AU5504800A - Rock bolt post grouting apparatus and method - Google Patents

Description

S&FRef: 519512

AUSTRALIA

PATENTS ACT 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT

ORIGINAL

9**9 a a a Name and Address of Applicant Actual Inventor(s): Address for Service: The ANI Corporation Limited Level 5, Merlin Centre 235 Pyrmont Street Pyrmont NSW 2009 Australia Mieczyslaw Rataj, Warren Roach, Mark Copping Spruson Ferguson St Martins Tower 31 Market Street Sydney NSW 2000 Rock Bolt Post Grouting Apparatus and Method Invention Title: ASSOCIATED PROVISIONAL APPLICATION DETAILS [33] Country [31] Applic. No(s) AU PQ2629 [32] Application Date 03 Sep 1999 The following statement is a full description of this invention, including the best method of performing it known to me/us:i .e 7 1 1 Batch No: c g-l' I c r 5815c Rock Bolt Post Grouting Apparatus and Method Technical Field This invention relates to improvements in rock reinforcement installations, and in particular relates to an apparatus and method for post grouting of rock bolt installations to increase load transfer between the rock and the bolt.

Background of the Invention The roof of an underground mine is secured using rock bolts (including rock cables known as cable bolts) to confine the rock. The rock bolts are inserted into a hole, predrilled into the rock.

Usually, the rock bolt is secured at the top of the hole by a mechanical or •.chemical anchor creating a point anchor. Alternatively, or additionally, the rock bolt is o secured in the hole by grouting along its length with a cement or polyester resin.

Grouting of the bolt along its entire length is the much preferred method to improve confinement of the rock through load transfer between the rock and bolt along its entire length rather than at a local area only. Grouting of the bolt also protects it from corrosion.

The current methods available for grouting cable bolts are typically complicated and often very messy. One current method of grouting a cable bolt involves taping a breather tube along the length of the cable bolt and inserting the cable bolt with breather tube into a hole in the rock. A short length of grout tube is then jammed into the bottom 1•of the hole beside the cable bolt, with the remaining opening of the hole being sealed with rugs or similar. Grout is then pumped into the hole through the grout tube. After allowing the grout to set for at least 24 hours, a collar assembly, formed of a roof plate, barrel and wedges, is fitted onto the tail of the cable bolt to secure the lower end of the bolt. The presence of the breather tube fastened to the side of the cable bolt and protruding therefrom, however, inhibits effective installation of a cable bolt utilising a chemical resin anchor when spinning of the bolt within the hole is required to mix the resin in situ. Such spinning of the bolt typically results in damage of the protruding breather tube as it scrapes the hole wall.

Another currently available method uses a hollow rigid rock bolt provided with a central hole extending along it length. The hollow rock bolt is typically first anchored at the top of the hole with a mechanical anchor. Grout is then pumped through the central bolt hole to the top of the bolt, where it flows under gravity down past the mechanical [R:\LIBLL]08348.doc:GJG:TCW anchor and through the passage between the bolt and rock hole wall. The flowing of grout under gravity, however, typically does not provide for full encapsulation of the bolt, with air pockets being formed along its length. Further, the central hole is typically required to have a diameter of about 10 mm to enable flow of the grout, resulting in a reduced strength bolt.

A further method utilises a plastic sleeve mounted on the bolt and extending along substantially the entire length of the bolt to the top of the hole, which is typically about 2 metres long. The sleeve communicates with a grouting chamber disposed below the roof plate. Grout is pumped into the grouting chamber and flows upwardly through 1o the passage defined between the sleeve and rock bolt to the top of the hole and then spreads down under gravity through the passage between the sleeve and the rock. As the grout flows between the sleeve and rock under gravity, full encapsulation is again a ••problem with the formation of air pockets. The plastic sleeve also divides the grout into two annular columns, jeopardising load transfer between the rock and rock bolt due to Is slippage at the plastic sleeve grout interface, and deformation of the plastic sleeve itself.

Further, there is no clear indication of when the operator should stop pumping, often resulting in incomplete grouting.

