Coupling for driven steel pipe piles and method of manufacturing same

Abstract

A coupling between lead and extension pile segments of a driven piling. The extension segment has a formed end, an opposite driven end and a body extending therebetween. The formed end has an inner diameter equal to an outer diameter of an exposed end of the lead segment and greater than an outer diameter of the extension segment's body. The formed end has an initial length prior to coupling the extension and lead segments; the formed end undergoes secondary end forming when a driving force is applied, such that the formed end has a final length exceeding the initial length after the extension and lead segments are coupled. In some embodiments, the extension segment has an external ring portion positioned upstream of the formed end, and the exposed end of the lead segment is cold extruded into and through the external ring portion of the extension segment.

Claims

1. A coupling between a lead pile segment and an extension pile segment of a driven piling, the coupling comprising: the lead pile segment; the extension pile segment having a formed end, an opposite driven end opposite of the formed end, and a body extending therebetween, the formed end having an inner diameter that is equal to or greater than an outer diameter of an exposed end of the lead pile segment and is greater than an outer diameter of the body of the extension pile segment; an external ring having an inner diameter sized to snugly fit over the outer diameter of the body of the extension pile segment, the external ring affixed to an exterior surface of the body of the extension pile segment and positioned upstream of the formed end; the coupling formed by inserting the exposed end of the lead pile segment into the formed end of the extension pile segment and applying a driving force to the driven end of the extension pile segment such that the formed end of the extension pile segment undergoes secondary end forming thereby increasing an initial length of the formed end prior to coupling the extension pile segment with the lead pile segment to a final length of the formed end after the driving force is applied to the driven end to couple the extension pile segment to the lead pile segment; and wherein the exposed end of the lead pile segment is cold extruded into and through a portion of the extension pile segment adjacent to the external ring to further increase a force resistance of the coupling.

2. The coupling of claim 1, wherein the initial length of the formed end is in the range of six inches to twelve inches.

3. The coupling of claim 1, wherein the external ring has a ring length in the range of three inches to six inches.

4. The coupling of claim 1, wherein the external ring is adjacent to and abuts against the formed end of the extension pile segment.

5. The coupling of claim 1, wherein prior to coupling the extension pile segment with the lead pile segment, the external ring is spaced apart from, and upstream of, the formed end of the extension pile segment at a selected distance, and wherein when the driving force is applied to the driven end of the extension pile segment, the final length of the formed end that results from the secondary end forming process is equal to a sum of the initial length of the formed end and the selected distance between the formed end and the external ring.

6. A method of manufacturing the extension pile segment of claim 1, the method comprising: selecting a structural pipe having a cylindrical body and an outer diameter, placing the structural pipe in an end forming machine, the end forming machine having a cylindrical mandrel with an outer diameter that is greater than the outer diameter of the cylindrical body, performing an end forming procedure on a first end of the structural pipe to obtain the formed end, the formed end having a selected length, affixing the external ring to the exterior surface of the cylindrical body.

7. The method of claim 6, wherein affixing the external ring is selected from a group consisting of: welding the external ring, and fastening the external ring with a plurality of fasteners.

8. The method of claim 6, wherein the external ring is positioned to abut against the formed end.

9. The method of claim 6, wherein the external ring is positioned spaced apart from, and upstream of, the formed end at a selected distance.

10. The method of claim 9, wherein the selected distance is in the range between six and twelve inches.

11. The method of claim 6, wherein the method includes the step of heating the first end of the structural pipe.

12. The coupling of claim 1, wherein the external ring is welded to the exterior surface of the body of the extension pile segment.

13. The coupling of claim 1, wherein the external ring is fastened to the exterior surface of the body of the extension pile segment using a plurality of fasteners.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) FIG. 1A is a profile view of a prior art pile coupling wherein the two pile segments are spliced together using a reinforcing backing ring;

(2) FIG. 1B is a sectional view of a prior art pile coupling comprising a welded fit splice sleeve;

(3) FIG. 1C is a sectional view of a prior art pile coupling comprising a drive fit splice sleeve;

(4) FIG. 2A is a sectional view of an embodiment of a pile coupling, wherein an extension pile segment includes a formed end;

(5) FIG. 2B is a sectional view of the embodiment of a pile coupling illustrated in FIG. 2A, where application of a driving force to the extension pile segment has resulted in secondary end forming of the extension pile segment;

(6) FIG. 3A is a sectional view of a further embodiment of a pile coupling, wherein an extension pile segment includes a formed end and an external ring portion positioned upstream of, and adjacent to, the formed end;

(7) FIG. 3B is a sectional view of the embodiment of a pile coupling illustrated in FIG. 3A, where application of a driving force to the extension pile segment has resulted in extrusion of the lead pile segment through the external ring portion of the extension pile segment.

