GB1595433A - Precast concrete piling - Google Patents

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; made in the form of single units. My Co-pending Application No. 45629/77 (Serial No 1595432) also relates to concrete piles and especially concerning such concrete piling constructed in interconnecting sections to permit variations in the length of the piles.

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 Louisiana.

A problem encountered with the use of precast concrete screw-threaded piling is encountered during handling of the piling between the manufacturing flexibility 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.

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 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 to provide a pile which avoids problems of erosion of the pile by electrolysis and similar electrochemical and chemical reactions.

According to the present invention there is provided a threaded concrete pile, comprising: a) a metallic upper head portion providing a connection for the application of rotational driving force thereto; b) a longitudinally extending metallic reinforcement core integrally connected to said upper portion; and c) a generally conically shaped cementitious body cast about said core, said body having an outer surface provided with substantially equally spaced spiral screw threads along the entire length thereof.

The metallic head is capable of being rotated by suitable machine-powered or manual driving tools; the metallic reinforcement core is directly 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 the body is preferably in the form of a solid mass of concrete disposed so as to embed the core and to be rotatable therewith. Preferably the body tapers from the head to the tip of the core, the equally spaced screw-threads along the entire length between the head and the tip facilitating insertion of the pile in earth by rotation of the head. 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 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 consists of a single longitudinally extending reinforcing bar having tied thereto at least one, and preferably several, cross-bars extending transversely of the longitudinal single bar.

The upper head portion 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 cementitious 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 transverse bores holes may be provided in the head 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.

Embodiments of the invention will now be described by way of example and with reference to the accompanying drawings, in which: Figure 1 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 2 is a fragmentary, enlarged, sectional view taken generally along the line 9-9 of Figure 1; Figure 3 is a fragmentary, sectional view, similar to Figure 2, but showing a modified embodiment of a head for a pile according to the invention; Figure 4 is a perspective view showing one embodiment of a core for a pile according to the present invention Figure 5 is a perspective view, partly cut away and in section, showing yet another embodiment of a pile according to the present invention;; Figure 6 is a partial schematic view of the lowermost tip portion of the pile illustrating the forces experienced by the tip during the insertion of the pile; Figure 7 is a partial schematic view of a thread portion illustrating the compressive lateral movement of a single thread against the "soil-socket" during insertion of the pile; and, Figure 8 is a partial schematic view of a plurality of threads.

Referring now to Figures 1 and 2 of 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 conventional driving socket tool (not shown), or the like, in order to rotate the head 112 when pile 110 is being installed.

The lower portion of head 112 terminates in a flared skirt 114 which comes down over the main portion of the pile 10 so as to form a transition. A core 116 (Figure 2) is connected to head 112 in a suitable manner for rotation with the head 112, and has a longitudinal axis extending from the head 112 to the tip 118 of the pile 110, about which axis core 116 is rotated by torque applied to the head 112.

A body 120 in the form of a solid mass constructed from a cementitious material cast about the core 116 is disposed so as to embed the core 116 and to rotate with the core 116 during installation of pile 110. In 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 the core 116 from head 112 to tip 118, and is provided with external spiral screw threads 124 along the entire length of body 120 for facilitating insertion of the pile 110 in earth (not shown) by rotation of head 112.

The threads 124 will preferably be supplied at a minimum thread pitch, or a minimum number of threads per foot which would be sufficient to give a 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 6, 7 and 8).

This in combination with the appropriate reinforcing cage 136 shown in Figure 4 and the appropriate attachment of the reinforcing cage 136 to the head which is provided for application of a torsional force will achieve the desired result.

Head 112 is provided with a transverse through bore 26 arranged for receiving a driving rod or leverage bar (not 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 3 of the drawings, a head is shown similar in configuration to head 112, but constructed as a sleeve 128 made for example of steel having a downwardly depending flared skirt 130 and provided with a transverse bore 132 similar to bore 126 for receiving a leverage bar or rod.

Sleeve 128, possible at the skirt 130 thereof, is fastened to the reinforcing 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 particular arts, these 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 develop 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 welding 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 reinforced (the reinforcement attached to core 136), would perform as satisfactorily as a metallic head 112 and the term "metallic head" or upper portion is intended to include such equivalent structures.

Figure 4 of the drawings shows one preferred construction of a core for a pile according to the invention, wherein the core is a framework 136 of longitudinally extending reinforcing bars 138 and longitudinally spaced collars 140, 142, 144, 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 continuously tapering, or linear slope, 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 defining a head associated with the core.For example, the portion of framework 136 which extends between collars 140 and 142 may be inserted into the sleeve 128 (Figure 3) 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 5 of the drawing.

Referring now more particularly to Figure 5 of the drawing, a core is shown which includes a single longitudinally extending reinforcing bar 156 having 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 bar 156.