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

i Summary of the Invention In one broad form the present invention provides a rock bolt grout seal comprising: a sleeve having first and second ends and defining a cavity extending between said first and second ends, said cavity adapted to receive a rock bolt inserted therethrough at said first end and extending therethrough at said second end, a grout injection port disposed at or adjacent to said first end and communicating with said second end, for injection of grout through said sleeve and out of said second end, and at least one circumferentially extending flexible rib disposed on an outer surface of said sleeve and adapted to engage the wall of a rock bolt hole into which, in use, said sleeve and rock bolt are received.

[R:\LIBLL]08348.doc:GJG:TCW Preferably said outer surface is provided with a plurality of said flexible ribs spaced therealong.

Preferably said sleeve has a length of 150 to 200 mm.

Typically said sleeve is formed of a flexible material.

In one embodiment, said grout injection port communicates with said cavity adjacent said first end.

Preferably an opening defined by said cavity'at said first end is of a reduced cross-section as compared to the interior of said cavity and an opening defined by said cavity at said second open end, said first end cavity opening being sized so as to be substantially sealed when said rock bolt is inserted therethrough.

Preferably, said cavity first end opening is offset from a central longitudinal axis of said cavity, the centre of said cavity first end opening being located on an opposing side of said cavity longitudinal axis to said grout injection port.

Preferably, said grout injection port comprises a flexible tube.

Preferably said grout injection port is sealed by a reduced thickness membrane of said sleeve adjacent said first end, said reduced thickness membrane having a thickness enabling it to be pierced so as to open said grout injection port.

Typically said sleeve is tapered adjacent said second end, at least one grout hole being provided through said sleeve, and communicating with said cavity, in the region of said taper for the flow of grout therethrough.

Typically said sleeve is formed of first and second sleeve portions, said first i sleeve portion including said first end and said grout injection port, said second sleeve portion including said second end and said at least one rib, said first and second sleeve portions being engaged in a substantially sealing manner enabling relative rotation of said first and second sleeve portions.

In an alternative and particularly preferred embodiment said grout injection port extends between said first and second ends adjacent to said cavity.

Preferably said grout injection port is in the form of a rigid tube.

Preferably an opening defined by said cavity at said second end is sized so as to be substantially sealed when said rock bolt is extended therethrough.

Preferably said seal is tapered adjacent said second end.

There is further disclosed herein a cable bolt having first and second ends and a circumferential exterior surface, said cable bolt being adapted to be inserted into a rock bolt hole with said second end leading and said first end trailing and protruding from said hole, said cable bolt being provided with a breather tube extending from said first end [R:\LIBLL]08348.doc:GJG:TcW toward said second end along said exterior surface, said breather tube replacing at least one wire of said cable bolt such that said breather tube is recessed into said exterior surface so as to be substantially flush therewith.

There is still further disclosed herein a method of post grouting a rock bolt installation comprising: inserting a rock bolt into said cavity of a rock bolt grout seal device as defined above, through said first end so as to extend through said second end, inserting said rock bolt grout seal device and rock bolt into a rock bolt hole such that said at least one flexible rib engages the wall of said rock bolt hole, said rock bolt lo having breather means communicating an upper region of said rock bolt hole with an exterior of said hole, securing said rock bolt, and ,injecting grout into said rock bolt hole via said grout injection port.

In one embodiment said rock bolt is a cable bolt as defined above, said breather 15 tube forming said breather means.

.••-*Brief Description of the Drawings Preferred forms of the present invention will now be described by way of example with reference to the accompanying drawings, wherein: 9*9* 9*Fig. l(a) is a front elevation view of a rock bolt grout seal according to one embodiment.

Fig. l(b) is a cross section of the rock bolt grout seal of Figure 1(a).

Fig. 1 is a plan view of the rock bolt grout seal of Figure 1 Fig. 2 is a cross sectional view of a rigid rock bolt installation in the roof of a mine incorporating the rock bolt grout seal of Figure 1 Fig. 3 is a cross sectional view of a cable bolt installation in the roof of a mine incorporating a rock bolt grout seal similar to that of Figure 1 Fig. 4 is a cross sectional view of a rigid rock bolt installation in the roof of a mine incorporating an alternative rock bolt grout seal.

