WO2003014517A1

WO2003014517A1 - A grouted friction stabiliser

Info

Publication number: WO2003014517A1
Application number: PCT/AU2002/001046
Authority: WO
Inventors: Gary Robert Davison
Original assignee: Bfp Technologies Pty Ltd.
Priority date: 2001-08-07
Filing date: 2002-08-07
Publication date: 2003-02-20
Also published as: AUPR686801A0; CA2690301A1; CA2456583C; CA2690916A1; CA2690301C; CA2456583A1; AU2002319006B2; CA2690916C

Abstract

In one aspect, the present invention provides a stabiliser for stabilising earth, rock or other structures, the stabiliser having a hollow elongate body portion including an opening extending substantially the entire length of the body portion and a closure member aligned to substantially cover the opening of the body portion, the closure member being configured to extend substantially parallel to an inner wall of the body portion in the vicinity of the opening. The present invention also provides a stabiliser assembly including: a stabiliser for stabilising earth, rock or other structures, the stabiliser having an elongate body portion including an opening extending substantially the entire length of the body portion; a closure member aligned to substantially cover the opening of the body portion; and a cartridge containing filler material in a bag of permeable material, the bag being shaped to substantially conform to the internal dimensions of the stabiliser body; wherein the closure member substantially covering the opening of the body portion significantly reduces the likelihood of a cartridge becoming ensnared upon the internal wall of a hole during insertion of the stabiliser assembly into a hole.

Description

A GROUTED FRICTION STABILISER

FIELD OF THE INVENTION

The present invention relates generally to devices used to anchor, secure or stabilise earthen formations, such as the roof or side walls of an underground mine or tunnel. Devices of this type are usually referred to by many names including rock stabiliser, rock-bolt, roof-bolt, friction stabiliser or split-set bolt.

The present invention relates particularly to a stabiliser structure that reduces known difficulties associated with such devices. Further, the present invention provides a cartridge and method of installation of stabilisers that reduces known difficulties associated with inserting filling material into stabilisers and installation of such filled devices.

BACKGROUND OF THE INVENTION Stabilisers generally comprise an elongate tube of a substantially circular cross-section with a channel or groove extending longitudinally along the entire length of the tube. Stabilisers are usually installed into a hole bored into an earthen formation requiring support with the hole being of a lesser diameter as compared with the outer diameter of the stabiliser body, During installation of a stabiliser into a hole, the tube is subject to radial compressive forces as a result of the interference fit between the tube and the surrounding rock or earthen formation and the channel or groove i allows the diameter of the tube to reduce to conform the diameter of the tube with that of the hole. Using this approach ensures that there is at least some frictional engagement between the stabiliser body and the earthen formation. In practice, stabilisers are usually supplied in a range of diameters, each diameter having a recommended load carrying capacity.

The known installation procedure includes determining the diameter of the tube associated with a recommended load carrying capacity, drilling a hole in the earthen formation, and forcing the tube into the hole using some form of impact tool. In the instance of underground mines, stabilisers are typically about 2.4 meters long, and have a diameter of approximately 45mm although other diameters are also available. It is not always realised that the actual diameter of the hole drilled into an earthen formation usually varies along the length of the hole. Figure 1 graphically illustrates this variance. The hole drilled has a nominal diameter of 45mm. It can be seen that the diameter of the hole varies from approximately 44 to 46 mm, and where the earthen formation is not stable (not shown), the diameter may vary markedly due to rocks dislodging from the side of the drilled hole. Assuming the hole is symmetrical (for the purposes of discussion), if a 45mm stabiliser of the prior art is installed into such a hole (the nominal diameter of which is symbolised by the dotted line 2) the stabiliser will be squeezed by the earthen wall of the hole at those parts where the diameter is less than 45 mm, such as point 3. This will give relatively good frictional engagement between the earthen wall of the hole and the stabiliser, and thus enable the stabiliser to be loaded. However, the stabiliser will have less frictional contact with the hole wall at points where the diameter is larger than 45 mm, such as point 4. At these points there is less loading ability provided by the stabiliser.

In the prior art, although a stabiliser having a diameter of 45 mm has the ability to be loaded up to 4 tonnes per meter of embedment, this can be severely reduced where the bored hole does not enhance frictional engagement between the stabiliser and the earthen formation over the full length of the stabiliser as embedded.

When a hollow stabiliser is inserted into earthen material it tends to deform and match the diameter of the bored hole in the earthen material. As the stabiliser is installed, narrow portions of the hole will cause the channel or groove to close at those portions. However, once a narrow portion of the hole is passed, the channel or groove will tend to open again as the stabiliser body expands to some extent. In this respect, as the diameter of the hole varies along its length, to some extent the diameter of the stabiliser body will conform to the variations in the hole diameter. It is known that by providing a grout internally to the stabiliser, after the stabiliser is embedded into the hole, the support capacity of the stabiliser is increased to approximately 12-16 tonnes per meter of embedment. The grout, once set, substantially reduces any subsequent radial deformation of the stabiliser which may occur as a result of the stabiliser being subject to increased forces by movement of surrounding material. Further, any load acting to dislodge or force the stabiliser out of the hole will be resisted as the load attempts to force larger diameter portions of the stabiliser body through narrower portions of the hole in which it is installed. Generally, grouting a friction stabiliser substantially increases the load carrying capacity of that stabiliser.

