WO2014179828A1

WO2014179828A1 - Apparatus and methods for stabilising rock

Info

Publication number: WO2014179828A1
Application number: PCT/AU2014/000496
Authority: WO
Inventors: Nic Stoel
Original assignee: Mining Consumables Pty Ltd
Priority date: 2013-05-07
Filing date: 2014-05-05
Publication date: 2014-11-13
Also published as: CL2015003268A1; AU2014262370A1; CA2911526A1; ZA201508841B

Abstract

The present invention provides an apparatus for stabilising a rock in a mine environment, the apparatus comprising a first component adapted to engage a first rock region, a second component adapted to engage a second rock region, and a yielding component, wherein in use the apparatus is inserted into a shaft in the rock, the shaft extending through a first rock region and a second rock region, the first component engages with the first rock region, the second component engages with the second rock region, the yielding component allowing movement of the first rock region with respect to the second rock region such that the apparatus is not disengaged from the rock.

Description

APPARATUS AND METHODS FOR STABILISING ROCK

FIELD OF THE INVENTION The present invention is directed to the field of rock stabilization, particularly as applied to mining activities. More specifically, the invention is directed to rock bolts that are capable of absorbing movement in rock strata.

BACKGROUND TO THE INVENTION

In mining and other activities requiring the excavation of rock, the problem of stabilising a rock face often presents. The act of excavating leads to disruption of the rock face, leading for the potential of dislodgement of rock from mine walls, ceilings and shafts. Rock bolts are well known contrivances, having been used for many years to stabilize excavations such as tunnels and cuts. When properly installed, the rock bolt transfers load from an unstable rock face, to a more stable adjacent rock mass.

The "Split Set" has been the industry standard rock bolt for many years. A friction bolt is inserted into a hole in the back and shoulders of the mine directly behind the cutting face. Despite being well used and cost effective, the Split Set has a number of problems.

A problem presents in situations where mine strata are dynamic. The movement in rock can be due to the excavation itself or to seismic activity. Many rock bolts of the prior art have no give, and will become dislodged or fracture when rock strata shift. Accordingly, the rock face becomes unstable, and may collapse.

Underground mining is progressing to greater depths in many countries in the world. Mining at depths of around 3000 m is already common, with depths of 5000 m being contemplated. Even at shallower depths than these, damaging seismicity frequently occurs. In some cases this may be due to the fact that high horizontal stresses occur. Such conditions are well known in Western Australia, as well as other locations globally.

Seismicity can cause rockbursts which result in dynamic loading of rock support elements. Rockbursts manifest as the violent ejection of rock from any of the surfaces of tunnels, and often in very localized areas. It has been observed that about a metre thickness of rock may be ejected, and that ejection velocities can be up to about 10 m/s.

Rockfalls are also typically seen in underground mining. These events have lead to fatalities, and also result in financial loss to mining companies. After a rockfall, production mining is ceased and a safety audit is carried out. It can take many weeks for a mine return to full production after clearing debris, securing the strata and conducting safety inspections.

Another problem is that some types of rock bolt take a significant length of time to set in place, meaning that production time in a mine is lost. For example, where rock bolts are used to stabilise the roof of a mine bore hole it is not possible for workers to work underneath immediately.

Another problem is that some rock bolts require grouting before any significant level of rock stabilization is achieved. As mentioned earlier the grouting process adds to the installation time, but an added problem is the grouting step can sometimes be forgotten completely.

A further problem is that some rock bolts require three or more teams of workers to install the bolt: at least a first team to drill the borehole, a second team to insert the bolt, and a third team to grout the bolt.

Yet a further problem is that a standard type of rock bolt having the ability to deal with rock movement is not available. On site, some modifications to rock bolts are made in order to cope with rock movement, however such modifications are ad hoc, and must always be overseen by an appropriately qualified engineer on a case-by-case basis.

