NZ581041A

NZ581041A - Screw pile with band affixed to upper screw portion to resist lateral forces

Info

Publication number: NZ581041A
Application number: NZ58104109A
Authority: NZ
Inventors: Daniel Hylton Coats
Original assignee: Fletcher Construction Company
Priority date: 2009-11-10
Filing date: 2009-11-10
Publication date: 2009-12-24

Abstract

An upper portion of a screw pile has a band secured to an upper helical blade portion with the band running parallel to pile axis so as to provide a degree of resistance against lateral forces.

Description

Patents Form No. 5 581041 1 THE PATENTS ACT 1953 COMPLETE SPECIFICATION A Pile We, The Fletcher Construction Company Ltd, trading as Piletech, a New Zealand company, of Unit 5, 26 Rosecommon Road, Wiri, Auckland, New Zealand, hereby declare this invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: 581041 2 Title A Pile Field of Invention This invention relates to a pile, for example of a type for use as part of the foundations of a building or other structure. A preferred embodiment of the invention relates to a screw pile which, when installed, is able to resist lateral loads.

Background Piles are commonly used as part of the foundations of a building or other structure. Sometimes these are referred to as anchors or piers and they may be screwed into the ground for connection to other building parts, for example to floor beams, etc. It is an object of a preferred form of the present invention to provide a useful and novel pile, or to at least provide the public with a useful choice.

The term "comprising" and derivatives thereof, for example "comprised, if and when used in this specification in relation to a feature or combination of features should be interpreted to allow for the option of additional unspecified features. The term should thus be interpreted as non-exclusive.

Summary of the Invention According to one aspect of the invention there is provided a pile having a shaft, a first blade at or adjacent to a leading end of the shaft, and a second blade at or adjacent to a trailing end of the shaft, a band secured to the second blade and substantially 25 aligned with the longitudinal dimension of the shaft, the pile formed such that when it in use it can be screwed into the ground such that the first blade facilitates penetration of the pile into the ground and such that the second blade and the band subsequently penetrate the ground to provide the pile with a degree of resistance against forces lateral to the pile when in use.

Preferably the first and/or second blade is/are substantially helical.

Preferably the band substantially follows the helical shape of the second blade.

Optionally the first and/or second blades are initially separate from the shaft but each comprises means for fitting them to the shaft. 581041 3 Optionally the means for fitting the first and/or second blade to the shaft in each case comprises a sleeve which is able to fit around the shaft.

Optionally the pile comprises an upper steel plate aligned substantially laterally with 5 respect to the shaft.

Optionally there is a third blade at or adjacent to the trailing end of the shaft.

Preferably the third blade, if present, is substantially helical.

According to a further aspect of the invention there is provided a pile having a shaft, a first blade at or adjacent to a leading end of the shaft, and an upper casing, the upper casing having a band and a second blade wherein the band is secured around the second blade, the pile formed such that when it is in use the shaft can be 15 installed in the ground by way of the first blade and the casing screwed down around the shaft by way of the second blade such that the second blade is in contact with or immediately next to the shaft such that lateral loads incident on the shaft are resisted by the combination of the second blade and the band.

Preferably the first and second blades are each substantially helical.

Description of the Drawings Some preferred embodiments of the invention will now be described by way of 25 example and with reference to the accompanying drawings, of which: Figure 1 illustrates, schematically, a pile when installed; Figure 2 illustrates, schematically, the pile prior to being assembled; Figure 3 illustrates a part of the pile; Figure 4 illustrates, schematically, a pile according to a further embodiment of the invention; Figure 5 illustrates, schematically, a pile according to a further embodiment of the invention; and Figure 6 illustrates, schematically, a pile according to a further embodiment of 35 the invention. 581041 4 Detailed Description As shown in figure 1 the pile 1 has a cylindrical shaft 2 with a pointed lower end 3. The pile of figure 1 has been screwed into the ground 4 except that a portion of its upper end 5 protrudes above ground level. To facilitate screwing of the pile into the 5 ground the pile has a helical lower blade 6. As the pile is turned the blade 6 cuts through earthen material to assist the pile to penetrate the ground. The term helical as used here and elsewhere in this document does not necessarily require a full helical twist. It is sufficient that there is at least part of a helical twist.