However, there are problems associated with the grouting of friction stabilisers. It can be difficult to pump grout into a stabiliser such that the grout travels the entire length of the stabiliser. Often air is trapped inside the stabiliser which then inhibits the flow of grout. Also, stabilisers are often used to stabilise an underground mine roof. In such situations, the stabiliser is inserted into the earthen roof of the mine vertically. If a grout with relatively low viscosity is pumped into the stabiliser, it will tend to fall out of the stabiliser under the action of gravity prior to setting.

Further, when pumping grout into stabilisers, the pumping process usually requires equipment that is relatively large and by necessity, the pumping procedure is effected after the hole boring process for an area has been completed and the drilling equipment removed from that area of the mine.

The two-step approach to installing and grouting friction stabilisers causes delays. There is also a requirement for separate drilling and grouting crews. The two-step process is considered costly, cumbersome and time consuming.

Some examples of prior art stabilisers are illustrated, in cross section, in Figures 2a, 2b, 2c and 2d.

US reissue patent Re 30,256 (Scott) discloses a stabiliser similar to that illustrated in Figure 2a. The stabiliser consists of a tube with a slot defined by edges 5 and 6 which are separate prior to installation. During the installation process, in those parts of a hole which are narrower than the nominal diameter of the stabiliser, the edges 5 and 6 are forced together (as shown by arrow 7). If portions of the hole are very narrow, the edges 5 and 6 will butt together and thus restrict any further radial compression of the stabiliser. This would make installation of the stabiliser very difficult or in some cases impossible. It has also been found in practice that the edges 5 and 6 and the inner and outer surface area are relatively exposed to water (from underground seepage) and over time the stabiliser will tend to rust and fail.

US patent 4,012,913 (Scott) discloses a stabiliser similar to that illustrated in Figure 2b. The stabiliser has offset edges 8 and 9 which are separated prior to installation. During the installation process, in the narrower parts of the hole, the edges 8 and 9 will be moved past each other as shown by arrow 10. However, this deformation causes further problems after installation as with further radial compression, the external surface area of the stabiliser reduces thus decreasing the area over which the surrounding material has the ability to develop a frictional force to act upon the stabiliser. Radial compression of a stabiliser of this type subsequent to installation can result in premature dislodgement of the stabiliser which is unsafe.

If this type of stabiliser is installed in a roof section of an underground mine, and sufficient load is applied to the stabiliser, say by a portion of the roof weakening and applying extra load to the stabiliser acting to dislodge the stabiliser, then just as the stabiliser exhibits compression and expansion as is it is inserted into the hole, equally and conversely, the stabiliser can expand and compress as it is forced out of a hole under the load of the mine roof section. In other words, the applied load may dislodge the stabiliser from the hole, with the stabiliser deforming in the direction of arrow 10 as the stabiliser is forced out of the hole and passes the narrower parts of the hole. As a result, it is generally considered that the effective bond strength due to friction between surrounding material and stabilisers of this type is relatively low.

A further problem with stabilisers of this type is a problem referred to as 'tangential gap'. Figure 2c illustrates this problem. Figure 2c is a representation of the part of Figure 2b "Compressed" marked "A". As previously mentioned, as the stabiliser is installed in a hole, edges 8 and 9 are moved passed each other. However, proximate the edge 8, there is always a gap 10b (referred to as the tangential gap) which is formed as a result of the stabiliser wall 9 moving inwardly of the stabiliser wall 8. The gap is formed between the stabiliser wall 9 and the hole wall 10a. This gap reduces the overall frictional engagement of the stabiliser with the earthen formation into which the stabiliser is installed as there is no frictional engagement along the portion of the stabiliser proximate the gap 10b.

US patent 5,297,900 (Witzand) discloses a stabiliser similar to that illustrated in Figure 2d. The stabiliser has edges 12 and 13 that are separated prior to installation. The stabiliser has a 'V shaped portion extending substantially along the entire length of the stabiliser. The 'V shaped portion is described as providing greater frictional resistance to movement between the bolt and the mine roof as compared with slotted stabilisers (as illustrated in Figures 2a and 2b). During the installation process, in those parts of a hole which are narrower than the nominal diameter of the stabiliser, the edges 12 and 13 are forced together (as shown by arrow 14). As occurs in the stabiliser of Figure 2a, if portions of the hole are very narrow, the edges 1 and 13 will butt together and thus prevent any further circumferential deformation of the stabiliser. This would make installation of the stabiliser very difficult or in some instances impossible. It has been also found in practice that many parts of the 'V shape remain open and exposed to the earthen hole wall and are thus relatively exposed to water (from underground seepage) and over time the stabiliser will tend to rust and fail.

The 'V shaped portion, being internal to the stabiliser, is considered to inhibit the flow of grout as it is pumped internally along the length of the stabiliser. Further, it is difficult to insert grout externally along the stabiliser proximate the 'V shaped portion which is desirable in order to reduce the likelihood of further radial compression of the stabiliser subsequent to installation. It is an object of the present invention to alleviate at least one of the problems associated with the prior art. Any discussion of documents, devices, acts or knowledge in this specification is included to explain the context of the invention. It should not be taken as an admission that any of the material formed part of the prior art base or the common general knowledge in the relevant art on or before the priority date of the claims herein.