It is generally desired by geotechnical engineers, shift supervisors, mine managers, and contractors for a one pass scheme to be available for use in deep mines, high stress environments and other complex situations.

It is an aspect of the present invention to overcome or ameliorate a problem with the prior art, or to provide an alternative to prior art rock bolts.

The discussion of documents, acts, materials, devices, articles and the like is included in this specification solely for the purpose of providing a context for the present invention. It is not suggested or represented that any or all of these matters formed part of the prior art base or were common general knowledge in the field relevant to the present invention as it existed before the priority date of each claim of this application.

SUMMARY OF THE INVENTION

Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment, but may. Furthermore, the particular features, structures or characteristics may be combined in any suitable manner, as would be apparent to one of ordinary skill in the art from this disclosure, in one or more embodiments.

Similarly it should be appreciated that the description of exemplary embodiments of the invention, various features of the invention are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of one or more of the various inventive aspects. This method of disclosure, however, is not to be interpreted as reflecting an intention that the claimed invention requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects lie in less than all features of a single foregoing disclosed embodiment. Thus, the claims following the Detailed Description are hereby expressly incorporated into this Detailed Description, with each claim standing on its own as a separate embodiment of this invention.

Furthermore, while some embodiments described herein include some but not other features included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the invention, and from different embodiments, as would be understood by those in the art.

For example, in the claims appended to this description, any of the claimed embodiments can be used in any combination. In the description provided herein, numerous specific details are set forth. However, it iws understood that embodiments of the invention may be practiced without these specific details. In other instances, well-known methods, structures and techniques have not been shown in detail in order not to obscure an understanding of this description.

In the claims appended to this description and the description herein, any one of the terms "comprising", "comprised of" or "which comprises" is an open term that means including at least the elements/features that follow, but not excluding others. Thus, the term comprising, when used in the claims, should not be interpreted as being limitative to the means or elements or steps listed thereafter. For example, the scope of the expression a method comprising step A and step B should not be limited to methods consisting only of methods A and B. Any one of the terms "including" or "which includes" or "that includes" as used herein is also an open term that also means including at least the elements/features that follow the term, but not excluding others. Thus, "including" is synonymous with and means "comprising". In a first aspect, the present invention provides an apparatus for stabilising a rock, the apparatus comprising: a first component adapted to engage a first rock region, a second component adapted to engage a second rock region, and a yielding component, wherein in use the apparatus is inserted into a shaft in the rock, the shaft extending through a first rock region and a second rock region, the first component engages with the first rock region, the second component engages with the second rock region, the yielding component allowing movement of the first rock region with respect to the second rock region such that the apparatus is not disengaged from the rock.

Applicant proposes for the first time a rock stabilising apparatus that is capable of providing instantaneous stabilisation, but also stabilisation under conditions of rock movement. This arrangement is a significant advance in the art because a miner can start work about a newly stabilised rock immediately, and safely, even before the yielding portion of the apparatus has managed to cure properly. The increased productivity of mining workers and the speed with which the mining process proceeds is of clear economic advantage and safety benefit of a true one pass static and dynamic scheme.

Furthermore, it is advantageous in underground mining that a drilling and bolting jumbo can quickly and safely support the ground directly behind the face so the next round of production drilling and blasting can continue. Bolting is not a "value adding" exercise in mining so reducing the time devoted to the activity is clearly beneficial. By way of example the time taken to install a prior art Split Set, insert a cable and grout it effectively can be broken down to three passes and explained as follows:

Installation of Split Set 1 minute

Installation of cable into the Split Set 5 minutes, 30 seconds

Grouting the bolt 2 minutes

Thus, the total time to install a Split Set, Cable and grout the combination is about 8 to 9 minutes

By comparison time taken to install a bolt of the present invention is around the same time as just installing a standard Split Set friction stabiliser {up to 60 seconds).

The time saved by using a bolt of the present invention is about 5 to 7 minutes per bolt, or a minimum of 200 hours of installation time per month (assuming use of 2,000 bolts per month).