In some embodiments of the invention the lower part of the shaft, incorporating the lower end 3 and the blade 6, may be butt welded to the remaining upper part of the shaft. The portion below the butt weld may comprise a steel tube to which the lower blade 6 is welded, optionally with a steel plug weld inside the tube. Alternatively, the portion of shaft below the butt weld may be a cast steel part incorporating the blade 6 15 and lower end 3.

With further reference to figure 1, the upper end of the pile also has a helical upper blade 7, optionally of larger pitch than the lower blade 6. An outer band 8 is fixed to the upper blade 7 by welding or any suitable means and runs parallel to the vertical 20 dimension of the shaft 2. For the sake of clarity the band 8 is only depicted in figure 1 at the outer edges of the upper blade 7, but it should be appreciated that the band in fact wraps and around and thus follows the direction of the blade 7 as indicated in figure 3. In some embodiments the band 8 may be in the form of a continuous casing supported by a helical blade top and bottom.

In some embodiments of the invention having a larger pitch for the upper blade 7 may facilitate spoiling of ground up inside the outer band 8 and minimise plugging. Further, the upper blade 7 may facilitate a greater force on the shaft 2 and band 8 to get these into the ground without the lower blade 6 pulling on the band and causing 30 undesirable disturbance of soil immediately above and below the lower blade 6.

The lower blade 6 and/or the upper blade 7 preferably extend outwards from a sleeve 9 and 10 respectively around the shaft 2. Each blade is preferably formed in two pieces 11, 12 bolted to one another as shown in detail in the inset to figure 1. In 35 some embodiments of the invention at least the helical upper blade 7 may be detachable. However in alternative embodiments the blades may be similarly secured to the shaft directly, ie without an intermediate sleeve. In still further 581041 embodiments the lower part of the shaft may be an initially separate piece, cast to incorporate the pointed lower end 3 and the lower blade 6, and collectively butt welded to the rest of the shaft 2.

Figure 1 also shows a slot 13 for facilitating the installation of services. The slot 13 is arranged to align with a matching slot in the upper sleeve 10. The upper sleeve 10 also has a lateral plate 14 arranged so that such sleeve is generally of a 'top hat' shape. The lateral plate 14 may be secured to the rest of the sleeve 10 by way of bolts, by welding, or any other suitable means. Preferably at least the upper parts of 10 the pile have a protective coating, for example a zinc based coating.

The pile 1 may be formed from suitable metallic materials, for example from steel or cast iron, or from a combination of these. At least parts of the pile may be 'hot dip galvanised' to protect them from corrosion, particularly at the ground surface 15 interface.

Referring to figure 2, in some embodiments of the invention the pile may be assembled in three parts, for example from the shaft 2 and the lower and upper sleeves 9 and 10.

It should be appreciated that when some prior art piles are screwed into the ground the helical blade at their leading end may auger the ground until there is enough downward force on the blade to overcome the end bearing resistance of the shaft and cause the pile to knife into the ground at approximately one helical pitch in depth 25 per revolution. This can result in undesirably displaced ground around the pile for up to 0.5 m to 1m in depth. The embodiment of the present invention described herein goes at least some way towards addressing this disadvantage. In this regard the outer band 8 can serve to provide at least a degree of casing around the shaft. Further, the helical upper blade 7 has an ability to react with undisturbed ground 30 around the shaft near the top of the pile. It may knife through the ground to prevent or reduce a tendency of the ground to plug up.

Piles according to the invention may be applied in a variety of constructions, for example as shear bases for traffic control structures, as piles needed for resisting 35 seismic action, and for structures that are required to resist high wind loads. Piles according to the invention can thus be used to advantage in situations requiring resistance to significant lateral forces. This may be facilitated by the band 8 and 581041 6 earthen material between that and the shaft 2.