The core 154 is illustrated in Figure 5 as being affixed to a head constructed as a framework forming a generally cylindrical open cage 170 embedded in a mass 172 of a cementitious or other suitable casting material. Provided within this mass 172, and disposed transversely to the longitudinal axis of bar 156, is at least one hole disposed for receiving a leverage bar (not shown). In Figure 5 a pair of such cross-holes of 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 as 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 only partial turns, as for an installation of a pile next to a building or other object where a 360 turn is impossible.

Figures 6 to 8 illustrates schematically the operation of the pile 10 of the present invention.

In Figure 6, there is a schematic illustration of the tip portion 18 of pile 10 showing forces acting upon the tip 18 and the proximate threads 24 while the pile is being driven into the earth. The force arrows 18a 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 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. These 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 as 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 desirable, and compacts the soil adjacent the pile as it is threaded into the soil.It should be appreciated, that because the pile has a taper, 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 furtherdown. This thickening of the pile is seen in Figure 7, where a single thread 24 is seen moving from a first position 25 to a second position 27. In figure 7, 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 into the soil. An improved 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. As increased effective pile diameter is seen as a result of this mechanical action. In Figure 8, 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 8.

Pile 10 can be constructed of any suitable structural concrete, such as four thousand pounds 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 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 fact for the pile itself as it is inserted.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 result which will lessen the friction of the thread surfaces 24a, 24b with the surrounding soil.

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 opening 26 and the lever pushed or pulled 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.

A pile according to the invention can be manufactured in any size or length, although 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 screwthreads 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. A screw-threaded concrete pile, comprising: a) a metallic upper head portion providing a connection for the application of rotational driving force thereto; b) a longitudinally extending metallic reinforcement core integrally connected to said upper portion; and c) a generally conically shaped cementitious body cast about said core, said body having an outer surface provided with substantially equally spaced spiral screw threads along the entire length thereof.

2. A concrete pile according to claim 1, wherein said core comprises a plurality of longitudinally extending, reinforcing bars, each integrally connected to said upper head portion and extending down substantially the full length of said body and a plurality of longitudinally spaced reinforcing collars, each of said collars being integrally connected to said longitudinally extending reinforcing bars.

3. A concrete pile according to claim 2, wherein said collars decrease in diameter from the top of the tip of said pile.

4. A concrete pile according to claim 1, wherein said core comprises a longitudinally extended bar extending down the centre of the pile substantially the full length of said body and a plurality of longitudinally spaced, laterally extending arms attached to said bar.

5. A concrete pile according to any one of claims 1 to 4, wherein said upper head portion has a substantially hexagonal shape.

6. A concrete pile according to any one of claims 1 to 5 wherein the head is constructed as a piece of solid material.

7. A concrete pile according to any one of claims 1 to 5 wherein the head is constructed as metal sleeve connected to the core.

8. A concrete pile according to any one of claims 1 to 5, wherein the head is constructed as a framework connected to the core and embedded in a solid mass.

9. A concrete pile according to any one of the preceding claims wherein said upper head portion is provided with a transverse through-hole adapted to receive means to impart rotational torque to the head.

10. A screw-threaded concrete pile according to claim 1 and substantially as hereinbefore described with reference to the accompanying drawings.

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

Claims (10)

**WARNING** start of CLMS field may overlap end of DESC **. 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 fact for the pile itself as it is inserted. 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 result which will lessen the friction of the thread surfaces 24a, 24b with the surrounding soil. 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 opening 26 and the lever pushed or pulled 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. A pile according to the invention can be manufactured in any size or length, although 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 screwthreads 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. A screw-threaded concrete pile, comprising: a) a metallic upper head portion providing a connection for the application of rotational driving force thereto; b) a longitudinally extending metallic reinforcement core integrally connected to said upper portion; and c) a generally conically shaped cementitious body cast about said core, said body having an outer surface provided with substantially equally spaced spiral screw threads along the entire length thereof.

2. A concrete pile according to claim 1, wherein said core comprises a plurality of longitudinally extending, reinforcing bars, each integrally connected to said upper head portion and extending down substantially the full length of said body and a plurality of longitudinally spaced reinforcing collars, each of said collars being integrally connected to said longitudinally extending reinforcing bars.

3. A concrete pile according to claim 2, wherein said collars decrease in diameter from the top of the tip of said pile.

4. A concrete pile according to claim 1, wherein said core comprises a longitudinally extended bar extending down the centre of the pile substantially the full length of said body and a plurality of longitudinally spaced, laterally extending arms attached to said bar.

5. A concrete pile according to any one of claims 1 to 4, wherein said upper head portion has a substantially hexagonal shape.

6. A concrete pile according to any one of claims 1 to 5 wherein the head is constructed as a piece of solid material.

7. A concrete pile according to any one of claims 1 to 5 wherein the head is constructed as metal sleeve connected to the core.

8. A concrete pile according to any one of claims 1 to 5, wherein the head is constructed as a framework connected to the core and embedded in a solid mass.

9. A concrete pile according to any one of the preceding claims wherein said upper head portion is provided with a transverse through-hole adapted to receive means to impart rotational torque to the head.

10. A screw-threaded concrete pile according to claim 1 and substantially as hereinbefore described with reference to the accompanying drawings.