WO2012000016A1

WO2012000016A1 - An apparatus for post-grouting a cable bolt, cable bolt assembly and method of installing a cable bolt

Info

Publication number: WO2012000016A1
Application number: PCT/AU2011/000697
Authority: WO
Inventors: David William Evans
Original assignee: Dywidag-Systems International Pty Limited
Priority date: 2010-06-30
Filing date: 2011-06-03
Publication date: 2012-01-05
Also published as: AU2011274289A1; AU2011274289B2

Abstract

A cable bolt assembly (400) including a cable (410) extending along the longitudinal axis L. The assembly (400) further includes a post-grouting apparatus (411) comprising (a) a load bearing grout delivery fitting (413) having a leading face (424) and a trailing face (430), a longitudinally extending grout receiving cavity (421) extending inwardly of the fitting from the leading face, a longitudinally extending passage (423) extending inwardly of the fitting from the trailing face and extending to the cavity, a grout delivery port (422) communicating with the cavity to provide for the delivery of grout thereto, and (b) a seal (427) mounted in the fitting and surrounding the passage to sealingly engage the cable that is to extend longitudinally through the fitting via the cavity and passage.

Description

AN APPARATUS FOR POST-GROUTING A CABLE BOLT, CABLE BOLT ASSEMBLY AND METHOD OF INSTALLING A CABLE BOLT

Field of the Invention

The present invention relates to strata control in civil engineering and mining operations and in particular relates to rock bolts (in the form of cable bolts) for securing the roof or wall of a mine, tunnel or other ground excavation. More particularly, the present invention relates to an apparatus for post-grouting a cable bolt, a cable bolt assembly and a method of installing a cable bolt.

Background of the Invention

To secure the roof and/or walls of underground mines, tunnels and other ground excavations, rock bolts in the form of long flexible cable bolts (otherwise referred to as strand bolts) are often utilised. In one form of installation, each cable bolt is fixed into a bore hole drilled into a rock face with both a two-component resin and cement grout. A resin cartridge containing the two-component resin is first inserted into the bore hole, followed by the cable bolt which is driven into the hole to puncture the resin cartridge. The cable bolt is rotated to mix the resin and form a point anchor securing the leading end of the cable bolt in the bore hole once the resin has set. The cable bolt is then pre- tensioned with a hydraulic jack and the trailing end of the cable bolt secured to the rock face at the opening of the bore hole utilising a barrel and wedge assembly that engages a bearing plate washer located against the rock face. A cement grout is then injected into the annular cavity between the cable bolt and the wall of the bore hole both to provide a degree of corrosion protection to the cable bolt and to provide for compressive load transfer between the wall of the bore hole and the cable bolt.

Various different arrangements for injecting grout into the annular cavity have previously been proposed. In one cement grouting method, a grout tube is inserted into the bore hole only a short distance, such that the grout injected into the grout tube is pushed up through the annular cavity from adjacent the bore hole opening. To evacuate air from the bore hole while the cement grout is being pumped from the bottom, a breather tube (typically in the form of a small diameter plastic rube) is located in the annular cavity extending toward the top of the bore hole. The bore hole must also be sealed at the rock face to ensure that the injected grout is pumped toward the top of the bore hole rather than merely escaping out through the bore hole opening. The breather tube is also subject to damage during installation, and requires a relatively large annular cavity between the cable bolt and bore hole wall for location of the breather tube.

In an alternate cement grouting method, the grout tube extends from the bore hole opening to adjacent the top of the bore hole, such that grout injected through the grout tube flows down through the full length of the bore hole. Utilising this method, no breather tube is required and there is no need to seal the bore hole opening in the rock face. A large diameter bore hole is required to be drilled into the rock to house the grout tube in the annular cavity between the cable bolt and bore hole wall. 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 cavity between the cable bolt and the bore hole should be as small as possible to achieve the best fixation of the cable bolt. A smaller annular cavity is also desired for effective load transfer between the cable bolt and bore hole wall via the cement grout.

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

In a first aspect, the present invention provides an apparatus for post-grouting a cable bolt having a longitudinal axis, the apparatus including:

a load bearing grout delivery fitting having a leading face and a trailing face, a longitudinally extending grout receiving cavity extending inwardly of the fitting from the leading face, a longitudinally extending passage extending inwardly of the fitting from the trailing face and extending to the cavity, a grout delivery port communicating with the cavity to provide for the delivery of grout thereto; and

a seal, mounted in the fitting and surrounding the passage, to sealingly engage the cable that is to extend longitudinally through the fitting via the cavity and passage.

