GB2418949A

GB2418949A - Screwpile with cement delivery port

Info

Publication number: GB2418949A
Application number: GB0520150A
Authority: GB
Inventors: Duncan Clift Mcgregor
Original assignee: Screwfast Foundations Ltd
Current assignee: Screwfast Foundations Ltd
Priority date: 2004-10-05
Filing date: 2005-10-04
Publication date: 2006-04-12
Anticipated expiration: 2025-10-04
Also published as: GB2418949B; GB0520150D0; GB0422062D0

Abstract

A screwpile 13 includes helical flights 16 where adjacent the trailing edge of each flight 16 is a port 21 that allows for the delivery of cement. An upstanding protuberance 20 may be present on the flights 16 adjacent said ports 21 to form a helical groove ahead of the port 21 during rotation of the screwpile 13, whereby the groove is filled with cement. The flights 16 may include cutting teeth 19.

Description

24 1 8949

SCREWPILES

This invention concerns screw piles of the kind which are driven into the ground to form a ground anchor to which a structure above ground may be bolted to provide a secure anchorage for the structure.

Screw piles of this kind typically comprise one or more tubular shafts with a number of helical flights mounted on the shaft wall near its lower end such that when the shaft is driven in rotation the helical flights pull the shaft into the ground and enable it to be driven down to the required depth.

In certain applications screw piles of this kind are used to penetrate rock formations which whilst sufficiently soft to allow penetration of the pile tend to fragment as the pile is driven so that the bore formed within the rock contains voids resulting in a loose fit of the pile within the ground.

It is an object of the present invention to provide a screw pile including means to introduce a gettable grout into the bore formed by the pile as it is driven so that when the grout is set a firm anchorage is provided for and by the screw pile.

According to the present invention a screw pile comprises at least one tubular shaft having about its circumference at least one helical flight having a leading edge - - - and a trailing edge determined by an intended direction of rotation of the shaft about - - . a longitudinal axis thereof when driven into the ground; characterized by at least one A..

port forming a passage through the wall of the tubular shaft adjacent said at least one : lo. helical flight to permit a fluid substance to be discharged outwards of the shaft through the port.

An upstanding protuberance on said at least one helical flight may be provided adjacent said port to form a helical groove in the ground ahead of the port during rotation of the shaft whereby the groove may receive the fluid substance discharged from the port.

The upstanding protuberance may be a blade attached to the helical flight and extending radially from the shaft at or near said trailing edge of the helical flight.

The leading edge of the helical flight may have at least one tooth to aid ground penetration during rotation of the shaft.

Several helical flights may be provided at longitudinally spaced locations on the shaft, with a port in the shaft wall adjacent the trailing edge of each flight and a radially extending blade at said trailing edge.

The or each radially extending blade may be of greater extent radially than 1 5 axially.

The axial extent of the or each radially extending blade with the associated flight is at least as great as that of the adjacent port thus, to create a helical groove having an axial width at least as great as that of the port.

The screw pile may comprise several lengths of tubular shaft connected together in axial alignment. eve e .e.

- - . The respective lengths of tubular shaft may be connected by means to ensure ...

lo. . 25 electrical earthing continuity between the lengths of shaft. .

Said connection means may include at least one expanding bolt. . .

.. . . . An upper end of the screw pile may have attached thereto an earthing lug to which is electrically bonded an earth lead for attachment to a structure to be mounted on the screw pile.

Further, according to the present invention there is provided a method of introducing a screw pile into the ground, comprising the steps of providing a screw pile comprising at least one tubular shaft having about its circumference at least one helical flight having a leading edge and a trailing edge determined by an intended direction of rotation of the shaft about a longitudinal axis thereof, and at least one port forming a passage through the wall of the tubular shaft adjacent said at least one helical plate; rotating the tubular shaft while driving same forwardly into the ground; introducing into the tubular shaft a gettable grout; and causing said grout to pass outwardly through said at least one port whereby the grout is caused to enter any voids created in the ground around the screw pile during rotation of the shaft.

The method may include the provision of at least one upstanding protuberance on said at least one helical flight adjacent said port, thereby, during rotation of the shaft, causing the protuberance to form a helical groove in the ground ahead of the port, and thus causing the grout to penetrate the helical groove formed by said protuberance.

An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Fig. 1 schematically illustrates a sub-frame for an over-ground structure such as a telecommunications mast, where the sub .

frame is located at four corners thereof upon screw piles .

. 25 constructed and driven in accordance with the invention; - - - Fig. 2 is a schematic illustration of such a screw pile being driven into the ground; . ..