SUMMARY OF THE INVENTION

In one aspect, the present invention provides a stabiliser for stabilising earth, rock or other structures, the stabiliser having a hollow elongate body portion including an opening extending substantially the entire length of the body portion and a closure member aligned to substantially cover the opening of the body portion, the closure member being configured to extend substantially parallel to an inner wall of the body portion in the vicinity of the opening.

The closure member may be separate from the stabiliser body portion or may be affixed to the body portion. In any event, the opening in the body portion should allow compression and deformation of the stabiliser body portion when subject to a sufficient compressive force such as will generally occur during installation of the stabiliser into a bored hole in an earth or rock structure.

In a preferred embodiment, the stabiliser body portion is a substantially cylindrical tube with a slot extending along the entire length of the tube, the slot being parallel to the longitudinal axis of the tube. In another embodiment, the closure member is a sleeve segment of substantially the same length of the stabiliser body and affixed along one of the sleeves longitudinal edges to the inner wall of the stabiliser body such that the sleeve substantially covers the slot whilst allowing the slot to partially close upon application of a sufficient radial compressive force to the stabiliser body. In this embodiment, the sleeve segment is shaped to conform with the shape of the internal wall of the stabiliser body and resides within the body portion. This embodiment is particularly useful in instances where filler material is inserted into the stabiliser body before installation of the stabiliser into a bored hole.

Accordingly, in another aspect, the present invention provides a method of installing a grouted friction stabiliser having a hollow elongate body portion including an opening extending substantially the entire length of the body portion and a closure member aligned to substantially cover the opening of the body portion, the closure member being configured to extend substantially parallel to an inner wall of the body portion in the vicinity of the opening, including the following steps: a. drilling a hole in the region to be stabilised, the hole having a smaller diameter than the diameter of the stabiliser to be installed; b. inserting filler material into the hollow elongate body portion to substantially fill said body portion; and c. inserting the stabiliser into the hole. Conforming the shape of the closure member to the shape of the inner wall of the stabiliser body in the vicinity of the opening has the added advantage of the closure member acting to guide the edges of the opening toward each other when a compressive force is applied and as deformation of the stabiliser body occurs.

In essence, it has been found that the closure member provides a means by which, upon circumferential compression of the stabiliser, the surface area of the body portion in contact with the surrounding earthen material does not decrease to the same extent as compared with some prior art arrangements. It has also been found that the closure member provides a means by which filler material is retained in the stabiliser when that filler material is inserted into a stabiliser prior to installation.

In another aspect, the present invention provides a cartridge for use in a stabiliser, the cartridge containing filler material in a bag of fluid permeable material the bag being shaped to substantially conform to the internal dimensions of a stabiliser body. There is preferably some clearance between the external dimensions of the bag and the internal dimensions of stabiliser body to enable relatively easy insertion of cartridges into stabiliser bodies.

Preferably, the filler material is grout that is activated by exposure to an activating fluid such as water and immersing the bag in a reservoir of water and removal therefrom commences the setting process. In yet another aspect, the present invention provides a method of installing a grouted friction stabiliser including the following steps: a. drilling a hole in the region to be stabilised, the hole having a smaller diameter than the diameter of the stabiliser to be installed, b. placing at least one cartridge containing a filler substance internal of the stabiliser; and c. inserting the stabiliser into the hole.

Preferably, the cartridge is immersed in a reservoir of activating fluid prior to placement of the cartridge into a stabiliser of the type according to the present invention. In another embodiment, the cartridge is placed into a stabiliser according to the present invention to form a stabiliser assembly and the assembly is immersed in a reservoir of activating fluid prior to insertion of the stabiliser assembly into the hole.

It is particularly advantageous that the stabiliser assembly include a stabiliser according to the present invention as the closure member substantially reduces the likelihood of a cartridge becoming ensnared with material of the inner wall of the bored hole during installation of the stabiliser assembly.

In a particularly preferred embodiment of the invention, the closure member of the stabiliser assembly is an integral part of the cartridge. In this embodiment, the closure member is adhered to the external surface of a cartridge. Installation of the cartridge according to this embodiment into a stabiliser body effects simultaneous installation of a cartridge and a closure member.

Preferably, the closure member adhered to the external surface of the cartridge is shaped to conform to the shape of the internal wall of the stabiliser body in the vicinity of the opening. In the instance where the opening is a slot and the stabiliser is a substantially cylindrical tube, the closure member is preferably a sleeve segment which is adhered to the external surface of the cartridge. Further, the sleeve segment preferably includes a protuberance on its surface for location within the slot (ie between the edges of the slot) of the stabiliser body. The protuberance acts to retain the closure member in position covering the opening along the longitudinal surface of the stabiliser body during insertion of the stabiliser into a hole. Of course, the protuberance should not protrude beyond the external notional diameter of the stabiliser body portion otherwise the protuberance would be likely to catch upon the wall of the hole as the stabiliser is installed.

In essence, the inventive method according to the present invention provides a manner in which filler material and a stabiliser can be installed into a hole in a substantially one-step process. Preferably, the filler sets and provides resistance to subsequent radial compression of the installed stabiliser.