Fig. 5 is a cross sectional view of another alternative rock bolt grout seal.

Fig. 6 is a cross sectional view of a particularly preferred rock bolt grout seal.

Fig. 7 is a perspective view of the rock bolt grout seal of Fig. 6.

[R:\LIBLL]08348.doc:GJG:TCW Detailed Description of the Preferred Embodiments Referring to Figures l(a) to 1(c) and Figure 2, a rock bolt grout seal 100 according to a preferred embodiment is in the general form of a sleeve 101 having first and second ends 103, 104 and defining a cavity 102. As depicted in Figure 2, showing a rock bolt installation incorporating the grout seal 100, the cavity 102 is adapted to receive a rock bolt 200, here a rigid rock bolt, inserted through the cavity at the first open end 103 and extending therethrough at the second open end 104. The grout seal 100 is provided with a grout injection port 105 which communicates with the cavity 102 adjacent the first open end 103. The grout injection port 105 is here in the form of a flexible tube 105 1o which can be connected to a grouting pump or gun to enable simple injection of grout into the cavity 102.

To restrict the escape of grout between the outside surface of the sleeve 101 and the wall 202 of the rock bolt hole 201 into which it is received, the outer surface of the sleeve is adapted to engage the rock bolt hole wall 202. To achieve this engagement, the Is outer surface of the sleeve 101 is provided with at least one, and preferably several, circumferentially extending flexible ribs 106. The flexible ribs 106 are spaced along the outer surface and engage the rock bolt hole wall 202 to inhibit the passage of grout back out of the rock bolt hole 201 after it has been injected through the cavity 102 and out the sleeve second open end 104. The flexibility of the ribs 106 enables them to be deflected over any irregularities in the rock bolt hole 201 as it is inserted, and generally maintain a seal between the sleeve 101 and rock bolt hole wall 202.

The ribs 106 enable the sealing of rock bolt holes 201 of varying diameter.

Standard rock bolt holes typically vary in diameter between about 43 to 50 mm, largely as a result of wear of the drill bit forming the hole, and oversizing of the hole through the drill rod mounting the drill bit impacting the hole wall. The ribs 106 should be sized such that they will engage the rock bolt hole wall 202 of the largest envisaged hole, and will deform or collapse as required to allow the seal to be inserted into a smaller hole.

Whilst it is not essential that the engagement provides a full, airtight seal between the sleeve 101 and rock bolt hole wall 202 to inhibit the flow of the viscous grout, an improved quality of seal will reduce the likelihood of the escape of any grout.

The ribs 106 may be generally planar as depicted, or may take any other suitable form, such as tapered, which will still provide flexibility. The ribs 106 may be sized such that they successively increase in diameter toward the second open end 104, as depicted in Figure This will result in progressively forceful engagement of the rock bolt hole wall 202, and a progressively improved seal, as the seal device 100 is inserted into the [R:\LIBLL]08348.doc:GJG:TCW rock bolt hole 201. Constant diameter ribs 106 could also be used. The ribs 106 will typically be located toward the second open end 104.

As well as the ribs 106 being flexible, the entire sleeve 101 may be formed of flexible material to enhance the ease with which the seal device 100 can be inserted into s the rock bolt hole 201. Alternatively, the sleeve 101 can be formed of a rigid material such as steel.

The opening defined by the first open end 103 is here of a reduced cross-section as compared to the cavity 102 and the second open end 104. The opening 103 is sized according to the rock bolt 200 size so as to substantially seal the first end 103 when the lo rock bolt 200 is inserted therethrough, thus restricting the flow of grout through the opening 103. The opening 103 will typically be slightly smaller than the diameter of the rock bolt 200 so as to provide an interference fit. It will be appreciated, however, that a larger opening could still be used as the opening 103 would typically be sufficiently sealed by the collar assembly 210 securing the rock bolt 200.

