AU608395B2 - Improvements in drilled or bored piles - Google Patents

Description

zkxMAnisaodONw 1N)rIFH0s ~qDV -Id 01 7TMU7 4 J -ul: COMMONWEALTH OF AUSTRALIA Paient Act 1952 6 8395

COMPLETE

S P E C I F I CAT N

(ORIGINAL)

Class Int. Class Application Number :PI 5918 Lodged :15 December 1987 Complete Specification Lodged Accepted Published .4 .4 ~4 ,9

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Priority: Related Art Name of Applicant Address of Applicant FRANKIPILE AUSTRALIA PTY. LIMITED

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ft c Actual Inventor Address for Service 4 ft 5th Floor, 69 Phillip Street PARRAMATTA NSW 2150 This document contains the Slav Tchepak amendments made under F.B. RIC C ection 49 and is correct for F.B. RICE CO., printing Patent Attorneys, printi 28A Montague Street, BALMAIN. 2041.

Complete Specification for the invention entitled: "IMPROVEMENTS IN DRILLED OR BORED PILEL" The following statement is a full description of this invention including the best method of performing it known to Us:- CI I- c 1 1 2 The present invention relates to the use of expandable sections in drilled or bored piles so as to give greater load bearing capacity and superior load deflection performance.

Drilled or bored piles have been used in the art for areas where the vibration, caused by driven piles, is a problem. Drilled or bored piles may be formed using an auger, the auger comprising a central, hollow, cylindrical shaft with helical flights extending rdially outward from the central shaft. The auger is drilled into the ground to a required depth. The hardenable pile material in a liquid form is then pumped into the drilled bore either c11C with the auger remaining in the bore or while the auger is I removed, as is disclosed in our copending Australian 15 patent application No. 18781/88 (which is incorporated herein by reference).

so i After the step of filling the bore with the s* hardenable material a steel reinforcement cage may Le dropped or driven into the bore.

aV20 There are a number of inherent disadvantages in these methods of forming bored piles, including the fact that 0 at these bored piles are only suitable for low loading, both 00, vertically and laterally and are susceptible to failure o a o under high loads.

oooo000000 25 Various methods for improving the load bearing capacity of drilled or bored piles have been attempted 0000 including the use of Steel tubes with thin folded walls whichi are attached to the pile and which form a bulb when expanded in the soil by injection of a cement grout.

This method also has several disadvantages, as it can only be used foir low load bearing applications since when used for high load bearing applications the equipment is cumbersome and heavy and the bulb is rigid under expansion due to its relatively thick walled steel construction.

Further, while undergoing expansion due to the supply of a 3 cement grout the steel tube extends radially but at the same time contracts vertically.

In a first aspect the present invention consists in a bored pile comprising a main portion having a first diameter and at least one expanded section centred on the longitudinal axis of said pile and extending outwardly from said pile, said expanded section being surrounded by a geotextile fabric bag and having a diameter greater than said first diameter.

A further aspect of the present invention consists in a method of forming a bored pile comprising boring or drilling a hole of a first diameter into the ground and filling said hole with a hardenable material characterized in that at least one expandable geotextile bag is provided 15 within said hole, said bag(s) being expanded outwardly to a second diameter greater than said first diameter by supplying hardenable material under pressure to said 0 bag(s).

A further aspect of the present invention consists in an expandable geotextile bag when used in a drilled or bored pile, said bag being placed within said hole a expanded outwardly by supplying a hardenable mate Ial under pressure to said bag.

In a particularly preferred embodiment he expanded t 25 section formed by expanding the geotext e bag has a diameter which is substantially grea r than the diameter of the pile. In this way, the sod surrounding the pile c is compacted thereby increasi the loading capacity of the pile.

The timing of placng the expandable bag in the drilled bore is not ssential to the invention. In certain piles th bag may be positioned and expanded prior or subsequen o the filling of the bore and forming the pile wher s with other piles the positioning and expand' g of the bag and the filling of the bore to form the ile is a simultaneous process.

The same criteria applies to a steel cage Rj P A V- -lm~u 3a A further aspect of the present invention consists in an expandable geotextile bag when used in a drilled or bored pile, said bag being placed within a bore for said pile of a first diameter and expanded outwardly to a second diameter by supplying a hardenable material under pressure to said bag, said second diameter being greater than said first diameter.