In one embodiment, the first component is substantially tubular, and the frictional engagement is achieved partially or completely by direct contact of an outer side of the first component and the inner wall of the shaft. In an embodiment, the first component is or comprises a friction rock bolt.

As used herein, the term "friction rock bolt" is intended to mean any part of the apparatus that frictionally engages with the rock, or facilitates the frictional engagement of the apparatus with the rock. The simplest method of frictional engagement is where an outer dimension of the bolt is larger than the drilled bore hole into which it is inserted. The bolt is forced into the narrow bore hole (usually by hammering) and the bolt presses firmly against the bore hole walls. Many types of friction bolts are known in the art with many being manufactured from high strength steel tubing, typically having a slot running along the entire length. One end is tapered for easy insertion into a borehole and the other has a welded ring flange to hold the bearing plate. With the bearing plate in place, the tube is driven into a slightly smaller hole, using the same standard percussion drill that made the hole. As the tube of the rock bolt slides into place, the full length of the slot narrows, causing radial pressure to be exerted against the rock over its full contact length. Due to its split shape, the friction bolt engages with the rock of the borehole wall over its complete length after installation. Friction bolts having alternative mechanisms are also contemplated to be amenable to the present apparatus. For example, friction bolts that rely on the swelling of a compound injected inside the bolt may be useful. These bolts are placed into an oversized borehole in a compressed state, with the expansion of the compound forcing the walls of the bolt against that of the borehole.

Friction bolts may also engage with a borehole by way of an expansion shell. The shell is inserted into the borehole, and via a mechanical means is expanded outwardly to engage the borehole wall. Typically the shell is expanded by way of rotating a threaded rod which causes the outward extension of the two or more leaflets that make up the shell.

Many commercially available friction bolts will be useful as the first component, or part of the first component in the context of the present apparatuses. Alternatively, designs based on commercially available friction bolts will be useful.

The Hardi Friction Rock Stabilizer (Hardi Rock Control, Europe) and Garford Clover Friction Rock Stabilizer (Garford Cable Bolts, Australia) are types of commercially available bolt useful in the context of the invention. Accordingly, in one embodiment the friction rock stabilizer is, or comprises, substantially a Hardi friction rock stabilizer or functional part thereof; or a Garford Clover Friction Rock Stabilizer or functional part thereof.

The Hardi Stabilizer has shown some success in mines throughout Europe, with tests showing that it outperforms the industry standard by a minimum of 50% on pullout tests. The bolt has, only because of its construction, a high friction with the rock in which the bolt is installed without the need of additional bonding materials. This friction, measured in kN. pull out strength, ensures immediate ground support after installation. The friction is the result of the spring action of the special V-profile of the Hardi bolt that is pressed into in a pre drilled hole with a smaller diameter than the Hardi bolt.

The Hardi bolt is further advantageous in that installation is facilitated given that it can be driven into the borehole with the same equipment used as for drilling the hole. It provides direct ground support and very high friction due to the spring action by the four memory zones in the V-profile. Typical specifications for the Hardi Friction Stabilizer follow:

Specifications HB-39

Type of steel : St-44-3 N, werkstof nr.1.0144, conform EN 10 025

Tensile strength steel min. 420 Mpa, typical 460 - 480 Mpa

Yield strength steel >320 Mpa

Elongation bolt > 30%

Wall Thickness nominal 2,00 mm. +/- 10%

Breaking load : 130 - 140 kN

Bolt diameter : 39.3 +/- 3 mm.

Recommended hole diam 36.0 - 38.0 mm

Bolt length 0.9 - 4.0 meter

Specifications HB-46

Type of steel : St-44-3 N, werkstof nr.1.0144,

conform EN 10 025

Tensile strength steel : min. 420 Mpa, typical 460 - 480 Mpa

Yield strength steel >320 Mpa

Elongation bolt > 30%

Wall Thickness nominal 2, 15 mm. +/- 10%

Breaking load : 160 - 170 kN

Bolt diameter : 46.5 +/- 3 mm.

