~ BACKGROUND OF THE INVENTION —

This invention relates to the establishment of foundations and in particular to deep piling utilising a flighted pile. It has particular but not exclusive application to the construction of foundations in ground of low bearing capacity, and for illustrative purposes reference will be made to such application. However, it is to be understood that this invention could be used in other applications, such as cable anchors.

— DISCUSSION OF THE PRIOR ART —

The rate with which foundations are completed, and their cost, is directly related to the techniques employed in establishing the foundations. In most cases, the technique is determined by the ground conditions and the design loads of the foundations in use. In ground conditions such as in sand and peat below a water table, two types of piles are generally used; driven piles and augered grout injected piles. Both these systems have major disadvantages in that driven piles cause settlement during the driving process, and must be driven to a greater depth then would otherwise be necessary to compensate for this. The effectiveness of a grout injected pile depends to a large degree on the apparatus, skill and experience of the installation crew, and thus demands a high level of training and supervision to produce consistent results.

— SUMMARY OF THE PRESENT INVENTION ~

The present invention aims to alleviate the above disadvantages and to provide piling apparatus, and methods of fabricating and placing same which will be reliable and efficient in use. Other objects and advantages of this invention will hereinafter become apparent.

With the foregoing and other objects in view, this invention in one aspect resides broadly in piling apparatus comprising:- an elongate core; at least one helical flight projecting outwardly from said elongate core by which said piling apparatus may be screwed downwardly into the ground; and an axially extending grouting passage formed through said elongate core through which grout may be pumped in use to provide a grout encapsulation about said piling apparatus.

The piling apparatus may be prefabricated utilising casting procedures, or other construction techniques, and may be adapted for use in a piling system whereby the piling apparatus may be driven so as to drill its own hole into ground down to its desired location whereat it may be grouted. The piling apparatus may be cast or fabricated from steel or other metal, pre-cast in concrete or otherwise constructed as a part of a piling system in a helical mould, and selected portions thereof may be provided with a wear- resistant outer coating, such as a sheet-metal jacket encapsulating the pile material about selected portions thereof such as the helical flight and/or the core. Where the pile material is concrete, reinforcement such as steel bars, or metallic or non-metallic fibres, may be included for enhancing the strength of the pile, or the concrete may be pre- or post-stressed. If desired, the piling apparatus may be formed from a hollow shell of metal such as steel.

Typically, the core may have an outside diameter in the range fifty to three hundred millimetres, and the outside diameter of the flight may range between one hundred to one thousand millimetres, although piling apparatus of other dimensions and proportions may be formed if desired. The grout passage may be formed to any desired size, but it is preferred that it be approximately twenty to thirty millimetres diameter such that concrete grout may be conveniently pumped therethrough. The piling apparatus may be produced in any desired length to suit the depth to which

it must be driven to anchor in a secure footing, but typically is produced in lengths ranging from two metres to eight metres.

The flight may be produced with proportions suited to the ground conditions in which it is to be placed. For instance, the flight may be formed in any desired size relative to the core, and with any desired helix angle. If desired, the flight may be formed with an overall diameter tapering along its length. If desired, the flight may be provided with penetration enhancement means, such as cutting teeth or the like formed on or attached to the leading edge thereof for assisting the cutting process as the pile is augered into the ground. The cutting teeth may include tungsten carbide inserts or other wear-resistant material in a form such as points or chisel bits.

In another aspect of this invention, a pile is disclosed having its exterior periphery formed in a helical shape such that rotation of said pile about its longitudinal axis may urge it axially through the ground with which said pile is engaged.

Suitably, the pile is formed with a cross-section which is circular, and successive circular cross-sections along the piling apparatus are disposed about a helical pile axis, whereby minimal ground disturbance may occur during installation of the piling apparatus into the ground. Of course, if desired, other pile cross-sections, such as elliptical or rectangular may be used.

The pile may be formed by casting from a castable material such as concrete, and may if desired be metal- reinforced internally or along the external surfaces in contact with the ground in use, whereby damage to the concrete during installation may be minimised.

