AU2006201823B2

AU2006201823B2 - Cable bolt

Info

Publication number: AU2006201823B2
Application number: AU2006201823A
Authority: AU
Inventors: Neville Hedrick
Original assignee: Garford Pty Ltd
Current assignee: Garford Pty Ltd
Priority date: 2005-05-06
Filing date: 2006-05-02
Publication date: 2012-02-09
Anticipated expiration: 2026-05-02
Also published as: AU2006201823A1

Abstract

There is provided a cable bolt 10 which comprises a multi-strand tendon 11 formed with one or more bulbs 12 and a mechanical anchor assembly 20 at one end thereof 5 the anchor assembly being arranged to grip mechanically with the interior of a bore hole. In mining, where movement of the rock surface is undesirable, cable bolts are used to stabilize the rock surface against collapse. The current invention provides a mechanical anchor assembly 20 which enables the securing of the cable bolt in a bore hole in a rock surface.

Description

AUSTRALIA PATENTS ACT 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT (Original) APPLICATION NO: LODGED: COMPLETE SPECIFICATION LODGED: ACCEPTED: PUBLISHED: RELATED ART: NAME OF APPLICANT: Garford Pty Ltd ACTUAL INVENTOR(S): Neville Hedrick ADDRESS FOR SERVICE: LORD AND COMPANY, Patent and Trade Mark Attorneys, of 4 Douro Place, West Perth, Western Australia, 6005, AUSTRALIA. INVENTION TITLE: "CABLE BOLT" DETAILS OF ASSOCIATED PROVISIONAL APPLICATION NO'S: Australian Provisional Patent Application Number 2005902291 Filed On 6 May 2005. The following Statement is a full description of this invention including the best method of performing it known to me/us: TITLE "CABLE BOLT" 5 The present invention relates to a cable bolt. Cable bolts are steel tendons inserted into bore holes in a rock surface to stabilise the rock surface against collapse. Tendons typically comprise a plurality of steel strands wound together. It is known to provide multi-strand cable bolts that are formed with bulbs or expanded portions in 10 order to increase the surface area of the tendon in contact with grout to more securely embed the tendon in the grout. The bulbs or expanded portions thus increase the radial confinement of the tendon within the borehole. It is also known to provide a rigid element within the bulbs or expanded portions. Cable bolts of this type are the subject of Australian Patent Number 640906. 15 In mining, where movement of the rock surface is undesirable, an end portion of the tendon disposed innermost in the bore hole may be secured therein by spinning the end portion in resin, attaching a resin dam to an opposing end of the spun end portion, and allowing the resin to cure. The remaining portion of the tendon disposed in the bore hole is then tensioned to stabilise the rock surface. The bore hole can then be 20 grouted safely a short time later. In the mean time, the rock surface is stabilised against collapse before grouting commences or during the grout curing period. In some areas or locations setting the end portion of the tendon disposed innermost in the bore hole in resin is not desirable or even possible. The present invention attempts to overcome at least in part the aforementioned 25 disadvantage of previously known cable bolts. 2 In accordance with one aspect of the present invention there is provided a cable bolt which comprises a multi-strand tendon formed with one or more bulbs and a mechanical anchor assembly at one end thereof, the anchor assembly being arranged to grip mechanically with an interior of a bore hole. 5 The present invention will now be described, by way of example, with reference to the accompanying drawing, in which: Figure 1 is a side view of a cable bolt in accordance with the present invention; Figure 2 is a cross sectional view of a mechanical anchor assembly forming part of the cable bolt of Figure 1; 10 Figure 3 is a side view of the mechanical anchor assembly of Figure 2 being inserted into a bore hole; Figure 4 is a side view of the mechanical anchor assembly of Figure 2 inserted in a bore hole; and Figure 5 is a plan view of the mechanical anchor assembly of Figures 1 to 4; and 15 Figure 6 is a perspective view of a wedge component of the mechanical anchor assembly of Figures 1 to 5. Referring to the Figures, there is shown a cable bolt 10 comprising a mechanical anchor assembly 20, a steel tendon 11 which contains one or more bulb portions 12. A rigid element 13 is contained within each bulb portion. Further there is provided a 20 further mechanical anchor assembly 14, at an end remote from the assembly 20. The mechanical anchor assembly 20 comprises a stop member 22, a coil spring 24 and a first plate 26 and a second plate 28. The stop member 22 is shaped like a ring that goes tightly around the steel tendon 11 to give support and a rigid surface against which the spring 24 bears. The spring 24 is mounted about the steel tendon 11. The 3 first plate 26 is mounted about the tendon 11 contiguously with the spring 24. The second plate 28 is mounted about the tendon 11 and is mounted contiguously with the plate 26. The second plate 28 has mounted thereto a plurality of opposed part circular wedges 5 36 having serrated outer surfaces 37. The wedges 36 are engaged with the second plate 28 by means of threaded or riveted connections 38. Further, as can be seen in Figures 3, 4 and 5 there are opposed gaps 40 between the part circular wedges 36. As can best be seen in Figures 2 and 5 disposed inwardly of the wedges 36 is a circular frusto conical shaped locking member 44. The member 44 has a hollow interior 10 through which the tendon 11 extends. Further, disposed within the member 44 is a relatively short circular wedge or collett 46 which extends snugly around the tendon 11. The wedge 46 has a sloping outer face which engages with an inner face of the member 44. The wedge 46 is formed of a plurality of wedge components 48 (see Figure 6) which fit together to complete a 15 circle around the tendon 11 and lock the member 44 in place relative to the tendon 11. The wedge components of the wedge 46 have roughened internal surfaces 50 as shown in Figure 6 to facilitate gripping of the steel tendon 11 by the wedge 46. The steel tendon 11 is composed of a plurality of outer strands helically wound around a centre strand to form the tendon. There are usually six outer strands wound 20 around the centre strand. The tendon 11 has one or more bulbs 12 spaced apart from one another along the length of the steel tendon 11. Each bulb 12 houses a rigid element 13 within a cavity defined by the outer strands and the centre strand as described in pending Australian Patent Application Number 2004260817. Preferably, the rigid element 13 is a solid sphere, such as a steel ball bearing. 4 Towards the opposite end of the steel tendon 11 there is provided a mechanical anchor assembly 14 of known type comprising wedge portions 18 and a locking member 16. The wedge portions 18 form a cone shaped arrangement which is hollow to allow the steel tendon 11 to pass through. The wedge portions 18 have gripping 5 ridges on the inside thereof to grip the steel tendon 11. The locking member 16 is provided to force the wedge portions 18 to grip the steel tendon 11. The locking member 16 has a cylindrical outer surface having a flat cut on an outermost end thereof and a rounded surface on an inner most end thereof. The locking member 16 has a hole through the centre to fit the steel tendon 11. The locking member 16, in 10 use, bears against a mine plate in known manner to assist in retaining the cable bolt 10 in place in a bore hole. In use, the cable bolt 10 is inserted into a bore hole drilled in a rock face with the anchor assembly 20 foremost as shown in Figure 3. As the cable bolt 10 is inserted the wedges 36 rub against the interior of the bore hole 15 and the wedges 36 are pressed against the spring 24 through the first and second plates 26 and 28. The spring 24 is compressed which causes the wedges 36 to move relative to the member 44 away from the adjacent end of the tendon. This movement tends to reduce the outer dimension of the assembly 20. The mechanical anchor assembly 20 is activated once an innermost end of the cable 20 bolt 10 is in the desired position. In this position the tendon 11 is pulled slightly outwardly of the bore hole which causes the spring 24 to extend and the wedges 36 to be therefore pushed laterally outward by engagement with the member 44. In this position the wedges 36 engage with the interior of the bore hole as shown in Figure 4. The tendon 11 is then tensioned up in known manner and the borehole is subsequently 5 filled with grout. The grout is allowed to cure and solidify. The cable bolt 10 is then firmly embedded in the grout. Modifications and variations as would be apparent to a skilled addressee are deemed to be within the scope of the present invention. 6