Preferably, the port extends at least partly laterally relative to said axis.

Preferably, the apparatus further includes a tube fixed to the fitting and extending longitudinally away from said leading face to an end extremity, and through which the cable is to pass.

Preferably, the apparatus further includes a sleeve mounted in the end extremity of said tube and extending longitudinally away from the tube. Preferably, said tube is formed of metal and said sleeve of plastics material, with the tube and sleeve configured so as to provide a passage surrounding the cable via which grout is delivered through the tube and sleeve.

Preferably, the fitting passage increases in transverse cross-section toward said trailing surface, and said apparatus includes at least one wedge located in the fitting passage adjacent said trailing face, each wedge being provided to securely fix the fitting to the cable.

Preferably, the fitting includes an annular cavity surrounding said passage and within which the seal is located.

A cable bolt assembly including the above assembly and a cable extending therethrough, with the seal sealingly connecting the fitting and cable.

Preferably, the cable bolt has a barrel and wedge assembly mounted on the cable, said apparatus further comprising:

an elongate sleeve fixed to the fitting and extending along the longitudinal axis between a sleeve leading end and a sleeve trailing end and being sized to be mounted on the cable; and wherein

the trailing face is configured to engage a leading end of the barrel and wedge assembly, and the leading face is configured to engage a bearing plate washer.

Typically, said fitting trailing face is formed with a concave region surrounding said cable aperture for engaging a convex leading end of said barrel and wedge assembly.

In one form, said fitting has an annular shoulder located in said cable aperture and facing said fitting trailing face, said seal being located adjacent said annular shoulder such that, in use, said seal is compressed between said annular shoulder and the barrel and wedge assembly to seal said cable aperture.

Typically, said forward facing fitting peripheral surface is in the form of a convexly curved body of revolution, typically semi-spherical.

In a third aspect, the present invention provides a cable bolt assembly comprising:

a) a cable extending along a longitudinal axis between a cable leading end and a cable trailing end;

b) a barrel and wedge assembly mounted on said cable toward said cable trailing end;

c) an elongate sleeve extending along said longitudinal axis between a sleeve leading end and a sleeve trailing end, said sleeve being mounted on said cable between said barrel and wedge assembly and said cable leading end; . d) a load bearing grout delivery fitting attached to said sleeve trailing end, said fitting having:

(i) a fitting trailing face configured to engage a leading end of said barrel and wedge assembly;

(ii) a cable aperture extending along said longitudinal axis through said fitting, said cable extending through said cable aperture;

(iii) a forward facing fitting peripheral surface; and

(iv) a grout delivery passage extending from a grout delivery passage inlet, located on an exterior surface of said fitting, through said fitting to a grout delivery passage outlet located in a wall of said cable aperture;

e) a seal for sealing said cable aperture between said cable and said fitting, said seal being located between said grout delivery passage outlet and said fitting trailing face; and

f) a washer mounted on said sleeve adjacent said fitting peripheral surface, said fitting peripheral surface being configured to engage said washer.

Typically, said fitting trailing face is formed with a concave region surrounding said cable aperture and said leading end of said barrel and wedge assembly is convexly curved.

In a preferred form, said grout delivery passage inlet is located on, or adjacent to, said fitting trailing face.

In one form, said grout delivery passage is inclined at an acute angle to said longitudinal axis.

In one form, said cable bolt assembly further comprises a drive head formed at or adjacent said cable trailing end for rotatably driving said cable.

Typically, said drive head comprises a regular prism welded onto said cable trailing end.

Preferably, said cable has at least one bulb formed towards said cable leading end, said bulb being formed by local radial deformation of strands of said cable.

In a preferred form, said cable bolt assembly is provided with a resin mixing formation toward said cable leading end.

In one form, said resin mixing formation comprises a wire attached to said cable toward said cable leading end and spirally extending along said cable. In a fourth aspect, the present invention provides a method comprising:

drilling a bore hole in a rock face of a strata to be secured;

inserting a resin filled cartridge having a frangible casing into said bore hole; inserting said cable into said bore hole such that said cable leading end engages said resin filled cartridge;

thrusting said cable further into said bore hole and rotating said cable so as to rupture said frangible casing and mix said resin;

allowing said resin to cure;

post-tensioning said cable, engaging said leading end of said barrel and wedge assembly with said fitting trailing face, engaging said fitting peripheral surface with said washer and engaging said washer with said rock face;

sealing said cable aperture between said cable and said fitting with said seal; and pumping grout through said grout delivery passage, through said cable aperture and along said sleeve between said sleeve and said cable to said cable leading end and back from said cable leading end between said sleeve and the wall of said bore hole toward said rock face.