Alternatively, the helical piling apparatus may include a tubular metal casing formed into a helix, and the tubular casing may be a thin-walled tube. For the purposes of this specification, the term "thin-walled" is to be taken to mean a tube of wall thickness less then ten percent of its outside

diameter, and may encompass thicknesses ranging between one and twenty millimetres.

The tubular casing may be partially or wholly filled with a castable material such as concrete before or after installation such that the tubular casing may be very thin relative to the casing diameter with minimal risk of buckling the casing during installation. Suitably, the casing may be less than one percent of the casing diameter, or even one- half percent of the casing diameter whereby the use of relatively expensive metal in the piling apparatus may be minimised.

The helical pitch along the piling apparatus may be of any desired ratio relative to the casing diameter. In a preferred embodiment, the helical pitch is between once and twice the casing diameter and is preferably one hundred and twenty percent of the casing diameter whereby a suitable compromise may be attained between the number of turns required to install the piling apparatus and the disturbance to the ground in which it is installed. An extension pile may be provided for forming a long pile in combination with a piling apparatus, and may include pile joining means whereby the extension pile may be joined to the piling apparatus. The joining means may include complementary flanges for joining by welding, but it is preferred that the joining means include complementary tapered portions formed on abutting ends of the helical piling apparatus and the extension pile. The tapered portions may be joined by frictional engagement, adhesive bonding, or by friction welding by relative rotation between the piling apparatus and the extension pile.

The helical piling apparatus may be provided with penetration assistance means, such as a conical or frusto- conical point formed thereon, and the conical point may include helical ridges such that rotation of the helical piling apparatus may urge the conical point into the ground. Preferably or in addition, however, the penetration means may include a spade-like cutting blade attached substantially across a diameter of the leading end of the helical piling

apparatus.

In another aspect, this invention resides in a method of forming helical piling apparatus as defined above from a straight cylindrical metal tube, said method including:- (a) providing a tube clamp apparatus;

(b) providing a tube bending apparatus adjacent said tube clamp apparatus;

(c) placing the metal tube in said tube clamp apparatus with a tube end projecting therefrom; (d) forming a bend in said tube end using said tube bending apparatus;

(e) rotating the metal tube about its tube axis by a selected incremental angle relative to said tube bending apparatus; (f) advancing the metal tube along said tube axis from said tube clamp apparatus towards said tube bending apparatus by a selected linear increment; and

(g) repeating steps (d) to (f) such that the metal tube is formed into a helical configuration.

Preferably, the tube clamp apparatus includes tube rotation means and tube axial advance means whereby the metal tube may be rotated and advanced automatically in predetermined increments between bending operations, and the bending apparatus includes bending increment control interlinked to the tube clamp apparatus whereby steps (d) to (f) may proceed automatically in repetitive sequence.

If desired, tube heating apparatus may be provided for heating the tube in the bending zone such that it may be softened and bend more easily in the bending zone. The heating apparatus may be in the form of a flame heating ring disposed about the tube, or an inductive heating loop similarly disposed.

In an alternative embodiment of the invention, a method of forming a helical pile casing is disclosed including:- providing a pair of forming plates, each said forming plate having its forming surface formed in a set of parallel grooves of cross-section equivalent to the transverse section

of the finished pile; placing said forming plates with their said forming surfaces facing one another and with respective said sets of parallel grooves inclined angularly relative to one another; placing a cylindrical tube between said forming plates, and sliding one said forming plate relative to other said forming plate whereby said tube may be rolled between said forming plates such that said tube may assume a helical shape.

