Rock bolt assembly

Abstract

There is disclosed a rock bolt assembly for installation in a borehole in a rock body. The assembly includes an elongated bolt, having a leading end and a trailing end. The assembly further includes an anchor end sleeve having an axial bore extending therethrough, with the anchor end sleeve being movably mounted onto the leading end of the bolt so that the anchor end sleeve extends beyond the leading end of the bolt. The anchor end sleeve is arranged to receive and enclose a grout cartridge within its bore. The anchor end sleeve is threadably mounted onto the bolt, so that during use the bolt is rotatable relative to the anchor end sleeve thereby to withdraw the anchor end sleeve onto the bolt and expose the grout cartridge.

Description

[0001] Rock bolt assembly

[0002] TECHNICAL FIELD

[0003] The present disclosure relates to a rock bolt assembly.

[0004] More particularly, the present disclosure relates to a rock bolt assembly adapted to be secured in a rock body such as used in mine and / or tunnel construction.

[0005] BACKGROUND

[0006] 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 fixed in the rock body and then used to locate bearing plates or thrust plates to apply a compression force onto the 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.

[0007] Many types of rock bolts are known, and they are generally in the form of an elongated element such as a tube, cable, rod or combinations thereof that is 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 chemical or mechanical means. Chemical fixations utilise an epoxy resin or cement to bond the anchor bolt within the hole, while mechanical fixations normally utilise friction force to jam the rock bolt in place.

[0008] The installation of chemical fixations is normally a multistage process and, in one example, involves drilling a borehole and then introducing the chemical into the borehole, such as a two-part epoxy resin or grout contained in a rupturable carrier cartridge. The rock bolt is then inserted into the borehole while spinning the rock bolt to rupture the cartridge and mix the epoxy resin as the rock bolt passes through the cartridge, whereafter the epoxy resin is allowed to cure and point anchor the rock bolt in the borehole. Finally, the borehole may be filled with grout to both secure the rock bolt along its full length within the borehole, and to protect the rock bolt from corrosion. It is important that the rock bolt is properly point anchored by the epoxy resin at the anchor end of the borehole, i.e. the cartridge must be inserted all the way to the anchor end of the borehole before the cartridge is ruptured, if the cartridge becomes stuck and / or ruptured at a middle part of the borehole, the epoxy resin will set and form a blockage in the borehole that will prevent the subsequent installation of the grout along the full length of the rock bolt. This will severely impact the proper working strength, support depth and lifespan of the rock bolt. The installation of a resin cartridge through broken ground is troublesome for a similar reason because the cartridge can be easily ruptured.

[0009] Ensuring the rock bolt is properly point anchored by the epoxy resin at the downhole end thereof can be particularly challenging - i.e. it is not possible for the operator to see into the borehole (which can be up to nine meters deep having a diameter of about 65 mm, and is obviously rather dark being in an underground environment), particularly after the rock bolt has been inserted into the borehole.

[0010] One method for inserting a cartridge into a borehole is described in the specification of patent AU 2004216606. The method uses a jumbo drill having a tube on to the shank of the drill, the cartridge is inserted into the tube whereafter the drill feeds the tube into the borehole. The cartridge is provided with a retaining cap that engages the borehole so that when the tube is withdrawn from the borehole the cartridge exits the tube. However, due to the confines in the mine passages, the machinery capabilities, and the tube lengths, that method tends to be useful only with boreholes up to two meters in depth.

[0011] 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.

[0012] SUMMARY OF THE DISCLOSURE

[0013] According to a first aspect of the disclosure, there is provided a rock bolt assembly for installation in a borehole in a rock body, the rock bolt assembly comprising:

[0014] an elongated bolt having a leading end and a trailing end;

[0015] an anchor end sleeve having an axial bore extending therethrough, the anchor end sleeve being movably mounted onto the leading end of the bolt, wherein the anchor end sleeve is arranged to extend beyond the leading end of the bolt to enable a grout cartridge to be received and enclosed within its bore; wherein the anchor end sleeve is threadably mounted onto the bolt, so that during use the bolt is rotatable relative to the anchor end sleeve thereby to withdraw the anchor end sleeve onto the bolt and expose the grout cartridge.