Claims

1. A cable bolt which comprises a multi-strand tendon formed with one or more spaced apart bulbs and a mechanical anchor assembly at one end thereof, the anchor assembly comprising a stop member mounted about the tendon, a plate means also mounted about the tendon and being spaced apart from the stop member, a coil spring mounted about the tendon and being disposed between the stop member and the plate means and being contiguous with the stop member and the plate means, a plurality of opposed part circular wedges having serrated outer surfaces being mounted to the plate means and extending away from the coil spring, the opposed part circular wedges having gaps therebetween, a frustoconical shaped locking member being disposed inwardly of the wedges, the frustoconical shaped locking member being hollow and the tendon extending therethrough, the arrangement being such that as the cable bolt is inserted into a bore hole the wedges rub against an interior of the bore hole so that the wedges press against the plate means causing the coil spring to be compressed such that the wedges move relative to the frustoconical member away from the adjacent end of the tendon thus tending to reduce the outer dimension of the anchor assembly, whereby once the tendon reaches a desired position the tendon may be pulled slightly outwardly of the hole so causing the spring to extend and the wedges to be pushed laterally outwardly by engagement with the frustoconical member and to engage with the interior of the bore hole.

2. A cable bolt according to claim 1, wherein the multi-strand cable comprises a plurality of outer strands helically wound around a central strand.

3. A cable bolt according to claim 1 or 2, wherein the or each bulb houses a rigid element.

4. A cable bolt according to claim 3, wherein the rigid element is a solid sphere. 7

5. A cable bolt according to any one of the preceding claims, wherein the stop member is shaped like a ring that extends tightly around the tendon to give support and a rigid surface against which the spring bears.

6. A cable bolt according too any one of the preceding claims, wherein a first plate is mounted about the tendon contiguously with the spring and a second plate is mounted about the tendon and is mounted contiguously with the first plate.

7. A cable bolt according to claim 6, wherein the second plate has the plurality of opposed part circular wedges mounted thereon.

8. A cable bolt substantially as hereinbefore described with reference to the accompanying drawings.