WO2018096508A1

WO2018096508A1 - Self-drilling rock bolt with internal mixer

Info

Publication number: WO2018096508A1
Application number: PCT/IB2017/057414
Authority: WO
Inventors: Donald Michael O'connor
Original assignee: Orica Mining Services South Africa (Pty) Ltd
Priority date: 2016-11-28
Filing date: 2017-11-27
Publication date: 2018-05-31
Also published as: ZA201608232B

Abstract

This invention concerns a self-drilling rock bolt for use with a two-component grout mixture for setting the rock bolt in a hole in a rock body. The body has an axial interior passage which defines a fluid flow path along which the grout mixture, in use, flows. The body further has an outer surface on which trapezoidal rib-like deformations (26) are located. A mixer (28) for mixing the two-component grout is located at least partially within the body such that the mixer is located in the fluid flow path.

Description

SELF-DRILLING ROCK BOLT WITH INTERNAL MIXER

BACKGROUND TO THE INVENTION

This invention relates to a self-drilling rock bolt and a method of installing the rock bolt. In particular, but not exclusively, the invention relates to a self-drilling rock bolt having a rib-like exterior surface and internal static mixer.

Rock bolts are commonly used for strengthening of rock, typically the rock surrounding underground excavations or behind free-standing rock surfaces, such as in road cuttings or rock faces. When installing rock bots, holes are drilled in the rock for receiving the rock bolts. The rock bolts are fixed in the holes by grouting with resin or cementitious fillers, by friction between the surfaces of the rock bolts and the rock walls of the holes, or a combination of grouting and friction. The invention of the present application relates to rock bolts that are fixed at least partially by grouting. Most commonly, the means to drill the holes and the drilling operation on one hand are distinct from the rock bolts themselves and the operations of inserting the rock bolts and fixing them in the holes with grout on the other hand. The holes are drilled using elongate, thick-walled tubular formations referred to as "drill steels". At their proximal ends the drill steels are formed to engage with drive mechanisms, which are also referred to as drifters, which provide thrust and percussive, rotary or rotary-percussive forces to the drill steels. At their distal ends, the drill steels have rock-engaging formations that break the rock by percussive, rotary or rotary-percussive action, thereby forming a hole that advances into the rock. The rock- engaging formations or "bits", as they are commonly referred to in the industry, may be fixed permanently to the drill steel by a method such as brazing ("integral bits") or they may fitted and removable from the drill steels by an engaging means such as a screw thread or friction on mutually-engaging conical surfaces. Drill steels almost invariably have an axially hollow core creating a passage through which a fluid such as water or air is forced during drilling. In use, the fluid cools the rock-engaging formations and carries away fragments of broken rock from the drilling interface. A person familiar with the art of rock drilling will know that drill steels are subjected to large impact, flexural and torsional stresses during drilling, which require them to be made from high-specification-steel.

It is also common practice to manufacture rock bolts from solid steel rod with deformations to enhance the grip of the rock bolt with the grout holding it in place in the hole. The deformations typically have heights of between 0.5 and 1 .0 mm. The steel rods from which rock bolts are made are often incorrectly referred to as "rebar" in the industry seeing that the deformations are similar to those found on steel reinforcing used in reinforced concrete. However, the deformations are optimised for the rod to perform as a rock bolt.

The grout used to fix the rock bolts in the holes may be delivered in a number of different ways. Most commonly, the grout is encapsulated or bulk cementitious grouts, or pre-packed capsules of two-component organic resins. In the latter case, the capsules are inserted into the holes before insertion of the rock bolt. During insertion of the rock bolt the capsules are disrupted and the two components mix and harden to fix the rock bolt in the hole, thereby reinforcing the rock. Bulk organic resins are also sometimes used.

The abovementioned components and practice of rock bolting as outlined above are extensively described in "The Minova Guide to Resin-Grouted Rockbolts", Minova International Limited, 2006 available from Minova Global (www.minoveglobal.com).

It will be appreciated that the process described above is a multi-step process comprising essentially of the steps of drilling the hole, withdrawing the drill rod(s) of the drill steel from the hole, charging the hole with grout and inserting the rock bolt in to the charged hole.

