AU2007201852A1 - Cable bolt - Google Patents

Description

S&F Ref: 804796

AUSTRALIA

PATENTS ACT 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT Name and Address of Applicant Actual Inventor(s): Address for Service: Invention Title: DYWIDAG-Systems International Pty Limited, an Australian company, ACN 093 424 349, of 25 Pacific Highway, Bennett's Green, New South Wales, 2290, Australia Mieczyslaw Stanislaw Rataj, Rhys James Hunter Spruson Ferguson St Martins Tower Level 31 Market Street Sydney NSW 2000 (CCN 3710000177) Cable bolt Associated Provisional Application Details: [33] Country:

AU

[31] Appl'n No(s): 2006902188 [32] Application Date: 27 Apr 2006 The following statement is a full description of this invention, including the best method of performing it known to me/us:- 5845c(768074_1) SCABLE BOLT Technical Field The present invention relates to mining equipment, and in particular, relates to a rock bolt (in the form of a cable bolt) for securing the roof or wall of a mine tunnel, or r other ground excavation.

00 Background of the Invention To reinforce the rock roof and/or walls of underground mines, tunnels and other ground excavations, long flexible cable bolts (otherwise referred to as strand bolts) are often utilised. Each cable bolt is fixed into a borehole drilled into the rock face with a two-component organic resin, a cement grout or both resin and grout. To increase the effective bond strength between the cable bolt and the resin or grout, the cable bolts are often provided with protuberances along the length of cable in any of various known is forms, commonly referred to as "cages", "bulbs" or "swaged buttons". These protuberances assist in preventing the otherwise constant cross-section cable bolts from being pulled through the resin/grout.

The most commonly used of these protuberances applied to cable bolts are bulbs, where the protuberance is created by bulging all the individual wires of the cable. When the cable bolt is pre-tensioned after first anchoring its top portion to the borehole wall with the use of resin, the bulbs tend to collapse under the pre-tensioning load. No bulbs are thus available for the grout to anchor to during the post-grouting process.

Accordingly, the bulbs must be secured from collapsing in such applications.

In one form, the bulbs are secured by way of ball bearings inserted into the cavity of the bulbs. This is relatively expensive, however, and not very reliable, as the ball bearings may be pushed out of the bulbs when the pre-tension is applied to the cable and the centre wire of the cable is straightened, ejecting the ball bearing.

For cement grouting applications, the grout is typically injected into the annular cavity between the cable bolt and the borehole wall by way of a grout tube. In one form, the grout tube is inserted into the borehole only a short distance, such that the grout injected into the grout tube is pushed up through the annular cavity from adjacent the rock face opening. To evacuate air from the borehole while the cement grout is being pumped from the bottom, a breather tube (typically in the form of a small diameter plastic tube) is located in the borehole extending toward the top of the borehole. The borehole must also (752903_1):PRW be sealed at the rock face to ensure that the injected grout is pumped toward the top of the Sborehole, rather than merely escaping out through the opening in the rock face.

In an alternate, preferred method, the grout tube extends firom the borehole opening INO to adjacent the top of the borehole, such that grout injected through the grout tube flows s down through the full length of the borehole. Utilising this method, no breather tube is required and there is no need to seal the borehole opening in the rock face. A large 00 diameter borehole is, however, required to be drilled into the rock to house the grout tube.

Such a relatively large diameter hole is generally, however, not desired for anchoring the top portion of the cable bolt with resin as the annular space between the cable bolt and the io wall of the borehole should be as small as possible to achieve the best fixation of the cable bolt. Accordingly, when larger diameter boreholes are utilised to provide for grout tubes, anchoring of the cable bolt is not always reliable.

Object of the Invention It is the object of the present invention to substantially overcome or at least ameliorate one or more of the above disadvantages.

Summary of the Invention The present invention provides a cable bolt comprising: a first cable and a second cable arranged side by side so as to form a cable assembly having a first end and a second end; a first pair of fixation points at which said first cable is fixed to said second cable; and a first insert mounted between said first pair of fixation points and separating said first cable and said second cable so as to create a first bulge in said cable assembly.

The cable bolt may further comprise a second pair of fixation points at which said first cable is fixed to said second cable, and a second insert mounted between said second pair of fixation points and separating said first cable and said second cable so as to create a second bulge in said cable assembly.

The cable bolt may further comprise one or more further pairs of fixation points at which said first cable is fixed to said second cable, and a further insert mounted between each said further pair of fixation points and separating said first cable and said second cable so as to create one or more further bulges in said cable assembly.

(752903_1):PRW SIn a preferred form, said first pair of fixation points is located adjacent said first end of said cable assembly.

In one form, each of said fixation points comprises a crimp fixed to said first IO cable and to said second cable.

Alternatively, each of said fixation points may comprise a swage fixed to said first cable and to said second cable.

~Each insert preferably has a pair of opposing concave faces for engaging said first cable and said second cable respectively.

The cable bolt may further comprise a grout tube extending from adjacent said second end of said cable assembly toward said first end of said cable assembly, said grout tube being fixed in relation to said cable assembly.