Brief Description of the Drawings

Preferred embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings wherein;

Figure 1 is a left side perspective view of a cable bolt assembly according to a first embodiment;

Figure 2 is a front elevation of the cable bolt assembly of Figure 1 ;

Figure 3 is a perspective view from below of the cable bolt assembly of Figure 1 ;

Figure 4 is a perspective view from above of the cable bolt assembly of Figure 1 ;

Figure 5 is a partially cross-sectioned rear view of the trailing region of the cable bolt assembly of Figure 1 ;

Figure 6 is an enlarged version of part of Figure 5;

Figure 7 is a cross-sectioned view of the post-grouting apparatus of the cable bolt assembly of Figure 1 ;

Figure 8 is an enlarged cross-sectional rear view of part of the apparatus of

Figure 7;

Figure 9 is a left side isometric view of the apparatus of Figure 8;

Figure 10 is a right side isometric view of the apparatus of Figure 8; Figure 1 1 is a partially cross-sectioned view of a rock bolt installation, using the rock bolt assembly.of Figure 1 , in a partially installed state;

Figure 12 is a partially cross-sectioned view of the rock bolt installation of Figure 11 in a fully installed state;

Figure 13 is a right side isometric view of a cable bolt assembly according to a second embodiment;

Figure 14 is an isometric view from above of the cable bolt assembly of Figure

13.

Figure 15 is an isometric view from below of a cable bolt assembly according to a third embodiment;

Figure 16 is an isometric view from above of the cable bolt assembly of Figure

15.

Figure 17 is an isometric view from below of a cable bolt assembly according to a fourth embodiment;

Figure 18 is an isometric view from above of the cable bolt assembly of Figure 17; ^{^}

Figure 19 is a partially cross-sectioned view of the trailing region of the cable bolt assemblies of Figures 15 to 18;

Figure 20 is a partially cross-sectioned view of a rock bolt installation, using the rock bolt assembly of Figures 15 and 16;

Figure 21 is a side isometric view of portion of the cable bolt assemblies of Figures 15 to 18;

Figure 22 is a schematic isometric view of the portion of Figure 21 ; and

Figure 23 is an enlarged view of part of the cable bolt assemblies of Figures 15 to 18.

Detailed Description of the Preferred Embodiments

A cable bolt assembly 00 according to a first embodiment is depicted in Figures 1 through 6. The cable bolt assembly 100 comprises a cable 110 extending along a longitudinal axis L between a cable leading end 110a and a cable trailing end 110b and a standard barrel and wedge assembly 120 mounted on the cable 1 10 toward the cable trailing end 1 10b. The cable bolt assembly 100 further comprises a^'post-grouting apparatus 130 for post-grouting the cable 110, mounted on the cable 110 adjacent the barrel and wedge assembly 120, between the barrel and wedge assembly 120 and the cable leading end 110a. The cable 1 10 is formed of a plurality of helically wound steel strands in the usual manner. The barrel and wedge assembly 120, best depicted in Figures 5 and 6, is also of a standard configuration including a barrel 121 having a longitudinally extending barrel aperture 122 that tapers toward the barrel leading end 121 a. A plurality of reverse tapered wedge elements 123 are mounted in the barrel aperture 122, extending about and engaging the cable 1 10.

The cable bolt assembly 100 here further comprises a drive head 170 formed at or adjacent the cable trailing end 1 10b for rotatably driving the cable 1 10 during the installation process as will be described below. In the particular embodiment depicted, the drive head 170 is in the form of a regular prism, particularly a rectangular prism, welded on to the cable trailing end 1 10b. The drive head 170 has a lateral cross-section that is entirely within the diameter of the cable 1 10 so as to enable the barrel and wedge assembly 120 to be assembled on to the cable 1 10 from the cable trailing end 1 10b and to allow cable tensioning equipment to grip the cable 1 10 adjacent the cable trailing end 1 10b without interference.