[0016] The bore of the anchor end sleeve may have an open leading end that is closed by a cap.

[0017] The anchor end sleeve may have a grooved outer wall.

[0018] The anchor end sleeve may have a castellated edge being arranged in use to shred a sheath of the grout cartridge to release grout from within the grout cartridge into the borehole.

[0019] The rock bolt assembly may further comprise a seal nut being mounted onto the leading end of the rock bolt, with the seal nut being located within the bore of the anchor end sleeve, and wherein the seal nut laterally traverses the bore and is in sliding contact with an inner wall of the anchor end sleeve. In one example the seal nut is arranged to be a locking nut to prevent the anchor end sleeve from being disconnected from the rock bolt. In another example the seal nut is arranged to seal off the bore of the anchor end sleeve during use after the anchor end sleeve has been fully withdrawn onto the bolt.

[0020] In one embodiment the rock bolt assembly comprises a grout cartridge enclosed within the bore of the anchor end sleeve.

[0021] The rock bolt assembly may further comprise

[0022] a collar end sleeve having an axial bore extending therethrough, the collar end sleeve being movably mounted onto the trailing end of the bolt, wherein the collar end sleeve is arranged to extend beyond the trailing end of the bolt to enable a grout cartridge to be received and enclosed within its bore;

[0023] wherein the collar end sleeve is threadably mounted onto the bolt, so that during use the collar end sleeve is rotatable relative to the bolt thereby to advance the collar end sleeve onto the bolt.

[0024] The bore of the collar end sleeve may have an open trailing end that is closed by a blind nut being joined to the trailing end of the collar end sleeve.

[0025] The collar end sleeve may have a grooved outer wall. The collar end sleeve may have at least one opening extending through its side wall so that the bore of the collar end sleeve is open to an outside of the collar end sleeve. In one example the collar end sleeve has a number of spaced apart slots extending through its side wall, wherein the slots are axially elongated and radially spaced around the collar end sleeve. During use, when the collar end sleeve is advanced onto the bolt, the collar end sleeve may express grout through the slots into the borehole.

[0026] The rock bolt assembly may further comprise a frangible shear pin traversing the bore of the collar end sleeve, which shear pin is arranged to engage with the bolt to non-rotatably join the collar end sleeve onto the bolt. In one example the shear pin extends through a hole traversing the collar end sleeve and the bolt.

[0027] In one embodiment the rock bolt assembly comprises a grout cartridge enclosed within the bore of the collar end sleeve.

[0028] According to a second aspect of the disclosure, there is provided a rock bolt assembly for installation in a borehole in a rock body, the rock bolt assembly comprising:

[0029] an elongated bolt having a leading end and a trailing end;

[0030] a collar end sleeve having an axial bore extending therethrough, the collar end sleeve being movably mounted onto the trailing end of the bolt, wherein the collar end sleeve is arranged to extend beyond the trailing end of the bolt to enable a grout cartridge to be received and enclosed within its bore;

[0031] wherein the collar end sleeve is threadably mounted onto the bolt, so that during use the collar end sleeve is rotatable relative to the bolt thereby to advance the collar end sleeve onto the bolt.

[0032] According to a third aspect of the disclosure, there is provided a rock bolt assembly for installation in a borehole in a rock body, the rock bolt assembly comprising:

[0033] an elongated bolt having a leading end and a trailing end;

[0034] an anchor end part provided at the leading end of the bolt, which anchor end part is arranged to be encased by grout within the borehole to be immovably secured to a region of the rock body surrounding the anchor end part;

[0035] an collar end part provided at the trailing end of the bolt, which collar end part is arranged to be encased by grout within the borehole to be immovably secured to a region of the rock body surrounding the collar end part; wherein an intermediate part of the bolt between the anchor end part and the collar end part is not encased by grout.

