WO2020154761A1

WO2020154761A1 - Rock bolt

Info

Publication number: WO2020154761A1
Application number: PCT/AU2020/050041
Authority: WO
Inventors: Matthew Hawkes; Anthony Walter CAPUTO; Edward John Robinson
Original assignee: Support Technologies Innovations Pty Ltd
Priority date: 2019-01-29
Filing date: 2020-01-23
Publication date: 2020-08-06
Also published as: PE20220103A1; CN113710872A; CL2021001965A1; AU2020213604A1

Abstract

There is disclosed a rock bolt for use as an anchor bolt or friction bolt in a borehole formed in a rock body. The rock bolt includes an elongated member with an internal axial passage having a leading end and an opposed trailing end. A plunger is configured to be supported by the elongated member at its leading end, with the plunger further supporting a ram that projects outwardly beyond the leading end of the elongated member. During use, the ram is configured to abut against the rock body to impart a ramming force onto the plunger and force the plunger into the internal axial passage of the elongated member and thereby outwardly deflect a part of the elongated member so it becomes wedged within the borehole.

Description

Rock bolt

TECHNICAL FIELD

The present disclosure relates to a rock bolt.

More particularly, the present disclosure relates to a rock bolt having an anchor for securing the rock bolt within a borehole in a rock body.

BACKGROUND ART

Rock bolts, also known as anchor bolts or friction bolts, are used in the mining industry to support and stabilise a rock body against creep movement or collapse. The rock bolts are then used to locate bearing plates or thrust plates to apply a compression force onto rock strata to stabilise the rock body. It is also known to use the rock bolts to support a wire mesh adjacent the rock face and to spray a settable concrete over the mesh to strengthen the rock face.

Rock bolts come in many different forms and are chosen based on various factors including the material and quality of the rock body to be reinforced and the amount of geological stress and movement common to particular rock bodies.

Rock bolts are generally in the form of an elongated element such as a tube, cable, rod or combinations thereof that are able to be fitted into a borehole drilled into the rock body and subsequently secured within the borehole. Rock bolts are typically secured in the borehole by mechanical or chemical means. One type of rock bolt is an anchor bolt which comprise an expansion sleeve surrounding the rock bolt and pulling or forcing a plunger attached to the rock bolt into the sleeve. The plunger causes the sleeve to expand by deflecting outwardly to press against the sides of the rock body in the borehole and thereby to jam the rock bolt in place and providing a point anchor.

Other types of rock bolts, such as friction bolts, are capable of yielding progressively under a load so as to avoid a sudden and catastrophic failure of the rock bolt. These kinds of bolts comprise a tube that is split longitudinally along its length, with the tube having a radius that is slightly larger than the radius of a borehole into which it is to be inserted. During insertion the tube is radially compressed to partially or completely close the split therein. The friction bolt is then held in place In the borehole due to friction contact between the tube and the surrounding rock body.

It is generally easier and quicker to insert a friction bolt than an anchor bolt. This is due to the friction bolt being installed by simply percussion hammering the friction bolt into the borehole, i.e. being a one step process. Most anchor bolts are more time consuming to install as it is a two-step process wherein first the anchor bolt must be inserted into the borehole and thereafter the plunger must be activated, e.g. by screwing a threaded rod to puli the plunger into the expansion sleeve.

It is to be understood that, if any prior art publication is referred to herein, such reference does not constitute an admission that the publication forms a part of the common general knowledge in the art, in Australia or any other country.

SUMMARY OF THE DISCLOSURE

According to a first aspect of the disclosure, there is provided a rock bolt for use as an anchor bolt or friction bolt in a borehole formed in a rock body, the rock bolt comprising an elongated member with an internal axial passage, the elongated member having a leading end and an opposed trailing end;

a plunger configured to be supported by the elongated member at its leading end; and

a ram supported by the plunger and configured to project outwardly beyond the leading end of the elongated member,

wherein, during use, the ram is configured to abut against the rock body to impart a ramming force onto the plunger and force the plunger into the internal axial passage of the elongated member and thereby outwardly deflect a part of the elongated member. The elongated member may be a tube having a slot extending along its axial length so that the tube is substantially C-shaped in cross-section view. In one embodiment a part of the elongated member near to its leading end tapers inwardly.

The plunger may comprise a plunger leading end and a plunger trailing end, the plunger leading end defining a bearing wall which, prior to insertion in a borehole, is configured to project outwardly beyond the leading end of the elongated member, the plunger further comprising a reducing tapered nose extending from the bearing wall towards the plunger trailing end, which nose is configured to be at least partially received within the internal axial passage at the leading end of the elongated member.

