CA2129220A1

CA2129220A1 - Cable bolt

Info

Publication number: CA2129220A1
Application number: CA002129220A
Authority: CA
Inventors: Maxwell Thomas Renwick
Original assignee: Individual
Current assignee: Infrabuild Wire Pty Ltd
Priority date: 1992-01-31
Filing date: 1993-02-02
Publication date: 1993-08-05
Also published as: EP0628114A4; WO1993015279A1; EP0628114A1

Abstract

A cable bolt (3) comprises a central wire (5), a plurality of core members (7) positioned at spaced intervals along the length of the central wire (5), and a plurality of outer wires (9) wound around the central wire (5) and the spaced apart core members (7) so that the width of the cable bolt (3) is greater at the locations of the core members (7) than at the sections between the core members (7).

Description

.. 1 Z~29~Z20 CABLR. BOLT

The ~re~ent invention relate~ to a cable bolt for , use in the ground ~tabili~ation.
Cable bolt~ are u~ed in a number of different a~plication~ in the mining and civil industrie~, such a~
for underground ~to~ing, ~illar ~u~ort, development su~port and in o~en pit and civil a~lication~ where slo~e 10 Rtabilisation i~ required. In general, cable bolt3 are ~-u~ed by drilling holes through ~otentially un~table ground into more solid Qtrata into which the cable bolt~ are located ~ecurely by grouting.
In some ~ituationR, cable bolt~ are located to extend through the ore body to be mined and are at lea~t ~artially exposed a~ the ore body around the cable bolt~ is removed by bla~ting. In other situationR, cable bolt~ are located to extend through ~otentially unRtable material which i8 not ~art of the ore body to be mined and, by ~tabilising the material, the cable bolt~ ~revent ~uch material mixing with the ore body to be mined and thereby increasing the volume to be ~roceRsed and accordingly the co t~ of winning the valuable mineral~.
~ A ba~ic form of conventional hitherto widely-used cable bolt (hereinafter referred to aR the "ba~ic form of cable bolt") compri~e~ a central wire and a ~lurality of outer wires (typically 6 or more) wound around the central wire in ~arallel ~irals. The wire~ are u~ually formed from h~gh ten~ile ~trength ~teel, and u~ually the cable . 30 bolt i~ ~tre~R relieved after it ia formed.
The foregoing ba~ic form of cable bolt ha~ been found to have relatively low load transfer with the re~ult that over time the mechanical interlock between cable bolt and grout i~ sub~tantially reduced.
.
~ ~ .
'~ , .