[0036] In one embodiment the anchor end part comprises an anchor end sleeve mounted on and surrounding the leading end of the bolt, which anchor end sleeve reduces an annulus of the borehole surrounding the leading end of the bolt, thereby to assist in reducing the volume of grout that is required to encase the anchor end part.

[0037] In one embodiment the collar end part comprises a collar end sleeve mounted on and surrounding the trailing end of the bolt, which collar end sleeve reduces an annulus of the borehole surrounding the trailing end of the bolt, thereby to assist in reducing the volume of grout that is required to encase the collar end part.

[0038] BRIEF DESCRIPTION OF DRAWINGS

[0039] The above and other features will become more apparent from the following description and with reference to the accompanying schematic drawings. In the drawings, which are given for purpose of illustration only and are not intended to be in any way limiting:

[0040] Figure 1 is a perspective view of rock bolt assembly;

[0041] Figure 2 is an exploded side view of a top / anchor end part of the rock bolt assembly shown in Figure 1;

[0042] Figure 3 is an exploded side view of a bottom / collar end part of the rock bolt assembly shown in Figure 1;

[0043] Figure 4 is a perspective view of an anchor end mixing sleeve shown in the anchor end part of Figures 1 and 2;

[0044] Figure 5 is a perspective view of a collar end mixing sleeve shown in the collar end part of Figures 1 and 3;

[0045] Figures 6A, 6B and 6C are partial sectional side views of the anchor end part showing installation stages during use of the rock bolt assembly when inserted and secured into a borehole; and

[0046] Figures 7A and 7B are partial sectional side views of the collar end part showing installation stages during use of the rock bolt assembly when inserted and secured into a borehole. DETAILED DESCRIPTION

[0047] In the drawings, and particularly with reference to Figure 1, there is shown a rock bolt assembly 10 that is adapted to be secured in a borehole drilled into a rock body, such as used in mine and / or tunnel construction.

[0048] It should be understood for the purposes of the description herein that the terms “anchor end” or “leading end” or “downhole”, and “collar end” or “trailing end” or “uphole” refer to operative drilling positions or rock bolt I cartridge insertion positions relative to the borehole. Thus the terms “anchor end” or “leading end” or “downhole" are used herein to refer to a position that is deeper within the borehole, while the terms “collar end” or “trailing end” or “uphole” refer to a position that is closer to the opening of the borehole. Furthermore, where reference is made to a “grout cartridge”, it should be understood that this can equally apply to and / or be interchangeable with an “epoxy resin cartridge”.

[0049] The rock bolt assembly 10 includes an elongated bolt 12 having an anchor end 14 and a collar end 16. The bolt 12 can optionally comprise multiple sections 18 that are axially joined together to obtain a bolt 12 of the desired length. In Figure 1, the bolt 12 is shown having two sections 18.1, 18.2 that are joined together by a coupling element 20. In other examples, more than two sections 18 can be joined together with multiple coupling elements 20. Alternatively, the bolt 12 can only include a single section 18, in which case no coupling element 20 will be required. The sections 18 can be provided with standardised dimensions all having the same elongated length, but it is also envisaged that the sections 18 can have differing lengths so that they can be joined together to enable a variation in the total length of the bolt 12. Also, the various sections 18 can be provided with differing diameters. For example, in a bolt 12 having two sections 18, its anchor end section 18.1 and its opposed collar end section 18.2 may have different diameters -alternatively, in a bolt 12 having three or more sections 18, its anchor end section 18.1 and its opposed collar end section 18.2 may have similar diameters, but each intermediate section 18 may have a different diameter. In embodiments where the various sections 18 have different diameters, the coupling elements 20 are reducing or enlarging coupling elements 20 as needed.