(8) FIG. 4A is a sectional view of a further embodiment of a pile coupling, wherein an extension pile segment includes a formed end and an external ring portion positioned upstream of, and spaced apart from, the formed end;

(9) FIG. 4B is a sectional view of the embodiment of a pile coupling illustrated in FIG. 4A, where application of a driving force to the extension pile segment has resulted in secondary end forming of the extension pile segment; and

(10) FIG. 4C is a sectional view of the embodiment of a pile coupling illustrated in FIG. 4A, where further application of a driving force to the extension pile segment has resulted in extrusion of the lead pile segment through the external ring portion of the extension pile segment.

DETAILED DESCRIPTION

(11) As shown in FIGS. 2A and 2B, an embodiment of the pile coupling of the present disclosure comprises an extension pile segment 20 having a formed end 22. The formed end 22 has a widened opening 22a that is preferably sized to snugly fit over the exposed end 32 of the lead pile segment 30 that has already been driven into the ground G, with the exposed end 32 protruding from the ground G. The extension pile segment 20 and the lead pile segment 30 may be constructed of bare pipe or galvanized pipe, with the galvanized pipe having a thick coating on the pipe. The formed end 22 of the extension pile segment as an inner diameter ID2 that is approximately equal to the outer diameter OD5 of the lead pile segment 30 and greater than the inner diameter ID1 of the body 24 of the extension pile 20. The formed end 22 also has an outer diameter OD2. The inner diameter ID2 of formed end 22 is substantially uniform through an initial length L1 of the formed end 22. The formed end 22 smoothly transitions to the cylindrical body 24 of the extension pile segment with a smooth, radiused bend 26. The inner diameter ID5 of the lead pile may be equal to the inner diameter ID1 of the body 24 of the extension pile 20, as shown in FIGS. 2A and 2B. However, the inner diameters ID1, ID5 of the body of the extension pile 20 and the lead pile 30, respectively, are not necessarily equal to one another; for example, in some embodiments, the subsequent extension pile segments 20 may have incrementally decreasing inner diameters ID1 and outer diameters OD1, which may allow for lowering the costs of the materials for the installed piling while providing the required resistance to lateral, tension and compression forces.

(12) When coupling an extension pile segment 20 to a lead pile segment 30 that is already driven into the ground G, the exposed end 32 of the lead pile segment 30 may optionally be trimmed off, to remove any damage to the end 32 that may have been caused by the driving hammer. Then, the formed end 22 is positioned over the exposed end 32 of the lead pile segment using the pile rig, and then a driving force is applied to the opposite, driven end (not shown) of the extension pile segment 20 in direction A. When the driving force is applied in direction A to the extension pile segment 20, the exposed end 32 of the lead pile segment is pushed further into the formed end 22 of the lead pile segment 20, thereby causing further radial deformation of the extension pile segment 20 through secondary end forming as the lead pile end 32 progresses axially into the body of extension pile 20, this process referred to herein as secondary end forming. Secondary end forming, when it occurs, increases the initial length L1 of the formed end 22, for example by a further distance of approximately, but not limited to, a distance of six to twelve inches (15 cm to 30 cm), to arrive at a final length L2 of the formed end 22, as shown in FIG. 2B.

(13) As the driving force A continues to be applied to the driven end of the extension pile segment 20, both the lead and extension pile segments 30, 20 are driven further into the ground G while at the same time providing for tighter coupling of the segments 20, 30 as the exposed end 32 of the lead pile segment 30 moves farther into the extension pile segment 20. Advantageously, in some embodiments by orienting the extension pile segment so that the formed end 22 is at the bottom of the segment and fitted over the exposed end 32 of the lead pile segment, damage to the formed end by the driving hammer of the pile rig may be avoided, which damage may otherwise occur if the extension pile segment were oriented in the opposite direction with the formed end 22 in direct contact with the drive hammer.