Typically, said grout tube is fixed to one or more of said inserts.

In one form, one or more of said inserts is provided with an aperture through which said grout tube is received.

Is The cable bolt may further comprise a generally tubular anchor fixedly mounted on said cable assembly toward said first end of said cable assembly.

The anchor may be fixed to a said fixation point.

Typically, said anchor is disposed adjacent said first pair of fixation points, between said first pair of fixation points and said second end of said cable assembly.

In a preferred form, said anchor has a generally closed anchor first end facing said first end of said cable assembly, and an opposing open anchor second end facing said second end of said cable assembly.

Preferably, said grout tube extends through said anchor second end into a cavity defined between said cable assembly and said anchor.

Typically, an outer peripheral face of said anchor is provided with a plurality of indentations or protrusions.

Brief Description of the Drawings A preferred embodiment of the present invention will now be described, by way of an example only, with reference to the accompanying drawings wherein: Figure 1 is perspective view of a cable bolt.

Figure 2 is a perspective view of an insert of the cable bolt of Figure 1.

Figure 3 is a fragmentary perspective view of the cable bolt of Figure 1 depicting a pair of fixation points with the insert of Figure 2 mounted therebetween.

(752903_1):PRW Figure 4 is a fragmentary perspective view of the cable bolt of Figure 1 depicting a Sgrout tube extending through the insert of Figure 2.

Figure 5 is a cross-sectional front elevational view of a cable bolt installation INO utilising the cable bolt of Figure 1.

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Detailed Description of the Preferred Embodiments 00 Referring firstly to Figure 1, a cable bolt 1 includes first and second cables 2, 3 arranged side by side so as to form a cable assembly 4 having an upper first end 4a and a lower second end 4b. Each of the cables 2, 3 is formed of several steel wires wound around a central king wire in the usual manner. Each cable 2, 3 will typically have a diameter of between 10 and 30 mm and a length of about 6 to 10 metres, depending upon the specific application.

The cable bolt has a first pair of fixation points 5, 6 at which the first cable 2 is fixed to the second cable 3. The first pair of fixation points 5, 6 is located adjacent the first end 4a of the cable assembly 4 and is in the form of a pair of crimps 7 crimped onto the cables 2, 3. The first pair of crimps 7 are typically separated by about 150 to 200mm.

Rather than using crimps, the first pair of fixation points 5, 6 may be in the form of swages or any other mechanism able to fix the first and second cables 2, 3.

A second pair of fixation points again in the form of crimps 7, is provided further along the cable assembly 4. One or more further pairs of fixation points 6" is/are provided spaced along the remaining length of the cable assembly 4. The mid-point of each pair of fixation points 5, 6 will typically be separated by about 0.5 to 1 metre.

A first insert 8 is mounted between the first pair of fixation points 5, 6 separating the first cable 2 and the second cable 3. The crimps 7 of the first pair of fixation points 6 lock the insert 8 in between the first and second cables 2, 3. The first insert 8, separating the first and second cables 2, 3, results in a first bulge being formed in the cable assembly 4 to assist in locking the cable assembly within the resin as will be discussed below. Further inserts 8' separate the first and second cables 2, 3 between each of the second and further pairs of fixation points 6".

As best depicted in Figures 2 and 3, each further insert 8' comprises a plastic body 9 having opposing concave faces 10, 11 which, in the embodiment depicted, extend around the periphery of the insert body 9 so as to define a peripheral concave body of revolution. The concave faces 10, 11 engage the matching cylindrical peripheral surface of the first and second cables 2, 3 respectively so as to assist in ensuring that the insert 8' (752903_1):PRW remains locked between the first and second cables 2, 3 by the crimps 7. Any of various Salternate forms of insert may be utilised as long as they maintain the separation between the first and second cables 2, 3. Each of the further inserts 8' further comprises a loop 12 IDintegrally formed with the insert body 9 and defining an aperture 13 extending perpendicular to the longitudinal axis of the insert body 9. As depicted in Figures 1 and 4, the aperture 13 is sized to receive a grout tube 14 (typically of 10 to 30mm diameter) 00 which is threaded along the cable assembly 4 from adjacent the cable assembly second end 4b. The loops 12 thus fix the grout tube 14 to the cable assembly 4. The first insert 8 is identical to each of the further inserts apart from omission of the loop 12.

A generally tubular anchor 15 is mounted on the cable assembly 4 toward the cable assembly first end 4a. Here the anchor 15 is located adjacent the lower fixation point 6 of the first pair of fixation points, and is in fact welded to the crimp 7. The anchor 15 has a closed anchor first end 15a facing the cable assembly first end 4a and an open anchor second end 15b facing the cable assembly second end 4b. The peripheral face of the anchor 15 is uneven, here being provided with a series of indentations 16 to improve the bond strength with the resin, as will be discussed below. Alternatively, the anchor face could be provided with protrusions to achieve the same effect. The anchor 15 will typically have a diameter of 40 to 80mm, generally selected to be the same or larger than the lateral extent of the bulges in the cable assembly 4, and will typically have a length of between 0.5 and 2 metres, depending upon the application. As seen in Figure 1, the grout tube first end 14a extends through the anchor second end 15b and into a cavity defined between the cable assembly 4 and the anchor A rock face plate 17 is fed onto the lower end of each of the first and second cables 2, 3 and grout tube 14 by way of three apertures suitably provided. A standard barrel and wedge assembly 18 is mounted on each of the first and second cables 2, 3 adjacent the rock face plate 17.