[0050] Figure 2 shows an exploded side view of an anchor end part 22 of the rock bolt assembly 10. The anchor end part 22 includes an anchor end sleeve 24 that is threadably engaged onto the terminal leading end of the anchor end section 18.1. The anchor end sleeve 24 is tubular in shape having an axial bore 26 with an inner diameter being larger than an outer diameter of the anchor end section 18.1. As can be more clearly seen in Figures 6A-C, at its uphole end the anchor end sleeve 24 has an inward flange 28 of reduced diameter that is threadably engaged onto a complementary thread of the anchor end section 18.1.

[0051] The anchor end sleeve 24 has a grooved outer wall 30 - in the exemplary embodiment the outer wall 30 has a continuous spiral groove 32 extending along the full axial length of the anchor end sleeve 24. In other examples the outer wall 30 can have one or more helically winding grooves, or the outer wall 30 can have multiple separate grooved bands. In yet other examples the outer wall 30 can have protrusions or deformations.

[0052] The anchor end sleeve 24 has a downhole castellated edge 34, which can be more clearly seen in Figure 4.

[0053] The anchor end sleeve 24 is initially arranged to extend beyond the terminal leading end of the anchor end section 18.1 as shown in Figure 6A. During use, the anchor end sleeve 24 is threaded further onto the anchor end section 18.1 in an uphole direction so that it is located over and surrounds the anchor end section 18.1 as is shown in Figure 6B.

[0054] When in its initial position shown in Figure 6A, the anchor end sleeve 24 is arranged to receive a grout cartridge 36 (or an epoxy resin cartridge) that is housed within the bore 26. The grout cartridge 36 is in the shape of an elongated sausage wherein grout 36.1 is provided within a thin-walled frangible sheath 36.2. A cap 38 is mounted onto the downhole end of the grout cartridge 36. The cap 38 has an annular skirt 40 which is arranged to be press-fit over the end of the grout cartridge 36 to mount the cap 38 thereto. The grout cartridge 36 and / or the skirt 40 are arranged to be initially frictionally held by the anchor end sleeve 24 when inserted into the bore 26, with the cap 38 abutting the castellated edge 34 (as shown in Figure 6A).

[0055] A seal nut 42 is located internally within the anchor end sleeve 24 and threadably mounted onto the leading end of the anchor end section 18.1 and / or bolt 12. The seal nut 42 has a central recess 43 for receiving a hex key spanner so that it can be tightened onto the anchor end section 18.1. The seal nut 42 has an outer diameter being substantially the same as the inner diameter of the bore 26 so that the seal nut 42 laterally traverses the bore 26. The seal nut 42 is in sliding contact with an inner wall of the anchor end sleeve 24. In one aspect the seal nut 42 is arranged to function as a locking nut to prevent the anchor end sleeve 24 from accidentally being disconnected by being unscrewed off from the anchor end section 18.1 during use. In another aspect the seal nut 42 is arranged to support the grout cartridge 36 during use while the anchor end sleeve 24 is withdrawn to its position shown in Figure 6B -this is described in more detail below. In yet another aspect the seal nut 42 is arranged to seal off the bore 26 after the anchor end sleeve 24 has been fully withdrawn onto the bolt 12 to its position shown in Figure 6B.

[0056] Figure 3 shows an exploded side view of a collar end part 44 of the rock bolt assembly 10. The collar end part 44 includes a collar end sleeve 46 that is threadably engaged onto the terminal trailing end of the collar end section 18.2. The collar end sleeve 46 is tubular in shape having a axial bore 50 with an inner diameter being larger than an outer diameter of the anchor end section 18.2. As can be more clearly seen in Figures 7A-B, at its downhole end the collar end sleeve 46 has an inward flange 52 of reduced diameter that is threadably engaged onto a complementary thread of the collar end section 18.2.

[0057] The collar end sleeve 46 has an outer wall 54 that is grooved for a part its axial length, with the remainder of the outer wall 54 being threaded. In the exemplary embodiment the outer wall 54 has a continuous spiral groove 56 extending from its downhole end to approximately mid-way along the axial length of the collar end sleeve 46. The outer wall 54 further has a thread 58 extending from its uphole end to the groove 56. In other examples the outer wall 54 can have one or more helically winding grooves, or the outer wall 30 can have multiple separate grooved bands, in place of the spiral groove 56.

