AU2008200540B2

AU2008200540B2 - Drills for piles

Info

Publication number: AU2008200540B2
Application number: AU2008200540A
Authority: AU
Inventors: Stuart Coutts
Original assignee: Catawa Pty Ltd
Current assignee: Catawa Pty Ltd
Priority date: 2007-02-05
Filing date: 2008-02-05
Publication date: 2014-05-15
Anticipated expiration: 2028-02-05
Also published as: AU2008200540A1

Abstract

TITLE: DRILLS FOR PILES A drilling assembly (20) for a method of drilling holes (10) for in situ cast piles (100) has cutting tools (30) selectively moved to an extended 5 position to form an enlarged chamber (11) at the bottom of the hole (11). Bentonite slurry (80) is pumped through the stem (21) of the drilling assembly (20), as the hole (10) and chamber (11) are formed; and then grout (90) (such as cement or geo-polymer) is pumped down the stem (21) as the drilling assembly (20) is rotated in a reverse direction and is withdrawn from 10 the hole (10).

Description

P/00/011 Regulation 3.2 AUSTRALIA Patents Act 1990 ORIGINAL COMPLETE SPECIFICATION STANDARD PATENT Invention Title: "DRILLS FOR PILES" The following statement is a full description of this invention, including the best method of performing it known to us: 1 TITLE: DRILLS FOR PILES BACKGROUND OF THE INVENTION 1. Field of the Invention THIS INVENTION relates to a drill assembly for piles, and a 5 method of drilling a hole for an in-situ cast pile. The term "pile" shall also be used to include rock belts, ground- or sand-anchors, tension piles or the like. 2. Prior Art AU-B-1 2848/88 (586947) and AU-B-23875/88 (634150), both in our name, disclose drill assemblies for drilling holes for belled piles, and the 10 methods for in-situ casting of the piles. In both specifications, the drill assemblies are rotated in one direction to drill the hole; reversed to cause the cutting tool(s) to extend and cut the bell; and then rotated in the original drilling direction to retract the cutting tools to be retracted as the drilling assembly is withdrawn from the hole. is In most applications, the drilling assemblies (and methods) have proved satisfactory. However, in certain soils, eg. clay, the reverse direction rotation, as the bell is produced, opposes the movement of the clay up the drilling flyte or spiral and clogging of the drilling assembly can occur. SUMMARY OF THE INVENTION 20 It is an object of the present invention to provide a drilling assembly where both the hole and bell are formed with the assembly rotating in the same direction. It is a preferred object to provide such an assembly where the assembly is withdrawn from the hole while rotated (slowly) in the reverse 25 direction.