Towards the cable leading end 110a, the cable 1 10 is provided with a bulb 1 1 1 formed in the cable 1 10 by local radial deformation of strands of the cable in a known manner. First and second crimped ferrules 1 12, 1 13 are secured to the cable 1 10 at each end of the bulb 1 1 1 to locally stabilise the cable 1 10 whilst forming the bulb 1 1 1 and to protect the welded end surface of the cable 1 10 from fraying whilst compressing the cable 110 during formation of the bulb 1 1 1.

The cable bolt assembly 100 depicted further comprises a resin mixing formation, here in the form of a wire 180 attached to the cable 1 10 toward the cable leading end 1 10a (trailing the bulb 1 1 1) and spirally extending along the cable 1 10 toward the cable trailing end 1 10b. Specifically, the wire 180 is attached to the cable 1 10 by being welded at the wire leading end 180a to the second ferrule 1 13 and at the wire trailing end 180b to a third ferrule 114 crimped on to the cable 110. The third ferrule 1 14 may also be sized to act as a resin dam, so as to inhibit the flow of resin beyond the third ferrule 1 14 toward the cable trailing end 1 10b. Alternatively, a separate resin dam may be mounted on the cable 1 10 adjacent the third ferrule 11 .

The cable bolt assembly 100 further comprises a standard bearer plate washer 190 having a central aperture 191 through which the post-grouting apparatus 130 and cable 1 10 extend. The post-grouting apparatus 130 is best depicted as part of the cable bolt assembly 100 in Figures 5 and 6 and in isolation in Figures 7 through 10. The post- grouting apparatus 130 generally comprises an elongate sleeve 140, load bearing grout delivery fitting 150 and a seal 131 best depicted in Figure 6. The sleeve 140 extends along the longitudinal axis L between a sleeve leading end 140a and a sleeve trailing end 140b. As best appreciated from Figure 5, the sleeve 140 is sized to be mounted on the cable 110. The sleeve 140 is here formed of two parts, being a leading sheath 141 formed of a plastics material and a trailing tube 142 that is here formed of steel. The sheath 141 is provided with a series of corrugations 143 to assist in anchoring the sheath 141 with respect to grout encapsulating the cable bolt assembly during installation as will be discussed further below. The sheath 141 extends into the tube 142, as best depicted in Figure 5 and is secured thereto by gluing, with a slightly pressed fit, The steel tube 142 typically extends over a relatively short length and being significantly more robust than the plastic sheath 141 is less likely to be damaged. The plastic sheath 141 will typically have a length of the order of 5 m or more, depending on the length of the cable 110. The sleeve 1 0 will typically have length between 1 m and 1.5 m shorter than the length of the cable bolt assembly 100, depending on the configuration of the leading region of the cable bolt assembly 100. The sleeve leading end 140a will typically be located about 50 to 200 mm from the third ferrule 114 (or any resin dam). For a cable diameter of 23.5 mm, the plastic sheath 141 here has an outer diameter of about 35 mm and the steel tube 142 has an outer diameter of about 38 mm.

The fitting 150 is attached to the sleeve trailing end 140b, typically by welding. Alternativel , the tube 142 could be integrally formed with the fitting 150. The fitting 150 is typically machined from steel. The fitting 150 has a cable aperture 151 communicating with the sleeve trailing end 140b and extending along the longitudinal axis L through the fitting 150 for receiving the cable 1 10. The cable aperture 151 opens onto a fitting trailing face 152 that is configured to engage the leading end of the barrel and wedge assembly 120, particularly the barrel leading end 121a. Specifically, the fitting trailing face 152 is here formed with a concave region 153 surrounding the cable aperture 151 for engaging the convexly curved barrel leading end 121a. The concave region 153 is typically generally semi -spherical so as to match the typical semi-spherical convex shape of the barrel leading end 121a.

The fitting 150 has a forward facing fitting peripheral surface 154 that is configured to engage the bearer plate washer 190. Particularly, the fitting peripheral surface 154 is configured to engage the rim 192 of the aperture 191 extending through the bearer plate washer 1 0. So as to allow for installations where the bearer plate washer 190 does not extend perpendicular to the cable 1 10, either as a result of irregularities in the rock face or drilling of a bore hole through the rock face at an angle other than perpendicular to the rock face, the fitting peripheral surface 154 is in the form of a convexly curved body of revolution. Typically, the fitting peripheral surface 154 is semi- spherical. Accordingly, if and when there is misalignment between the bearer plate washer 190 and the cable 1 10, load may be reliably transferred between the bearer plate washer 190 and the fitting 150 about the entire periphery of the rim 192 of the roof plate washer 1 0.