The plunger trailing end may comprise a cylindrical prop being configured to axially align the plunger within the internal axial passage of the elongated member. In one embodiment the leading end of the elongated member may be crimped onto the nose of the plunger. In another embodiment the leading end of the elongated member may be in close frictional fit with the nose of the plunger.

The plunger may comprise an axial bore wherein the diameter of the bore is larger at the plunger leading end and the diameter of the bore reduces along its length towards the plunger trailing end. The bore may be tapered along a part of the axial length of the plunger. In such case the bore may be tapered in a Morse taper. Alternatively, the bore may have an internal reducing step or rabbet.

The ram may be an elongated rod having a ram leading end and a ram trailing end, wherein in use the ram leading end is configured to abut the rock body and the ram trailing end is supported by the plunger. The ram trailing end may be contoured to assist in the ram being supported by the plunger.

The ram may be configured, in use, to impart a temporary ramming force to the plunger such that the ramming force is relieved after a counter force threshold value is exceeded. In one embodiment the ram is made of a ductile material that is able, in use, to undergo plastic deformation so as to relieve the ramming force. In such case, the ram may be configured to be extruded through the bore of the plunger. In another embodiment the ram may be made of a brittle material that is able, in use, to collapse or fracture. According to a second aspect of the present disclosure, there is provided a method of installing a rock bolt in a borehole formed in a rock body, the method comprising the steps of:

supporting a plunger at a leading end of the rock bolt, and joining a ram to the plunger so that the ram projects outwardly beyond the leading end of the rock bolt; inserting the rock bolt into the borehole so that the ram is coaxially aligned with and positioned downhole of the rock bolt; and forcing the rock bolt into the borehole so that the ram abuts the rock body to impart a ramming force onto the plunger and force the plunger into an internal axial passage of the rock bolt and thereby outwardly deflect a part of the rock bolt.

The method may comprise the step of relieving the ramming force imparted by the ram after the plunger is sufficiently inserted into the internal axial passage of the rock bolt.

In one embodiment the ramming force may be relieved by the ram undergoing plastic deformation. In such case the ram may be extruded through an axial bore extending through the plunger. In another embodiment the ramming force may be relieved by the ram fracturing and breaking apart. The method may include the step of joining the rock bolt to the plunger by crimping the leading end onto the plunger.

According to a third aspect of the disclosure, there is provided a plunger for use with a rock bolt or friction bolt in a borehole formed in a rock body, the plunger comprising a body having a leading end and an opposed trailing end; and

a ram supported by the body and configured to project outwardly beyond the leading end,

wherein, during use, the ram is configured to abut against the rock body to impart a ramming force onto the body and force the body into an internal axial passage of a rock bolt and thereby outwardly deflect a part of the rock bolt. The body may comprise an axial bore, wherein the diameter of the bore is larger at the leading end and smaller at the trailing end. The bore may be tapered along a part of the axial length of the body. In such case the bore may be tapered in a Morse taper. Alternatively, the bore may have an internal reducing step or rabbet.

The ram may be an elongated rod having a ram leading end and a ram trailing end, wherein in use the ram leading end is configured to abut the rock body and the ram trailing end is supported by the body. The ram trailing end may be contoured to assist in the ram being supported by the body.

The ram may be made of a ductile material that is able, in use, to undergo plastic deformation. Alternatively, the ram may be made of a brittle material that is able, in use, to collapse or fracture. BRIEF DESCRIPTION OF DRAWINGS

The above and other features will become more apparent from the following description with reference to the accompanying schematic drawings given as an example. The drawings are for the purpose of illustration only and are not intended to be in any way limiting, wherein:

Figure 1 is a perspective view of a rock bolt comprising a split sleeve friction bolt and an plunger arrangement arranged to provide anchor point therefore;

Figure 2 is an enlarged side view of the plunger arrangement shown in Figure 1 ; Figure 3 is a sectional side view of the plunger arrangement shown in Figure 2; Figure 4 is a sectional side view depicting the use of the rock bolt of Figure 1 , wherein the rock bolt is in a partially installed non-anchoring position;

Figure 5 is a sectional side view depicting the use of the rock bolt of Figure 1 , wherein the rock bolt is in a partially installed anchoring position; and

Figure 6 is a sectional side view depicting the use of the rock bolt of Figure 1 , wherein the rock bolt is in a fully installed anchoring position.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring to Figure 1 , there is shown a rock bolt 10 for use as an anchor bolt or friction bolt in a borehole formed in a rock body. The installation and use of the rock bolt 10 is shown in Figures 4 to 6 where the rock bolt 10 is shown in successive partially and fully installed positions within a borehole 12 provided in a rock body 14.