I15 The reduced cross section opening 103 is here offset from the centre of the cavity 102, as best depicted in Figures l(b) and 2. The centre of the opening 103 is located on an opposing side of the cavity longitudinal axis to the grout injection port 105. This configuration provides a clear passage 203 between the rock bolt 200 and the wall of the cavity 102 on the same side as the grout injection port 105, increasing the ease with which the injected grout can pass through the cavity 102 and out its second open end 104 into the rock bolt hole 201.

The opening 103 could, alternately be positioned coaxially with the cavity 102, albeit with a reduced width of passage for flow of grout. The rim 107 of the cavity first open end 103 may be configured as desired to mate with particular collar assemblies 210 being used.

The grout injection port flexible tube 105 may extend from the sleeve perpendicular to the axis of the cavity 102, extend at an angle beyond the cavity first end 103, or be curved away from the cavity first end 103 as depicted to facilitate passing of the flexible tube 105 through the collar assembly 210 without the need to' flex, and perhaps kink, the tube 105. The tube 105 is here provided with a cap 108 for sealing the tube 105 after the injection of grout.

With reference to Figure 2, to produce a post grouted rock bolt installation using the seal of the preferred embodiment, the flexible tube forming the grout injection tube 105 will typically first be extended through a hole 215 provided in a mine plate 212 of the collar assembly 210. The grout injection tube 105 is provided with barbs 109 which [R:\LIBLL]08348.doc:GJG:TCW prevent the tube 105 from being pulled back through the hole 105, thus anchoring the seal 100 against being pushed up the rock bolt hole 201. The rock bolt 200, which is in the form of a rigid rock bolt in the embodiment of Figure 2, is then inserted through the mine plate 212 and into the seal 100 through the first open end 103 so as to extend through the second open end 104. A mechanical or chemical anchor device may then be fitted to the end of the rock bolt 200 or rock bolt hole 201 for securing the rock bolt at the top of the hole in the usual manner.

The seal 100 and rock bolt 200 are then inserted into the rock bolt hole 201. The collar assembly 210, formed of the mine plate 212, a ball washer 213 and nut 214 as 1o depicted in Figure 2, which will have been located on the rock bolt 200, will help force the seal device into the rock bolt hole 201. As the seal 100 is inserted into the rock bolt :hole 201, the flexible ribs 106 will engage the rock bolt hole wall 202 and deform to accommodate the shape and size of the hole 201. The rock bolt 200 is then secured by S setting the anchor device and tightening the collar assembly 210 with the nut 214.

Grout is then injected into the cavity 102 via the grout injection port 105 extending through the collar assembly 210. The grout will flow upwardly through the passage 203 formed by the sleeve 101 and rock bolt 200 toward the cavity second open end 104 and up into the remainder of the rock bolt hole 201 where it will fill the gaps between the bolt 200 and rock bolt hole wall 202, providing the desired means for load transfer therebetween. The ribs 106 act as a barrier against grout leaking out of the hole 201. The seal will typically be of the order of 150 to 200 mm long, as compared to the typical rock bolt hole length of the order of 2 m, such that a great majority of the length of the hole is filled with a single annular column of grout.

To ensure the grout flows through the hole and fully encapsulates the rock bolt 200, it is necessary to evacuate air trapped in the rock bolt hole 201 as the grout is injected. To achieve this, the rock bolt is provided with breather means which communicate the upper region of the rock bolt hole 201 with the exterior of the hole. In the embodiment depicted in Figure 2, this breather means is in the form of a central breather hole 208 extending along the length of the rock bolt 200. Whilst the central rock bolt hole currently employed to directly inject grout needs to be approximately 10 mm in diameter to enable the grout to flow therethrough, a central breather hole 208 for evacuation of air need typically only be approximately 5 to 7 mm in diameter, thus helping to maintain structural integrity of the rock bolt 200.

When a mechanical anchor is used to secure the top of the bolt in the hole, a breather hole 208 which extends to and opens onto the top end of the bolt will suffice, as [R:\LIBLL]08348.doc:GJG:TCW air in the rock bolt hole 201 will be able to pass through the mechanical anchor. If a chemical anchor is used, however, the top end of the bolt 200 will largely be sealed from the remainder of the hole by the chemical anchor. In such circumstances it will be appropriate to provide a side opening, communicating with the central breather hole 208, below the chemical anchor.

