WO2024038298A1

WO2024038298A1 - A rock bolt assembly and associated method

Info

Publication number: WO2024038298A1
Application number: PCT/IB2022/057619
Authority: WO
Inventors: Werner Cornelius BELLINGHAM
Original assignee: Rocbolt Technologies (Pty) Ltd.
Priority date: 2022-08-15
Filing date: 2022-08-15
Publication date: 2024-02-22

Abstract

A rock bolt assembly is for engaging a hole in a rock wall and includes an elongate element, an anchoring part at a dead end, and a washer or rock plate at the live end, the washer or rock plate configured to bear directly against the rock wall. The rock bolt assembly comprises a flange or end stop provided on the elongate element outwardly of the washer or rock plate and a spring provided around the elongate element between the flange and the washer or rock plate. The spring urges the flange and the washer or rock plate apart. When the elongate element is installed in the hole and the spring is compressed against its bias by displacing the flange towards the washer or rock plate, the spring is configured to urge the flange, and hence the elongate element, outwardly thereby tensioning the elongate element and deploying the anchoring part.

Description

A Rock Bolt Assembly and Associated Method FIELD OF INVENTION This invention relates to rock bolts for mining and construction and more specifically to a rock bolt assembly having a spring for quick and easy installation or tensioning. BACKGROUND OF INVENTION A conventional rock bolt assembly or roof bolt assembly with an expansion unit at its dead end (inner/buried end) is known in mining. At a live end (outer/exposed end) of the rock bolt, either a threadable live end (with exposed thread), or a non- threadable live end, are known. This roof bolt assembly may have a drawback in that it must be able to thread through the hole of a washer to create tension in the bolt against the rock face, and therefore requires additional discipline in drilling holes that are longer than the bolt being installed, correct tensioning techniques, etc. If done correctly, this can be time-consuming and may need checking. If done incorrectly, catastrophic failures can result. The Applicant desires a rock bolt assembly which can be installed in a hole in a rock wall relatively easily and quickly, even without specialised tools or advanced skills. The Applicant also desires a rock bolt assembly with a simple tensioning mechanism that is easy to use and even provides an indication of pre-tension or tension. SUMMARY OF INVENTION The invention provides a rock bolt assembly for engaging a hole in a rock wall, the rock bolt assembly comprising: an elongate element having a dead end, which is intended to be inserted into the hole in the rock wall, and a live end, which is intended to be at or outside the hole; an anchoring part provided at the dead end of the elongate element, the anchoring part being configured to engage with the rock wall in response to tensioning of the elongate element; a washer or rock plate at the live end of the elongate element, the washer or rock plate configured to bear directly against the rock wall; wherein the rock bolt assembly comprises: a flange or end stop provided on the elongate element outwardly of the washer or rock plate; and a spring provided around the elongate element between the flange and the washer or rock plate, the spring being configured to urge the flange and the washer or rock plate apart, wherein when the elongate element is installed in the hole and the spring is compressed against its bias by displacing the flange towards the washer or rock plate, the spring is configured to urge the flange, and hence the elongate element, outwardly thereby tensioning the elongate element and deploying the anchoring part. The elongate element may be a rigid shank or rod, e.g., a smooth or threaded shank, resembling a bolt. Instead, the elongate element may be a wire rope or flexible cable; this is still referred to as a “rock bolt assembly”. The spring may at least partially deploy the anchoring part in that the anchoring part may be deployed additionally by another mechanism (e.g., curing of adhesive); instead, the spring may entirely deploy the anchoring part in that the anchoring part is deployed only by the spring. The anchoring part may be in the form of an expansion part. The expansion part may comprise an expansion shell. The expansion part may be configured to deploy the expansion shell to engage with the rock wall in response to tensioning of the elongate element. The expansion part may comprise a locking barrel and wedge to deploy the locking barrel. The anchoring part may include, or may configured to interact with, an adhesive. The anchoring part may comprise a shell or bulb allowing for a resin spin anchor installation. By spinning the anchoring part into a fast-setting resin capsule at a top of the dead end of the hole, the resin may set and cause the spring to tension during the process, e.g., whilst spinning the elongate element into the hole, the resin is mixed, and the spring may compress under the compressive load of a standard roof bolter. Once the spring is compressed (indicating that the elongate element is fully inserted), the resin may set and retain most of the pre-tension created by the spring during installation. The term “adhesive” may be used to include resin, epoxy, grout, cement, or any other settable or curable material to adhere the elongate