2 It is a further preferred object to provide an assembly where the assembly, after drilling the hole, is briefly rotated in the reverse direction, to release (or move) the cutting tool(s) from the retracted (non-belling) position. It is a still further preferred object to provide a method of 5 forming an in-situ cast pile using the assembly as hereinbefore described. Other preferred objects will become apparent from the following description. In one aspect, the present invention resides in a drill assembly for drilling holes in the ground including: 10 a stem connectable at one end to a drilling machine and having a drilling head at the other end; a helical drilling flyte or spiral around or within the stem; and at least one cutting tool hingedly mounted on the stem, (or in a cavity in the periphery of a housing around the stem), movable between a 15 retracted non-cutting position adjacent the stem (or within the cavity), and an extended position to cut a respective substantially annular chamber around the hole; and control means operable to retain the cutting tool in the retracted position when the stem is rotated in the drilling direction of the 2o helical flyte or spiral as the hole is drilled but operable to release the cutting tool to move to the extended position to cut the annular chamber when the stem is further rotated in the drilling direction. The drilling head may include a drilling point, drilling plate, drilling teeth and/or at least one helical flyte. 25 The control means may include mechanical latches, pawls, 3 links, cables, hydraulic rams or the like to restrain or move the or each cutting tool. The control means may also move the or each cutting tool towards the extended position and includes wedges, links, hydraulic or 5 pneumatic rams, hydrostatic motors or the like. The control means may move the cutting tool to the retracted position and/or retain it in that position, when the stem is rotated in the opposite direction. The stem may comprise a drilling rod, auger or casing. 10 Preferably, the stem is hollow to allow the passing of drilling fluid, chemicals, air, foam, geo-polymer and/or grout down through the stem and into the hole and/or the chamber formed by the drill assembly. Where the cutting tools are moved by hydraulic or pneumatic rams, or hydrostatic motors, suitable hydraulic hoses/air lines may be provided within the stem and are connected 15 to a source of pressurised oil/air by a rotary coupling. A plurality of the cutting tools may be provided along the length of the stem to enable a plurality of "bells" to be formed which enable a tapered shear column to be cast in-situ. The or each cutting tool may have a downwardly inclined top 20 face so that the top of the annular chamber is upwardly convergent. In a second aspect, the present invention resides in a method of drilling a hole for an in-situ cast pile (or rock bolt, ground-or-sand anchor or tension pile) including the steps of: drilling the hole to the required depth using the drill assembly 25 hereinbefore described, the stem being rotated in the drilling direction; 4 causing the or each cutting tool to be released and/or extended at least partially from the retracted position; rotating the drill assembly in the drilling direction to cause the or each cutting tool to be fully extended and cut a respective annular 5 chamber around the hole; raising the drill assembly while rotating to increase the height of the chamber; reversing the direction of the stem to return the or each cutting tool to its retracted position; and 10 withdrawing the drill assembly from the hole (preferably while the drill assembly is rotated in the reverse direction). Drilling fluids or chemicals and/or air may be pumped down the stem to raise the material in the hole to the surface. In a third aspect, the present invention resides in a method of 15 in-situ casting of piles including: drilling a hole as hereinbefore described; pumping grout down the stem and out through a hole in the stem adjacent the drilling point when the annular chamber has been cut and as the drill assembly is withdrawn from the hole; and 20 allowing the grout to set. Preferably, the or each cutting tool acts to assist in the distribution of the grout within the chamber and the hole. The grout may include, or comprise, geo-polymer. BRIEF DESCRIPTION OF THE DRAWINGS 25 To enable the invention to be fully understood, preferred 5 embodiments will now be described with reference to the accompanying drawings, in which: FIG. 1 is a schematic drawing of the steps of drilling and casting the pile; s FIG. 2 is a sectional plan view of the drill assembly of the first embodiment; FIG. 3 is a similar view of the drill assembly of the second embodiment; FIG. 4 is a schematic side elevational view of the drill assembly 10 of the second embodiment; and FIGS. 5 to 7 are sectional views, taken on lines A-A, B-B and C-C, respectively, on FIG. 4. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 15 Referring to FIG. 1, in step 1, the hole 10 is drilled with this drill assembly 20 rotated in the drilling direction (indicated by the clockwise arrow) until the desired depth is reached. Preferably, the base of the pile 100 will be formed in a cohesionless material strata below the water table. The direction of rotation may be briefly reversed (step 1(a)) to 20 allow the cutting tool(s) to be released and/or at least partially extended from the retracted position. The direction of rotation is returned to the drilling direction (step 2) and the cutting tool(s) 30 to extend to the extended (cutting) position to enable the annular chamber 11 to be cut (the hole and chamber being filled 25 with bentonite slurry 80 (or other drilling mud) as the annular chamber 11 is 6 formed. The direction of rotation is reversed (step 3) and the cutting tool(s) 30 retracts. As the drilling assembly 20 is retracted (under slow reverse rotation), cement grout 90 is pumped down the stem and displaces the s bentonite slurry 80. Before the cement grout 90 sets, suitable reinforcing steel may be placed in the pile 100 (step 4). When the grout 90 sets, the pile 100 is completed. Referring to FIG. 2, the drilling assembly 20 is generally of the type shown in AU-B-12848/88 (586947) and has a stem 21, with a central 10 bore 22 and radial grout passages 23. A helical drilling flyte or spiral (not shown) is provided around the stem 21 and has a drilling direction indicated by arrow A. A pair of cutting tools 30, with a series of hardened teeth 31 are hingedly mounted on pivot pins 32 supported by pairs of radial brackets 33 15 on the stem 21. (The tools 30 may be received, in their retracted position shown in solid lines, in respective cavities in a housing (not shown) about the stem 21, the pins 32 being mounted in the housing.) A latch member 40 for each cutting tool 30 has its inner end pivotally mounted on a pivot pin 41 supported by a pair of brackets 42 on the 20 stem 21. The latch member 40 has a nose 43 which is engageable with the tip of its cutting tool 30 to releasably secure the latter in the retracted position. When the hole 10 is drilled (FIG. 1, step 1), the latch members 40 engage the cutting tools 30 and retain them in the retracted position. 25 When the direction of rotation is briefly reversed (ie. the 7 direction of rotation is opposite to arrow A), the material in the hole 10 will engage the latch members 40 and move them in the direction of arrow B to release the cutting tools 30. The drag on the cutting tools 30 from the material will cause them to become at least partially extended. 5 The direction of rotation is then returned to the drilling direction (arrow A) and the cutting tools 30 will swing outwardly to the extended (cutting) positions shown in dashed lines. As the cutting tools 30 swing outwardly, the latch members 40 will swing inwardly (in the direction of arrow C) to be against the stem 21. 10 When the annular chamber 11 has been cut (and the holes 10 in chamber 11 filled with bentonite slurry 90 pumped down bore 22 in stem 21), as shown in step 2, the direction of rotation of the stem 21 is reversed (step 3) and the drilling assembly 20 is rotated slowly in the reverse direction (ie. opposite to arrow A). The slurry 80 in the chamber 11 causes the cutting is tools 30 to swing inwardly to the retracted position and the drilling assembly 20 is raised. The grout 90 pumped down the bore 22 of the stem 21 will displace the bentonite slurry 80 up the helical flyte or spiral and the chamber 11 and hole 100 will be progressively filled with grout (see step 4). Alternative methods and apparatus, not illustrated, may be 20 used to extend (and optionally retract) the cutting tool(s) 30 and examples of these are hereinafter discussed: (1) each cutting tool is provided with a hydraulic or pneumatic ram - the rams may be single-acting for extension only, or double acting and the fluid lines may pass down through the bore 22 in the stem 21 25 or be laid under the flytes or spiral adjacent the stem; 8 (2) an electric motor can have a pair of opposed hand nuts which receive screw-threaded shafts connected to the cutting tools; (3) each cutting tool can have a respective solenoid with an operating rod to extend and retract the tools; 5 (4) a mechanical linkage can extend down the bore 22 in stem 21 and have, eg. a finger or link to urge the cutting tool(s) to the at least partially extended position; (5) the stem can have a drilling point connected to the stem by a ram or screw-threaded coupling, and by extending the ram or reverse 10 rotation of the stem, the drilling point is advanced from the stem to release the cutting tools, or latches therefor, clamped between the drilling point and the stem; (6) the drilling