After the rock bolt hole 201 is full of grout, the flexible tube forming the grout injection port 105 can be sealed with the cap 108. For an injection port tube without a cap, the tube can be bent double and secured with a cable tie.

Figure 3 depicts a typical installation using a cable bolt 250. A collar assembly 260 used with a cable bolt 250 is typically in the form of a mine plate 212, barrel 261 and wedges 262 which secure the barrel 261 to the cable bolt 250 in the usual manner. To "enable the barrel 261 and wedges 262 to be adequately secured to the cable bolt 250, the breather means, in the form of a breather tube 270, is recessed into the exterior surface of the cable bolt 250 such that it is substantially flush with the exterior surface 251.

This is here achieved by replacing at least one wire of the cable bolt 250 with a breather tube 270 of similar diameter. The breather tube 270 extends from the bottom, or first end, of the cable bolt 250 protruding from the rock bolt hole 201 to just short of the chemical anchor 280 which is employed in the embodiment depicted in Figure 3 to secure the top, or second end, of the cable bolt 250 in the rock bolt hole 201. Recessing the breather tube 270 into the exterior surface 251 enables the cable bolt to be spun in the hole for resin mixing of a chemical anchor without damage to the breather tube 270.

If a mechanical anchor were to be used, the breather tube 270 could be made to extend to the top of the cable bolt 250. Recessing the breather tube 208 into the exterior surface 251 of the cable bolt will also prevent the collar assembly 260 from crushing the breather tube 208 and blocking the flow of air therethrough.

An alternative embodiment seal 300 is depicted in Figure 4 in a rigid rock bolt 200 installation. Rather than forming the grout injection port as a tube, as per the embodiment of Figures 1 to 3, the grout injection port 305 is here sealed by a reduced thickness membrane 308 of the sleeve adjacent the first open end 303. The membrane 308 has a thickness which enables it to be readily pierced by pushing a grout injection tube through a hole 215 in the mine plate 212 so as to open the grout injection port 305.

In the preferred embodiment the membrane 308 extends around the seal first open end 303, allowing piercing of the membrane to form the open injection port 305 at any angular position around the first open end. The injection port opens into a chamber 309 which communicates with the seal cavity 302.

[R:\LIBLL]08348.doc:GJG:TCW More than one hole 215 may be provided in the mine plate 212 so that access to the membrane 308 can be provided at different positions. This will be particularly beneficial when a rock bolt 200 is installed at an angle to the rock face, with the result that the chamber 309 may be compressed on one side, inhibiting the flow of grout through that side of the chamber 309. The injection port 305 can then be accessed and opened into the chamber 309 via another hole 215 on the other side of the rock bolt 200.

A further alternative embodiment seal 400 is depicted in Figure 5. In a similar manner to the embodiment of Figures 1 through 3, the seal 400 is in the form of a sleeve 401 with at least one, and preferably several, circumferentially extending flexible ribs 406 being provided on the outer surface of the sleeve 401, and a grout injection port 405 adjacent the first open end 403 of the cavity 402 of the sleeve 401.

In this embodiment, the sleeve 401 is tapered adjacent the cavity second open end 404. The opening defined by the cavity second opened end 404 is of a reduced cross **section as compared to the cavity 402 as a result of the taper, with the opening 404 here 15 being of generally the same size as the first opened end 403 and the rock bolt to be passed therethrough. To enable grout injected into the cavity 402 through the injection port 405 to pass out through the end of the sleeve and into the rock bolt hole, at least one, and here *o four, grout holes 410 are provided in the sleeve at the tapered region. The tapered end of the sleeve 400 eliminates installation problems which could exist with the seal of the embodiments depicted in Figures 1 through 4. The tapered end prevents fouling of the leading end of the seal against obstacles such as the edge of the hole in the rock or a wire mesh which is typically preinstalled against the rock surface. Any such fouling could restrict or prevent the seal from being pushed into the rock hole.