In a particularly preferred embodiment the expanded section formed by expanding the geotextile bag has a diameter which is substantially greater than the diameter of the pile. In this way, the soil surrounding the pile is compacted thereby increasing the loading capacity of the pile.

S, The timing of placing the expandable bag in the drilled bore is not essential to the invention. In certain piles the bag may be positioned and expanded prior for subsequent to the filling of the bore and forming the pile whereas with other piles the positioning and t expanding of the bag and the filling of the bore to form the pile is a simultaneous process.

The same criteria applies to a steel cage tee tt t C 4 reinforcement which may be included in the pile. That Xs, the bag can be positioned and/or expanded either prior fr subsequent to the placement of the steel cage reinforcement within the pile.

It must be stated here that the present invention is not restricted to the use of only one bag per pile. It can be envisaged that several bags can be used per pile to cope with vertical and lateral stresses associated with the use of bored or drilled piles.

A further embodiment of the present invention consists in at least one expandable geotextile bag being oso placed at the bottom of said hole such that a pile is 0 "000 formed with one expanded section at the bottom. This 0 00 00 0 o.0 particular configuration has been found to give greatly 15 increased loading capacity and soil compaction around the 0 00 o ao pile.

00o 0 o o 0 A further preferred embodiment includes the 0 90 expandable geotextile bag being of a spherical or conical shape in order that the expanded section formed from the 0 00 o00° 20 particularly shaped geotextile bag conforms to the 0oo particular load requirements of the pile.

It is also envisaged ,hat the expandable geotextile 00 0 o~ bag may be installed into a bore hole which has been oao..O drilled using any excavation or drilling tools. In 0 0 particular the auger used in our copending application 000oo0 0oo 18781/88 would provide increased stability and soil oOoo0 compaction around the pile. Further, the bore hole may in D 0 certain ground conditions require temporary or permanent support. This may be offered by casings, which may be driven or installed by other means, hollow auger flights or stabilising drilling fluids, such as water or bentonite. Usually, where temporary excavation support is used during formation of the bore hole, this is removed and replaced by the pressure exerted by the hardenable material in the bore hole shaft.

5 As far as the properties of the hardenable material, which is pumped into the expandable bag, are concerned, it is preferred that the grout should have a water-cement ratio of 0.45 to 0.50 and anti-shrinkage additives. Also, plasticizers may be used to facilitate pumping of the grout. As the geotextile may be permeable, water may permeate into the soil. Thus, the quality of the grout in the expanded section improves significantly. It should be noted here that the hardenable material in the expandable bag is not necessarily the same as the hardenable material of the pile. Indeed it will be recognised by those skilled in the art that both hardenable materials chosen will depend upon the loading characteristics of the pile.

When the bag is expanded while the grout in the pile 15 is still soft, the bag will first expand vertically in the s direction of least resistance. At high pressure the °o expanded section will assume the shape of the geotextile bag. Theoretically, relatively high tensile stresses can occur in the geotextile bag, when not confined in the 0 00 0° o° 20 vertical direction. The maximum stress will depend on the o0. bag diameter and the expansion pressure. Assuming an expansion pressure of 50 bar in a bag diameter of D 0.7m, 00 0 0 the tensile force is about 900kN/m. Preferably, the .oooo geotextile fabric is of high tensile strength and is chosen from those which are available in the market.

o.oo In order that the nature of the present invention may be more readily understood, preferred embodiments thereof will now be described with reference to the accompanying drawings in which:- Figures 1A-1D are a schematic of the present invention using the "auger cast" technique; Figures 2A-2C are a schematic of the present invention using a second cast-in-situ technique; Figures 3A 3B are two embodiments of the expandable geotextile bag shape.

6 -6- Figure IA shows the auger 1 drilling a bore 2 for the pile.

In Figure 1B the auger has stopped drilling, the tip of the auger 3 is provided with an outlet 4 which is in communication with the hollow central shaft Hardenable material 6, such as grout or concrete is pumped at constant pressure down the central shaft whilst the auger 1 is removed, leaving a cilumn of liquid grout.

In Figure 1C the expandable geotextile bag 7 is then lowered into the liquid column pipe with its associated plumbing 10 connected to a supply of hardenable material 6, in this case the same as the pile composition. The material is pumped into the bag which expands in all directions as shown by arrows 8, to form the expanded bulb and pile 9 (Figure 1D) and left to harden with associated plumbing 10 attached.