Recommended hole diam 43.0 - 46.0 mm

Bolt length 0.9 - 6.0 meter

In one embodiment of the apparatus, the second component is adapted to frictionally engage the second rock region. The frictional engagement may be achieved partially or completely by direct contact between the second component and the inner wall of the shaft.

In one embodiment the second component comprises an expansion means such that the frictional engagement is achieved partially or completely by direct contact between the expansion means and the inner wall of the shaft. As mentioned supra, a number of expansion means are known in the art. In one embodiment, the frictional engagement is achieved partially or completely by contact between the second component and a bonding material, and contact between the bonding material and the inner wall of the shaft. As used herein, the term "bonding material" is intended to include any grout (cement or resin based), glue or similar substance. Cement based grouts are generally pumped into a borehole containing an apparatus of the present invention, while resin based grouts take the form of a two-part cartridge which is inserted into a drilled borehole before a bolt is installed. This method of resin grout is activated by "spinning" (rotating) the bolt/tendon into the pre-inserted cartridge as the bolt enters the borehole enabling the two part catalyst-mastic to mix and become active.

In one embodiment the expansion means is a mechanical expansion shell, optionally of the type disclosed supra. The apparatus of the present invention comprises a yielding component. As used herein the term "yielding component" is intended to include any dedicated or non-dedicated part, region, area, or mechanism of the apparatus that permits movement of the apparatus without breakage, significant deformation, or dislodgment of the apparatus from the borehole. The yielding component may be operably linked to the first component or the second component or both first and second components. In some embodiments the yielding component is attached to, or incorporated into the first and/or second components. The yielding component may in some embodiments also be the first and/or second components.

In one embodiment, the yielding component is adapted to allow movement under seismic conditions that can be encountered at depths of greater than 1000, 2000, 3000, 4000 or 5000 meters.

In one aspect, the yielding component is, or comprises, substantially a cable bolt. These bolts are usually composed of multiple-strand cable and are typically longer than friction bolts, and may be meters in length. The strands of the cable may be twisted open to form "bird cages" which act to mix and become interwoven in bonding materials such as grouts and resins. Some cable bolts include anchorage by way of an expansion shell, as described supra. In a preferred embodiment, the yielding component is or comprises or is the same or is similar to that described in international patent application PCT/AU2003/001667 (to GARFORD PTY LTD; published as WO/2004/055327, the contents of which is herein incorporated by reference). The mechanism of the Garford dynamic cable bolt may be used as a yielding component in the context of the present apparatus. Accordingly, in a particularly preferred embodiment the yielding component is, or comprises, substantially a Garford dynamic cable bolt, or functional portion thereof. The Garford bolt incorporates a specially designed mechanical Dynamic device which is attached to the cable at a specified point depending on the yield requirement of the bolt. The Dynamic device is anchored in the borehole using cement or resin grout. A polyethylene debonding sheath along the bolt length prevents bonding of the steel element with the cement or resin grout, enabling the bolt to be pulled through the Dynamic Device repeatedly.

The Garford dynamic cable bolt may have one, more or all of the following properties:

Mimimum Typical

15.2mm Seven Wire Compact Strand

Yield Force (kn) 212 285

Tensile Strenth (kn) 300 310

Mass Per Metre (kg) 1.176

Yielding Sleeve is Nitrocarburised.

In addition or alternative to the mechanical properties cited supra, the Garford solid bolt may have one, more or all of the following features:

Static Yield Force Capacity 150kn (min) to 180kn (max).

Dynamic Yield Force Capacity 80kn to 120kn.

Various yield loads can be achieved by modifying the yielding mechanism.

Ultimate Displacement Capacity 300mm (standard) - Larger capacity may be specified.

Ultimate force Capacity 250kn (25 tonne) at displacement capacity.