Fig. 3 illustrates a leading end of the screw pile with a lowermost helical flight; Fig. 4 is a partial view taken in the direction of arrow X in Fig. 3; and Fig. 5 is an enlarged view showing a connection between two aligned shafts of the screw pile with earth continuity bolts.

Referring now to the drawings, in this example a sub-frame 10 for mounting a telecommunications mast (not shown) comprises a cruciform frame 11 defining four spaced feet 12 each to be mounted on a screw pile as generally indicated at 13. Each screw pile comprises a plurality of axially aligned shafts 14 of tubular construction joined by bolts 15 passed diametrically through the respective ends of the adjacent shafts. Helical flights 16 are located at longitudinally spaced positions on the shafts 14 and a drilling tip 17 is provided at the lowermost and leading end of the screw pile 13.

As shown in Fig. 3, the drilling tip 17 has a number of tungsten tipped teeth 18 to provide initial penetration and breaking of the ground ahead of the shaft 14.

Each helical flight 16 defining a single turn on the shaft 14 has a pair of tungsten tipped teeth 19 at its leading edge as determined by the intended direction of rotation of the shaft about a longitudinal axis thereof. Mounted on the shaft 14 and flight 16 and extending radially thereof at its trailing edge is a radially extending blade 20 which as can be seen in Fig. 4 is of a generally triangular shape so that its dimension . axially in respect of the shaft 14 diminishes in a radially outwards direction . . terminating some two thirds of the way across the trailing edge of the flight 16.

A .

In accordance with the invention the shafts 14 adjacent the trailing edge of :: each helical flight 16 are bored as shown at 21 providing a port through the wall of the shaft where the diameter or axial extent of the port is approximately as great as . - . that of the blade 20 and the thickness of the flight 16. . -

As illustrated in Fig. 2, as the screw pile is driven in rotation and penetrates the soft rock formation, preferably using a hydraulic torque head, a gettable grout is pumped into the upper end of the shaft 14 under pressure. Thus, the grout passes outwardly through the port 21 to fill a helical groove formed by the blade 20 during rotation of the screw pile. Thus, the grout enters the fissures in the broken rock and serves to cement any rock fragments together to form a concrete matrix which securely fixes the pile in place. The cement matrix serves also as a protection against corrosion in that all voids are filled, thus to leave no air spaces around the pile.

Also as shown in Fig. 2, typically there may be three helical flights provided at spaced intervals along the length of at least the lower part of the shaft 14, each provided with a blade 20 adjacent a port 21.

During penetration of the ground the tungsten tipped teeth 18 and 19 serve to aid the passage of the pile by breaking the rock formations ahead of the screw pile.

Each blade 20 is of greater extent radially than axially and is tapered in height to avoid excessive resistance to rotation of the screw pile but the axial extent of the blade is at least as great as that of the adjacent port thus, with the associated flight 16, to create a helical groove having an axial width at least as great as that of the port.

Referring now to Fig. 5, in order to ensure electrical earth continuity in the screw pile, where aligned lengths of shaft 14 are bolted together, at least one part of . the interconnection of the shafts is by way of expanding bolts 25 which tightly . .

interconnect the shaft lengths which, in the example of Fig. 5, are connected by an see...DTD: outer sleeve 26. . *e c .e

I:: Referring again to Fig. 1, at the top of each screw pile there may be provided an earthing lug 27 connected by earth bonding tape 28 to the base of the sub-frame 10 ..

using stubs 29 bolted or welded to the sub-frame at positions where a mast will be e.e bolted to the frame. The tapes 28 may extend to other earth bonding or to a corrosion electrode. Thus, electrical earthing continuity through the screw piles is ensured by using the expansion bolts in connection with the earthing lugs 27 and 29 and earth bonding tape 28. . .e I.

a..-* . ... ..*

Claims

1. A screwpile comprising at least one tubular shaft having about its circumference at least one helical flight having a leading edge and a trailing edge determined by an intended direction of rotation of the shaft about a longitudinal axis thereof when driven into the ground; characterized by at least one port forming a passage through the wall of the tubular shaft adjacent said at least one helical flight to permit a fluid substance to be discharged outwards of the shaft through the port.

2. A screwpile according to claim 1 including an upstanding protuberance on said at least one helical flight adjacent said port to form a helical groove in the ground ahead of the port during rotation of the shaft whereby the groove may receive the fluid substance discharged from the port.

3. A screwpile according to claim 2 wherein the upstanding protuberance is a blade attached to the helical flight and extending radially from the shaft at or near said trailing edge of the helical flight.

4. A screwpile according to any preceding claim wherein the leading edge of the helical flight has at least one tooth to aid ground penetration during rotation of the shaft ... .