In a still further aspect, the present invention provides a grout delivery system adapted to be installed in a stabiliser, the delivery system including: a container adapted to contain a predetermined quantity of filler material, the container having a substantially porous portion, which when exposed to activating fluid , allows the fluid to contact a portion of the filler material contained in the container, and wherein the container has a profile which is substantially elongate relative to its cross-sectional area, the container being of a size which facilitates insertion of the container into a stabiliser.

In essence, the filler material delivery system provides a relatively easy means to install filler material into a stabiliser. By providing a means by which the filler material can be inserted into the stabiliser prior to installation of the stabiliser into the earthen formation, a number of the disadvantages of the prior art are overcome.

In a final aspect, the present invention provides a stabiliser assembly including: a stabiliser for stabilising earth, rock or other structures, the stabiliser having an elongate body portion including an opening extending substantially the entire length of the body portion; a closure member aligned to substantially cover the opening of the body portion; and a cartridge containing filler material in a bag of permeable material, the bag being shaped to substantially conform to the internal dimensions of the stabiliser body; wherein the closure member substantially covering the opening of the body portion significantly reduces the likelihood of a cartridge becoming ensnared upon the internal wall of a hole during insertion of the stabiliser assembly into a hole. In a preferred embodiment, the stabiliser assembly includes an end-ring affixed to the stabiliser body at a region toward the end that is impacted for the purpose of inserting the stabiliser into a hole. In this embodiment, the end-ring extends partially around the entire outer circumference of the stabiliser body and is affixed to the body by welding both sides of the ring in the region of abutment with the external surface of the stabiliser body. In another embodiment, a plurality of end-rings are affixed to the stabiliser body wherein each of the plurality of end-rings extend partially around the entire outer circumference of the stabiliser body and are affixed to the stabiliser body by welding both sides of each of the plurality of rings to the stabiliser body in the region of abutment of each ring with the external surface of the stabiliser body. It is particularly preferred that welded joints residing between end-rings abut each side of those end-rings.

Although end-rings need not fully extend around the entire circumference of a stabiliser body portion, they preferably at least traverse that portion of the circumference of the stabiliser body portion that includes the opening. Throughout this specification, in relation to the invention, the word 'grout' is used to mean any substance capable of acting to reduce radial compression of a stabiliser once the grout has been inserted into a stabiliser. Such substances are usually inserted into a stabiliser in a fluid form having been activated and require a period of time to enable the substance to 'set' thereby transitioning to a solid form. Further, the word 'stabiliser' is used to mean any form of earth stabiliser, rock stabiliser, tubular pin, anchoring device or a device which serves to facilitate stability of formations, such as an earthen, rock or man-made formations.

BRIEF DESCRIPTION OF THE DRAWINGS Preferred embodiments of the present invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a graph illustrating the possible variation of hole diameter along the length of a bored hole in an earthen formation;

Figures 2(a), 2(b), 2(c) and 2(d) are cross sectional illustrations of examples of prior art stabilisers; Figure 3 is a perspective view of a stabiliser according to one embodiment of the present invention;

Figures 4(a) and 4(b) are cross sectional views of stabilisers according to embodiments of the present invention;

Figures 4(c) and 4(d) are cross sectional and perspective views respectively of a further embodiment of the present invention using a sleeve, with locating lugs;

Figures 5(a), 5(b), 5(c) and 5(d) illustrate, in cross section, alternative stabilisers according to the present invention;

Figure 6 is a flowchart illustrating a method of installing a stabiliser according to the present invention;

Figure 7 is a perspective view of a cartridge;

Figures 8(a) to 8(c) are further cross sectional views of alternative embodiments of the present invention;

Figures 8(d) to 8(g) are various views of cartridge enclosures according to the present invention;

Figures 9(a) and 9(b) are a cross sectional and perspective view respectively of a particularly preferred embodiment of the present invention; and

Figures 10(a) to 10(c) illustrate various embodiments of end-ring arrangements for a stabiliser body.

DESCRIPTION OF PREFERRED EMBODIMENTS

With reference to Figure 3, one embodiment of a stabiliser according to the present invention is illustrated. The stabiliser has a generally elongate and hollow body 15, which is of a predetermined length. In underground mines, the preferred length of a stabiliser is approximately 2.4 metres. In the embodiment illustrated, the body portion 15 has a generally cylindrical shape as defined by the stabiliser wall 16. There is a 'step' 21 and a closure member in the form of an 'overlapping' portion 17, which extends along substantially the entire length of the body portion 15. The overlapping portion 17 could extend over only a small part of the length of the body portion, or extend intermittently along the length of the body portion.

Figure 4(a) illustrates in greater clarity, in cross section, the overlapping portion 17 of Figure 3. In addition, the stabiliser includes a first stop 18, and a second stop 19. It is these two stops which serve to prevent the body portion of the stabiliser according to the present invention being radially compressed too far (ie beyond the point where the stabiliser loses its effective bond strength with the earthen formation into which it is installed (not shown)).