The borehole 12 has an opening 16 at a rock face 18 and has a borehole base 20 remote from the rock face 18. It should be understood for the purposes of the description below that the terms“leading” and“trailing” refer to operative drilling positions or rock bolt insertion positions relative to the borehole 12. Thus“leading” is used herein to refer to a position deeper within the borehole 12 or to a feature or part of the rock bolt 10 that is furthest or distal to the opening 16. Conversely,“trailing” refers to a position closest to the opening 16 or to a feature or part of the rock bolt 10 that is closest or proximal to the opening 16. Similarly, the terms“downhole” and“uphole” respectively refer to positions being closer to the base 20 and opening 16. The rock bolt 10 includes a load bearing elongated member in the form of a hollow bar or tube 30 having an internal axial passage. The tube 30 has a tube leading end 32 and an opposed tube trailing end 34. The tube 30 is configured to be inserted and secured in the borehole 12 with the tube leading end 32 located uphole within the borehole 12 while the tube trailing end 34 protrudes from the borehole 12 beyond the rock face 18. In the present example, the tube 30 has a slot 36 extending along its axial length resulting in the tube 30 being substantially C-shaped in cross-section or end view, i.e. the tube 30 is of a type that is conventionally known in the art as a split set. However, in other examples it is envisaged that the tube 30 can be fully closed in the form of a pipe.

The tube 30 is typically made of metal, such as steel so that it has a suitably high tensile strength. It will be appreciated that the outer diameter of the tube 30, as well as the thickness of its sidewall and its inherent resilience to compression, can be preselected so that the rock bolt 10 is able to exert a desired outward pressure on the rock body 14 surrounding the borehole 12 into which it has been inserted. In most cases this is achieved by having the outer diameter of the tube 30 (pre-installation) being slightly larger than the diameter of the borehole 12. Accordingly, when the tube 30 is inserted into the borehole 12, the tube 30 is circumferentially compressed and this results in the full or partial closure of the slot 36. In some examples the tube 30 may be formed with a knurled outer surface to increase its friction coefficient with the rock body 14. The tube 30 is tapered inwardly along a part of its axial length near to the tube leading end 32. The taper assists the tube 30 to be inserted into the borehole 12 during use.

A ring or collar 38 is welded around the tube 30 at the tube trailing end 34. In use the collar 38 is configured to press a bearing plate 40 against the rock face 18. In some embodiments, a small tab 39 of metal can be located internally of the collar 38 to bridge the slot 36, which tab 39 enables the collar 38 to be welded to the tube 30 around its full circumference and thereby strengthening the joint of the collar 38 to the tube 30.

The rock bolt 10 further comprises a plunger 42 and ram 44. In some examples the plunger 42 is provided separately from the tube 30 and is arranged to be joined thereto when the tube 30 is to be inserted into the borehole 12. In the exemplary embodiment the plunger 42 is joined to the tube 30 from the outset. The plunger 42 and ram 44 are more clearly illustrated in Figures 2 and 3.

The plunger 42 comprises a body 46 through which extends an axial bore 48. The plunger 42 has a plunger leading end 50 and a plunger trailing end 52. The body 46 is substantially cylindrical for a part of its length near the plunger leading end 50 - this part being configured to act as a bearing wall 54 in use; a leading middle part of the body 46 has a reducing taper 56; a trailing middle part 58 of the body 46 is again substantially cylindrical for a part of its length; and a cylindrical prop 60 is provided towards the trailing end of the body 46. The middle parts 56, 58 and the prop 60 are configured to act as a nose 62, while the opening of the bore 48 through the prop 60 is configured to act as a nozzle in use. Accordingly, the plunger 42 has a larger diameter bearing wall 54 at the plunger leading end 50, a smaller diameter waist in the middle parts 56, 58 of the plunger 52, and a larger diameter prop 60 at the plunger trailing end 52.