The seal 400 of the embodiment depicted in Figure 5 is constructed with the sleeve forming first and second sleeve portions 401a and 401b. The first sleeve portion 401a forms the end of the sleeve 401 which remains projecting from the rock bolt hole, and includes the cavity first opened end 403 and the grout injection port 405. The second sleeve portion 401b forms the end of the sleeve which is first inserted into the rock bolt hole, and includes the cavity second open end 404 and the ribs 406. The sleeve first and second portions 401a, 401b are engaged in a substantially sealing manner which enables relative rotation of the first and second sleeve portions 401a, 40lb. The sleeve first and second portions 401a, 401b are engaged by means of a circumferential rim 41 1, provided in a reduced wall section thickness end section 412 of the first sleeve portion 401a, which engages a corresponding circumferential groove 413 provided in a mating end section 414 of reduced wall thickness on the second sleeve portion 401b. The reduced wall thickness [R:\LIBLL]08348.doc:GJG:TCW sections 413, 414 overlap providing continuous inner and outer surfaces of the overall sleeve, with the interface between the two sections 413, 414 preventing grout from escaping from the cavity 402.

When the seal 400 is in location in a rock bolt hole with a collar assembly fitted as described above in relation the first embodiment, with the grout injection tube 405 extending through a hole in the mine plate 212, the sleeve first portion 401a is free to rotate without imparting any significant torsional loads on the sleeve second portion 401b, which will be engaged with the rock bolt wall by the ribs 406. Accordingly, when the washer 213 and nut 214 are rotated by an installation spanner during setting of the mechanical anchor or during resin mixing of the chemical anchor, and the mine plate 212 and grout injection port 405 is rotated as a result, the torsional load applied to the sleeve :"by the grout injection port 405 will result in rotation of the sleeve first portion 401a without transferring significant torsional loads to the sleeve second portion 401b. Such torsional loads could otherwise typically twist and damage the seal.

A particularly preferred rock bolt grout seal is depicted in Figures 6 and 7. This seal 500 differs from the earlier embodiments primarily in that the grout injection port 505 does not communicate with the cavity 502, but extends between the first and second ends 503, 504 of the seal 500 adjacent to the cavity 502, without communicating with the same. Here the grout injection port 505 is in the form of a rigid tube which is here formed of steel. This seal 500 is particularly robust as compared to the embodiments described above. Formation of a separate rigid grout tube 505 extending along the length of the seal 500 separate to the cavity 502 assists in ensuring that the large forces and torques applied to the seal during installation by installation machinery and any rough rock formations will not squash the seal (and in particular the grout injection tube 505 or a cavity communicating with the grout injection port) as can be the case with the earlier described embodiments having a flexible grout injection port communicating with the cavity. Such squashing of the grout injection port cavity can impede the flow of grout.

The opening defined by the cavity 502 at the seal second end 504 is of a reduced cross-section as compared to the interior of the cavity 502 and sized such that this opening is substantially sealed where a rock bolt 200 is inserted therethrough, as depicted in Figure 6. Whilst this arrangement leaves the section of rock bolt 200 located within the seal 500 unsupported by grout, the typical seal length of 150 to 200 millimetres represents only a small portion of the length of the rock bolt 200 which is left unsupported. The second end 504 of the seal 500 is tapered in a similar manner to the embodiment of Figure 5 to assist in ease of insertion of the seal 500 into the rock bolt hole 201.

[R:\LIBLL]08348.doc:GJG:TCW 11 Other modifications of the seal and rock bolt will be appreciated by the person skilled in the art.

[R:\LIBLL]08348.doc:GJG:TCW

Claims (14)

1. A rock bolt grout seal comprising: a sleeve having first and second ends and defining a cavity extending between said first and second ends, said cavity adapted to receive a rock bolt inserted therethrough at said first end and extending therethrough at said second end, a grout injection port disposed at or adjacent to said first end and communicating with said second end, for injection of grout through said sleeve and out of said second end, and at least one circumferentially extending flexible rib disposed on an outer surface of said sleeve and adapted to engage the wall of a rock bolt hole into which, in use, said sleeve and rock bolt are received.