[0058] The collar end sleeve 46 has at least one opening extending through its side wall so that the bore 50 of the collar end sleeve 46 is open to an outside of the collar end sleeve 46. In one example, a number of spaced apart openings will extend through the side wall of the collar end sleeve 46 in the region of the groove 56. In the exemplary embodiment, the openings are slots 48 that are axially elongated and radially spaced around the collar end sleeve 46 -this can be more clearly seen in Figure 5.

[0059] The collar end sleeve 46 has a frangible shear pin 60 traversing and extending across the bore 50, with the shear pin 60 being located within or adjacent to the flange 52. In the exemplary embodiment the shear pin 60 extends through a hole 62 traversing the flange 52 and the bolt 12 so that the collar end sleeve 46 is non-rotatably mounted onto the bolt 12. In another embodiment the shear pin 60 may simply abut against the terminal trailing end of the of the collar end section 18.2 when the collar end sleeve 46 is initially threadably mounted onto the collar end section 18.2.

[0060] A blind nut 64 is threadably mounted onto the thread 58 at the uphole end of the collar end sleeve 46.

[0061] The collar end sleeve 46 is initially arranged to extend beyond the terminal trailing end of the collar end section 18.2 as shown in Figure 7A. During use, the shear pin 60 is severed to allow the collar end sleeve 46 to be advanced and threaded further onto the collar end section 18.2 in a downhole direction so that it is located over and surrounds the collar end section 18.2 as is shown in Figure 7B.

[0062] When in its initial position shown in Figure 7A, the collar end sleeve 46 is arranged to receive a grout cartridge 66 (or an epoxy resin cartridge) that is housed within the bore 50. The grout cartridge 66 is in the shape of an elongated sausage wherein grout 66.1 is provided within a thin-walled frangible sheath 66.2. The grout cartridge 66 is held in place within the bore 50 by the shear pin 60 and / or section 18.2, and the blind nut 64 (as shown in Figure 7A).

[0063] Referring now in particular to Figures 6A-6C and 7A-7B, during use a borehole 100 is drilled into a rock body 102. The borehole 100 has a downhole end wall 104 and an annular side wall 106. The rock body 102 has an outer rock face 108 surrounding the opening to the borehole 100.

[0064] The rock bolt assembly 10 is then assembled by first making up a bolt 12 of a length that is the roughly the same as the length of the borehole 100. Thereafter the anchor end part 22 and collar end part 44 are attached to the bolt 12, with each part respectively housing its grout cartridge 36, 66.

[0065] The rock bolt assembly 10 is then pushed axially into the borehole 100 until the cap 38 abuts against the end wall 104 (see Figure 6A). At this time the rock bolt assembly 10 is not rotated. While being so inserted into the borehole 100, the cap 38 and anchor end sleeve 24 protect the grout cartridge 36 against accidental damage by sharp or rough edges of the rock body 102. While holding the bolt 12 in its axial position within the borehole 100, a drill rig (not shown) can be attached to the blind nut 64 and activated to rotate the bolt 12 - due to the presence of the shear pin 60 the collar end sleeve 46 is initially held non-rotatably on the collar end section 18.2 so that the rotation force from the drill rig is transferred from the blind nut 64 and collar end sleeve 46 to the bolt 12. The rotation of the bolt 12 causes the anchor end sleeve 24 to be threadably rotated onto the anchor end section 18.1, i.e. the anchor end sleeve 24 is withdrawn away from and uncovers the grout cartridge 36. Once the anchor end sleeve 24 is fully withdrawn, its bore 26 is sealed off by the seal nut 42 (see Figure 6B). The seal nut 42 holds the grout cartridge 36 and cap 38 pressed against the end wall 104.