A closure member in the form of an overlapping portion 20 is shown. One purpose of this overlapping portion 20 is to provide a means by which grout (not shown) inserted into the stabiliser is contained substantially within the stabiliser. It is preferred that the overlapping portion 20 also serves to guide the first stop 18 and second stop 19 to abut each other in the event that the stabiliser is radially compressed to the extent that the first and second stops 18 and 19 meet. The overlapping portion 20 may be fixed to the body portion 15 by, for example welding, or other suitable means. The overlapping portion 20 may alternatively be an integral part of the body portion 15. In this respect, a substantially flat piece of material, typically steel, may be formed in the shape of a substantially hollow tube. Prior to forming a tube shape, the flat piece of material may have a 'step' formed in the material such that upon forming a tube, the material on one side of the step may form the overlapping portion 20.

Alternatively, the overlapping portion 20 may be coupled to the body portion 15 via a step 21. The step 21 optionally serves as an additional abutment against which stop 19 can come to rest if the stabiliser of the present invention is significantly radially compressed. Alternatively, with reference to Figure 4(b), the closure member may be separate to the stabiliser body yet shaped to substantially conform with the shape of the stabiliser. Preferably, any separate closure member is provided with a locating means to locate the closure member with the slot or opening along the stabiliser body so that it does not move away from the opening during installation. An example of an embodiment with a separate closure member is detailed in Figures 4(c) and 4(d).

In Figure 4(c), a sleeve segment 22 having a locating protuberance 23 is positioned such that the protuberance 23 resides within the slot defined by edges 24 and 25. The sleeve segment 22 substantially reduces, and ideally prevents, grout escaping from the stabiliser 15 during installation of a stabiliser into a hole and whilst grout is setting within the stabiliser. In this regard, the sleeve may be made of a degradable material (if needed). The protuberances 23 are incorporated as necessary, to substantially prevent the sleeve segment 22 from moving during installation of the stabiliser and whilst grout is setting to prevent unset grout escaping from the stabiliser. The protuberances should not protrude beyond the notional outer diameter of the stabiliser body portion through the opening of the stabiliser. In one embodiment, the sleeve segment serves to substantially prevent the longitudinal slot of the body portion 15 being exposed.

The sleeve segment may also be made to incorporate a 'groove' which interlocks or fits with the step 21 of the stabiliser embodiment shown in Figure 4(b).

The sleeve may have many embodiments but should be constructed such that:

• The annular space between the sleeve segment and the inner surface of the stabiliser is minimised;

• The cross section area of the sleeve segment is minimised;

• The sleeve segment remains in contact with the inner surface of the hollow body portion of the stabiliser; and

• The sleeve segment is shaped to conform to the inside of the stabiliser's surface and substantially form a barrier across the slot or opening in the stabiliser body to prevent egress of grout from the inside of the stabiliser during installation of the stabiliser and during setting of the grout but not necessarily the latter .

Figures 5a to 5d illustrate cross sectional views of alternative stabilisers according to the present invention. The first stop 18, second stop 19, and closure member 20 is identified in each alternative embodiment.

Filler material may be inserted into a stabiliser body before the stabiliser is installed. Alternatively, grout may be encapsulated in a bag that is installed into a stabiliser body either before or after installation of the stabiliser into a bored hole.

CARTRIDGES

In another aspect, the present invention provides an improved cartridge that assists the installation of filler material into stabilisers. According to this aspect of the invention, grout or other filler substance, is preferably encapsulated in a porous container, such as a bag (refer Figure 7). The bag may be shaped to substantially conform to the internal dimensions of a stabiliser body, but preferably has external dimensions less than the internal dimensions of the stabiliser to enable the cartridge to be relatively easily installed into the stabiliser body. Further, where the grout contained in a bag is activated by fluid, the bag preferably allows the ingress of such fluid for the purpose of activating the grout. Where the grout is activated by water, after drilling a hole, by inserting one or more wetted bags into a stabiliser, and then installing the stabiliser into an earthen formation, the grout sets. A flowchart illustrating the steps of this method is represented in Figure 6. In another embodiment, cartridges are placed into a stabiliser body prior to immersing the stabiliser body into a bath of activating fluid. In this embodiment, stabilisers are removed from the bath of fluid and immediately placed onto the head of an impact tool for insertion into a bored hole.

In either embodiment of the method of installing stabilisers described above, the two-step process known in the prior art is replaced with a one-step process wherein fully grouted friction stabilisers are installed without the requirement for any additional equipment as compared with the equipment required to bore holes and install stabilisers. The only additional requirement to effect the improved method of installation is a supply of cartridges, a supply of activating fluid and a reservoir or bath to hold the activating fluid. None of these additional requirements involve a significant requirement for additional space and as such they are relatively easily to accommodate and do not significantly affect the operations of a drilling crew.

Of course, the improved method of installing grouted friction stabilisers has many advantages including a substantial improvement in productivity and efficiency of mine operations as a result of reducing the overall resources required to install the devices. Similarly, the provision of a method that can install fully grouted stabilisers as part of a single process avoids the set-up time and capital expenditure usually required for additional pumping equipment. Further, as the load carrying capacity of a grouted friction stabiliser is superior to that of a non-grouted stabiliser, to support any particular formation, fewer grouted stabilisers will be required as compared with non-grouted stabilisers.