In some embodiments of the invention the upper part of the pile may be modified as shown in figure 4. In this embodiment the helical upper blade 7a is attached to the 5 band 8a. The band 8a is in turn fixed to the upper plate 14a. These parts collectively form a casing. When the shaft 2a has been installed in the ground 4a the casing is screwed down around the shaft 2a so that there is a small clearance (eg 0.5 - 5 mm) between the shaft 2a and the upper blade 7a. If, after installation, the shaft 2a becomes subject to lateral loads and tends to tilt, it immediately comes into contact 10 with the blade 7a so that such tilting is resisted. This is facilitated by the band 8a and earthen material between that and the shaft 2a.

As shown in figure 5, in some embodiments of the invention there may be more than one helical blade 7a, 7b arranged at the upper part of the shaft, depending on the 15 requirements of the building project at hand. In such cases the helical blades may be detachably bolted to the shaft and the shaft itself may be longer than would be the case if there was just one upper helical blade. While figure 5 shows the helical upper blades 7a and 7b welded to the shaft directly, in alternative embodiments they may be welded to a sleeve similar to the sleeve 10 described in relation to figure 1.

Referring to figure 6, in still further embodiments of the invention an arrangement of two or more upper blades 7c and 7d may be applied in situation similar to that of figure 4, ie where the blades are fixed to an outer band 8b and the band proceeds from a fixed upper plate 14b.

Preferably in all cases the upper helical blade(s) have a larger pitch While some preferred embodiments of the invention have been described by way of example, it should be appreciated that modifications and improvements can occur 30 without departing from the scope of the following claims.

Claims

581041 7 What We Claim Is

1. A pile having a shaft, a first blade at or adjacent to a leading end of the shaft, and a generally helical second blade at or adjacent to a trailing end of the shaft, a 5 band secured to the second blade and substantially aligned with the longitudinal dimension of the shaft, the pile formed such that when it in use it can be screwed into the ground such that the first blade facilitates penetration of the pile into the ground and such that the second blade and the band subsequently penetrate the ground to provide the pile with a degree of resistance against forces lateral to the 10 pile when in use.

2. A pile according to claim 1, wherein the first and/or second blade is/are substantially helical. 15

3. A pile according to claim 2, wherein the band substantially follows the helical shape of the second blade.

4. A pile according to claim 1, 2 or 3, wherein the first and/or second blades are initially separate from the shaft but each comprises means for fitting them to the 20 shaft.

5. A pile according to claim 4, wherein the means for fitting the first and/or second blade to the shaft in each case comprises a sleeve which is able to fit around the shaft. 25

6. A pile according to any one of the preceding claims, comprising an upper steel plate aligned substantially laterally with respect to the shaft.

7. A pile according to any one of the preceding claims, wherein there is at least a 30 third blade at or adjacent to the trailing end of the shaft.

8. A pile according to claim 7, wherein the third blade is substantially helical.

9. A pile according to claim 1 substantially as herein described. 35

10. A pile substantially as herein described with reference to the accompanying drawings. 581041 8

11. A pile according to any one of the preceding claims when installed in the ground such that the first and second blades are below ground level. 5

12. A construction comprising a pile according to any one of the preceding claims installed in the ground to provide resistance to loads lateral to the pile and incident on the construction.

13. A pile having a shaft, a first blade at or adjacent to a leading end of the shaft, and 10 an upper casing, the upper casing having a band and a generally helical second blade wherein the band is secured around the second blade, the pile formed such that when it is in use the shaft can be installed in the ground by way of the first blade and the casing screwed down around the shaft by way of the second blade such that the second blade is in contact with or immediately next to the shaft such 15 that lateral loads incident on the shaft are resisted by the combination of the second blade and the band.

14. A pile according to claim 13 wherein the first and second blades are generally helical. 20

15. A pile according to claim 13 or 14, with the shaft installed in the ground and the casing installed as set out in claim 13. 25 The Fletcher Construction Company Ltd trading as Piletech 30 By Its Attorney A.J. Pietras & Co