It has been suggested to employ one-step bolting systems in which it is preferred to exclude the step of withdrawing the drill rods. This preference may arise from a desire to save time and reduce complexity by excluding a step, or because the rock is so weak that the drilled hole collapses after withdrawing the drill rods, thereby preventing the charging of the hole with grout and the insertion of the rock bolt. Systems in which the drilling formations are left in the hole are commonly referred to in the industry as one-step bolting systems. In one-step bolting systems the drilling formations also act as the rock bolt and the axial hole in the drill steel is also used as the conduit for introducing grout into the hole, for fixing the rock bolt therein. Drill steels which are also used as rock bolts are commonly referred to as one-step rock bolts, self-drilling rock bolts or self- drilling anchors.

Most commonly, one-step bolting systems use rods with an axial hollow conduit and an external surface formed into a continuous coarse thread which has a rounded or trapezoidal form. The rounded thread is commonly referred to as "rope" thread and the trapezoidal thread is commonly referred to as "T" thread. Typically the rods have nominal outer diameters of between 25 and 51 mm. To enable the rods to be used for drilling, they are fitted with bits. The bits may be screwed directly onto the bolts, using the threaded outer surface of the rods, or may be frictionally engaged as described above. Detailed descriptions of such bolts and accessories may be found in suppliers' catalogues, such as produced by Minova MAI or Ischerbeck.

The grouts used in one-step bolting systems are typically one-component cement slurries, one-component resin grouts or two-component cement or resin grouts. Both one-component cement slurries and one-component resin grouts are relatively slow-setting, i.e. setting times typically exceeding 20 minutes. In application in which faster setting is desired, two-component grouts are normally used to achieve a setting time after mixing in the range of 5 to 60 seconds. This rapid setting requires that mixing of the two components to initiate the setting reaction take place contemporaneously with, and in close proximity to, the introduction of the mixed grout into the hole via the axial passage in the drill rods. Such a system is described in grated Australian patent AU2005297473 entitled "Method for Embedding Rock Anchors".

A disadvantage of the known self-drilling rock bolts used in one-step bolting systems is that the height of the deformations constituting the thread is relatively large in relation to the overall outer diameter of the bolt. For example, the rope thread profile per ISO 1720 and 10208 standards has a half-amplitude of 1 .5 mm. On a 25 mm diameter bolt, the radius is 12.5 mm, thereby resulting in a root radius of only 1 1 mm. As a result, these known self-drilling bolts are relatively weak under the high thrust and impact loads associated with high-powered drilling. In the industry it is common to experience bending and fracturing of the bolts, thereby reducing the utility of one-step bolting system. It is an object of this invention to alleviate at least some of the problems experienced with known one-step bolting system and, in particular, known self-drilling rock bolts used such one-step systems.

It is a further object of this invention to provide a self-drilling rock bolt and a method of installing such rock bolt that will be useful alternatives to existing bolts and methods of installing the known bolts.

SUMMARY OF THE INVENTION

In accordance with a first aspect of the invention there is provided a self- drilling rock bolt for use with a multi-component grout mixture for setting the rock bolt in a hole in a rock body, the self-drilling rock bolt including:

a body having a first end which is, in use, a proximal end and a second end which is, in use, a distal end, the body having an axial interior passage running between the proximal and distal ends which defines a fluid flow path along which the grout mixture, in use, flows, and an outer surface on which rib-like deformations are located; and

a mixer for mixing the two-component grout, the mixer being located at least partially within the body such that the mixer is located in the fluid flow path.

In the preferred embodiment of the rock bolt the rib-like deformations are trapezoidal.