(14) The Applicant has found that the secondary end forming process, whereby the initial length L1 of the formed end 22 is increased to reach a final length L2, provides for a stronger coupling with increased frictional resistance to compressive, lateral and tension loads, as compared to other prior art coupling methods. With this increased frictional resistance, the extension pile segment 20 resists being pulled upwardly in direction B, bending laterally, or compressing downwardly in direction A. The Applicant has found that optionally applying a fillet weld 34, at the junction between the lead pile segment 30 and the extension pile segment 20, may provide additionally increased resistance to tension forces applied to the extended pile in direction B. Preferably, the fillet weld 34 (which is only shown on one side of the diagram in FIG. 2A, for clarity) would be applied before driving the extended pile, such that the exposed end 32 is no longer moving further into the extension pile segment 20. Thus, in such embodiments where a fillet weld 34 is applied to the coupling 10, no secondary end forming would occur, and the formed end serves the function of fitting over the exposed end 32 of the lead segment. Although the optional installation method of applying a fillet weld 34 involves field welding, the Applicant finds such field welding is minimal as compared to other coupling methods known in the art. Furthermore, applying fillet weld 34 avoids the cost of requiring a pre-manufactured coupling sleeve added to the pile segments, as is known in the prior art and shown, for example in FIGS. 1B and 1C.

(15) In other embodiments, such as shown in FIGS. 3A to 4C, the extension pile segment 20 further comprises an external ring portion 40. In the illustrated embodiments, the external ring portion 40 comprises a metal ring 42 having an inner diameter ID3 that is approximately equal to an outer diameter OD1 of the body 24 of the extension pile segment 20, and an outer diameter OD3. In other words, in some embodiments the external ring portion 40 comprises a metal ring 42 that is sized to snugly fit over the body 24 of the extension pile segment 20. The outer diameter OD5 of the lead pile segment 30 may also be substantially equal to the outer diameter OD1 of the body 24 of the extension pile segment 20. The metal ring 42, in some embodiments, may be fillet welded to the exterior surface 24a of the body 24, preferably with fillet welds 44 on opposite sides of the metal ring 42.

(16) In the embodiment illustrated in FIGS. 3A and 3B, the external ring portion 40 is positioned upstream of, and adjacent to, the smooth radiused bend 26 of the extension pile segment 20. As shown in FIG. 3A, the ring portion 40 may be positioned adjacent to, so as to abut against, the radiused bend 26 that transitions into the formed end 22. When the formed end 22 is fitted over the exposed end 32 of the lead pile 30, and a driving force is applied in direction A to a driven end (not shown) of the extension pile segment 20, the extension pile segment 20 will travel downwards in direction A and the lead pile segment 30 will at the same time be pushed further inside the formed end 22, until the exposed end 32 of the lead pile segment 30 comes up against the smooth radiused bend 26 of the formed end 22, abutting against the external ring portion 40.

(17) Once the exposed end 32 abuts against the external ring portion 40, secondary end forming is prevented by the external ring portion 40 because the external ring portion 40 prevents radial deformation of the cylindrical body 24 of the extension pile segment 20. In such an embodiment, the initial length L1 of the formed end 22 remains constant, as the secondary end forming process is prevented up to a threshold driving force applied by the piling rig hammer. If the driving force is increased beyond that threshold, the exposed end 32 of the lead pile segment 30 will begin to extrude through the inner diameter ID1 of extension pile segment 20, as shown in FIG. 3B. The resulting extruded portion 36 of the exposed end 32 of the lead pile segment 30 has an inner diameter ID4, and an outer diameter OD4 that is approximately equal to the inner diameter ID1 of the body 24 of the extension pile segment 20. Furthermore, a final length L3 of the coupling 10 is greater than the initial length L1 of the formed end 22 of the extension pile segment 20. Applicant has discovered that this extrusion action greatly increases the friction resistance between the inner wall of extension segment 20 and the outer wall of lead segment 30, providing a further increase in the resistance of the coupling 10 to compressive, lateral (bending moment) and tension loads applied to the installed pile.

