GB2397327A

GB2397327A - Telescopic screw pile

Info

Publication number: GB2397327A
Application number: GB0400863A
Authority: GB
Inventors: Duncan Mcgregor
Original assignee: SCREW FAST FOUNDATIONS Ltd
Current assignee: SCREW FAST FOUNDATIONS Ltd
Priority date: 2003-01-16
Filing date: 2004-01-15
Publication date: 2004-07-21
Anticipated expiration: 2024-01-15
Also published as: GB0400863D0; GB2397327B; GB0300997D0

Abstract

A screwpile is formed from two lengths (10, 13) of tubing arranged in a telescopic relationship so that the effective length of the screwpile may be adjusted. Multiple sets of bolt holes (12) in the first length of tubing (10) can be aligned with bolt holes (18) in the second length of tubing (13) so that the two lengths of tubing (10, 13) may be bolted together to achieve the required length of the screwpile.

Description

À À À . . Àe Àe À e À À e À À À À À À À À À ÀÀ .

A SCREWPILE

THIS INVENTION concerns a screwpile of the kind used for ground anchorage and/or compressive resistance of objects such as masts and other structures where screwpiles are driven into the ground and serve to support the structure.

The height at the top of the finished pile is usually required to be at a predetermined level above ground.

When driving screwpiles into hard ground it is sometimes difficult to force the piles to a sufficiently deep level to achieve the desired height or alternatively it may be necessary to remove an upper section of the pile when further penetration is not possible.

In softer ground it would be necessary to add extra lengths of screwpile and to drive them deeper than required in order to obtain a firm anchorage.

À À À À . À c. À À À . ÀÀ À À À À . . . . À À À e. . À Both of these variations can cause disruption to the work on site and so it is an object of the present invention to provide an adjustable length screwpile to allow for unexpected variations in ground hardness.

According to the present invention there is provided a screwpile, comprising at least two lengths of screwpile axially aligned in telescopic relationship such that the effective length of the screwpile may be adjusted, and means to attach the lengths of screwpile together at a predetermined overall length.

The screwpile may have first and second lengths, the first length of screwpile having at least one helical flight on its outer surface to enable ground penetration thereby.

The second length of screwpile may have a drive plate for rotating the screwpile.

The first length of screwpile may have a plurality of sets of bolt holes for selective alignment with a corresponding set of bolt holes in the second length of screwpile.

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eae e À Àe *À À . À À Àe A third length of screwpile may be located between and aligned with the first and second lengths and have a plurality of sets of bolt holes for selective alignment with corresponding sets of bolt holes in the first and second screw piles.

An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Fig. 1 shows a first tubular length of screwpile; and Fig. 2 shows a second tubular length of screwpile with a drive plate mounted thereon.

Referring now to the drawings, a first tubular length of screwpile 10 carries, in its lower region, one or more helical flights 11 on its outer surface to enable ground penetration upon rotation of the screwpile.

In this example, the screwpile length 10 has four longitudinally spaced sets, each of three bolt holes 12 whose axes extend diametrically through the tubular screwpile. 4t

4 À t ' À À . À4 '.4 C lee . À 4 À . 1 Referring now to Fig. 2 a second tubular length 13 of screwpilehaving an inner diameter slightly in excess of the outer diameter of screwpile length 10, is attached at 14 and 15 by welding to a larger diameter tubular member 16 having a drive plate 17 at its upper end.

The screwpile length 13 has one set of three bolt holes 18 at its lower end.

In use, the first screwpile length 10 has its upper end inserted into the lower end of the second screwpile length 13 and the two lengths are arranged such that one set of bolt holes 12 (preferably below the uppermost set) and the bolt holes 18 are aligned so that three fixing bolts may be passed therethrough to attach the two screwpile lengths together. The drive plate 17 is rotated which causes rotation of the entire screwpile and, due to the helical flights 11, the screwpile may thus penetrate the ground. When penetration has reached almost the level of the aligned bolt holes 12 and 18, the fixing bolts may be removed, and the bolt holes 18 in the second screwpile length may then be aligned with one of the further (higher) sets of bolt holes 12 in the first screwpile length.

The screwpile continues to be driven into the ground until resistance is met at the lower end of the first screwpile length 10 at which e r 8 8 8 e# 8 8.. À 8 8 8 8 ee 866 8 e ed8 e e À e e 8. À eve c time the over all length of the screwpile may be adjusted to the required upper level by selecting the appropriate set of bolt holes 12 to be aligned with the bolt holes 18.

Typically, in many circumstances rock or very dense soils will occur at greater depths and so the first screwpile length 10 may have only one set of bolt holes 12 at its upper end. In this case, a third length of screwpile may be provided which is telescopically engagable with the first and second screwpiles and is located between them. In this case, the third screwpile length may have several longitudinally spaced sets of bolt holes similar to the bolt holes 12 in Fig. 1. Thus, the first and second screwpile lengths as illustrated may be telescopically adjustable with respect to the third screwpile length and the bolts inserted through the appropriate aligned sets of bolt holes.

The embodiment described and illustrated in the drawings is for use when boring into rock, the helical flights 11 being designed for that purpose. However, different configurations of helical flights may be provided as required.

Typically, the first and second screwpile lengths may be some 2m long each, with the sets of bolt holes 12 at 300mm spacing.

À: .ee: a: À : Bea:: :: Be: I. À. À It will be appreciated that in addition to enabling an installer to select the appropriate level for the upper end of the screwpile, since the screwpile consists of at least two axially aligned lengths, there is a considerable advantage when operating in areas of limited headroom when compared with a one-piece screwpile of sufficient length to obtain the necessary level of penetration.

As with standard screwpiles, the screwpile lengths described herein may be of galvanised steel, and the boring tip and helical flights may be chosen as required and in accordance with ground investigation carried out prior to installation.

In view of the adjustability in length of the screwpile the rotational torque may be applied at the lowest possible level thus to avoid any twisting of the screwpile lengths. In the event that the screwpile is to be removed the second screwpile length may be adjusted downwardly as the screwpile is progressively lifted from the ground. À À

Claims

ce ace c ece see e. es. CLAIMS

1. A screwpile comprising at least two lengths of screwpile axially aligned in telescopic relationship such that the effective length of the screwpile may be adjusted, and means to attach the lengths of screwpile together at a predetermined overall length.

2. A screwpile according to Claim 1, having first and second lengths, the first length of screwpile having at least one helical flight on its outer surface to enable ground penetration thereby.

3. A screwpile according to Claim 2, wherein the second length of screwpile has a drive plate for rotating the screwpile.

4. A screwpile according to Claim 2 or Claim 3, wherein the first length of screwpile has a plurality of sets of bolt holes for selective alignment with a corresponding set of bolt holes in the second length of screwpile.

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5. A screwpile according to any preceding claim, including three lengths of screwpile such that a third length may be located between and aligned with first and second lengths and having a plurality of sets of bolt holes for selective alignment with corresponding sets of bolt holes in the first and second screwpiles.

6. A screwpile substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.