The self-drilling rock bolt may include engaging means carried at the distal end of the body for engagement with a drill bit. The engaging means may be in the form of an external thread. The engaging means may be in the form of a tapered or conical portion for engagement with a complementary shaped socket of a drill bit. The engaging means may have a taper angle of about 1 1 to 12 degrees. The self-drilling rock bolt may further include connecting means carried at the proximal end of the body for connection to a drive-chuck of a drifter used for drilling. The connecting means may be in the form of an external thread, which could be in the form of a rope thread, for example. The rope thread may have a length of about 100 to 150 mm. Alternatively, the connecting means may be in the form of planar surfaces substantially parallel to the longitudinal centre axis of the bolt, typically forming a polygon in cross-section, for example a hexagon. The planar surfaces may have a length of about 50 mm to about 200 mm.

In one embodiment of the rock bolt the mixer includes a capsule in which at least one, preferably a number of, mixing elements is located. The capsule may be located in a recess within the body of the rock bolt, the recess being located at the proximal end of the body. The capsule may be tubular and may have an external diameter of 13mm.

In one embodiment of the rock bolt the length of the mixer is about 100mm. The mixer may include 10 individual mixing elements each having a length of about 10mm.

In the preferred embodiment, the body of the rock bolt has a nominal outer diameter of 25 mm and an interior passage of diameter 9 to 1 1 mm.

The mixing elements are preferably tight-fitting in the tube, and the tube is preferably tight-fitting in the recess in the bolt, thereby preventing the grout mixture from by-passing the mixer.

In accordance with a second aspect of the invention there is provided a method of installing a self-drilling rock bolt in a hole in a rock body, the method including:

drilling the hole in the rock body using a self-drilling rock bolt including body having a first end which is, in use, a proximal end and a second end which is, in use, a distal end, the body having an axial interior passage running between the proximal and distal ends which defines a fluid flow path along which the grout mixture, in use, flows, and an outer surface on which rib-like deformations are located;

charging the hole with grout by pumping the grout though the axial hollow interior passage along the fluid path;

mixing the grout by using a mixer located at least partially within the body of the self-drilling rock bolt as the grout is being pumped through along the fluid path; and

fixing the rock bolt in the hole in the rock body by means of the grout gripping the side wall of the hole and the rib-like deformations carried on the surface of the rock bolt.

The step of mixing the grout may include mixing a two-component grout mixture.

The grout may be mixed using a number of individual mixing elements located in the fluid flow path in the rock bolt.

The method may include locating the individual mixing elements in a capsule and inserting the capsule in a recess at the proximal end of the body of the rock bolt.

The mixing elements are preferably tight-fitting in the capsule and the capsule is preferably tight-fitting in the recess in the rock bolt, thereby preventing the grout from by-passing the mixer.

The rib-like deformations are trapezoidal.

The method may include engaging the distal end of the body of the rock bolt with a drill bit.

The method may further include engaging the distal end of the body of the rock bolt with the drill bit using threaded connection, or a complementary shaped conical connection between the distal end and a socket of the drill bit. The distal end may have a taper angle of about 1 1 to 12 degrees. The method may include connecting the proximal end of the body of the rock bolt to a drive-chuck of a drifter used for drilling.

The method may also include connecting the proximal end of the body of the rock bolt to the drive-chuck of the drifter using a threaded connection in the form of a rope thread.

The method may also include connecting the proximal end of the body of the rock bolt to the drive-chuck of the drifter by complementary engagement of planar surfaces substantially parallel to the longitudinal centre axis of the bolt, typically forming a polygon in cross-section, for example a hexagon.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in more detail, by way of example only, with reference to the accompanying drawings in which:

Figure 1 shows a perspective view of a portion of a prior art rock bolt, the exterior surface of which carries a rope thread;

Figure 2 shows an exploded perspective view of a self-drilling rock bolt in accordance with the invention;

Figure 3 shows a plan view of the self-drilling rock bolt of Figure 2;

and

Figure 4 shows a cross-sectional view of the self-drilling rock bolt of

Figure 2; and Figure 5 shows an enlarged detailed view of the bolt of self-drilling rock bolt of Figure 2.