(18) In a further embodiment of the coupling 10, such as illustrated in FIGS. 4A to 4C, the external ring portion 40 may be spaced apart from, and positioned upstream of, the smooth radiused bend 26 of the formed end 22 of the extension pile segment 20. This arrangement of the extension pile segment 20 allows for a controlled amount of secondary end forming to occur, as determined by the distance H between the smooth radiused bend 26 of formed end 22 and the external ring portion 40, thereby controlling the final length L2 of the formed end 22. As shown in FIG. 4A, the formed end 22 has an initial length L1, prior to applying a driving force to the extension pile segment 20. To install the extension pile segment 20 onto a lead pile segment 30, the formed end 22 is placed over the exposed end 32 of the lead pile segment 30. Then, the piling rig hammer applies a driving force, in direction A, to a driven end (not shown) of the extension pile segment 20.

(19) As the driving force A is applied to the driven end of the extension pile segment 20, as illustrated in FIG. 4B, the exposed end 32 of the lead pile segment is pushed further into the extension pile segment 20, thereby radially deforming the portion of the pile body 28 that extends between the external ring portion 40 to the smooth radiused bend 26 of formed end 22 of the extension pile segment 20. As the lead pile segment 30 extends further into the extension pile segment 20 in direction B, secondary end forming occurs whereby the final length L2 is greater than the initial length L1 of the formed end 22. In other words, the final length L2 of the formed end 22 is approximately equal to the initial length L1 of the formed end 22 and the distance H between the smooth radiused bend 26 of formed end 22 and the external ring portion 40. As shown in FIG. 4B, the secondary end forming process halts when the exposed end 32 of the lead pile segment 30 reaches, and abuts against, the external ring portion 40 of the extension pile segment 20. Advantageously, by selecting the distance H between the smooth radiused bend 26 of the formed end 22 and the external ring portion 40, the final length L2 of the formed end 22, produced by the secondary end forming process, may be configured for a given coupling. Controlling the amount of secondary end forming that occurs when installing the extension pile segment allows the installer to control the amount of frictional resistance that results from the secondary end forming process, thereby providing a stronger coupling between the two pile segments that has a higher resistance to compression, lateral (bending moment) and tension forces.

(20) In the embodiments that include an external ring portion 40, as shown for example in FIGS. 3A to 4C, the Applicant has found that the exposed end 32 of the lead pile segment 30 continues to push into the extension pile segment 20 through the external ring portion 40 when a sufficient driving force is applied, whereby the exposed end 32 of lead pile segment 30 is cold extruded through the external ring portion 40. Advantageously, the Applicant has found that the cold extrusion process through the external ring portion 40, inside extension pile segment 20, provides a tighter coupling 10 and has an increased resistance to tension forces in direction B, as compared to other coupling methods described herein.

(21) As discussed above, one method of manufacturing the external ring portion of the extension pile segment 20 includes pushing the body 24 of the extension pile segment 20 through a metal ring 42, wherein the metal ring 42 sized to snugly slide over the body 24 of the extension pile segment 20. Once the metal ring 42 is in the desired position, such as abutting against the smooth radiused bend 26 of formed end 22 or spaced apart from the smooth radius bend 26 of formed end 22 at a distance H, the metal ring 42 is fillet welded into place on either side of the ring.

(22) It will be appreciated that other methods of manufacturing an extension pile segment having an external ring portion 40 are intended to be included in the scope of the present disclosure. For example, not intended to be limiting, in some embodiments the metal ring 42 may be secured to the exterior surface 24a of the body of the extension pile segment using a plurality of fasteners. In other embodiments, the external ring portion 40 may not be formed of a separate metal ring 42, but instead, may be a portion of the body 24 of the pile segment 20 that has a thicker wall, the thicker wall extending outwardly of the outer diameter OD1 of the body 24. The integrally formed external ring portion 40, in other words, may be a thickened or reinforced portion of the pile body 24, reinforced such that it resists radial deformation by secondary end forming when the extension pile segment 20 is driven in direction A on top of the lead pile segment 30. Such thickened or reinforced external ring portions 40 that are integrally formed with the cylindrical body 24 of the pile segment may be manufactured, for example, by molding the pile segment, by heating a portion of the pile body via induction heading and then pushing the opposite ends of the pile towards one another with a mandrel inside so that the outer wall of the pile body is pushed radially outwards through the heated portion, or by any other method known to a person skilled in the art.