5. A screwpile according to any preceding claim including several helical flights . provided at longitudinally spaced locations on the shaft, with a port in the shaft :: wall adjacent the trailing edge of each flight and a radially extending blade at said trailing edge.

. ..

6. A screwpile according to claim 3 or claim 5 wherein the or each radially extending blade is a greater extent radially than axially.

7. A screwpile according to any one of claims 3, 5 and 6 wherein the axial extent of the or each radially extending blade with the associated flight is at least as great as that of the adjacent port thus, to create a helical groove having an axial width at least as great as that of the port. s

8. A screwpile according to any preceding claim comprising several lengths of tubular shaft connected together in axial alignment.

9. A screwpile according to claim 8 wherein the respective lengths of tubular shaft are connected by means to ensure electrical earthing continuity between the lengths of shaft.

10. A screwpile according to claim 9 wherein said connection means includes at least one expanding bolt.

11. A screwpile according to any preceding claim wherein an upper end of the screwpile has attached thereto an earthing lug to which is electrically bonded an earth lead for attachment to a structure to be mounted on the screwpile.

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

12. A method of introducing a screwpile into the ground, comprising the steps of providing a screwpile comprising at least one tubular shaft having about its : .. circumference at least one helical flight having a leading edge and a trailing . Em. edge determined by an intended direction of rotation of the shaft about a o.

longitudinal axis thereof, and at least one port forming a passage through the .e . 25 wall of the tubular shaft adjacent said at least one helical plate; rotating the tubular shaft while driving same forwardly into the ground; introducing into the tubular shaft a gettable grout; and causing said grout to pass outwardly through .e * . said at least one port whereby the grout is caused to enter any voids created in .e the ground around the screwpile during rotation of the shaft.

13. A method according to claim 12 including the provision of at least one upstanding protuberance on said at least one helical flight adjacent said port thereby, during rotation of the shaft, causing the protuberance to form a helical groove in the ground ahead of the port and thus causing said grout to penetrate the helical groove formed by the protuberance.

14. A screwpile substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings. ë I eve he bee ëe.

- e .e e ë lo

Amendments to the claims have been fled as follows A screwpile comprising at least one tubular shaft having about its circumference at least one helical flight having a leading edge and a trailing edge determined by an intended direction of rotation of the shaft about a longitudinal axis thereof when driven into the ground, and at least one port forming a passage through the wall of the tubular shaft adjacent said at least one helical flight to permit a fluid substance to be discharged outwards of the shaft through the port; characterized by an upstanding protuberance on said at least one helical flight adjacent said port to form a helical groove in the ground ahead of the port during rotation of the shaft whereby the groove may receive the fluid substance discharged from the port.

2. A screwpile according to claim 1 wherein the upstanding protuberance is a blade attached to the helical flight and extending radially from the shaft at or near said trailing edge of the helical flight.

3. A screwpile according to claim 1 or claim 2, wherein the leading edge of the helical flight has at least one tooth to aid ground penetration during rotation of the shaft.

4. A screwpile according to any preceding claim including several helical flights provided at longitudinally spaced locations on the shaft, with a port in the shaft wall adjacent the trailing edge of each flight and a radially extending blade at said trailing edge.

5. A screwpile according to claim 2 or claim 4 wherein the or each radially extending blade is a greater extent radially than axially.

6. A screwpile according to any one of claims 2, 4 and 5 wherein the axial extent of the or each radially extending blade with the associated flight is at least as )1 great as that of the adjacent port thus, to create a helical groove having an axial width at least as great as that of the port.

7. A screwpile according to any preceding claim comprising several lengths of tubular shaft connected together in axial alignment.

8. A screwpile according to claim 7 wherein the respective lengths of tubular shaft are connected by means to ensure electrical earthing continuity between the lengths of shaft.

9. A screwpile according to claim 8 wherein said connection means includes at least one expanding bolt.

10. A screwpile according to any preceding claim wherein an upper end of the screwpile has attached thereto an earthing lug to which is electrically bonded an earth lead for attachment to a structure to be mounted on the screwpile.

A method of introducing a screwpile into the ground, comprising the steps of providing a screwpile comprising at least one tubular shaft having about its circumference at least one helical flight having a leading edge and a trailing edge determined by an intended direction of rotation of the shaft about a longitudinal axis thereof, and at least one port forming a passage through the wall of the tubular shaft adjacent said at least one helical plate; rotating the tubular shaft while driving same forwardly into the ground; introducing into the tubular shaft a gettable grout; and causing said grout to pass outwardly through said at least one port; and providing at least one upstanding protuberance on said at least one helical flight adjacent said port thereby, during rotation of the shaft, causing the protuberance to form a helical groove in the ground ahead of the port and thus causing said grout to penetrate the helical groove formed by the protuberance. z-