Energy absorption Capacity at 300mm displacement 30kj - larger capacity may be specified.

Dome Plate 150 x 150 x 8mm Dome Plate.

Radius Barrel and 3 part Wedge.

Standard equipment is used to for strand tensioning and barrel and wedge installation.

The mechanism of the Garford solid bolt may also be used as a yielding component in the context of the present apparatus. Accordingly, in a particularly preferred embodiment the yielding component is, or comprises, substantially a Garford solid bolt, or functional portion thereof. This bolt may be characterised as a yielding rock bolt arranged to be inserted into a hole in a rock surface, characterised by comprising a shaft formed of a solid metal bar, the shaft having a first end and a second end, the shaft having a relatively, wide portion adjacent the first end thereof and a relatively narrow portion adjacent the wide portion, an anchor member having a longitudinal bore mounted about the shaft at the relatively narrow portion and adjacent the wide portion, the longitudinal bore having at least a portion of lesser dimension than the relatively wide portion.

The energy absorption ability of the dynamic solid bolt is achieved by attaching a treated dynamic device to the bolt. When the seismic event occurs the solid bolt is able to be pulled through the dynamic device hence enabling the bolt to absorb the energy and remain intact. The polyethylene sleeve acts as a debonding agent that allows the solid bolt to slip through the dynamic device. The dynamic device is mechanical therefore enabling repeatability in regard to the energy absorption process.

The Garford solid bolt may have one, more or all of the following mechanical properties:

Minimum Typical

Core Diameter - Bar (mm) 21 .45 21 .7

Cross Sectional Area - Bar (mm2) 361 370

Yield Strength (MPa) 550 580

Yeild Force (kN) 199 215

Tensile Strength (MPa) 850 915

Tensile Force (kN) 307 339

Elongation (%) 12 16

Mass per metre - Bar (kg/m) 3.0 -

In addition or alternative to the mechanical properties cited supra, the Garford solid bolt may have one, more or all of the following dynamic properties:

Static Force Capacity 140kN

Dynamic Force Capacity 100kN

Displacement Capacity up to 500mm

Another type of yielding component that is contemplated to be useful is the sliding mechanism described in United States Patent No 7,955,034 (to MEIDL) which has a sliding control element having a sliding body cage having at least one recess for receiving a sliding body that is in contact with a lateral surface of an anchor bolt rod, wherein each recess for receiving the sliding body is disposed in the sliding body cage tangentially relative to the lateral surface of the anchor bolt rod, a lateral enveloping surface of each recess projects by a predefined dimension into a free cross section of the through-opening, and each sliding body fills the transverse cross section of the recess associated with it. As a further example, the yielding component may be the same or similar to the yielding tendon described in United States Patent No. 6,390,735 (to GAUDREAU et al). Other yielding designs are based on frictional pulling resistance mechanisms. For example, tendon threads may be designed to yield under stress, allowing a nut or clamp to move with respect to the tendon. Other deformable structures may be provided. See for example, United States Patent Nos. 3,967,455; 5,791 ,823; and 5,882,148.

Another type of yielding component is found in the COMRO Cone Bolt in 1992, a groutable tendon equipped with a cone anchor. For the Cone Bolt, energy dissipation is achieved when a wedge located downhole at the grouted end of the tendon plows through the filling material confined in the borehole, until the force on the face is no greater than the residual strength of the tendon-grout-rock hole system. The Cone Bolt can sustain slow or rapid convergence of tunnel walls. It will be appreciated that the apparatus may be point anchored, or non-point anchored. The skilled person is enabled to select an appropriate apparatus for a given application.

In one embodiment, the apparatus comprises grouting means. As used herein, the term "grouting means" is intended to include any physical or functional feature of the apparatus that allows or facilitates the ingress of a bonding material into and/or about the apparatus. The grouting means may comprise one of more of a grouting collar, a grouting channel, and a grouting breather tube.