element (directly or indirectly) to the walls of the hole in the rock wall. The flange may be a nut. The nut may be fixed to the elongate element (e.g., welded, crimped, adhered, swaged, etc.). The nut may be displaceable, e.g., rotatable, relative to the elongate element. The nut may be engageable with, and rotatable on, a thread of the elongate element to displace the nut inwardly or outwardly along the elongate element. The nut may be configured to be rotated to displace it inwardly towards the washer or rock plate, thereby to compress the spring against its bias and further tension the elongate element. The flange may be in the form of a collar, head, lug, or enlarged formation at the live end of the elongate element. The flange may be fixed to the elongate member, e.g., being longitudinally stationary or not being rotatable. The flange may be formed by forging, crimping, swaging, hammering, etc. The spring may be a first spring. The expansion part may also comprise a spring, that is, a second spring. Compression/expansion of the second spring against its bias may cause the expansion part to deploy the expansion shell. A compliance of the first spring may be lower than a compliance of the second spring. In other words, the first spring may be a stiffer (e.g., heavy duty) spring, while the second spring may be a less stiff (e.g., lighter or medium duty) spring. The compliance of the first spring may be an order of magnitude or greater less than the compliance of the second spring (that is, it may be significantly stiffer than the second spring). The washer or rock plate may define an inwardly projecting channel to accommodate at least a portion of the spring. The spring and lug may not project as far outwardly from the washer or rock plate as they would have had there been no channel. This may be useful for low-profile installations, e.g., in low-ceiling mines. A compressive force of the spring may be over 45 kg. It may be in the region of 45–100 kg for hand actuation and over 100 kg (e.g., 100–500 kg) for tool actuation, even as high as 1–2 tons for tool actuation. The invention extends to a method of installing a rock bolt assembly as defined above, the method including: Inserting the rock bolt assembly in the hole in the rock wall, such that the washer or rock plate abuts the rock wall around the hole; urging the live end of the elongate element inwardly against the bias of the spring, thereby to compress the spring; and releasing the live end of the elongate element such that the spring urges the elongate element outwardly relative to the washer or rock plate, thereby tensioning the elongate element and deploying the anchoring part. A compression force of the spring may be 45–100 kg and the urging of the live end of the elongate element inwardly against the bias of the spring may be done by hand, e.g., by a person pushing it inwardly. A compression force of the spring may be over 100 kg and the urging of the live end of the elongate element inwardly against the bias of the spring may be done by a tool like a hammer or jackhammer. The method may include visually observing the spring after tensioning. A compression of the spring may indicate tensioning (e.g., sufficient tensioning), while lack of compression of the spring may indicate tensioning failure. BRIEF DESCRIPTION OF DRAWINGS The invention will now be further described, by way of example, with reference to the accompanying diagrammatic drawings. In the drawings: FIG.1 shows a broken side view of a first embodiment of a rock bolt assembly, in accordance with the invention; FIG.2 shows a broken side view of a second embodiment of a rock bolt assembly, in accordance with the invention; FIG.3 shows a broken side view of a third embodiment of a rock bolt assembly, in accordance with the invention; FIG.4 shows a broken side view of a fourth embodiment of a rock bolt assembly, in accordance with the invention; FIG.5 shows a sectional side view of the rock bolt assembly of FIG.1, installed in a rock wall; FIG.6 shows a sectional side view of the rock bolt assembly of FIG.3, installed in a rock wall; FIG.7 shows a sectional side view of the rock bolt assembly of FIG.4, installed in a rock wall; FIG.8 shows a broken sectional side view of a fifth embodiment of a rock bolt assembly, in accordance with the invention, pre-installation; and FIG.9 shows a sectional side view of a fifth embodiment of the rock bolt assembly of FIG.8 installed in a rock wall. DETAILED DESCRIPTION OF EXAMPLE EMBODIMENT The following description of an example embodiment of the invention is provided as an enabling teaching of the invention. Those skilled in the relevant art will recognise that changes can be made to the example embodiment described, while still attaining the beneficial results of the present invention. It will also be apparent that some of the desired benefits of the present invention can be attained by selecting some of the features of the example embodiment without utilising other features. Accordingly, those skilled in the art will recognise that modifications and adaptations to the example embodiment are possible and can even be desirable in certain circumstances and are a part of the present invention. Thus, the following description of the example embodiment is provided as illustrative of the principles of the present invention and not a limitation thereof. FIG.1 illustrates a first embodiment of a rock bolt assembly 100 in