0 00 It should be noted here that the bag can be held at any height in the pile art more than one bag can be placed o 00 20 in the pile.

0 00 0o o0 In a further embodiment shown in Figure 2A an auger or drilling tool 21' of a different type to Figure 1A is 00 0 Co drilled into the ground and forms bore hole 22'.

ooooo0 The expandable geotextile bag 27' is lowered into the 25 bore hole 12' after which hardenable material is pumped 0 00 0o0 into the bore hole through opening 11 and into the oooo: geotextile bag through opening 11 and pipe 10. (Fig. 2B).

Once the bore hole is full the auger 21' is removed and the geotextile bag is expanded to form expanded section 29. (Fig. 2C).

Note that in both cases in Figures 1C and 2C that a steel reinforcement cage is not illustrated. This reinforcement cage can be placed in the wet liquid pile before or after expansion of the bag to form the bulb.

Another important aspect is soil compaction around I 7 the pile which may occur as a result of the bag expansion. The soil will be displaced in the direction of least resistance i.e. towards the pile shaft (see Figure 3A). Under unfavourable conditions, a reduction of the pile shaft (necking) can thus occur just above the expanded bulb. The shape of the geotextile bag may therefore be chosen to be conical to overcome this disadvantage (see Figure 3B).

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Claims (14)

1. A bored pile comprising a main portion having a first diameter and at least one expanded section centred on the longitudinal axis of said pile and extending outwardly from said pile, said expanded section being surrounded by a geotextile fabric bag and having a diameter greater than said first diameter. 2, A bored pile as claimed in claim 1 wherein the diameter of each expanded section is substantially greater than said first diameter, in order to produce an increased compaction of soil around said pile.

3. A bored pile as claimed in claim 1 or 2 wherein said pile includes a steel reinforcement cage. oak, 4. A bored pile as claimed in any one of claims 1-3 wherein a plurality of expanded sections are located between the bottom of the pile and ground level. A bored pile as claimed in any one of claims 1-4 wherein said pile is provided with one expanded section at the bottom of said pile.

6. A bored pile as claimed in any one of claims wherein said expanded section is spherical in shape.

7. A bored pile as claimed in any one of claims Swherein said expanded section is conical in shape. set

8. A method of forming a bored pile comprising boring or 8 drilling a hole of a first diameter into the ground and C filling said hole with a hardenable material characterized in that at least one expandable geotextile bag is provided within said hole, said bag(s) being expanded outwardly to a second diameter greater than said first diameter by supplying hardenable material under pressure to said bag(s).

9. A method of forming a bored pile as claimed in claim 8 wherein an expandable geotextile bag is provided within said hole prior to the filling of said hole with hardenable material. pRA7Bi e V KA >L 1_ 2 i i I i A method of forming a bored pile as claimed in claim 8 wherein an expanded geotextile bag is provided within said hole during the filling of said hole with hardenable material.

11. A method of forming a bored pile as claimed in claim 8 wherein an expandable geotextile bag is provided within said hole subsequent to the filling of said hole with hardenable material.

12. A method of forming a bored pile as claimed in any one of claims 8-11 in which a steel reinforcement cage is placed in said hole.

13. A method of forming a bored pile as claimed in any one of claims 8-12 wherein the diameter of each said expandable geotextile bag is substantially greater than the diameter of the hole, in order to produce an increased compaction of soil around said pile.

14. A method of forming a bored pile as claimed in any one of claims 8-13 wherein one expandable geotextile bag is placed at the bottom of said hole. A method of forming a bored pile as claimed in any one of claims 8-14 wherein said geotextile bag is spherical in shape.

16. A method of forming a bored pile as claimed in any one of claims 8-14 wherein said geotextile bag is conical in shape.

17. An expandable geotextile bag when used in a drilled or bored pile, said bag being placed within a bore for said pile of a first diameter and expanded outwardly to a second diameter by supplying a hatdenable material under pressure to said bag, said second diameter being greater than said first diameter.

18. A bored pile substantially as hereinbefore described with reference to the accompanying drawings. a a a a, t

19. A method of forming a bored pile substantially as hereinbefore described with reference to the accompanying drawings. An expandable geotextile bag when used in a drilled or bored pile. substantially as hereinbefore described with reference to the accompanying drawings. DATED this 4 day of January 1991 FRANKIPILE AUSTRALIA PTY LIMITED c Patent Attorneys for the Applicant: F B. RICE CO. a 000000 0 0