an outer surface provided with a screw-thread extending along the entire length thereof; and (d) connector means associated with said pair of pile sections for attaching said pile sections together for rotation with one another. Torsional and tensile stresses are transmitted from the metallic head to the integrally connected reinforcement core, with the tensile and torsional stresses developed throughout the pile, thereby preventing failure of the concrete.

The body advantageously is constructed 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.

In a 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.

The upper head portion of each pile section may be constructed in any one of several preferred ways, among which are the use of a solid, preferably metallic cast head, the use of a metal sleeve affixed directly to the reinforcing bars of the core, and the extension of the reinforcing bars to form a framework about which a metallic or cementitous head may be formed. Advantageously, but not necessarily, the head is in the form of a hexagon, similar to a conventional 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 desirable 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.

The connector means may be in the form of a socket in one section into which a correspondingly shaped projection on the meeting end of another section is received, or they may take the form of 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 arrangement 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. But this arrangement, the amount of torque which can be exerted on the pile is greatly increased.

As mentioned above, 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 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 reinforcing element pitched to the pitch of the screw-threads of the section and disposed helically 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.

Embodiments of the invention will now be described by way of example and with reference to the accompanying drawings, in which: Figure 1 is an exploded, perspective view showing a first embodiment of a pile formed by inter-connectable sections; 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 plan view of the top of a bottom section of a pile constructed accord ing to a second embodiment of the present invention; Figure 5 is an enlarged, fragmentary, sectional view taken along the line 5 5 of Figure 4; Figure 6 is a plan view of the top of a bottom section of a third embodiment of a pile;; Figure 7 is a perspective view showing a modified connector key for use with any of the above embodiments; Figure 8 is a partial schematic view of the lowermost tip portion of a preferred embodiment of the present invention illustrating the forces experienced by the tip during insertion of the pile; Figure 9 is a partial schematic view of a thread portion of the preferred embodiment of the present invention illustrating the compressive lateral movement of a single thread against the "soil-socket" during insertion of the pile; and Figure 10 is a partial schematic view of a plurality of threads on a portion of the preferred embodiment of the present invention.

Referring now more particularly to Figures 1 to 3 of the drawings, a first embodiment of an extendible pile according to the present invention is shown as including a cylindrical head section 10 and a substantially conical or tapered tip section 12 attached together for rotation with one another by a connector arrangement 14. While only a pair of sections 10 and 12 have been shown, it will be appreciated that additional cylindrical 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 by itself as a pile, if desired, by attaching a suitable turning handle or device, neither or 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 region 18 disposed at the lower portion of the tapered tip section 12. This tip 18 may take the form of a cutter 20 (Figure 1) if desired, although a conventional point or dome shape (Figure 8) may also be used. Each of the sections 10 and 12 also includes an internal frame 22, 24, respectively, formed of longitudinally extending reinforcing 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 longitudinal 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 sections 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 cementitious material cast about the associated frame 22, 24.

Each respective body 38, 40 embeds the core formed by the associated 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 screwthreads 42, 44 along the entire length of each section 10, 12. These 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 26 of section 10 in any suitable manner sufficient to transmit torsional stresses from head 16 to frame 22.

In addition to the central frame 22 extending along the longitudinal axis of the core of the associated sections 10, 12 each of the sections 10, 12 further includes a spiral reinforcing element 46, 48 having a pitch similar to the pitch of the associated screwthreads 42, 44 and disposed helically around the respective frames 22, 24 in radially spaced relationship 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 elements 46 and 48 from the associated frames 22 and 24 permits the elements 46, 48 to be disposed at the base of, or even within, the associated thread 42 or 46 for reinforcing the threads 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 particular conditions expected to be encountered, in general the number 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 efficiency of insertion of the resulting pile into the ground which is to anchor the pile.