slurry can be pumped at high pressure through the ports 23 (or selectively operable secondary ports) to at least 15 partially extend the cutting tools; (7) each cutting tool is fixed on its pivot pin 32 which is journalled in the brackets 33, and which has a screw-threaded extension received in a nut at the distal end of the piston rod of a hydraulic ram. As the piston rod is extended and retracted, the nut rotates the pivot pin 32 to 20 extend, or retract, the cutting tool 30 respectively; (8) a ram has a piston rod with a wedge shaped extension which passes between each tool 30 and its latch 40 and a cable connected to the other tool 30. As the piston rod extends, the wedge both releases the latch 40 and swings out the tool 30 a small distance (and the cable allows 25 the second tool 30 to also be swung out). As the piston rod is retracted, the 9 cable causes the second tool 30 to be retracted (while its piston rod and cable retracts the first tool 30); (9) a ram has a piston rod with a wedge-shaped extension at its distal end, operable to engage a complementary cam- or wedge-face 5 on the cutting tool 30; (10) a hydrostatic motor is interposed between the drilling stem and the drilling point, blade or plate, preferably enclosed within a protective housing. A hydraulic pipe is connected to the hydrostatic motor and connects it to a source of pressurised hydraulic fluid. The pipe can (a) 10 extend down the exterior of the drilling stem; (b) be spirally-wound around the drilling stem, eg., adjacent the root of the auger flyte or (c) extend through the drilling stem, eg., surrounded by an annular passage for the grout. The pipe is connected to the source by a rotary connector at the head of the drilling stem. A suitable gear-train can interconnect the hydrostatic 15 motor to the cutting tool 30 to amplify (or multiply) the torque output of the hydrostatic motor, to allow a very compact motor to be used. In a further alternative embodiment not illustrated, the hole 10 is drilled with a conventional auger. When the desired depth is reached, that auger is withdrawn (and the hole may be filled with slurry as the auger is 20 withdrawn to prevent collapse). The cutting tools are fitted to the auger and it is fed down the hole. When the auger is rotated in the drilling direction, the cutting tools will extend and the chamber 11 is formed. The direction is reversed and the auger (and tools) withdrawn. By monitoring the torque required to rotate the drilling assembly 25 20 when the bell is being formed, the strength of the soil about the bell (and 10 thereby the load capacity of the pile) can be monitored. If the torque is below a preset level, then the load capacity of the pile will be compromised, and further piles may be required to achieve the desired load capacity. Referring to FIGS. 3 to 7, the drill assembly 120 of a second 5 (illustrated) embodiment has a tubular stem 121, with circular bore 122; and an upper portion 124 of the stem 121 (see FIG. 5) has a square bore 125, with an annular mounting plate 126 for attachment to the drill string (not shown). As shown in FIGS. 4 to 7, angled nozzles 127 extend from the 10 stem 121 to enable the bentonite slurry 80, cement grout 90 (or geo-polymer) to be injected into the hole 10 (and bell chamber 11). A conventional (ie., off-the-shelf) drilling head 170 is fitted to the lower end of the stem 121, and will be selected to suit the soil (eg., sand, rock) in which the hole 10 for the pile 100 is to be drilled. 15 In the embodiment illustrated, a "twisted" bit 171 precedes teeth 172 extending from a helical flyte 173. The cutting tools 130 have an enlarged-thickness hub (not shown) pivotally mounted on pivot pins 132 received in bores 134 in vertically spaced radial brackets 133. 20 As shown in FIG. 3, abutment stops 139 limit the radial extension of the cutting tools 130 in their extended positions. The operation of the drilling assembly 120 is substantially as hereinbefore described, where the cutting tools 130 can be extended/retracted by any of the methods hereinbefore described. 25 As previously stated, different drilling heads 170 can be 11 selected to suit different soil conditions (eg., sand, alluvial soils, clays, muds, shale, rock); and different grouts (eg., cement, geo-polymer), with or without reinforcing, may be used to form the piles 100. It is preferred that the nozzles 127 be (at least loosely) packed 5 with material (eg., paper, fabric) to prevent the ingress of soil, rock filings or the like as the hole 10 is drilled, the pressure of the bentonite slurry 80 removing the temporary plugs and flowing through the nozzles 172 into the hole 10. Other alternative embodiments will be apparent to the skilled 10 addressee. Various changes and modifications may be made to the embodiments described and illustrated without departing from the present invention.