The fitting 150 has a grout delivery passage 155 that extends from a grout delivery passage inlet 156, located on the exterior surface of the fitting 150, through the fitting 150 to a grout delivery passage outlet port 157 that is located in a wall 158 of the cable (cavity) aperture 151. The passage 155 extends away from the axis L so as to have a direction of extension component perpendicular to the axis L as well as component parallel to the axis L. Accordingly the passage 155 extends at least partly laterally relative to the axis L, ant at an acute angle to the axis L. The grout delivery passage inlet 156 will typically be internally threaded for engagement with an externally threaded end fitting of a grout pumping hose and extend, at least partly, laterally from the passage. In the arrangement depicted, the grout delivery passage 155 extends at an acute angle to the longitudinal axis L, with the grout delivery passage inlet 156 being located on, or adjacent to, the fitting trailing face 152. This provides for ready access to the grout delivery passage 155 during installation and directs the grout up the cable aperture 151 into the sleeve 140.

Within the cable aperture 151 there is provided an annular projection 159 that defines an annular shoulder 160 facing the fitting trailing face 152. As best seen in Figure 6, the seal 131, which is typically in the form of an elastomeric ring, is located adjacent the shoulder 160 in a recess 161 defined between the annular shoulder 160 and the barrel leading end 121a so as to be mounted in the fitting 150. As will be discussed further below, during installation the seal 131 is compressed between the barrel 121 and the shoulder 160, laterally expanding to fill the recess 161 and effectively seal the cable aperture 151 between the cable 1 10 and the fitting 150. ~

Installation of the cable bolt assembly 110 will now be described with particular reference to Figures 1 1 and 12. A bore hole 200 is drilled into the rock face 201 of the strata 202 to be secured. For a cable diameter of 23.5 mm, a bore hole diameter of between 45 and 55 mm will be typical. A resin cartridge 203 containing a two-component resin is then inserted into the bore hole 200, followed by the cable bolt assembly 100 with the cable leading end 110a leading. The cable bolt assembly 100 is mounted on the dolly of regular cable bolt installation equipment, with the drive head 170 engaging a mating socket of the dolly. The cable 1 10 is thrust toward the bore hole blind end 200a and at the same time rotatably driven by way of the drive head 170, which is driven by the installation dolly. The cable leading end 1 10a thus compresses the resin cartridge 203 against the bore hole blind end 200a, rupturing the frangible casing of the cartridge 203 and allowing the two-component resin 204 to mix. As the cable 110 is thrust further toward the bore hole blind end 200a and the resin 204 flows down over the leading region of the cable 110, the spirally extending wire 180 acts to pump the resin 204 toward the bore hole blind end 200a and thoroughly mix the same. To ensure the wire 180 pumps the resin toward the bore hole blind end 200a, rather than draw the resin 204 down the bore hole 200, the cable 110 should be rotated in the appropriate direction. For example, for a left-handed spiral, the cable 1 10 should be rotated with "right-handed" rotation installation equipment.

Pumping of the resin toward the bore hole blind end 200a increases the pressure in the resin 204 and acts to push the mixing resin 204 into voids formed in the bulb 111. This ensures that the mixed resin 204 substantially fills the voids, curing to form a solid mass that prevents the bulb 11 1 from collapsing upon the application of a tensile load, allowing the bulb 1 1 1 to effectively serve as a point anchor as intended. The wire 180 itself also assists in anchoring the cable 110 within the resin 204. Flow of resin 204 toward the cable trailing end 1 10b is inhibited by the third ferrule 114, if appropriately sized, or alternatively by way of a separate resin dam as described above.

Whilst the cable 110 is being rotated by way of the drive head 170, the post-^{^} grouting apparatus 130 will typically remain stationary, given the relatively loose fit on the cable 1 10 and friction that will typically act on the sheath 141 by virtue of inevitable contact with the wall of the bore hole 200. It is also envisaged that the cable 1 10 might be inserted and rotated prior to assembly of the post-grouting apparatus 130, bearer plate washer 190 and barrel and wedge assembly 120 onto the cable 1 10.

Once the resin has been mixed, rotation of the cable 110 is ceased, allowing the resin to cure, thereby anchoring the leading region of the cable 110 within the bore hole 200. Once the resin has cured, the post-grouting apparatus 130, bearer plate washer 190, barrel and wedge assembly 120 are assembled onto the trailing region of the cable bolt 110 if not already assembled.