Grouting methods may include the use of a pumpable cement grout or pumpable resin, resin or cement cartridges by which activation of the grout may use spinning of the bolt being installed or other methods. In one embodiment, the apparatus comprises tensioning means. It may be necessary to pretension point anchored bolts in order for the bolt to take up static loading and, in the case of yielding cable bolts, to engage the dynamic component which may be put under load to improve function. Typically, cable bolts with dynamic capabilities are tensioned but dynamic solid bar bolts generally do not require tensioning for the dynamic component to function adequately (i.e. once rock joint separation or seismic rock movement has occurred) due to the fact that a corrosion attack can inhibit the ability of the yielding device if there is slack in the system. The tensioning means may comprise one or more of a tensioning collar, a threaded bolt, and a tensioning anchor means. In some embodiments of the apparatus the grouting collar also functions as the tensioning collar, and/or the tensioning anchor means also functions as the expansion means. In the preferred embodiment, the one-pass scheme does not require tensioning post- installation as the bolt will have been pre-tensioned during the manufacturing process.

Preferably the apparatus is of a substantially unitary construction. In this way, the apparatus can be easily inserted (and optionally grouted and/or tensioned) by a single team of workers, and in some embodiments require only one pass to install. This saves manpower, and importantly time. A unitary apparatus also provides for reproducibility in performance, as is required in many mining applications.

By way of construction, the yielding component (e.g. bar or cable) of the bolt may be inserted inside the friction rock stabilizer so that the bar or cable runs from the collar end of the bolt, along the entire length of the friction stabilizer component and continues past the distal end of the friction bolt for a length sufficient to provide anchorage into an adjacent section of more stable rock (i.e. where there is less likely to be significant joint separation). The yielding component may be positioned at the distal end of the stranded cable, or indeed positioned elsewhere on the cable or bar.

Once the cable or bar has been installed inside the friction stabilizer component, the distal end of the friction bolt may be squeezed or crimped in order to join the friction component and yielding component. A small diameter tube may then be attached to the distal end of the bolt, positioned in the recessed or folded "V" portion of the friction stabilizer bolt for a desired length, running up past the end of the friction bolt and then attached to the yielding cable or yielding bar by a method such as tack welding, or by the use of ties. The small diameter tube acts as an air release mechanism during the grouting process, which essentially take airs from the top of the borehole and enables it to escape past the incoming grout and be expelled down through the exterior fold on the friction stabilizer tube and out of the borehole.

In a further aspect the present invention provides a method for stabilising a rock, the method comprising the step of inserting into a borehole pre-d rilled into the rock an apparatus as described herein. Installation may be achieved using a drilling and bolting jumbo with standard attachments, preferably with no further equipment being required. To the best of the Applicant's knowledge, a grouted friction bolt with dynamic capabilities has not been installed in a single pass prior to the filing date of the present specification. Prior art methods require two or more discrete processes, with each discrete process often being performed by a separate worker, or separate teams of workers. In the present method, the grouting process may be achieved relatively rapidly by a grouting coupling being pressed or clamped over the grouting/collar ring and then ably grouting at pressure during another pass of workers. It is contemplated that a standard jumbo with the correct driving dolly will be able to install the bolt successfully including the grouting step which may occur in the same pass as insertion of the bolt. In one embodiment the method comprises the step of tensioning the apparatus.

In another embodiment the method comprises the step of introducing a grouting material within or about the first component and/or the second component and/or yielding component. In a further embodiment the method comprises drilling a shaft capable of accepting an apparatus as described herein.

In another embodiment of the method, the method is devoid of the step of adding a yielding component to the first component and/or second component

In a preferred embodiment, the apparatus is installed as a non-point anchored scheme but transfers to point anchored scheme as dynamic movement occurs.

PREFERRED EMBODIMENT OF THE INVENTION

The present invention will now be more fully described by the following non-limiting examples, and in which:

Fig 1 is a cut-away lateral view of a non-point anchored rock bolt.