2. The rock bolt grout seal of claim 1, wherein said outer surface is provided with a plurality of said flexible ribs spaced therealong. S3. The rock bolt grout seal of either of claims 1 and 2, wherein said sleeve is has a length of 150 to 200 mm.

4. The rock bolt grout seal of any one of claims 1 to 3, wherein said sleeve is formed of a flexible material. The rock bolt grout seal of any one of claims 1 to 4, wherein said grout injection port communicates with said cavity adjacent said first end.

6. The rock bolt grout seal of claim 5, wherein an opening defined by said cavity at said first end is of a reduced cross-section as compared to the interior of said cavity and an opening defined by said cavity at said second open end, said first end cavity opening being sized so as to be substantially sealed when said rock bolt is inserted therethrough.

7. The rock bolt grout seal of claim 6, wherein said cavity first end opening is offset from a central longitudinal axis of said cavity, the centre of said cavity first end opening being located on an opposing side of said cavity longitudinal axis to said grout injection port.

8. The rock bolt grout seal of any one of claims 5 to 7, wherein said grout injection port comprises a flexible tube.

9. The rock bolt grout seal of any one of claims 5 to 7, wherein said grout injection port is sealed by a reduced thickness membrane of said sleeve adjacent said first end, said reduced thickness membrane having a thickness enabling it to be pierced so as to open said grout injection port. [R:\LIBLL]08348.doc:GJG:TCW The rock bolt grout seal of any one of claims 5 to 9, wherein said sleeve is tapered adjacent said second end, at least one grout hole being provided through said sleeve, and communicating with said cavity, in the region of said taper for the flow of grout therethrough.

11. The rock bolt grout seal of claim 5, wherein said sleeve is formed of first and second sleeve portions, said first sleeve portion including said first end and said grout injection port, said second sleeve portion including said second end and said at least one rib, said first and second sleeve portions being engaged in a substantially sealing manner enabling relative rotation of said first and second sleeve portions.

12. The rock bolt grout seal of any one of claims 1 to 4, wherein said grout injection port extends between said first and second ends adjacent to said cavity. The rock bolt grout seal of claim 12, wherein said grout injection port is in the form of a rigid tube. *ooo The rock bolt grout seal of either of claims 12 and 13, wherein an s15 opening defined by said cavity at said second end is sized so as to be substantially sealed when said rock bolt is extended therethrough. •15. The rock bolt grout seal of any of claims 12 to 14, wherein said seal is tapered adjacent said second end.

16. A cable bolt having first and second ends and a circumferential exterior o' 20 surface, said cable bolt being adapted to be inserted into a rock bolt hole with said second end leading and said first end trailing and protruding from said hole, said cable bolt being provided with a breather tube extending from said first end toward said second end along said exterior surface, said breather tube replacing at least one wire of said cable bolt such that said breather tube is recessed into said exterior surface so as to be substantially flush therewith.

17. A method of post grouting a rock bolt installation comprising: inserting a rock bolt into said cavity of a rock bolt grout seal device as defined in any one of claims 1 to 15 above, through said first end so as to extend through said second end, inserting said rock bolt grout seal device and rock bolt into a rock bolt hole such that said at least one flexible rib engages the wall of said rock bolt hole, said rock bolt having breather means communicating an upper region of said rock bolt hole with an exterior of said hole, securing said rock bolt, and injecting grout into said rock bolt hole via said grout injection port. [R:\LIBLL]08348.doc:GJG:TCW

18. The rock bolt grout seal of claim 17, wherein said rock bolt is a cable bolt as defined in claim 16, said breather tube forming said breather means.

19. A rock bolt grout seal substantially as hereinbefore described with reference to Figures l(b) and Figure 4 or Figure 5 of the accompanying drawings. A rock bolt grout seal substantially as hereinbefore described with reference to Figures 6 and 7 of the accompanying drawings.

21. A cable bolt substantially as hereinbefore described with reference to Figure 3 of the accompanying drawings. Dated 30 August, 2000 ~The ANI Corporation Limited Patent Attorneys for the Applicant SPRUSON FERGUSON C 0 a s se *o*0° [R:\LIBLL]08348.doc:GJG:TCW