The cable 110 is then pre-tensioned in the usual manner utilising hydraulic cable tensioning equipment gripping the cable 110 behind the barrel and wedge assembly 120 and tensioning the cable 1 10 whilst driving the barrel and wedge assembly 120 toward the rock face 201, thereby engaging the barrel leading end 121a with the fitting trailing face concave region 153 and consequently engaging the fitting peripheral surface 154 with the rim 192 of the bearer plate washer 190 and consequently engaging the bearer plate washer 190 with the rock face 201. Tension developed in the cable 1 10 in the post-tensioning process is thus transferred to the rock face 201 via the barrel and wedge assembly 120, fitting 150 and roof plate washer 190. At the same time, the seal 131 is compressed within the recess 161, laterally expanding the seal 131 into engagement with the cable 110, thereby sealing the cable aperture 151 between the cable 1 10 and the fitting 150.

Following post-tensioning, a grout pumping hose is attached to the grout delivery passage inlet 156 and grout 205 is pumped through the grout delivery passage 155, through the cable aperture 51 , and sleeve 140. When the grout 205 reaches the leading end 140a of the sleeve 140, it flows back down the bore hole 200 between the sleeve 140 and the wall of the bore hole 200. Post-grouting is completed when signs of grout 205 having reached the opening of the bore hole 200 are provided, typically by grout appearing in gaps between the bearer plate washer 190 and rock face 200. The seal 131 prevents grout 205 from passing through the cable aperture 151 beyond the fitting trailing face 152 and into the barrel aperture 122 which would foul the barrel and wedge assembly 120, potentially inhibiting its effective operation. The grout 205 is then allowed to set. The post-grouting of the cable bolt assembly 1 10 provides for additional load transfer between the cable 110 and the strata 202 and, importantly, provides three layers of corrosion protection of the cable 1 10 along the grouted length of the cable 1 10, which is particularly important in aggressive corrosive environments.

A cable bolt assembly 300 according to a second embodiment is depicted in Figures 13 arid 14. The cable bolt assembly 300 is generally identical to the cable bolt assembly 100 of the first embodiment described above except that it omits the spirally extending wire 180 of the first embodiment and the cable 310 is provided with a series of three spaced bulbs 3 1 located toward the cable leading end 310a. The ferrules mounted on the cable at each end of the bulbs in the first embodiment have also been omitted. In the absence of the ferrules, a resin dam 315 is mounted on the cable 310 adjacent the third bulb 31 1 so as to inhibit the flow of resin beyond the resin dam 315. The trailing region of the cable bolt assembly, particularly the post-grouting apparatus 130, barrel and wedge assembly 120, drive head 170 and bearer plate washer 190 are otherwise identical to those described above in relation to the first embodiment. In the absence of the spirally_, extending wire, the three bulbs 311 act to mix the resin during installation and provide additional point anchoring of the cable. It is also envisaged, but less preferred, that the bulbs 31 1 may also be omitted, leaving the plain cable to mix the resin and to form a point anchor by way of the resin.

In the embodiments of Figures 15 to 18 there is provided a cable bolt assembly 400. The assembly 400 has some of the features of the assemblies of Figures 1 to 15. The assembly 400 includes a cable 410 extending along a longitudinal axis L between a cable leading end 410a and a cable trailing end 410b, as well as a post-grouting apparatus 41 1. The apparatus 411 includes an elongated sleeve 412, a load bearing grout delivery fitting 413 and a seal 414. Engaged with the fitting 413 are wedges 415. The sleeve 412 includes a longitudinally extending tube 416 secured to the fitting 413 so as to extend longitudinally therefrom toward the end 410a and a sheath 417. Received within the tube

416 and extending therefrom is the sheath 417. As is illustrated in the Figures, the sheath

417 has an outer diameter enabling it to be received within the end extremity of the tube 416, but to surround the cable 410 while still providing a longitudinally extending annular passage 418 between the inner surface of the sheath 417 and the outer surface of the cable 40. If required, the sheath 417 may include corrugations 419 extending angularly about the axis L.

The tube 416 would be typically formed of metal and fixed to the fitting 413. The sheath 417 would be secured to the end extremity of the tube 416 by an adhesive and/or an interference fit therewith.

The tube 41 is sized so as to surround the cable 410 and to provide an annular longitudinally extending passage 420 between the cable 410 and the interior surface of the tube 416.