[0066] Subsequently, and while continuing to apply the rotation force by the drill rig, the bolt 12 is again advanced axially further into the borehole 100. The compression of the grout cartridge 36 and its contact against the castellated edge 34 of the anchor end sleeve 24 operate to shred the sheath 36.2 of the grout cartridge 36 to release the grout 36.1 contained therein. In some examples, also the cap 38 will be shredded and / or deformed or pressed flat against the end wall 104. The continuous rotation and downhole axial advancement of the anchor end sleeve 24 mixes the grout 36.1 (or resin components) and expresses the grout 36.1 around the outside of the anchor end part 22 and part of the anchor end section 18.1 (see Figure 6C). The seal nut 42 stops or largely restricts the grout 36.1 from entering into the bore 26 - this is advantageous because normally grout 36.1 that enters into the bore 26 tends to not be mixed properly.

[0067] The rotation of the bolt 12 and the axial advancement thereof is continued until the bolt has penetrated the borehole to a predetermined depth at which the operator will know it is correctly installed. This may be indicated to the operator by a marking indictor on the collar end sleeve 46. It should be appreciated that the continuous rotation of the bolt 12 will also continue to withdraw the anchor end sleeve 24, in the event it was not initially fully withdrawn, while the shredding of the sheath 36.2 and the mixing of the grout 36.1 occur.

[0068] Once no more axial advancement of the rock bolt assembly 10 is detected, and after the rotation has been continued for a sufficient time to fully mix the grout 36.1, the drill rig is stopped so that the grout 36.1 can set hard. Depending on the characteristics of the grout used, the grout 36.1 could fully set hard within a few minutes or less. The groove 32 assists the grout 36.1 adhering to and gripping the anchor end sleeve 24. Thereafter, the drill rig is again started to reapply rotation force to the blind nut 64 and collar end sleeve 46. Due thereto that the anchor end part 22 is now fixedly joined to the rock body 102, the rotation force applied by the drill rig is sufficient to break the shear pin 60, thereby allowing the collar end sleeve 46 to rotate relative to the collar end section 18.2.

[0069] The rotation of the collar end sleeve 46 causes it to be threadably rotated and advanced onto the collar end section 18.2, i.e. the collar end sleeve 46 moves further over the collar end section 18.2 so that the grout cartridge 66 is compressed between the collar end section 18.2 and the blind nut 64. This compression causes the sheath 66.2 of the grout cartridge 66 to rupture and release the grout 66.1 contained therein, which is then expressed through the slots 48 and around the outside of the collar end part 44 and part of the collar end section 18.2 (see Figure 7B). The rotation of the collar end sleeve 46 mixes the grout 66.1 (or resin components). Finally the blind nut 64 butts up against or is threaded onto the terminal end of the collar end section 18.2 to fully compress the grout cartridge 66 and ensure that all the grout 66.1 is extruded therefrom and mixed.

[0070] After the collar end sleeve 46 is fully threaded onto the collar end section 18.2, the drill rig is stopped so that the grout 66.1 can set hard. Depending on the characteristics of the grout used, the grout 66.1 could fully set hard within a few minutes. The groove 56 assists the grout 66.1 adhering to and gripping the collar end sleeve 46. Thereafter the blind nut 64 can be removed to allow attachment of other rock support elements, e.g. such as pressure plates, onto the bolt 12.

[0071] If the rock body 102 experiences a seismic event or ground shifting, the grouting of the collar end part 44 to the rock body 102 assists in spreading any load imparted onto the rock bolt assembly 10 to the rock body 102, i.e. the load is not carried fully and solely by the rock support elements, but the load is carried jointly by the rock support elements and a region of the rock body 102 surrounding the collar end part 44.

[0072] In contrast to other conventional rock bolt assemblies where the bolts are grouted and encased along their full length, the discrete grouting of the anchor end part 22 and the collar end part 44 to the rock body 102 permits the intermediate un-grouted part of the bolt 12 to retain its tensile elongation properties. This assists in avoiding sudden / catastrophic failures of the bolt 12. The rock bolt assembly 10 allows the grout cartridges 36, 66 to be inserted into the borehole 100 without the grout cartridges 36, 66 experiencing any contact with the rock body 102, i.e. the grout cartridges 36, 66 are protected from potential damage by protrusions or sharp edges from the rock body 102.