Fig2. is a lateral view of a point anchored rock bolt which is capable of being tensioned and grouted.

Fig 3 is a cross-sectional view of the point anchored rock bolt of Fig 2, showing detail of the tensioning/grouting collar.

Fig. 4 is a perspective view of the grouting/tensioning component of the rock bolt of Fig. 2. Fig. 5 is a cut-away view of the rock bolt of Fig. 2, showing detail of the grouting and tensioning means. Turning first to Fig 1 there is shown an apparatus according to the present invention having a first friction bolt component 2 having a V-profile resilient means 4, a breather tube 6, a flange 7 and a grouting collar 8. A stranded cable 10 runs through the lumen of the friction bolt component 2, and is attached (not shown) to a region about the grouting collar 8. The distal end of stranded cable 10 is fitted with a yielding component 12 of the type used in the Garford cable bolt.

In use, the apparatus is inserted in a borehole drilled into a rock face. The apparatus is inserted upper end (with reference to the figure) first, and driven into the borehole until the flange 7 abuts the rock face. At this point, the friction bolt component 2 is firmly engaged with the wall of the borehole thereby supplying a certain level of stabilisation. The resilient means 4 provides a higher level of frictional engagement. This form of the invention is non- point anchored.

Subsequently, the apparatus may be grouted by introducing an appropriate material via the grouting collar 8 into the grouting channel 4. The grout displaces air via the breather tube 6, while extending into and about the apparatus. Figs 2, 3, 4 and 5 show an apparatus adapted to be anchored to a point in the rock to be stabilized. This apparatus invention having a first friction bolt component 20 having a V- profile resilient means 22, a breather tube 24, and a tensioning/grouting collar 26. A threaded solid bolt 28 runs through the lumen of the friction bolt component 20, and is attached (not shown) to a region about the grouting collar 26. The distal end of the threaded solid bolt 28 is fitted with a yielding component 30 of the type utilized in the Garford cable bolt. The debonded portion of the bolt 28 is shown at 32. The distal end of the bolt 28 is fitted with a mechanical expansion shell 34 used to anchor the distal end of the apparatus.

In use, the apparatus is driven into a borehole until the tensioning/grouting collar 26 abuts the rock face. At this point, the tensioning/grouting collar 26 may be rotated such that the threaded bolt 28 is urged toward the rock face, and drawing the mechanical expansion shell 34 toward the rock face also. This results in expansion of the expansion shell 34 such that it frictionally engages with the borehole wall, thereby acting as a point anchor. Once the required amount of tension is applied, the apparatus may be grouted via the grouting collar 26, as described for the apparatus of Fig 1 .

Figs 3 and 5 show greater detail of the tensioning means. It will be noted that the tensioning means has a barrel 36 which is capable of rotating by rotating the nut 37 within the friction bolt component 20. The barrel 36 has a threaded sleeve 38 which rotates in concert with barrel, thereby acting to draw the threaded bolt 28 downward (by reference to the figure). The apertures 40 allow passage of grouting material through the barrel 36 and into the remainder of the apparatus, these being more clearly shown in Fig 4. It should be appreciated that in the above description of exemplary embodiments of the invention, various features of the invention are sometimes grouped together in a single embodiment, figure, or description thereof, for the purpose of streamlining the disclosure and aiding in the understanding of one or more of the various inventive aspects. This method of disclosure, however, is not to be interpreted as reflecting an intention that the claimed invention requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects lie in less than all features of a single foregoing disclosed embodiment. Thus, the claims following the Detailed Description are hereby expressly incorporated into this Detailed Description, with each claim standing on its own as a separate embodiment of this invention.

Furthermore, while some embodiments described herein include some but not other features included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the invention, and form different embodiments, as would be understood by those skilled in the art. For example, in the following claims, any of the claimed embodiments can be used in any combination.