The fitting 413 includes an end annular cavity 418 that communicates with the passage 420 that in turn communications with the cavity 418. The cable 410 extends through the cavity 418. Extending laterally from the cavity 413 is a grout port 422.

The fitting 413 further includes a longitudinally extending passage 423 through which the cable 410 passes, with the passage 423 increasing in diameter past the wedges 415. The internal surfaces of the passage 423 adjacent the wedges 41 have an inclination relative to the axis L so as to match the external surfaces of the wedges 415. As best seen in Figure 19, the wedges 415 surround the cable 410. The passage 423 extends inwardly of the fitting 413 from the fitting trailing face 430.

The leading portion of the fitting 413 is arcuate in configuration so as to provide an end (leading) face 424 that bears against the bearing plate washer 425. The cavity 418 extends upwardly of the fitting 413 from the face 424;

Surrounding the passage 423 is an annular slot 426 within which there is located an annular resilient seal 427 that engages the external peripheral surface of the cable 410 to aid in sealingly connecting the fitting 413 and cable 410.

In operation of the above cable bolt assembly 400, the bore hole 200 is drilled into the rock face 201. A resin cartridge 203 containing a 2-component resin is then inserted into the bore hole 200, followed by the cable bolt assembly 400. The leading end 410a engages the cartridge 203 to move it longitudinally of the bore hole 200. The cable bolt assembly 400 is mounted on the dolly of a regular cable bolt insertion equipment, with the drive head 428 engaged and driven by the dolly. The cable leading end 410a thus compresses the resin cartridge 203 against the hole blind end, rupturing the frangible casing of the cartridge 423 and allowing the 2-component resin to mix. As the cable 410 is thrust further towards the bore hole blind end the resin flows down over the leading region of the cable 410. Spiral wire 429 acts to pump the resin towards the bore hole blind end as the cable 4 0 is rotated about the axis L.

The fitting 413 and wedges 415 rotate with the cable 410 to minimise damage to the seal 427. The plate 425 may or may not rotate with the cable 410.

Once the resin has been mixed and rotation of the cable 410 ceased, the resin is allowed to cure thereby anchoring the leading region of the cable 410 within the bore hole 200.

Once the resin has cured, the post-grouting apparatus 411 , bearing plate washer 425 and wedges 415 are assembled onto the trailing region of the cable 410 if not already assembled.

The cable 410 is then pre-tensioned by hydraulic cable tensioning equipment engaging the cable 410 adjacent the end 410b. While this is occurring the wedges 415 are driven further into the passage 423 so as to engage in a clamping manner the external surfaces of the cable 410 to securely connect the fitting 413 to the cable 410 which in turn compresses the washer 425 against the face 210. Once pre-tensioning has been completed, a duct is connected to the port 422 for delivery of grout to the cavities 421, 420 and 418 for delivery to the annular end opening 431 at the end extremity of the sheath 417. The grout flows upwardly toward the resin now surrounding the end extremity of the cable 410, and then downwardly over the outer surfaces of the sheath 417 and tube 16. The grout is then allowed to set.

Preferably, the port 422 extends generally perpendicular to the longitudinal axis L. However it should be appreciated that the port 422 need only have some lateral direction of extension relative to the axis L, that is in the direction of flow of the grout through the assembly 400.

It may also be advantageous to locate between the wedges 415 and seal 426 a backing ring that abuts the end extremity of the wedges 415 and the seal 16 to aid in supporting the seal 416 and to perhaps compress the seal 41 so as to urge it into sealing contact with the outer surface of the cable 410.

If the cable bolt assembly 400 is to be installed in an assembled condition, preferably the wedges 415 would be partly driven into the fitting 414 so as to apply compression force to the cable 410 to retain the fitting 414 and wedges 415 secured to the cable 410. Just prior to installation the washer 425 would be placed on the fitting 414 and the cable bolt assembly 400 inserted.

In a further preferred embodiment, it may be advantageous to infuse or impregnate the cable 410 with a resin to inhibit longitudinal movement of liquid from the cavity 421 toward the wedges 415. In that regard it should be appreciated the cable 410 has internal longitudinal extending passages or recesses that would possibly duct liquid past the seal 412.

Preferably, the fitting 414 is a "solid of revolution", so that it has a circular transverse cross-section apart from the port 422.

The above described preferred embodiment provides a number of advantages including three layers of corrosion protection over a substantial length of the cable 410, the three layers being an inner layer of grout, the sleeve 417 and an outer layer of grout.