It is particularly advantageous to install cartridges into a stabiliser body prior to insertion of the stabiliser into a bored hole in the earthen formation especially when the stabilisers are to be installed in the roof of a mine. However, when installing a stabiliser containing cartridges, exposure of the cartridges through the slot or opening of the stabiliser body can cause the cartridge to catch on material forming the inner wall of a bored hole and prevent the cartridge from progressing through the bored hole with the stabiliser. In some instances, where a cartridge has become ensnared with material forming the inner wall of a bored hole, the stabiliser body has continued to travel through the hole (by the action of an impact tool acting on the head of the stabiliser) whilst the cartridge has remained relatively stationary. This has caused stabilisers to be installed without cartridges extending along the full length of the stabiliser which is undesirable.

As a result, it is preferable that the closure member of a stabiliser according to the present invention, provide sufficient closure to prevent the catching or ensnarement of cartridges on the inner wall of a bored hole. Of course, in the instance of using a cartridge, the requirement for the closure member to close the slot or opening of the stabiliser body is not as stringent as compared with the instance of pumping grout into a stabiliser before it is installed.

The 'cartridges' enable a relatively easy insertion of cementious material into a stabiliser. In one embodiment, the cartridge has the following properties:

• Inclusion of an outer water permeable bag or containing device that is of sufficient strength that it will be not be easily ruptured during handling or during installation of the cartridge into the stabiliser. The bag may be made of fibrous material such as paper or dress makers "fusing", cloth or similar material. The bag is preferably permeable to enable the ingress of water to activate the cementious material within the bag. The cementious material may 'set' or harden in a relatively short period of time, such as in use within a mine in order to accelerate the progress of the mine, or it may set or harden over a longer period of time. The contents of the bag will determine the 'setting' time, as will the permeability of the bag.

• The length of bag may be typically between 300mm and 600mm. In one embodiment, the bag length is designed so that multiple bags fill the stabiliser over its total length. It is thought that a number of relatively smaller bags are easier to handle and install into a stabiliser as compared with a single bag or a few relatively large bags. The length of the bag may vary. The length suggested has been found to facilitate ease of handling in a mining application.

• In the instance of a substantially cylindrical stabiliser body, the bag diameter may be 2-3mm less than the inner stabiliser tube diameter. This facilitates ease of installation of the bag into the stabiliser prior to or shortly after installation of the stabiliser.

• In one embodiment, the bag is filled with Portland cement and a shrink resisting additive that will not allow linear shrinkage of more than 0.5%.

• In other embodiments, it may be advantageous to use a filler material that swells upon contact with water, the material, after setting, having a relatively low shrinkage under stress. • The filler material may contain one or more of a combination of the following materials:

Plaster of Paris, epoxy resin, earthen materials, bituminous materials, polyurethane foam, or other materials that exhibit desirable properties such as relatively high resistance to strain when subject to stresses.

To further assist the installation of cartridges into the body of a stabiliser, cartridges of the type depicted in Figure 7 may be enclosed within structures of the type depicted in Figures 8(d) to 8(g). In this respect, Figure 8(d) comprises a perforated tube, Figure 8(e) is a spiral structure shaped such that it may be wrapped around a cartridge, Figure 8(f) is a structure similar to a document binder comprising a curved portion to which curled prongs are attached and Figure 8(g) is a cylindrical tube with a slot along its longitudinal axis. The slot is formed at an angle to the bisection through the diameter of the tube such that one side of the cylinder will overlap the other when the cylinder is radially or circumferentially compressed beyond the stage where the slot becomes closed. Of course, Figures 8(d) to 8(g) are not an exhaustive representation of the structures that may be used for containing cartridges within a stabiliser assembly according to the present invention.

Whilst a permeable bag may be necessary to enable the ingress of an activating fluid into the bag, permeable materials do not generally provide substantial rigidity. Hence, the grout bags can be difficult to handle.

Enclosure of a cartridge within one of the structures depicted, improves the ability to handle cartridges by substantially containing the bag within a structure that may display the desirable characteristics of rigidity whilst still enabling the grout bag to be exposed to fluid when either immersed or sprayed with fluid. In some embodiments, a portion of the structure enclosing the cartridge acts as the closure member of the stabiliser. In a particularly preferred embodiment, a closure member is affixed to a cartridge and forms an integral part of the cartridge such that installation of a cartridge into a stabiliser forms a stabiliser assembly including the stabiliser body, a cartridge residing within the stabiliser body and a closure member residing internally within the stabiliser and aligned with the slot or opening of the stabiliser body. A particularly preferred embodiment of the invention is illustrated in Figures

9(a) and 9(b) which provides a cross sectional and perspective view respectively of the preferred embodiment of the stabiliser assembly.

With reference to Figure 9(a), a stabiliser assembly 30 includes a substantially cylindrical stabiliser body having a slot (defined by edges 27 and 28) extending the entire length of the stabiliser body.

Included within the stabiliser body is a cartridge 32 that has a closure member 34 affixed to the cartridge 32. The closure member 34 includes a protuberance 36 that is located in the slot (ie between the edges 27 and 28). When inserting the cartridge 32 into the stabiliser, alignment of the protuberance 36 with the slot and sliding the cartridge into the stabiliser ensures that the closure member 34 is aligned with the slot and thus closes this opening of the stabiliser until the stabiliser assembly is installed into a bored hole.