In the exemplary example the entrance to the bore 48 is similarly shaped to outside of the plunger 42, i.e. having a larger cylindrical opening at the plunger leading end 50, having a middle conical or reducing tapered section, which then again becomes cylindrical and extends through to a smaller opening at the plunger trailing end 52. However, in other examples, the bore 48 can include an internal reducing step or rabbet instead of the tapered section. The plunger 42 is normally made of a material that is harder than the material of which the tube 30 is made. In the current example, the plunger 42 is also made of steel.

The ram 44 is in the form of an elongated rod. In some examples the ram 44 is substantially cylindrical along its entire length. In other examples the ram can be non- cylindrical in shape, e.g. being a square rod. In the exemplary example, the ram 44 is cylindrical and exhibits a contoured trailing end that is congruent in shape to that of the bore 48. The ram 44 is configured to have an outer diameter to enable the ram 44 to be joined to the plunger 42 by inserting the ram trailing end into the bore 48 so that it is securely held in place. Accordingly, the major outer diameter of the ram 44 will be equivalent to the diameter of the bore 48 so that it will be in close fit therewith when the ram 44 is inserted into the bore 48. In one example the taper of the bore 48 and the congruent taper of the ram 44 are configured to be Morse tapers.

The ram 44 is configured, in use, to impart a temporary ramming force to the plunger 42 but to relieve the ramming force after a counter force threshold value is exceeded. This is achieved by the ram 44 abutting against the plunger 42 at the tapered section of the bore (or against the internal reducing step).

In the exemplary embodiment the ram 44 is made of a ductile material so that, in use, the ram 44 is initially rigid and able to impart a ramming force onto the plunger 42 but that after the ramming force exceeds the threshold value the ram 44 undergoes plastic deformation so that the ram 44 is extruded through the bore 48 and thereby relieves the ramming force. In some examples the ram 44 is made of plastics material such as but not limited to high-density polyethylene, polypropylene, polyvinyl chloride, nylon or combinations thereof. Such plastics materials may be reinforced with fibres. In other examples the ram 44 is made of metal, such as copper, aluminium, magnesium or iron or their ductile alloys.

In other embodiments the ram 44 can be made of a brittle material so that, in use, the ram 44 is initially rigid and able to impart a ramming force onto the plunger 42 but that after the ramming force exceeds the threshold value the ram 44 collapses or fractures and breaks up to relieve the ramming force. In some examples the ram 44 is made of brittle plastics material, such as polycarbonate, or wood.

Referring now to Figures 4 to 6, in use the borehole 12 is drilled into the rock body 14 to a desired depth. If not yet assembled as shown in Figure 1 , the ram 44 is inserted into the plunger 42, and thereafter the plunger 42 is joined to the tube 30 by inserting its nose 62 into the tube leading end 32 so that the plunger 42 and ram 44 are axially aligned with the tube 30. Once the plunger 42 is inserted into the bore 48, the cylindrical prop 60 assists in keeping the plunger 42 axially aligned with the tube 30. The leading end of the tube 30 is then crimped over the prop 60 onto the waist in the middle parts 56, 58 of the plunger 52. There is a slight clearance gap between the outer circumference of the prop 60 and the inner circumference of the tube 30 so that the prop 60 is still easily movable longitudinally within the tube 30. Ideally the clearance gap will be about 0.5 - 1 mm in extent around the prop 60 so that the total diametrical clearance will be about 1 - 2 mm. However, in other embodiments the leading end of the tube 30 may be in close frictional fit with the prop 60 so that it is not necessary to crimp the tube 30 to the plunger 60.

The rock bolt 10 is then inserted into the borehole 12 with the plunger 42 and ram 44 being located downhole of the tube 30. This insertion is normally performed by percussion hammering the rock bolt 10 into the borehole 12 until the bearing plate 40 abuts against the rock face 18. During such insertion the tube 30 is circumferentially compressed and engages in a friction fit with the rock body 14.

During the initial stages of insertion, as illustrated in Figure 4, the plunger 42 and ram 44 are held centrally within the borehole 12 and do not contact the rock body 14. Thus, at this stage of the insertion, only the tube 30 experiences circumferential compression. This circumferential compression is not sufficient to close the clearance gap around the prop 60and so, at this stage, the plunger 42 is still relatively easily axially moveable within the internal axial passage of the tube 30. Subsequently, as shown in Figure 5, as the rock bolt 10 nears its fully inserted position, the ram 44 contacts the base 20 at a downhole end of the borehole 12. The ram 44 bears against the base 20 and acts as a buttress between the base 20 and the plunger 42 to block further downhole movement of the plunger 42, i.e. the ram 44 starts to impart a ramming force onto the plunger 42 and force the plunger 42 into the internal axial passage of the tube 30. Thus, as the tube 30 is further inserted into the borehole 12, the tube leading end 32 slides over and past the plunger 42 so that the plunger enters the internal axial passage of the tube 30. In so doing, the tapered tube leading end 32 is forced to“ride up” the ramp formed by the plunger’s taper 56 and be outwardly deflected so that the tube leading end 32 expands and becomes wedged between the plunger’s bearing wall 54 and the rock body 14.