W093/15279 :. PCT/AU93/00~

~29~20 In order to improve the load tranRfer capability it i~ known to use a barrel and wedge as~embly with the baQic form of cable bolt. Howe~er, thiq has not proven to be altogether ~uccessful in termQ of ~erformance and also 5 , iQ a relatively expen~ive technique. It iQ also known to ~wage ~teel block~ at ~paced interval~ along the length of the basic form of cable bolt. Whilst this technique haR
proven to be Rucce~Rful in term~ of improving load tran~fer, the costs are unacce~tably high.
A further known a~proach to improve the load transfer capability i~ to modify the configuration of the ba~ic form of cable bolt. The modified form, known aR a -"birdcage", comprises a ~lurality of enlarged diameter regionq along the length of the cable bolt formed by selectively unwinding the cable bolt at the regionq ~o that the wire~ can ~eparate and bulge outwardly.
Whilst this technique is successful in term_ of ~erformance, the costs are relatively high. There are a number of factors which contri~ute to the relatively high costs, and one factor is the necessity to manufacture the cable bolt off-site in relatively short lengths which are difficult and costly to ~tore and transport on-Rite. --In addition to the foregoing, many equipment manufacturers are now offering machine~ which are operable on-site to bore a hole for a cable bolt, cut a required len~th of cable bolt off a ~ool to suit the hole, locate the cable bolt in the hole, and grout the hole. This technology i~ being widely acce~ted by the mining industry a a mea,ns of im~roving efficiency. However, the baqic ._ form of cable bolt, and not the swaged and birdcage systems, is the only cable bolt wh~ch can be efficiently coiled into a s~ool and thus meet~ the criteria for the technology. However, against this, a8 is indicated above, the basic form of cable bolt is not altogether satisfactory W093/15279 21~ PCT/AU93/00 ..... ,, . ~;
since it ha~ a relatively low load tran~fer ca~ability.
An object of the ~resent invention i~ to provide a cable bolt which alle~iate~ the di~advantages de~cribed in the ~receding ~aragraph~.
5 , According to the ~resent invention there ic pro~ided a cable bolt com~ri~ing, a central wire, a ~lurality of core members ~o~itioned at ~aced intervals along the length of the central wire, and a ~lurality of outer wire3 wound around the central wire and the spaced apart core members 80 that the wiath of the cable bolt i~
- greater at the locations of the core members than at the sectionQ between the core mem~ers.
The term "core member" is~under~tood herein to include any member that increa~e~ the effective width of the central wire and, a~ a con~equence, the effective width of the cable bolt at the location of the core member.
It i~ ~referred that the central wire and the outer wire be formed from steel.
It is preferred that there be 6 or more outer 20 wire~. -It i~ ~referred that the core m~her com~rise~ a relati~ely wide middle section and relatively narrow end~
and a central ~a~age extending from end to end for recei~ing the central wire therethrough. It is ~referred ~articularly that the core member ta~er~ from the middle section to each end.
It is ~refarred that the core member be formed from a ~lurality of longitudinal ~ections which fit together around the central wire.
,. , It is ~referred that the core member be formed from sub~tantially incom~ressible material.
It is ~referred that the core member increase the diameter of the central wire by at least 20%.
According to the ~resent in~ention there is also .

W093/15279 -- PCT/AU93~00 2 9h~ ~ 0 4 provided a method of forming a cable bolt comprising, winding a plurality of outer wire~ around a central wire having a plurality of core member~ fitted to the central wire at s~aced interval~ along the length thereof. -5 , It i~ preferred that the method further compriseQ
coiling the cable bolt onto a q~ool.
According to the present invention there i~
~rovided a method of forming a cable bolt from a baRic form of cable bolt com~ri3ing a central wire and a ~lurality of outer wires around the central wire, the method com~ri~ing radially di~lacing the outer wire~ from the central wire to form a s~ace between the central wire and the outer wireq, and fitting a core member to the central wire in the s~ace. ~;:
It iQ ~referred that the method further compri~e~
re~eating the radial diR~lacement and core member placement ste~Q to fit a ~lurality of the core member~ along the length of the central wire.
It i~ ~referred that the method further compri~es coiling the cable bolt onto a 8~001.
The ~re~ent invention i8 de~cribed further with reference to the accom~anying drawing which i~ a side elevation of a ~art of a ~referred embodiment of a cable bolt of the ~re~ent invention.
,25 The ~referred embodiment of the cable bolt 3 of the ~reRent invention shown in the drawing compri~eR a central ~teel wire 5, a ~lurality of core memberq 7 (only;~
one of which i~ shown in the drawing) at ~aced intervals along th~ length of the central wire 5, and a plurality of outer ~teel wire~ 9 wound around the central wire 5 and the R~aced a~art core members 7.
Each core member 7 is formed from substantially incom~re~ible material such as steel and com~rises a relatively wide middle section 11 and relatively narrow ~ . . -.~.
:

W093/15279 Z~29~0 PcT/Au93/oo~

end~ 13 with a central ~a~age 15 extending between the end~ 13. Each core member 7 ta~ers from the middle ~ection 11 to the ends 13 and iR formed in 2 halve~ which (although not evident in the drawing) can conveniently be located , together around the central wire 5.
The core members 7 cau~e the cable bolt 3 to have a variable thickneQ~ along the length thereof with a maximum thicknesQ which is at least 20% greater than the minimum thickness Tl of the cable bolt 3.
The effect of the core member~ 7 and the windings of the outer wires 9 around the core members 7 is that the cable bolt 3 ha~ a ~imilar load Sransfer capability to that of swaged cable bolts.
However, unlike swaged cable bolts, in accordance with a first preferred embodiment of a method of the ~resent invention, the cable bolt 3 is manufactured with conventional technology used to form the basic form of cable bolt and thereafter coiled onto spool~ which can conveniently be stored and transported on-site.
S~ecifically, the preferred embodiment com~ri~es:

a) fitting core members at spaced intervals along the length of a central wire prior to wrapping outer wires onto the assembly of the central wire and core members, and then;

b) overwra~ing outer wires onto the ass~mhly of the central wire and core members.