DESCRIPTION OF THE ILLUSTRATED EMBODIMENT

Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of "including," "comprising," or "having" and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless specified or limited otherwise, the terms "mounted," "connected," "supported," and "coupled" and variations thereof are used broadly and encompass both direct and indirect mountings, connections, supports, and couplings and are thus intended to include direct connections between two members without any other members interposed therebetween and indirect connections between members in which one or more other members are interposed therebetween. Further, "connected" and "coupled" are not restricted to physical or mechanical connections or couplings. Additionally, the words "lower", "upper", "upward", "down" and "downward" designate directions in the drawings to which reference is made. The terminology includes the words specifically mentioned above, derivatives thereof, and words or similar import. It is noted that, as used in this specification and the appended claims, the singular forms "a," "an," and "the," and any singular use of any word, include plural referents unless expressly and unequivocally limited to one referent. As used herein, the term "include" and its grammatical variants are intended to be non-limiting, such that recitation of items in a list is not to the exclusion of other like items that can be substituted or added to the listed items.

Referring to the drawings, in which like numerals indicate like features, a non-limiting example of a self-drilling rock bolt in accordance with the invention is generally indicated by reference numeral 10.

The self-drilling rock bolt 10 in accordance with the invention is intended for use in applications in which the bolt is fixed in place inside a hole drilled into a rock body using grout. In particular, it is envisaged that the self- drilling rock bolt 10 would be particularly useful in applications in which a two-component grout mixture is used. In such applications the grout mixture is typically in the form of a fluid and is pumped though the bolt. More about this is said below. The self-drilling rock bolt 10 is intended to form part of a one-step bolting system in which the rock bolt 10 is used as both the drilling formation or drill steel and the rock bolt reinforcing the surrounding rock body.

Turning now to Figures 2 to 6 the self-drilling rock bolt 10 in accordance with the invention will be described in detail. In Figure 2 it can be seen that the rock bolt 10 has an elongate, tubular body 12. The body has a first end 14 which is, in use, a proximal end and a second end 16 which is, in use, a distal end. In use, the distal end is located at the blind end of the hole drilled into the rock body and the proximate end is located at the opening of the drilled hole. Best seen in Figure 5 the tubular body 12 has an internal bore in the form of an axial hollow internal passage 18 running between the proximal and distal ends 14, 16. The passage 18 defines a fluid flow path for the grout mixture.

In one embodiment of the invention the body 12 is manufactured from "NCA" type hollow steel manufactured by ArcelorMittal South Africa Limited. Some of the properties of the steel are as follows: Yield Strength 600 MPa

Tensile Strength 850 MPa.

Elongation 15% Min.

Impact tests at 20 degrees 4 joules min.

In the illustrated embodiment the body 12 of the rock bolt 10 has a nominal outer diameter of about 25 mm and the diameter of the interior passage is between about 9 and 1 1 mm.

The self-drilling rock bolt 10 has engaging means carried at the distal end 16 of the body 12 for engagement with a drill bit. In this illustrated embodiment of the rock bolt 10 the engaging means is in the form of a tapered or conical portion 20 for engagement with a complementary shaped socket of the drill bit (not shown in the accompanying drawings). In the preferred embodiment of the rock bolt 10 the conical engaging means 20 has a taper angle of between about 1 1 to 12 degrees.

It is however envisaged that in an alternative embodiment not illustrated in the accompanying drawings the engaging means could be in the form of an external thread. In this alternative embodiment the external thread would engage a complementary shaped internal thread located on the drill bit.

Returning to the illustrated embodiment of the rock bolt 10, the body 12 carries connecting means at its proximal end 14 for connection to a drive- chuck of a drifter used for drilling (not illustrated in the accompanying drawings). From Figures 2 to 6 it can be seen that the connecting means is in the form of an external thread 22. In particular, the external thread 22 is in the form of a continuous rope thread for engagement with a complementary shaped thread located on the chuck of the drifter. In the preferred embodiment of the rock bolt 10 the length of the rope thread 22 is between about 100 and 150 mm.

In an alternative embodiment of the rock bolt of the invention not shown in the accompanying drawings the connecting means may be in the form of planar surfaces substantially parallel to the longitudinal centre axis of the bolt. The planar surfaces could be arranged to form a polygon in cross- section, particularly a hexagon, thereby forming a hexagonal drive arrangement. The planar surfaces may have a length of between about 50 mm to about 200 mm.