If desired, the tube may be at least partially filled with a ductile material such as bismuth, lead or an alloy which may support the tube such that tube surface buckling during rolling may be minimised, and which may be subsequently removed by a removal process such as the application of heat to the formed pile, whereby the ductile material therein may be fluidised and drained therefrom. In a further aspect of this invention, a method of forming a helical pile casing is disclosed, said method including:- providing a continuous length of flat sheet material; passing said flat material through forming rollers such that ridged material is formed; winding said ridged material helically to form a helically-ridged cylinder; and joining abutting edges of said ridged material. In a further aspect, this invention resides in a method of forming an inground foundation pile, including:- providing piling apparatus having an elongate core, at least one helical flight projecting outwardly from said elongate core and by which said piling apparatus may be screwed downwardly into the ground, and an axially-extending grouting passage formed through said elongate core and through which grout may be pumped in use to provide a grout encapsulation about said piling apparatus; installing said piling apparatus in the ground by rotating same and applying an axial preload thereto,

and injecting grouting material about said flight through said grouting passage whereby the supporting capacity of said piling apparatus may be enhanced. In a further aspect, this invention resides in driving apparatus for installing a helical pile formed from a thin- walled tubular casing having its peripheral wall formed with a helical ridge therein, said driving apparatus including:- a driver base engageable with the ground; a drive nut engageable with the outer surface of said helical ridge and supported by said driver base; rotary drive means for rotating said drive nut relative to said driver base about the pile axis of a helical pile casing engaged therewith; and nut thrust means for urging said drive nut toward the ground relative to said driver base along said pile axis.

The drive nut may include pile clamp means adapted for selectively clamping frictionally or otherwise to the outer surface of the helical pile, whereby rotation of the drive nut about the pile axis may rotate a helical pile engaged therewith. The drive nut may also or alternatively include low-friction surfaces or anti-friction bearings such as roller bearings engageable with the outer surface of the helical pile whereby axial movement of the drive nut may rotate the helical pile.

The driver base may engage frictionally with the ground for resisting the torsional and lifting loads applied thereto during the driving operation. If desired, the driver base may be provided with ground-engagement means such as one or more helical augers or the like supported thereon and engageable with the ground for resisting applied loads whereby the necessary driver base mass may be minimised.

In another aspect of this invention, a method of forming an inground helical pile is disclosed, said method including:- providing a thin-walled tubular casing having its peripheral wall formed with a helical ridge therein;

providing a helical pile-driving apparatus having a base engageable with the ground, a drive nut engageable with the outer surface of said helical ridge, rotary drive means for rotating said drive nut about the pile axis of a helical pile casing engaged therewith, and nut thrust means for urging said drive nut toward the ground along said pile axis; engaging said tubular casing with said drive nut; and operating said nut thrust means and/or said rotary drive means such that said tubular casing is screwed into the ground.

Preferably, the tubular casing is hollow during the driving operation, and is filled with concrete after driving to complete the inground pile. If desired, a driving mandrel may be provided, and may be formed to engage with the inner wall of the tubular casing during the driving operation such that driving forces applied by the drive nut or the ground may be prevented from buckling the tubular casing, such that a tubular casing of thin wall section relative to its diameter may be used. The driving mandrel may be screwed into the tubular casing before driving commences, and may be clamped therein, or supported at a desired height therein by support means such as a crane or the like.

— BRIEF DESCRIPTION OF THE DRAWINGS -

In order that this invention may be more easily understood and put into practical effect, reference will now be made to the accompanying drawings which illustrate a preferred embodiment of the invention, wherein:-

FIG. 1 is a part-sectional side view of a helical pile and a helical pile installation apparatus according to the invention;

FIG. 2 and 3 are pictorial views of the helical pile casing;

FIG. 4 is a side view of the helical pile casing shown in FIGS. 2 and 3;

FIG. 5 is a cross-sectional side view of the installed

helical pile;

FIG. 6 is a plan view of an alternative embodiment of the piling apparatus;

FIG. 7 is a transverse cross-section through the piling apparatus of FIG. 6, and

FIG. 8 shows the piling apparatus shown in FIGS. 6 and 7 installed and grouted in position as a foundation pier.

— DESCRIPTION OF THE PREFERRED EMBODIMENTS —

The installation apparatus 10 shown in FIG. 1 has a crawler undercarriage 11 upon which a machine frame 12 is supported. The machine frame 12 carries a hydraulic power pack 13 on its upper surface and a pile driving assembly 14 is pivoted to its front end 15 and braced in a vertical position by braces 16 attached between its rear end 17 and the upper end of the pile driving assembly 14.