(23) In a preferred method of manufacturing the formed end of the extension pile segment, a segment of structural pipe having the desired outer diameter is placed in an end forming machine or device, comprising a mandrel having a diameter that exceeds the outer diameter of the structural pipe segment. The mandrel is forced into one opening of the structural pipe, which deforms and widens the opening of the structural pipe to create the formed end, wherein the inner diameter 102 of the formed end 22 is substantially equal to the outer diameter of the mandrel. The end forming process, which may be performed on an ambient temperature structural pipe (cold end forming) or on a heated structural pipe (hot end forming), is relatively quick and inexpensive, and a structural pipe made of any material suitable to the end forming process may be used. In some cases, the end of the pipe to be formed may be heated if material properties or pipe wall thickness requires heating to perform the end forming process, as would be known to a person skilled in the art. Advantageously, recycled, re-purposed or left-over sections of structural pipe may be used to create the pile segments disclosed herein, which may reduce waste by using leftover portions of pipe to manufacture new pile segments. Pile segments of different lengths may be used in the methods described herein.

(24) The embodiments of pile couplings for a driven steel pipe pile, discussed above, advantageously offer a simple and flexible system of pile couplings that may be readily configured for designing piles that meet specification for different levels of resistance to compression, lateral, and/or tension loads. As compared to other pile couplings, the different embodiments of pile couplings disclosed herein may be configured for greater resistance to, in particular, tension loads, which may pull the coupling apart when applied to the uppermost end of the pile, and lateral (bending) loads, which may cause the pile to bend, if the piles are not configured for sufficient resistance to these loads. Advantageously, the pile couplings disclosed herein are relatively inexpensive to manufacture, while offering flexibility in configuration for resistance to different loads.

(25) For example, where no or minimal tension load resistance is required, an extension pile having a formed end may be added to the lead pile, and the driving force used to couple the pile segments together may be less than the yield strength of the formed end, whereby no secondary end forming will occur. Where no secondary end forming occurs, in such coupling embodiments, the pile will not resist uplift.

(26) When the driving (compressive) force applied to the extension pile, having a formed end, exceeds the yield strength of the formed end, then secondary end forming will occur (as illustrated, for example, in FIGS. 2A and 2B). When secondary end forming occurs, there is increased friction between the inner wall of the formed end and the outer wall of the exposed end of the lead pile segment, thereby offering increased tension force resistance.

(27) For embodiments in which an external ring portion is added to the extension pile segment, upstream of and spaced apart from the formed end, and the driving (compressive) force applied is adjusted such that the exposed end of the lead pile segment only pushes into the extension pile segment until it abuts against the external ring portion (via the secondary end forming process; see FIG. 4B), then this configuration of pile coupling will offer approximately the same level of tension force resistance as is offered by the pile coupling configuration described above (with secondary end forming occurring but without a external ring portion added to the extension pile segment). However, in this embodiment, the final length of the formed end of the extension pile, and therefore the extent of secondary end forming that occurs, may be configured by selecting the distance between the external ring portion and the formed end of the extension pile segment. Additionally, configuring the pile coupling to have a specified final length of the formed end (via the secondary end forming process) may also increase the pile's resistance to lateral (bending) forces.

(28) For embodiments where the extension pile segment includes a external ring portion, and sufficient force is applied to the extension pile segment to cause the lead pile segment to extrude through the external ring portion, such pile coupling configurations offer greater resistance to tension forces, as compared to the other embodiments described above. Examples of such coupling configurations are illustrated, for example, in FIGS. 3B and 4C.

(29) Pile couplings may also be configured by fitting a formed end of an extension pile segment over the exposed end of a lead pile segment, and applying a fillet weld to the coupling prior to applying the driving force. Although such embodiments involve some field welding, this method may be less costly than other prior art couplings due to the absence of a separate coupling sleeve device. Configurations of pile couplings involving welding offer the greatest amount of resistance to tension, lateral and compressive forces.