In accordance with a second ~referred embodiment of the method of the ~resent invention, the cable bolt 3 is manufactured from the basiC form of the cable bolt and thereafter coiled onto 8~0018 which can conveniently be ~` stored and trans~orted on-site. S~ecifically, the W0~3/15279 PCT/AU93/00~
X1~9;~20 preferred embodiment of the method compri~e~, repea'edly:

a) radially di~lacing the outer wire~ away from the central wire of the basic form of cable bolt to 5 , form a 3~ace between the outer wire~ and the central wire; and b) fitting one of the core members to the central wire in the ~ace.
The cable bolt 3 ha~ the following ~-characteristics.

a) A load transfer ca~ability equal to or ~u~erior to that of swaged or birdcage cable bolt~.

b) The stiffness of the cable bolt 3 can be varied by decou~ling the cable bolt 3 from the grout ;
along the length of the cable bolt between adjacent core members 7 or by varying the transverse thicknes~ of the core member~.

c) A ca~ability of being coiled onto s~ool~ in lengths of hundreds of metres whereby, a~ a consequence, the cable bolt is not re~tricted to manufacture in relatively ~hort length~.

d) A com~atibility with existing mechanical installation equi~ment.
Many modifications may be made to the ~referred embodiment of the cable bolt deQcribed above without departin~ from the s~irit and Rcope of the ~resent in~ention.

W093/15279 20 PCT/AU93/UO~

sy way of exam~le, it is noted that, whil~t in the ~referred embodiment the core members 7 have a particular configuration, the ~resent invention is not ~o limited and extend~ to any suitable configuration which has ~ the effect of increa~ing the effecti~e diameter of the central wire 5 and thereby the effective diameter of the cable bolt.
In thi~ regard, one alternative configuration of core member~ 7 com~rises length~ of wire wra~ed around the central wire 5 at s~aced inter~als along the length of the central wire 5.

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Claims

CLAIMS:

1. A cable bolt comprising, a central wire, a plurality of core members positioned at spaced intervals along the length of the central wire, and a plurality of outer wires wound around the central wire and the spaced apart core members so that the width of the cable bolt is greater at the locations of the core members than at the sections between the core members.

2. The cable bolt defined in claim 1, wherein the central wire and the outer wire are formed from steel.

3. The cable bolt defined in claim 1 or claim 2, comprising 6 or more outer wires.

4. The cable bolt defined in any one of the preceding claims, wherein the core member comprises a relatively wide middle section and relatively narrow ends and a central passage extending from end to end for receiving the central wire therethrough.

5. The cable bolt defined in claim 4, wherein the core member tapers from the middle section to each end.

6. The cable bolt defined in claim 4 or claim 5, wherein the core member is formed from a plurality of longitudinal sections which fit together around the central wire.

7. The cable bolt defined in any one of the preceding claims, wherein the core member is formed from substantially incompressible material.

8. The cable bolt defined in any one of the preceding claims, wherein the core member increases the diameter of the central wire by at least 20%.

9. A method of forming a cable bolt comprising, winding a plurality of outer wires around a central wire having a plurality of core members fitted to the central wire at spaced intervals along the length thereof.

10. A method of forming a cable bolt from a basic form of cable bolt comprising a central wire and a plurality of outer wires around the central wire, the method comprising radially displacing the outer wires from the central wire to form a space between the central wire and the outer wires, and fitting a core member to the central wire in the space.

11. The method defined in claim 10, comprising repeating the radial displacement and core members placement steps to fit a plurality of the core members along the length of the central wire.

12. The method defined in any one of claims 9 to 11, further comprising coiling the cable bolt onto a spool.