The pile driving assembly 14 includes a pair of slides 20 along which a nut carrier 21 may be urged by a pair of actuators 22. Within the nut carrier 21 are machined circular bearing tracks 23, and nut carrier rollers 24 and 25 mounted within them support a drive nut 26 for free rotation therein. The drive nut has a gear ring 27 formed about it. A slew drive motor 30 drives through a slew drive shaft 31 a pinion 32 which engages with the gear ring 27. The slew drive motor 30 and the actuators 22 are driven by the hydraulic power pack 13.

The bore of the drive nut 26 is formed with mounting bosses 33 and recesses 34 within which pile drive rollers 35 are mounted. The latter are formed with cylindrical, barrel- shaped or waisted surfaces according to their locations within the drive nut 26 to provide maximum surface contact with the helical surface of a helical pile 36 passing therethrough. A brake assembly 37 mounted on the drive nut 26 allows the helical pile 36 to be locked to it such that operation of the slew drive motor 30 may rotate the helical pile 36.

The helical pile 36 has a tubular body 40 to the lower

end of which a hollow frusto-conical penetrator 41 and a pointed cutting bit 42 are attached. The upper end 43 of the helical pile is swaged to a diameter such that an extension pile of similar diameter to the body 40 may slide over it. A helical mandrel 44 which is a sliding fit within the body 40 is inserted within the helical pile 36 before it is driven to support the body 40 against collapse during the driving process.

The helical pile 36 is prepared for driving by raising the nut carrier 21 to the upper ends of the slides 20 using the actuators 22, and then inserting the pile 36 through the drive nut 26 until it rests on the ground 45. The helical mandrel 44 is inserted into the pile 36. The slew drive motor 30 is then locked to prevent rotation of the drive nut 26, and the actuators 22 are extended to urge the drive nut downward. As the latter is unable to rotate, it forces the helical pile 36 to rotate and to enter the ground 45.

If the ground conditions are inappropriate for use of this downthrust driving technique, the brake assembly 37 may be energised to lock the drive nut 26 to the helical pile 36, permitting the slew drive motor 30 to be used to rotate the helical pile 36 as it is forced into the ground 45 by the actuators 22, operation of the latter and the slew drive motor 30 being synchronised to produce the helical driving action appropriate to the axial pitch of the helix formed in the pile 36.

After the helical pile 36 has been driven to a depth appropriate to the achievement of the desired bearing capacity, the drive nut 26 is raised to release it from the pile 36, the helical mandrel 44 is removed, and concrete 46 is poured into the pile 36 to complete the installation, as shown in FIG. 5. Reinforcing bars 47 may be added to the concrete 46 for anchoring construction framework to the helical pile 36. The piling apparatus 60 shown in FIGS. 6, 7 and 8 comprises a cylindrical core 61 with a helical flight 62 formed about its lower end 63. The upper end 64 of the core 61 is engageable with a cylindrical recess 65 formed in a

drive head 66. A recessed sector 67 formed in the upper end 14 engages with a driving dog 70 formed within the recess 65 to provide torque transmission means between the drive shaft 66 and the piling apparatus 60. A grout passage 71 is formed through the core 61, and grout delivery tubes 72 connect the grout passage 71 to grout nozzles 73 distributed about the lower end 63 and the flight 62. A cutting head 75 is attached to the leading edge 74 of the flight 62. The piling apparatus 60 is formed from reinforced concrete, and the surfaces of the flight exposed to contact with the ground during driving are enclosed within a fabricated steel jacket 76.

The piling apparatus 60 is driven into the ground 77 to a desired depth by rotation and preload applied through the drive head 66, which is then removed. Grout may then be pumped from the upper end 64 through the grout passage 71 and out of the grout nozzles 73 to form, after setting, a region of grout encapsulation 78 about the flight 62. It will of course be realised that while the above has been given by way of illustrative example of this invention, all such and other modifications and variations thereto as would be apparent to persons skilled in the art are deemed to fall within the broad scope and ambit of this invention as is herein defined in the appended claims.