It will be appreciated that a friction force (F_f) existing between the tube 30 and both the plunger 42 and the rock body 14 will increase as the tube 30 slides further over the plunger 42 and engages a larger length of the bearing wall 54. At some stage during insertion (as shown in Figure 6), the friction force F_f will cause the plunger 42 to become wedged within the tube 30 so that the tube 30 will no longer be able to slide over and past the plunger 42, i.e. the plunger 42 will no longer move further into the internal axial passage of the tube 30. The plunger 42 will then move together with the tube 30 as the rock bolt 10 is fully inserted into the borehole 12. This final movement of the plunger 42 compresses the ram 44. After the compression force exceeds the threshold value, the ram 44 exhibits plastic deformation and starts extruding through the bore 48 and thereby relieves the ramming force. Depending on the type of material used for the ram 44 as well as the dimensions of the borehole 12, it is envisaged that in some embodiments the ram 44 may start extruding through the bore 48 at an earlier stage while inserting the rock bolt 10 into the borehole 12, i.e. prior to the plunger 42 becoming fully wedged within the tube 30. Nevertheless, even so the ram 44 will still be able to impart a ramming force onto the plunger 42 being enough to force the plunger 42 into the internal axial passage of the tube 30 so that the tube leading end 32 eventually becomes wedged between the plunger’s bearing wall 54 and the rock body 14.

Once fully inserted, the rock bolt 10 functions as a combination of an anchor bolt and a friction bolt, i.e. the frictional fixation of the tube 30 surrounding the plunger 42 acts as a point anchor of an anchor bolt while the frictional engagement of the rock body 14 along the length of the tube 30 acts as a friction bolt.

Accordingly, from the above description, it should be understood that the rock bolt 10 enables the insertion of an anchor bolt (i.e. a rock bolt with an anchor point) in a single step process, for example such as by using only percussion hammering. Furthermore, the use of the ram 44 and its ability to plastically deform avoids the need to accurately drill the borehole 12 to a specified depth and within specified radial tolerances. This is due to the ram 44 experiencing plastic deformation only once the friction force F_f has reached the threshold value which correlates to the anchor being properly frictionally engages with the rock body 14. It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the rock bolt as shown in the specific embodiments without departing from the spirit or scope of the disclosure as broadly described. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive. For example, it should be appreciated that the same functioning can be achieved using a solid plunger having no central bore extending therethrough. Such a plunger will merely have a recess in the plunger’s leading end for receiving and holding the ram. During use the ram will still be able to plastically deform, collapse or fracture once the yield stress exceeds the threshold value - the plastic deformation will merely occur at a different location, such as adjacent the base 20. In the claims which follow and in the preceding description, except where the context requires otherwise due to express language or necessary implication, the word “comprise” or variations such as“comprises” or“comprising” is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the rock bolt.

Claims

1. A rock bolt for use as an anchor bolt or friction bolt in a borehole formed in a rock body, the rock bolt comprising

an elongated member with an internal axial passage, the elongated member having a leading end and an opposed trailing end;

wherein, during use, the ram is configured to abut against the rock body to impart a ramming force onto the plunger and force the plunger into the internal axial passage of the elongated member and thereby outwardly deflect a part of the elongated member.

2. A rock bolt as claimed in claim 1 , wherein the elongated member comprises a tube having a slot extending along its axial length so that the tube is substantially C-shaped in cross-section view.

3. A rock bolt as claimed in claim 1 or 2, wherein a part of the elongated member near to its leading end tapers inwardly.

4. A rock bolt as claimed in any one of claims 1 to 3, wherein the plunger comprises a plunger leading end and a plunger trailing end, the plunger leading end defining a bearing wall which, prior to insertion in a borehole, is configured to project outwardly beyond the leading end of the elongated member, the plunger further comprising a reducing tapered nose extending from the bearing wall towards the plunger trailing end, which nose is configured to be at least partially received within the internal axial passage at the leading end of the elongated member.