accordance with the invention. The rock bolt assembly 100 is intended for engaging a hole drilled in a rock wall, e.g., for use in mining or construction, to perform an anchoring, support, and/or safety function. By way of naming convention, a “live end” of the rock bolt assembly 100 is intended to be at a face of the hole, or projecting out of the hole, such that it can usually be observed or accessed when installed. Conversely, a “dead end” of the rock bolt assembly 100 is intended to be inside the hole and after installation can usually not be seen or accessed at all. The rock bolt assembly 100 comprises an elongate element 102 in the form of a rigid rod or shaft; more specifically, in this example, the elongate element 102 is a rigid steel rod 102 which can support and maintain a tensile force between its ends, that is, its live and dead ends. Some or all of the rod 102 may be threaded; in this example, both the live and dead ends have a threaded portion 104 which may be used for engaging complementary structures, e.g., nuts, threaded collars, etc. The large washer or rock plate 110 (further referred to merely as a washer 110) is provided at the live end of the rod 102. The washer 110 may be a conventional washer used on various prior art rock bolt assemblies. Regardless of the particular configuration of the washer 110, its function is to bear directly against the rock wall around the hole. The washer 110 has an aperture configured to accommodate the rod 102 which freely passes through the aperture. The washer 110 may be mounted to the rod 102 with a loose or rattle fit, so that the washer may easily travel longitudinally along a length (even just a short length) of the rod 102. A spring 112 is provided between the washer 110 and a flange 114 provided on the rod 112 outwardly of the washer 110. The spring 112 in this example is a helical coil spring made of metal (e.g., steel), but other configurations may be practicable. The flange 114 is provided by a nut 114 which engages the rod 102. The nut 114, on the one hand, and the washer 110, on the other hand, serve as extremities which constrain the spring 112 and which the spring 112 can bear against. When the spring 112 is compressed against its bias, e.g., the nut 114 and the washer 110 are moved together, the spring 112 tends to urge the nut 114 and the washer 110 apart. The nut 114 may be fixed to the rod 102, e.g., forged, swaged, adhered, etc. In fact, in a different embodiment (not illustrated), the flange may be provided by a head integral with the rib 102, e.g., of similar construction to a bolt having an integrally formed head. Instead, the nut 114 may be displaceable relative to the rod 102. For example, the nut 114 may be threaded and may cooperate with the threaded portion 104 of the rod 102. Accordingly, the nut 114 may be rotatable to displace it, thereby to permit longitudinal displacement of the nut 114 along the rod 102. This may be useful for additional tensioning (see further below). A load indicator (or similar indicating component) may be provided at the live end of the rock bolt assembly 100, e.g., between the spring 112 and the nut 114 or between the spring 112 and the washer 110. Prior art indicators may be used and thus need not be discussed further, other than to note that it is an option to include this feature. An anchoring part in the form of an expansion part 120 is provided at the dead end of the rock bolt assembly 100. The expansion part 120 may be a conventional part used in prior art assemblies. In this example, the expansion part 120 comprises an expansion shell 122 which is configured to be urged outwardly to bear against, and engage, sides of the hole and thereby to anchor the rock bolt assembly 100 in the hole. The expansion part 120 also comprises a support structure 124, a spring (being a second spring 126), and a deployment member 128. The second spring 126 is connected between the support structure 124 and the deployment member 128 and holds the expansion part 120 in an undeployed/unengaged state during, e.g., transportation and initial insertion. When the rod 102 is tensioned, the deployment member 128, which is flared/conical in shape, is displaced towards the expansion shell 122 against the bias of the second spring 126 which urges the expansion shell 122 outwardly to bear against and thereby engage sides of the hole. The spring 112 at the live end (which in this case would be the first spring 112) may be a stiffer or less compliant spring than the second spring 126. The spring 112 (whether the only spring or the first spring) may have a force of 45–500 kg when fully compressed. This force may be defined by characteristics of the spring 112, e.g., thickness, number of coils, material, etc. The compressive force (which may be the force required to compress the spring 112 and/or the force exerted by the spring 112 when fully compressed) may be influenced by intended application. For example, if the spring 112 is intended to be compressed by a user (e.g., a mine worker or installer) manually or by hand, that is, without tools, the compressive force may be lower, e.g., 45–100 kg. If the spring 112 is intended to be compressed by a tool, like a hammer or jackhammer, the compressive force may be higher, e.g., 100– 500 kg. The compressive force may be applied to the spring by pressing, striking, etc. The expansion part 120 may be used with other engagement means like an adhesive. Prior