Use of the cable bolt 1 will now be described with particular reference to Figure Firstly, a borehole 100 having a diameter slightly larger than that of the anchor 15 is drilled into the rock face 101 in the usual manner. A known two component resin cartridge is then inserted into the borehole 100, followed by the cable bolt 1, with the cable assembly first end 4a leading. The cable bolt 1 is driven into the resin cartridge, puncturing the same, allowing the two component resin 102 to mix and flow down over the bulge created by the first pair of fixation points 5, 6 and first insert 8 and into the narrow annular cavity defined between the wall 103 of the borehole 100 and anchor The anchor closed end 15a will generally prevent resin 102 from entering the cavity (752903_1):PRW defined between the anchor 15 and cable assembly 4, thereby preventing resin from Sblocking the grout tube first end 14a. The cable bolt 1 is then spun in the usual manner to mix the two component resin by way of the anchor 15, particularly the indentations 16 IND thereof, and the first insert 8 and bulge defined in the cable assembly 4 by the first insert 8.

Once the resin 102 cures, securing the anchor 15 and top end portion of the cable 00 bolt 1 to the borehole wall 103, the rock face plate 17 and barrel and wedge assemblies 18 are mounted and both cables 2, 3 are pre-tensioned utilising a typical cable bolt tensioner to achieve the desired pre-tension loads. A grout hose (not depicted) is then attached to io the grout tube 14, and cement grout 104 is pumped up through the grout tube 14, flowing back down through the annular cavity defined between the cable bolt 1 and the borehole wall 103 below the anchor 15 until grout is visible at the rock face plate.

The bulge defined by the first pair of fixation points 5, 6 increases the effective bond strength between the resin encased upper end of the cable bolt 1 and the resin 102, whilst the bulges formed by the second and further pairs of fixation points 6", which are each located below the anchor 15, increase the effective bond strength between the cable bolt and the cement grout 104. In fully grouted applications that do not utilise resin bonding of the cable bolt upper end, the anchor 15 may be disposed of.

(752903 I):PRW

Claims (13)

1. 2. The cable bolt of claim 1 further comprising a second pair of fixation o points at which said first cable is fixed to said second cable, and a second insert mounted between said second pair of fixation points and separating said first cable and said second cable so as to create a second bulge in said cable assembly.
2. 3. The cable bolt of claim 2 further comprising one or more further pairs of fixation points at which said first cable is fixed to said second cable, and a further insert mounted between each said further pair of fixation points and separating said first cable and said second cable so as to create one or more further bulges in said cable assembly.
3. 4. The cable bolt of any one of claims 1 to 3 wherein said first pair of fixation points is located adjacent said first end of said cable assembly.
4. 5. The cable bolt of any one of claims 1 to 4 wherein each of said fixation points comprises a crimp fixed to said first cable and to said second cable.
5. 6. The cable bolt of any one of claims 1 to 4 wherein each of said fixation points comprises a swage fixed to said first cable and to said second cable.
6. 7. The cable bolt of any one of claims 1 to 6 wherein each said insert has a pair of opposing concave faces for engaging said first cable and said second cable respectively.
7. 8. The cable bolt of any one of claims 1 to 7 further comprising a grout tube extending from adjacent said second end of said cable assembly toward said first end of said cable assembly, said grout tube being fixed in relation to said cable assembly.
8. 9. The cable bolt of claim 8 wherein said grout tube is fixed to one or more of said inserts. The cable bolt of claim 9 wherein one or more of said inserts is provided with an aperture through which said grout tube is received. (752903_1):PRW
9. 11. The cable bolt of any one of claims 1 to 10 further comprising a Sgenerally tubular anchor fixedly mounted on said cable assembly toward said first end of said cable assembly. IN 12. The cable bolt of claim 11 wherein said anchor is fixed to a said fixation s point.
10. 13. The cable bolt of either one of claims 11 and 12 wherein said anchor is 00 disposed adjacent said first pair of fixation points, between said first pair of fixation points and said second end of said cable assembly.
11. 14. The cable bolt of any one of claims 11 to 13 wherein said anchor has a 1o generally closed anchor first end facing said first end of said cable assembly, and an opposing open anchor second end facing said second end of said cable assembly. The cable bolt of claim 14 wherein said grout tube extends through said anchor second end into a cavity defined between said cable assembly and said anchor.
12. 16. The cable bolt of any one of claims 11 to 15 wherein an outer peripheral face of said anchor is provided with a plurality of indentations or protrusions.
13. 17. A cable bolt substantially as hereinbefore described with reference to the accompanying drawings. Dated 26 April, 2007 DYWIDAG-Systems International Pty Limited Patent Attorneys for the Applicant/Nominated Person SPRUSON FERGUSON (7529031 ):PRW