Claims

1. A drill assembly for drilling holes in the ground including: a stem connectable at one end to a drilling machine and having a drilling head at the other end; 5 a helical drilling flyte or spiral around or within the stem, operable to drill a hole when the stem is rotated in a drilling direction; at least one cutting tool hingedly mounted on the stem, or in a cavity in the periphery of a housing around the stem, movable between a retracted non-cutting position adjacent the stem, or within the cavity, and an 10 extended position when the stem is briefly rotated in an opposite direction, the or each cutting tool being operable to cut a respective substantially annular chamber around the hole when the stem is further rotated in the drilling direction; and control means operable to retain the or each cutting tool in the 15 retracted position when the stem is rotated in the drilling direction of the helical flyte or spiral as the hole is being drilled but operable to release the or each cutting tool to move to the extended position to cut the annular chamber when the stem is rotated in the opposite direction.

2. An assembly as claimed in Claim 1, wherein: 20 the drilling head includes a drilling point, drilling plate, drilling teeth and/or at least one helical flyte.

3. An assembly as claimed in Claim I or Claim 2, wherein: the control means includes mechanical latches, pawls, links, cables, hydraulic rams or the like to restrain or move the or each cutting tool. 25

4. An assembly as claimed in Claim 3, wherein: 13 the control means also moves the or each cutting tool towards the extended position and includes wedges, links, hydraulic or pneumatic rams, hydrostatic motors or the like.

5. An assembly as claimed in Claim 3 or Claim 4, wherein: 5 the control means also move the or each cutting tool to the retracted position and/or retain it in that position, when the stem is rotated in the opposite direction after the annular chamber has been formed.

6. An assembly as claimed in any one of Claims 1 to 5, wherein: the stem comprises a drilling rod, auger or casing and the stem 10 is hollow to allow the passing of drilling fluid, chemicals, air, foam, geo polymer and/or grout down through the stem and into the hole and/or the annular chamber formed by the drill assembly.

7. An assembly as claimed in Claim 6, wherein: when the or each cutting tool is moved by hydraulic or 15 pneumatic rams, or hydrostatic motors, suitable hydraulic hoses/air lines are provided within the stem and are connected to a source of pressurised oil/air by a rotary coupling.

8. An assembly as claimed in any one of Claims 1 to 7, wherein: a plurality of the cutting tools are provided along the length of 20 the stem to enable a plurality of spaced annular chambers to be formed which enable a tapered shear column to be cast in-situ.

9. An assembly as claimed in any one of Claims 1 to 5, wherein: the or each cutting tool has a downwardly inclined top face so that the top of the annular chamber is upwardly convergent. 25

10. A method of drilling a hole for an in-situ cast pile as 14 hereinbefore defined including the steps of: drilling the hole to the required depth using the drill assembly as claimed in any one of Claims 1 to 9, the stem being rotated in the drilling direction; 5 causing the or each cutting tool to be released and/or extended at least partially from the retracted position while briefly rotating the stem in an opposite direction;; further rotating the stem in the drilling direction to cause the or each cutting tool to be fully extended and cut a respective annular chamber 1o around the hole; raising the drill assembly while rotating the stem in the drilling direction to increase the height of the chamber; rotating the stem in the opposite direction to return the or each cutting tool to its retracted position; and 15 withdrawing the drill assembly from the hole while the stem is rotated in the opposite direction.

11. A method as claimed in Claim 10, wherein: drilling fluids or chemicals and/or air are pumped down the stem to raise the material in the hole to the surface. 20

12. A method of in-situ casting of piles including: drilling a hole by the method of Claim 10; pumping grout down the stem and out through a hole or nozzle in the stem adjacent the drilling point when the annular chamber has been cut and as the drill assembly is withdrawn from the hole; and 25 allowing the grout to set. 15

13. The method of Claim 12, wherein: the or each cutting tool acts to assist in the distribution of the grout within the chamber and the hole; and the grout includes, or comprises, geo-polymer.