Figure 9(b) provides a perspective view of the stabiliser assembly 30. As will be noted, the closure member 34 does not necessarily extend the entire length of the stabiliser body and may be segmented along the cartridge 32. The precise dimensions of the closure member will vary depending upon the characteristics of the material employed to form that member. However, the requirement to sufficiently close the opening of a stabiliser body prior to installation such that catching or ensnarement of a cartridge is avoided remains the objective of such a member.

In the preferred embodiment of Figure 9(a) and 9(b), the closure member 34 is formed from plastic materials and is affixed to cartridges with adhesive prior to insertion into a stabiliser body. After the adhesive has cured, the cartridge is installed into a stabiliser body thus simultaneously effecting installation of a cartridge and a closure member. Of course, the closure member may be incorporated into the grout bag, be bonded to the inside of the bag or alternatively form part of the bag itself. Similarly, the closure member may be constructed in any one of a range of shapes including those depicted in Figures 8(b) and 8(c) where the vertex of the "V" shaped closure member effectively forms a protuberance for the purpose of locating the closure member with the opening of the stabiliser body.

When stabilising an earthen or rock formation, a plate is generally mounted and secured on one end of a stabiliser prior to installation and the stabiliser is installed into the hole such that the plate is forced up against the surface of the earthen or rock formation. In instances where stabilisers are installed into the roof of a mine, the plate applies a distributed upward force to the surface of the formation thereby reducing the likelihood of portions of the surface of the formation separating and dropping away from the mine roof.

With reference to Figure 10(a), a stabiliser body portion 40 is detailed with a plate 43 mounted on one end thereof. The plate is secured to the end of the stabiliser body portion 40 by an end-ring 38. The end-ring 38 does not completely encircle the circumference of the stabiliser body portion 40 but at least traverses that portion of the circumference where the slot resides. In addition to the end- ring 38 acting to secure the plate 43, by traversing the portion of the circumference that includes the slot the end-ring 38 also provides structural support to the end of the stabiliser and prevents the end of the stabiliser from splaying when struck by an impact tool during installation.

Once installed, a grouted friction stabiliser has an improved load carrying capacity as compared with non-grouted stabilisers. As a result, a greater force acting downwardly upon the stabiliser body and the plate is be required to dislodge a grouted stabiliser.

Previously, stabilisers with a lesser load carrying capacity have been known to slip through the hole to a small extent when subject to increased forces acting to dislodge the stabiliser. An increased loading on a stabiliser may be caused by various factors and is usually related to a change in the earthen or rock formation. For example, internal forces in a formation may act to force an outer slab of material to separate from the formation. In this instance, a small slippage of a stabiliser with respect to its hole can relieve the pressure acting to force the slab of material to separate.

However, with the improved load carrying capacity of a grouted friction stabiliser the propensity for the stabiliser to slip is reduced and it has been found that the end-ring affixed to the end of the stabiliser body portion is more likely to fail and separate from the stabiliser when it is subjected to increased forces acting to dislodge the stabiliser. This is of course undesirable as failure of an end-ring fails to secure the plate and hence material may fall from the formation. Accordingly, in a preferred embodiment of the invention, the end-ring 38 is affixed to the stabiliser body portion 40 by welding the end-ring 38 to the body portion on both sides of the end-ring 38. As can be seen in Figure 10(a), the end- ring 38 is affixed to the body portion 40 by two weld joints 42 and 44.

In another embodiment detailed in Figure 10(b), the end-ring is in the form of a sleeve 46 which is also affixed to the body portion 40 by two weld joints 48 and 50. In yet another embodiment detailed in Figure 10(c), the end-ring arrangement includes two sleeves 52 and 54 both of which are affixed to the body portion 40 by weld joints 56, 58 and 60. In this particular embodiment, weld joint 56 completely fills the gap between the sleeves 52 and 54. In each of the end-ring arrangements detailed in Figures 10(a), 10(b) and

10(c), the weld joints preferably extend around the entire abutment region between the ring or sleeve and the body portion.

As the present invention may be embodied in several forms without departing from the spirit of the essential characteristics of the invention, it should be understood that the above described embodiments are not to limit the present invention unless otherwise specified, but rather should be construed broadly within the spirit and scope of the invention as defined in the appended claims. Various modifications and equivalent arrangements are intended to be included within the spirit and scope of the invention and appended claims.

Claims

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

1. A stabiliser for stabilising earth, rock or other structures, the stabiliser having a hollow elongate body portion including an opening extending substantially the entire length of the body portion and a closure member aligned to substantially cover the opening of the body portion, the closure member being configured to extend substantially parallel to an inner wall of the body portion in the vicinity of the opening.

2. A stabiliser according to claim 1 , wherein the stabiliser body is a substantially cylindrical tube and the opening is a slot extending the entire length of the body.

3. A stabiliser according to claim 2 wherein the slot is substantially parallel to the longitudinal axis of the stabiliser body.

4. A stabiliser according to any one of the preceding claims wherein the closure member is a sleeve segment with one of the longitudinal edges of the sleeve segment being affixed to the internal wall of the stabiliser body and the other longitudinal edge remaining free to move relative to the stabiliser body thus allowing the opening to close upon application of a sufficient compressive force whilst retaining the sleeve segment in a position relative to the opening to substantially cover the opening.

5. A stabiliser according to any one of the preceding claims wherein the closure member is shaped to substantially conform with the shape of the inner wall of the stabiliser body in the vicinity of the opening.