Returning to Figure 2 it can be seen that the body 12 has an exterior surface 24 carrying rib-like deformations 26 for improving the grip between the grout and the rock bolt in use. The rib-like deformations 26 are essentially in the form of upstanding ribs protruding from the exterior surface of the body 12. The ribs are arranged in at least one row in which they are aligned parallel to one another. In the illustrated embodiment the ribs are arranged in two substantially diametrically opposed rows. In comparing the known bolt of Figure 1 with the self-drilling rock bolt 10 of the invention it can be seen that the deformations 26 of the bolt 10 differ significantly from those of the known bolt of Figure 1 . The rib-like deformations 26 of the bolt 10 have a trapezoidal shape in cross-section as shown in Figure 6. This is contrast to the rounded or rope thread of the known bolt of Figure 1 . The trapezoidal shape of the deformations 26 of the rock bolt 10 has a significant advantage in that its height is substantially reduced in comparison with the roped thread of the known bolt of Figure 1 . As a result of the reduced height of the deformations 26 the rock bolt 10 has a greater effective diameter than the known bolt of Figure 2, thereby addressing the weaknesses of the known bolt of Figure 1 described above. The self-drilling rock bolt 10 in accordance with the invention is accordingly improved for both acting as a drill steel during drilling and acting as a rock bolt when fixed in the hole with grout.

Referring still to Figures 2 to 6 it can be seen that the rock bolt 10 includes a mixer 28 for mixing the two-component grout. The mixer 28 is a static mixer located at least partially within the body 12 such that it is located in the fluid flow path. In the preferred embodiment the mixer 28 is located completely inside the body 12 of the rock bolt 10. Referring in particular to Figure 3, it can be seen that the mixer 28 includes a number of individual mixing elements 30 which are receivable in a capsule 32. In the accompanying drawings the capsule 32 is in the form of an aluminium tube shaped to contain the individual mixing elements 30. Although the tube 32 is made from aluminium in the preferred embodiment, the invention is not limited to the use of aluminium. It is envisaged that instead of aluminium, other material such as an alloy, brass, steel or similar material could be used. The individual mixing elements 30 are made from a plastics material and are referred to as X-type mixers by the manufacturer StaMixCo LLC. It has been found that this X-type mixer provides good mixing over a relatively short distance, despite the high viscosity of the fluids constituting the two-component resin grout. In the preferred embodiment of the rock bolt 10 the mixer 28 includes 10 mixing elements 30, which each has a length of about 10 mm. Accordingly, the overall length of the mixer 28 is about 100 mm.

It is envisaged that instead of using individual mixing elements 30, the mixer could be in the form of a single, integrally formed mixing element which spans the entire length of the mixer 28. In this alternative embodiment the capsule 32 may be discarded seeing that the capsule is mainly included in the illustrated rock bolt 10 to facilitate handling of the individual mixing elements 28. In the alternative embodiment in which a single mixing element is used it may not be necessary to pre-load the mixing element into a capsule.

Returning to the illustrated embodiment of the rock bolt 10, and in particular to Figure 6 which shows a cross-sectional view of the rock bolt, it can be seen that the capsule 32 is receivable in a recess 34 within the body 12 of the rock bolt 10. In this particular embodiment the recess 34 is enlarged compared to the axial passage 18 in order to receive the capsule. The diameter of the recess is about 13 mm. As shown in Figure 6 the capsule 32 containing the mixing elements 30 are located at the proximal end 16 of the body 12 when located in the recess 34. In this configuration the grout is mixed as it is introduced into the fluid flow path running through the rock bolt 10. In use, the grout is typically delivered into the rock bolt 10 by means of a pumping system which pumps the grout into the proximal end 14, through the static mixer 28, along the internal passage 18 and out the distal end 16. To prevent the fluids of the grout from by-passing the mixer 28 through any annular gap between either the mixer and the capsule or the capsule and the inner surface of the passage 18 in the bolt, the mixing elements 28 are tight-fitting in the capsule 32 and that the capsule 32 is in turn tight-fitting in the recess 34.