To connect the parts of the piling 10 and 12 together, the part 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 while the recess 56, including the bottom surface thereof' is entirely defined by co-operating 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 by being screwed therein.A socket 60. which may also be formed from a steel casing is provided extending inwardly of section 10 along the axial extent thereof from the inner end surface of recess 56, while a mating socket 62 is provided in projection 54, so as to communicate with an opening 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 recess 56 to cause the sections 10 and 12 to resist torque and rotate with one another even when the sections are being rotated and driven into the ground. It will be appreciated that suitable reinforcing members connect the recess 56, and its associated socket 60, as well as the socket 62 to the remainder of the integral reinforcing element 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 similar connection of reinforcement members 34, 36, to socket 62 provides integral connections which will develop the torsional stresses created at the joint into the reinforcing steel and throughout the pile. Thus, no failure of the concrete will result at the connection because of the application of torsional or tensile stresses applied directly to the concrete.

Note in Figure 2 that threads 42, 44 "feather" at the end portions of sections 38, 40 near the joint. With 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 sockets 70 and 72 fashioned and arranged in a manner similar to the sockets 60 and 62 and having associated therewith facing plates 74 and 76 across the abutting surfaces of the sections 56 and 68. These facing 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, sections 16 and 68 are constructed in essentially the same manner as sections 10 and 12.

It should be understood that the reinforcement shown in Figure 5 is integrally connected to the socket 70 such as by welding so that torsional stress applied to socket 70 through the connection means will be transmitted to the reinforcing frame 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 the reinforcement which is in each case integrally welded to or a similar connection formed with the reinforcing steel. Thus, a development of 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 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 extending splines 88. It will be appreciated that the sockets associated with key 84 must be suitably configured in order to receive the splines 88.

Figures 8 to 10 illustrate schematically the operation of the pile 10 of the present invention.

In Figure 8, there is a schematic illustration of the tip portion 18 of pile 12 showing forces acting upon the tip 18 and the proximate threads 24 while the pile is being driven into the earth. The force arrows 1 8a indicate upward pressure bearing on the tip 18 as it is descending into the soil. During this insertion, the upper surface of each thread 24 will be pushing upwardly on the soil which contacts it. Force arrows 13 which schematically illustrate this downwardly directed force of the 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 8 further illustrates this force which is downwardly bearing on the upper face 24b of thread 24. Note in Figure 8, 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. The se force arrows illustrate the bearing of the 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 transmitted through the lower face 24a of thread 24.Force arrows 15 indicate the force which opposes and supports pile 10 by the soil which bears against this face 24a thus supporting the pile.

As can be seen and has been more fully discussed above, the thread vertical spacing or pitch is constant. This vertical spacing or pitch is illustrated by the arrow indicated by P in Figure 15. Thread spacing P is constant, so that there will be no disturbance of the female thread socket which is created by the threads 24 as the pile is inserted progressively 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 desireable, and compacts the soil adjacent the pile as it is threaded into the soil.It should be appreciated, that because the final pile section has a taper, and each successive thread pushes the soil further outwardly 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 9, where a single thread 24 is seen moving from a firts position 25 to a second position 27. In Figure 9, 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 centre of the pile to the tip of the thread at any given point as contrasted with the diameter of the pile measured from the centre 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 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 as it is gradually inserted intol the soil. An improved soil condition is seen adjacent to 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 10, arrow D illustrates the increased effective diameter of pile 10. The radius of the piling shaft 23 is indicated by arrow S.

The thread projection is indicated by arrow T in Figure 10.

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 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 provides 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 utilise a pile 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 pile diameter is achieved when the pile structure 10 of the present invention is properly installed. It is desirable to provide a pile having a pitch of about six or more threads per foot. This 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 soil so that the soil is merely. displaced and compacted forming a "soil-socket" which forms a female thread in face for the pile itself as it is inserted.The tip of the pile can be provided with driving and cutting force if necessary. In face, 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 threadably rotated, which socket is 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 jointed 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 Figure 1) passes into the soil. Thereafter, 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 pile. Thus, once the pile connection is perfected as is illustrated by Figures 2 and 5 for example, a constant pitch smooth thread will be seen.

The means for applying torsion to the pile at its uppermost point can be any suitable torsional force. Thus, for example, a leverage bar can be inserted into a transverse opening in the head 16 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 utilised 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.