6. A method of installing a grouted friction stabiliser, the method including the steps of: a. drilling a hole in the region to be stabilised, the hole having a smaller diameter than the diameter of the stabiliser to be installed, b. placing at least one cartridge containing a filler substance internal of the stabiliser; and c. inserting the stabiliser into the hole.

7. A method according to claim 6 wherein at least one cartridge is exposed to activating fluid to activate setting of the filler material prior to placement in the stabiliser.

8. A method according to claim 6 wherein the stabiliser is immersed in activating fluid subsequent to placement of a cartridge into the stabiliser and prior to insertion of stabiliser into a hole.

9. A method according to any one of claims 6, 7 or 8 wherein the stabiliser is a stabiliser according to any one of claims 1 to 5.

10. A method according to any one of claims 6 to 9 wherein the filler material is grout and the activating fluid is water.

11. A cartridge for use in a stabiliser, the cartridge containing filler material in a bag including at least a portion of fluid permeable material said bag shaped to substantially conform to the internal dimensions of a stabiliser body.

12. A cartridge according to claim 11 wherein the filler material is grout which is is activated by exposure to water and removal therefrom commences a setting process.

13. A cartridge according to either claim 11 or 12 including a closure member attached thereto.

14. A cartridge according to claim 13 wherein the closure member is a sleeve segment adhered to the external surface of the cartridge.

15. A cartridge according to claim 14 wherein the sleeve segment is shaped to conform with the shape of the internal wall of a stabiliser body in the vicinity of an opening in the wall of the stabiliser body.

16. A cartridge according to either claim 14 or 15 wherein the closure member includes a locating protuberance for aligning the closure member with an opening in the wall of a stabiliser body.

17. A cartridge according to either claim 11 or 12 wherein the cartridge is contained within a relatively rigid structure said structure including apertures to enable the ingress of activating fluid.

18. A filler delivery system adapted to install filler into a stabiliser, the delivery system including: a containing device adapted to contain a predetermined quantity of filler, which when activated, allows the filler to harden to a relatively incompressible state, and wherein the containing device has a profile which is substantially elongate relative to its cross-sectional area, the containing device being of a size which facilitates insertion of the device into a stabiliser.

19. A filler delivery system according to claim 18, wherein the filler includes a cementious material.

20. A filler delivery system according to either claim 18 or 19, the containing device having a substantially porous portion.

21. A filler delivery system according to any one of claims 18, 19 or 20 wherein the filler is activated to harden by exposure to water.

22. A stabiliser assembly including a stabiliser for stabilising earth, rock or other structures, the stabiliser having an elongate hollow body portion including an opening extending substantially the entire length of the body portion; a closure member aligned to substantially cover the opening of the body portion; and a cartridge containing filler material in a bag including at least a portion of fluid permeable material, the bag being shaped to substantially conform to the internal dimensions of the hollow interior of the stabiliser body; wherein the closure member substantially covering the opening of the body portion significantly reduces the likelihood of a cartridge becoming ensnared upon the wall of a hole during insertion of the stabiliser assembly into said hole.

23. A stabiliser assembly according to claim 22 including an end-ring affixed to the stabiliser body at a region toward the end that is impacted for the purpose of inserting the stabiliser into a hole.

24. A stabiliser assembly according to claim 23 wherein said end-ring extends partially around the entire outer circumference of the stabiliser body and is affixed to the body by welding both sides of the ring in the region of abutment with the external surface of the stabiliser body.

25. A stabiliser assembly according to claim 22 wherein a plurality of end-rings are affixed to the stabiliser body at a region toward the end that is impacted to install the stabiliser into a hole.

26. A stabiliser assembly according to claim 25 wherein each of the plurality of end-rings extend partially around the entire outer circumference of the stabiliser body and are affixed to the stabiliser body by welding both sides of each of the plurality of rings to the stabiliser body in the region of abutment of each ring with the external surface of the stabiliser body.

27. A stabiliser assembly according to claim 26 wherein welded joints residing between end-rings abut each side of those end-rings.

28. A stabiliser assembly according to any one of claims 23 to 27 wherein the end-ring at least traverses that portion of the circumference of the stabiliser body portion that includes the opening.

29. A method of installing a grouted friction stabiliser having a hollow elongate body portion including an opening extending substantially the entire length of the body portion and a closure member aligned to substantially cover the opening of the body portion, the closure member being configured to extend substantially parallel to an inner wall of the body portion in the vicinity of the opening, including the following steps: a. drilling a hole in the region to be stabilised, the hole having a smaller diameter than the diameter of the stabiliser to be installed; b. inserting filler material into the hollow elongate body portion to substantially fill said body portion; and c. inserting the stabiliser into the hole.

30. A stabiliser according to claim 1 substantially as hereinbefore described with reference to Figures 3 to 10(c).

28. A method according to claim 6 substantially as hereinbefore described with reference to Figures 3 to 10(c).

29. A cartridge according to claim 11 as hereinbefore described with reference to Figures 3 to 10(c).

30. A filler delivery system according to claim 18 substantially as hereinbefore described with reference to Figures 3 to 10(c).

31. A stabiliser assembly according to claim 22 substantially as hereinbefore described with reference to Figures 3 to 10(c).