In the description provided herein, numerous specific details are set forth. However, it is understood that embodiments of the invention may be practiced without these specific details. In other instances, well-known methods, structures and techniques have not been shown in detail in order not to obscure an understanding of this description.

Thus, while there has been described what are believed to be the preferred embodiments of the invention, those skilled in the art will recognize that other and further modifications may be made thereto without departing from the spirit of the invention, and it is intended to claim all such changes and modifications as falling within the scope of the invention. For example, components and functionality may be added or deleted from diagrams and operations may be interchanged among functional blocks. Steps may be added or deleted to methods described within the scope of the present invention.

Claims

CLAIMS:

1. An apparatus for stabilising a rock, the apparatus comprising

a first component adapted to engage a first rock region,

a second component adapted to engage a second rock region, and

a yielding component,

wherein in use the apparatus is inserted into a shaft in the rock, the shaft extending through a first rock region and a second rock region, the first component engages with the first rock region, the second component engages with the second rock region, the yielding component allowing movement of the first rock region with respect to the second rock region such that the apparatus is not disengaged from the rock.

2. An apparatus according to claim 1 wherein the first component is adapted to frictionally engage the first rock region.

3. An apparatus according to claim 2 wherein the first component is substantially tubular, and the frictional engagement is achieved partially or completely by direct contact of an outer side of the first component and the inner wall of the shaft.

4. An apparatus according to claim 2 wherein the first component is or comprises a friction rock bolt.

5. An apparatus according to claim 3 wherein the friction rock stabilizer is, or comprises, substantially a Hardi friction rock stabilizer or functional part thereof; or a Garford friction rock stabilizer, or functional part thereof.

6. An apparatus according to any one of claims 1 to 4 wherein the second component is adapted to frictionally engage the second rock region.

7. An apparatus according to claim 6 wherein the frictional engagement is achieved partially or completely by direct contact between the second component and the inner wall of the shaft.

8. An apparatus according to claim 7 wherein the second component comprises an expansion means such that the frictional engagement is achieved partially or completely by direct contact between the expansion means and the inner wall of the shaft.

9. An apparatus according to claim 6 wherein the frictional engagement is achieved partially or completely by contact between the second component and a bonding material, and contact between the bonding material and the inner wall of the shaft.

10. An apparatus according to claim 8 wherein the expansion means is a mechanical expansion shell.

1 1 . An apparatus according to any one of claims 1 to 10 wherein the yielding component is, or comprises, substantially a Garford cable bolt or functional part thereof.

12. An apparatus according to any one of claim 1 to 1 1 comprising grouting means.

13. An apparatus according to claim 12 wherein the grouting means comprises one of more of a grouting collar, a grouting channel, and a grouting breather tube.

14. An apparatus according to any one of claims 1 to 13 comprising tensioning means.

15. An apparatus according to claim 14 wherein the tensioning means comprises one or more of a tensioning collar, a threaded bolt, and a tensioning anchor means.

16. An apparatus according to any one of claims 13 to 15 wherein grouting collar also functions as the tensioning collar.

17. An apparatus according to claim 15 wherein the tensioning anchor means also functions as the expansion means.

18. An apparatus according to any one of claims 1 to 17 wherein the apparatus is a substantially unitary construction.

19. A method for stabilising a rock, the method comprising the step of inserting into a borehole pre-d lled into the rock an apparatus according to any one of claims 1 to 18.

20. A method according to claim 19 comprising tensioning the apparatus.

21 . A method according to claim 20 or claim 21 comprising introducing a grouting material within or about the first component and/or the second component.

22. A method according to any one of claims 19 to 21 comprising drilling a shaft capable of accepting an apparatus according to any one claims 1 to 18

23. A method according to any one of claims 19 to 22 devoid of the step of adding a yieldable component to the first component.

24. An apparatus according to any one of claims 1 to 18 substantially as hereinbefore described by reference to the drawings.