5. A rock bolt as claimed in claim 4, wherein the plunger trailing end comprises a cylindrical prop being configured to axially align the plunger within the internal axial passage of the elongated member.

6. A rock bolt as claimed in claim 4 or 5, wherein the leading end of the elongated member is crimped onto the nose of the plunger.

7. A rock bolt as claimed in claim 4 or 5, wherein the leading end of the elongated member is in close frictional fit with the nose of the plunger.

8. A rock bolt as claimed in any one of claims 1 to 7, wherein the plunger comprises an axial bore.

9. A rock bolt as claimed in claim 8, wherein the diameter of the bore is larger at the plunger leading end and the diameter of the bore reduces along its length towards the plunger trailing end.

10. A rock bolt as claimed in claim 8 or 9, wherein the bore is tapered along a part of the axial length of the plunger.

11. A rock bolt as claimed in claim 10, wherein the bore is tapered in a Morse taper.

12. A rock bolt as claimed in any one of claims 1 to 11 , wherein the ram is an

elongated rod having a ram leading end and a ram trailing end, wherein in use the ram leading end is configured to abut the rock body and the ram trailing end is supported by the plunger.

13. A rock bolt as claimed in claims 12, wherein the ram trailing end is contoured to assist in the ram being supported by the plunger.

14. A rock bolt as claimed in any one of claims 1 to 13, wherein the ram is

configured, in use, to impart a temporary ramming force to the plunger such that the ramming force is relieved after a threshold value is exceeded.

15. A rock bolt as claimed in any one of claims 1 to 14, wherein the ram is made of a ductile material that is able, in use, to undergo plastic deformation.

16. A rock bolt as claimed in claim 15, when depending from any one of claims 8 to 14, wherein the ram is configured to be extruded through the bore of the plunger.

17. A rock bolt as claimed in any one of claims 1 to 14, wherein the ram is made of a brittle material that is able, in use, to fracture or collapse.

18. A method of installing a rock bolt in a borehole formed in a rock body, the method comprising the steps of:

supporting a plunger at a leading end of the rock bolt, and joining a ram to the plunger so that the ram projects outwardly beyond the leading end of the rock bolt;

inserting the rock bolt into the borehole so that the ram is coaxially aligned with and positioned downhole of the rock bolt; and

forcing the rock bolt into the borehole so that the ram abuts the rock body to impart a ramming force onto the plunger and force the plunger into an internal axial passage of the rock bolt and thereby outwardly deflect a part of the rock bolt.

19. A method as claimed in claim 18, further comprising the step of relieving the ramming force imparted by the ram after the plunger is sufficiently inserted into the internal axial passage of the rock bolt.

20. A method as claimed in claim 19, further comprising the step of the ram

undergoing plastic deformation.

21. A method as claimed in claim 20, further comprising the step of the ram being extruded through an axial bore extending through the plunger.

22. A method as claimed in claim 19, further comprising the step of the ram

collapsing or fracturing and breaking apart.

23. A method as claimed in any one of claims 18 to 22, further comprising the step of joining the rock bolt to the plunger by crimping the leading end onto the plunger.

24. A plunger for use with a rock bolt or friction bolt in a borehole formed in a rock body, the plunger comprising

a body having a leading end and an opposed trailing end; and a ram supported by the body and configured to project outwardly beyond the leading end,

wherein, during use, the ram is configured to abut against the rock body to impart a ramming force onto the body and force the body into an internal axial passage of a rock bolt and thereby outwardly deflect a part of the rock bolt.

25. A plunger as claimed in claim 24, wherein the body comprises an axial bore.

26. A plunger as claimed in claim 25, wherein the diameter of the bore is larger at the leading end and smaller at the trailing end.

27. A plunger as claimed in claim 25 or 26, wherein the bore is tapered along a part of the axial length of the body.

28. A plunger as claimed in claim 27, wherein the bore is tapered in a Morse taper.

29. A plunger as claimed in any one of claims 24 to 28, wherein the ram is an

elongated rod having a ram leading end and a ram trailing end, wherein in use the ram leading end is configured to abut the rock body and the ram trailing end is supported by the body.

30. A plunger as claimed in claims 29, wherein the ram trailing end is contoured to assist in the ram being supported by the body.

31. A plunger as claimed in any one of claims 24 to 30, wherein the ram is made of a ductile material that is able, in use, to undergo plastic deformation.

32. A plunger as claimed in any one of claims 24 to 30, wherein the ram is made of a brittle material that is able, in use, to fracture.