A person skilled in the art will appreciate various other possible modifications to the cable bolt assembly, post-grouting apparatus and methods described above.

Claims

CLAIMS:

1. An apparatus for post-grouting a cable bolt having a longitudinal axis, the apparatus including:

2. The apparatus of claim 1 , wherein the port extends at least partly laterally relative to said axis.

3. The apparatus of claim 2, further including a tube fixed to the fitting and extending longitudinally away from said leading face to an end extremity, and through which the cable is to pass.

4. The apparatus of claim 3, further including a sheath mounted in the end extremity of said tube and extending longitudinally away from the tube.

5. The apparatus of any one of claims 1 to 4, wherein said tube is formed of metal and said sheath of plastics material, with the tube and sheath configured so as to provide a passage surrounding the cable via which grout is delivered through the tube and sheath.

6. The apparatus of any one of claims 1 to 5, wherein the fitting passage increases in transverse cross-section toward said trailing surface, and said apparatus includes at least one wedge located in the fitting passage adjacent said trailing face, each wedge being provided to securely fix the fitting to the cable.

7. The apparatus of any one of claims 1 to 6, wherein the fitting includes an annular cavity surrounding said passage and within which the seal is located.

8. The assembly of any one of claims 1 to 7, wherein said port is generally perpendicular to said axis.

9. A cable bolt assembly including the assembly of any one of claims 1 to 8, and a cable extending therethrough, with the seal sealingly connecting the fitting and cable. '

10. The apparatus of claim 1 or 2, wherein the cable bolt has a barrel and wedge assembly mounted on the cable, said apparatus further comprising:

1 1. The apparatus of claim 10, wherein said fitting trailing face is formed with a concave region surrounding said cable aperture for engaging a convex leading end of said barrel and wedge assembly.

2. The apparatus of claim 10 or 11 , wherein said fitting has an annular shoulder located in said cable aperture and facing said fitting trailing face, said seal being located adjacent said annular shoulder such that, in use, said seal is compressed between said annular shoulder and the barrel and wedge assembly to seal said cable aperture.

13. The apparatus of claim 10, 11 or 12, wherein said forward facing fitting peripheral surface is in the form of a convexly curved body of revolution.

14. A cable bolt assembly comprising:

c) an elongate sleeve extending along said longitudinal axis between a sleeve leading end and a sleeve trailing end, said sleeve being mounted on said cable between said barrel and wedge assembly and said cable leading end;

d) a load bearing grout delivery fitting attached to said sleeve trailing end, said fitting having:

(iii) a forward facing fitting peripheral surface; and

(iv) a grout delivery passage extending from a.grout delivery passage inlet, located on an exterior surface of said fitting, through said fitting to a grout delivery passage outlet located in a wall of said cable aperture; · e) a seal for sealing said cable aperture between said cable and said fitting, said seal being located between said grout delivery passage outlet and said fitting trailing face; and

15. The assembly of claim 14, wherein said fitting trailing face is formed with a concave region surrounding said cable aperture and said leading end of said barrel and wedge assembly is convexly curved. ·

16. The assembly of claim 14 or 15, wherein said forward facing fitting peripheral surface is in the form of a convexly curved body of revolution.

17. The assembly of claim 14, 15 or 16, wherein said^'grout delivery passage inlet is located on, or adjacent to, said fitting trailing face.

18. ^' The assembly of an one of claims 14 to 17, wherein said grout delivery passage is inclined at an acute angle to said longitudinal axis.

19. The assembly of any one of claims 16 to 18, wherein said cable bolt assembly further comprises a drive head formed at or adjacent said cable trailing end for rotatably driving said cable.

20. The assembly of any one of claims 14 o 19, wherein said drive head comprises a regular prism welded onto said cable trailing end.

21. The assembly of any one of claims 14 to 20, wherein said cable has at least one bulb formed towards said cable leading end, said bulb being formed by local radial deformation of strands of said cable.

22. The assembly of any one of claims 14 to 21, wherein said cable bolt assembly is provided with a resin mixing formation toward said cable leading end.

23. The assembly of claim 22, wherein said resin mixing formation comprises a wire attached to said cable toward said cable leading end and spirally extending along said cable.

24. A method of installing the cable bolt assembly defined above, said method comprising:

drilling a bore hole in a rock face of a strata to be secured;

thrusting said cable further into said bore hole and rotating said cable so as to rupture said frangible casing and mix said resin; allowing said resin to cure;