[0073] A further advantage provided by the rock bolt assembly 10 is that both the anchor end sleeve 24 and the collar end sleeve 46 occupy annulus space in the borehole 100, i.e. reducing the size of the annulus of the borehole surrounding the anchor end part 22 and the collar end part 44. This assist in reducing the volume of grout that is required to encase the anchor end part 22 and the collar end part 44 to fix these to the rock body 102 and allows the rock bolt assembly 10 to be used with drill rigs arranged to drill the more common borehole diameter of 45mm due to the sleeves 24, 26 reducing the annulus. In contrast, prior art grout / resin rock bolts require a much smaller diameter borehole to be drilled because most of these conventional bolts have a bolt diameter of ~20-25mm, which thus require drilling of smaller borehole diameters of about 30-36mm. For this the drill rig must also stock and run a second smaller set of drill consumables, not just drill bits but drill rods, couplings etc.

[0074] It will be appreciated by persons skilled in the art that numerous variations and / or modifications may be made to the rock bolt assembly and its use 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.

[0075] 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 a non-limiting and 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 the various embodiments. A reference to an element by the indefinite article "a" does not exclude the possibility that more than one of the elements is present, unless the context clearly requires that there be one and only one of the elements. Reference numerals

[0076] 10 rock bolt assembly 44 collar end part 12 bolt 46 collar end sleeve 14 anchor end 48 slots

[0077] 16 collar end 50 bore

[0078] 18 section (of bolt) 52 flange

[0079] 20 coupling element 54 outer wall 22 anchor end part 56 groove

[0080] 24 anchor end sleeve 58 thread

[0081] 26 bore 60 shear pin 28 flange 62 hole

[0082] 30 outer wall 64 blind nut 32 groove 66 grout cartridge 34 castellated edge 66.1 grout

[0083] 36 grout cartridge 66.2 sheath 36.1 grout

[0084] 36.2 sheath 100 borehole 38 cap 102 rock body 40 skirt 104 end wall 42 seal nut 106 annular wall 43 recess 108 rock face

Claims

1. CLAIMS1. A rock bolt assembly for installation in a borehole in a rock body, the rock bolt assembly comprising:3.an elongated bolt having a leading end and a trailing end;4.an anchor end sleeve having an axial bore extending therethrough, the anchor end sleeve being movably mounted onto the leading end of the bolt, wherein the anchor end sleeve is arranged to extend beyond the leading end of the bolt to enable a grout cartridge to be received and enclosed within its bore;5.wherein the anchor end sleeve is threadably mounted onto the bolt, so that during use the bolt is rotatable relative to the anchor end sleeve thereby to withdraw the anchor end sleeve onto the bolt and expose the grout cartridge.

2. A rock bolt assembly as claimed in claim 1, wherein the bore of the anchor end sleeve has an open leading end that is closed by a cap.

3. A rock bolt assembly as claimed in claim 1 or 2, wherein the anchor end sleeve has a grooved outer wall.

4. A rock bolt assembly as claimed in any one of claims 1 to 3, wherein the anchor end sleeve has a castellated edge being arranged in use to shred a sheath of the grout cartridge to release grout from within the grout cartridge into the borehole.

5. A rock bolt assembly as claimed in any one of claims 1 to 4, further comprising a seal nut being mounted onto the leading end of the rock bolt, with the seal nut being located within the bore of the anchor end sleeve, and wherein the seal nut laterally traverses the bore and is in sliding contact with an inner wall of the anchor end sleeve.

6. A rock bolt assembly as claimed in claim 5, wherein the seal nut is arranged to be a locking nut to prevent the anchor end sleeve from being disconnected from the rock bolt.

7. A rock bolt assembly as claimed in claim 5, wherein the seal nut is arranged to seal off the bore of the anchor end sleeve during use after the anchor end sleeve has been fully withdrawn onto the bolt.