By using the internal, static mixer 28 it is not necessary to flush residual materials out of the mixer after every bolting operation. This is a significant advantage over external mixers. The static mixer 28 is a single-use item that can simply be retained in the rock bolt 10 after use.

Although the method of installing the self-drilling rock bolt 10 in accordance with the invention should be clear from the above description of the rock bolt 10, it will now be described briefly for the sake of clarity. The method commences with the drilling of a hole into a rock body using the self-drilling rock bolt 10. This step includes engaging a drill bit with the distal end 1 6 of the body 12 of the rock bolt 10 using the engaging means 20. The proximal end 14 of the rock bolt 10 is, in turn, connected to the chuck of the drifter used to provide the driving forces during drilling. Once the hole is drilled it is charged with grout by pumping the grout though the axial hollow interior passage 18 such that it flows along the fluid path. It should be understood that the rock bolt 10 remains in the hole while the hole is being charged. In other words, the rock bolt 10 is not removed from the hole after drilling. As mentioned above, a two-component grout is used in the preferred method of installing the rock bolt 10. In order to mix the two components of the grout the static mixer 28 is used. By locating the static mixer 28 in the fluid flow path along which the grout flow while charging the hole the grout is pumped through the static mixer 28, thereby mixing the two components of the grout as it flows through the mixer. The grout is prevented from bypassing the mixing elements 30 or the mixer 28 altogether by providing a tight-fitting between the mixing elements 30 and the capsule 32 and between the capsule 32 and the recess 34. The grout is pumped along the fluid flow path defined by the internal passage 18 and exits the rock bolt 10, thereby filling the void between the rock bolt of the wall of the drilled hole in which it is located. In use, the deformations 26 improve the grip between the rock bolt 10 and the grout.

It will be appreciated that the above is only one embodiment of the invention and that there may be many variations without departing from the spirit and/or the scope of the invention. It is easily understood from the present application that the particular features of the present invention, as generally described and illustrated in the figures, can be arranged and designed according to a wide variety of different configurations. In this way, the description of the present invention and the related figures are not provided to limit the scope of the invention but simply represent selected embodiments.

The skilled person will understand that the technical characteristics of a given embodiment can in fact be combined with characteristics of another embodiment, unless otherwise expressed or it is evident that these characteristics are incompatible. Also, the technical characteristics described in a given embodiment can be isolated from the other characteristics of this embodiment unless otherwise expressed.

Claims

1 . A self-drilling rock bolt for use with a two-component grout mixture for setting the rock bolt in a hole in a rock body, the self-drilling rock bolt including:

a body having a first end which is, in use, a proximal end and a second end which is, in use, a distal end, the body having an axial interior passage running between the proximal and distal ends which defines a fluid flow path along which the grout mixture, in use, flows, and an outer surface on which rib-like deformations are located; and a mixer for mixing the two-component grout, the mixer being located at least partially within the body such that the mixer is located in the fluid flow path.

2. A self-drilling rock bolt according to claim 1 , wherein the rib-like deformations are trapezoidal.

3. A self-drilling rock bolt according to either claim 1 or 2, including engaging means carried at the distal end of the body for engagement with a drill bit.

4. A self-drilling rock bolt according to claim 3, wherein the engaging means is in the form of an external thread.

5. A self-drilling rock bolt according to claim 3, wherein the engaging means is in the form of a tapered or conical portion for engagement with a complementary shaped socket of a drill bit.

6. A self-drilling rock bolt according to claim 5, wherein the engaging means has a taper angle of about 1 1 to 12 degrees.

7. A self-drilling rock bolt according to any one of claims 1 to 6, including connecting means carried at the proximal end of the body for connection to a drive-chuck of a drifter used for drilling.

8. A self-drilling rock bolt according to claim 7, wherein the connecting means is in the form of an external thread.

9. A self-drilling rock bolt according to claim 8, wherein the external thread of the connecting means is in the form of a rope thread.