An individual pile section can be manufactured in accordance with the invention to any size or length, although a piling 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 friction 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 certain soil conditions, with only a steel leverage bar and capable personnel.

WHAT I CLAIM IS: 1. An extendible reinforced concrete pile system comprising: (a) at least two screw-threaded pile sections placeable and connectable in line together, each of said pile sections being substantially threaded along its entire length with threads of at least substantially the same pitch as that of the adjacent section; (b) a reinforcement core provided in each pile section, each of said cores comprising at least one longitudinally extending reinforcement bar and at least one laterally extending member, each of said members being integrally connected to said longitudinal bar; (c) a cementitious body cast about said core, said body having an outer surface provided with a screw-thread extending along the entire length thereof' and (d) connector means associated with said pair of pile sections for attaching said pile sections together for rotation with one another.

2. A system according to claim I, wherein at least one of said sections tapers from the end by which it is connected to the adjoining section towards its other end.

3. A system according to claim 1 or claim 2 wherein at least six of said threads are provided for each foot of pile length.

4. A system according to any one of claims 1 to 3 wherein the core comprises a plurality of longitudinally extending reinforcement bars extending substantially along the full length of each pile section, a plurality of longitudinally spaced reinforcing collars each of which is integrally connected to the longitudinally extending reinforcing bars and at least one helical reinforcing element having a pitch at least substantially equal to the pitch of the external screw thread and embedded in said cementitious body.

5. A system according to any one of claims 1 to 4 wherein the or each reinforcing bar extends substantially parallel with the exterior of the respective pile section.

6. A system according to any one of claims 1 to 5 wherein said connector means are metallic, and the reinforcing bar or bars and said connector means are integrally attached together within each of the pile sections.

7. A system according to any one of claims 1 to 5 wherein said connector means comprises a socket on one of said pile sections and a corresponding interlocking projection on the other of said pile section, said socket and said projection each being provided with a proximate metallic reinforcing member, said reinforcing member being connected to said core.

8. A system according to any one of claims 1 to 6 wherein said connector means is comprised of a socket on each of said pile sections and an interlocking structural key, said key having projections for attaching said key to each of said sockets to form a connection, and each of said sockets is provided with a proximate metallic reinforcing member, said reinforcing member being connected to said core.

9. A system according to any one of claims 1 to 8 wherein the end portion of each section adjacent said connection means is provided with feathered thread portions such that the connection of said sections provides a uniform, equally spaced continuous thread pitch throughout the region of the pile section adjacent said connection means.

10. A system according to claim 8 wherein the key is a length of rod provided with a plurality of splines.

I I. A system according to any one of claims 8 to 10, wherein said connector means includes a plurality of opposed sockets provided in each of the sections and arranged for receiving a like numbers of keys associated with the sockets.

12. An extendible reinforced concrete

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. the largest thread diameter of the uppermost end of pile section 12 (see Figure 1) passes into the soil. Thereafter, 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 pile. Thus, once the pile connection is perfected as is illustrated by Figures 2 and 5 for example, a constant pitch smooth thread will be seen. The means for applying torsion to the pile at its uppermost point can be any suitable torsional force. Thus, for example, a leverage bar can be inserted into a transverse opening in the head 16 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 utilised 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. An individual pile section can be manufactured in accordance with the invention to any size or length, although a piling 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 friction 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 certain soil conditions, with only a steel leverage bar and capable personnel. WHAT I CLAIM IS:

1. An extendible reinforced concrete pile system comprising: (a) at least two screw-threaded pile sections placeable and connectable in line together, each of said pile sections being substantially threaded along its entire length with threads of at least substantially the same pitch as that of the adjacent section; (b) a reinforcement core provided in each pile section, each of said cores comprising at least one longitudinally extending reinforcement bar and at least one laterally extending member, each of said members being integrally connected to said longitudinal bar; (c) a cementitious body cast about said core, said body having an outer surface provided with a screw-thread extending along the entire length thereof' and (d) connector means associated with said pair of pile sections for attaching said pile sections together for rotation with one another.

12. An extendible reinforced concrete

pile system substantially as hereinbefore described with reference to the accompanying drawings.