8. A rock bolt assembly as claimed in any one of claims 1 to 7, which comprises a grout cartridge enclosed within the bore of the anchor end sleeve.

9. A rock bolt assembly as claimed in any one of claims 1 to 8, further comprising a collar end sleeve having an axial bore extending therethrough, the collar end sleeve being movably mounted onto the trailing end of the bolt, wherein the collar end sleeve is arranged to extend beyond the trailing end of the bolt to enable a grout cartridge to be received and enclosed within its bore;13.wherein the collar end sleeve is threadably mounted onto the bolt, so that during use the collar end sleeve is rotatable relative to the bolt thereby to advance the collar end sleeve onto the bolt.

10. A rock bolt assembly as claimed in claim 9, wherein the bore of the collar end sleeve has an open trailing end that is closed by a blind nut being joined to the trailing end of the collar end sleeve.

11. A rock bolt assembly as claimed in claim 9 or 10, wherein the collar end sleeve has a grooved outer wall.

12. A rock bolt assembly as claimed in any one of claims 9 to 11, wherein the collar end sleeve has at least one opening extending through its side wall so that the bore of the collar end sleeve is open to an outside of the collar end sleeve.

13. A rock bolt assembly as claimed in any one of claims 9 to 12, wherein the collar end sleeve has a number of spaced apart slots extending through its side wall, wherein the slots are axially elongated and radially spaced around the collar end sleeve.

14. A rock bolt assembly as claimed in claim 13, wherein during use when the collar end sleeve is advanced onto the bolt, the collar end sleeve expresses grout through the slots into the borehole.

15. A rock bolt assembly as claimed in any one of claims 9 to 14, further comprising a frangible shear pin traversing the bore of the collar end sleeve, which shear pin is arranged to engage with the bolt to non-rotatably join the collar end sleeve onto the bolt.

16. A rock bolt assembly as claimed in claim 15, wherein the shear pin extends through a hole traversing the collar end sleeve and the bolt.

17. A rock bolt assembly as claimed in any one of claims 9 to 16, which comprises a grout cartridge enclosed within the bore of the collar end sleeve.

18. A rock bolt assembly for installation in a borehole in a rock body, the rock bolt assembly comprising:22.an elongated bolt having a leading end and a trailing end;23.a collar end sleeve having an axial bore extending therethrough, the collar end sleeve being movably mounted onto the trailing end of the bolt, wherein the collar end sleeve is arranged to extend beyond the trailing end of the bolt to enable a grout cartridge to be received and enclosed within its bore;24.wherein the collar end sleeve is threadably mounted onto the bolt, so that during use the collar end sleeve is rotatable relative to the bolt thereby to advance the collar end sleeve onto the bolt.

19. A rock bolt assembly for installation in a borehole in a rock body, the rock bolt assembly comprising:26.an elongated bolt having a leading end and a trailing end;27.an anchor end part provided at the leading end of the bolt, which anchor end part is arranged to be encased by grout within the borehole to be immovably secured to a region of the rock body surrounding the anchor end part;28.an collar end part provided at the trailing end of the bolt, which collar end part is arranged to be encased by grout within the borehole to be immovably secured to a region of the rock body surrounding the collar end part;29.wherein an intermediate part of the bolt between the anchor end part and the collar end part is not encased by grout.

20. A rock bolt assembly as claimed in claim 19, wherein the anchor end part comprises an anchor end sleeve mounted on and surrounding the leading end of the bolt, which anchor end sleeve reduces an annulus of the borehole surrounding the leading end of the bolt, thereby to assist in reducing the volume of grout that is required to encase the anchor end part.

21. A rock bolt assembly as claimed in claim 19 or 20, wherein the collar end part comprises a collar end sleeve mounted on and surrounding the trailing end of the bolt, which collar end sleeve reduces an annulus of the borehole surrounding the trailing end of the bolt, thereby to assist in reducing the volume of grout that is required to encase the collar end part.

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