10. A self-drilling rock bolt according to claim 9, wherein the rope thread has a length of about 100 to about 150 mm.

1 1 . A self-drilling rock bolt according to claim 7, wherein the connecting means is in the form of planar surfaces substantially parallel to the longitudinal centre axis of the bolt.

12. A self-drilling rock bolt according to claim 1 1 , wherein the planar surfaces are arranged to form a polygon in cross-section.

13. A self-drilling rock bolt according to claim 12, wherein the polygon is a hexagon.

14. A self-drilling rock bolt according to any one of claims 1 1 to 13, wherein the planar surfaces have a length of between about 50 mm to about 200 mm.

15. A self-drilling rock bolt according to any one of claims 1 to 14, wherein the mixer includes a capsule in which at least one mixing element is located.

16. A self-drilling rock bolt according to claim 15, wherein a number of individual mixing elements are located in the capsule.

17. A self-drilling rock bolt according to claim 16, wherein the capsule is located in a recess within the body of the rock bolt, the recess being located at the proximal end of the body.

18. A self-drilling rock bolt according to claim 17, wherein the capsule is tubular and has an external diameter of about 13mm.

19. A self-drilling rock bolt according to any one of claims 15 to 18, wherein the length of the mixer is about 100mm.

20. A self-drilling rock bolt according to any one of claims 15 to 19, wherein the mixer includes 10 individual mixing elements each having a length of about 10mm.

21 . A self-drilling rock bolt according to any one of claims 15 to 20, wherein the mixing elements are tight-fitting in the tube, and wherein the tube are tight-fitting in the recess in the bolt, thereby preventing the grout mixture from by-passing the mixer.

22. A self-drilling rock bolt according to any one of claims 1 to 21 , wherein the body of the rock bolt has a nominal outer diameter of about 25 mm and an interior passage having a diameter of about 9 to 1 1 about mm.

23. A method of installing a self-drilling rock bolt in a hole in a rock body, the method including:

charging the hole with grout by pumping the grout though the axial interior passage along the fluid path;

mixing the grout by using a mixer located at least partially within the body of the self-drilling rock bolt as the grout is being pumped through along the fluid path;

24. A method according to claim 23, wherein the step of mixing the grout includes mixing a two-component grout mixture.

25. A method according either claim 23 or 24, wherein the grout is mixed using a number of individual mixing elements located in the fluid flow path in the rock bolt.

26. A method according to claim 25, including locating the individual mixing elements in a capsule and inserting the capsule in a recess at the proximal end of the body of the rock bolt.

27. A method according to claim 26, wherein the mixing elements are tight-fitting in the capsule and the capsule is tight-fitting in the recess in the rock bolt, thereby preventing the grout from by-passing the mixer.

28. A method according to any one of claims 23 to 27, wherein the rib-like deformations are trapezoidal.

29. A method according to any one of claims 23 to 28, including engaging the distal end of the body of the rock bolt with a drill bit.

30. A method according to claim 29, including engaging the distal end of the body of the rock bolt with the drill bit using threaded connection, or a complementary shaped conical connection between the distal end and a socket of the drill bit.

31 . A method according to claim 30, wherein the distal end has a taper angle of about 1 1 to about 12 degrees.

32. A method according to any one of claims 23 to 31 , including connecting the proximal end of the body of the rock bolt to a drive- chuck of a drifter used for drilling.

33. A method according to claim 32, including connecting the proximal end of the body of the rock bolt to the drive-chuck of the drifter using a threaded connection in the form of a rope thread.

34. A method according to claim 32, including connecting the proximal end of the body of the rock bolt to the drive-chuck of the drifter by engaging planar surfaces substantially parallel to the longitudinal centre axis of the bolt with a complementally shaped socket of the drive-chuck.

35. A method according to claim 34, wherein the planar surfaces are arranged to form a polygon in cross-section.

36. A method according to claim 35, wherein the polygon is a hexagon.

37. A self-drilling rock bolt according to claim 1 substantially as herein described with reference to the illustrated embodiment.

38. A method of installing a self-drilling rock bolt according to claim 19 substantially as herein described with reference to the illustrated embodiment.