art adhesive examples may be used and include cement, grout, epoxy, resin, etc. It is an option to use the additional adhesive, or the expansion part 120 may be used without any additional adhesive. The washer 110 in this embodiment is an outwardly-domed washer 110 having a dogear at one corner for optional connection to accessories. Other washer configurations are contemplated (see below). FIG. 2 illustrates a second embodiment of a rock bolt assembly 200 in accordance with the invention, which is similar to the rock bolt assembly 100 in many ways and the same or similar reference numerals denote the same or similar features. Most notably, the rock bolt assembly 200 has a different washer 210 which is inwardly domed. The configuration of the washer 110, 210 may be dictated by the application of the mine bolt assembly 100, 200 and/or may be modified to interact with the spring 112 differently. As the washer 210 is concave rather than convex, the extremity (e.g., the nut 114) of the rock bolt assembly 200 may project out of the rock wall less than that of the rock bolt assembly 100. FIG.3 illustrates a third embodiment of a rock bolt assembly 300 in accordance with the invention, which, again, is similar to the rock bolt assembly 100 in many ways and the same or similar reference numerals denote the same or similar features. The rock bolt assembly 300 has a different washer 310 which defines and inwardly projecting channel 311 to accommodate a portion of the spring 112 inwardly of an outer exterior of the washer 310. A collar 315 may be provided to limit inward displacement of the nut 114. An advantage of this rock bolt assembly 300 is that in applications where space is limited, e.g., low seam installations, an outward distance which the live end (particularly the nut 114) projects can be minimised. FIG.4 illustrates a fourth embodiment of a rock bolt assembly 400 in accordance with the invention. This rock bolt assembly 400 differs more significantly from the previous three rock bolt assemblies 100, 200, 300 in that it has a wire or flexible cable 402 as the elongate element rather than a rigid rod 102. The wire cable 402 is at least partially bendable but can nonetheless maintain a tensile force (even if it cannot maintain a compressive force as well as a rod). Some installations may prefer wire cable-based rock bolt assemblies 400 over rod-based assemblies 100, 200, 300. A washer 410 is provided together with an intermediate nut 411 against which the spring 112 can bear (the spring 112 thus bearing indirectly against the washer 410). The intermediate nut 411 is not fixed to the wire cable 402 but can travel along it. The flange is provided by a tubular collar 414 fixed in place on the wire cable 402 with wedges 415. Accordingly, even though the configuration appears slightly different from previous embodiments, the spring 112 is still configured to act between the collar 414 (or fixed flange) and the washer 410 (via the intermediate nut 411. An expansion part 420 is also slightly differently configured in that it is configured for use with the flexible wire cable 402, but its principle of operation is the same. Again, the expansion part 120 may (in itself) be a conventional part used in prior art assemblies. The expansion part 420 comprises an expansion shell 422 which is configured to be urged outwardly to bear against, and engage, sides of the hole and thereby to anchor the rock bolt assembly 400 in the hole. The expansion part 420 also comprises a support structure 424, a spring (being a second spring 426), and a deployment member 428. The rock bolt assembly 400 may be inserted into the hole differently from the rock bolt assemblies 100, 200, 300 as it cannot reliably maintain a compressive force – it may be inserted using prior art techniques. Further, insertion of any of the rock bolt assemblies 100, 200, 300, 400 may be done in accordance with prior art techniques; notably, it is the tensioning of the elongate element 102, 402 which may differ in accordance with the invention, as will now be described. FIG.5 illustrates the rock bolt assembly 100 installed in a hole 12 drilled in a rock wall 10. The hole 12 may be drilled in accordance with prior art drilling techniques. The rock bolt assembly 100 is fed into the hole 12 with the expansion part 120 first, until the washer 110 abuts the rock wall 10. Then, the live end, e.g., the nut 114, is pushed (by hand or by tool) inwardly towards the hole 12 against the bias of the first spring 112 which causes the first spring 112 to compress between the washer 110 and the nut 114. The nut 114 is pushed inwardly as far as it will travel, that is, until the first spring 112 is fully compressed, as illustrated in FIG.5. Next, the nut 114 is released, that is, the pushing force is stopped. The first spring 112 urges the washer 110 and nut 114 apart. As the washer 110 abuts the rock wall 110 and therefore cannot move, the nut 114 and the rod 102 to which it is connected are urged outwardly, which causes the expansion part 120 to deploy. As the expansion part 120 may be a prior art part, the deployment mechanism need not be described in depth, but will be discussed briefly. The first spring 112 is far stiffer than the second spring 126 and therefore easily expands the second spring 126 and urges the deployment member 128 downwardly. A bottom edge of the expansion shell 122 (or a retaining ring thereof) is in contact with sides 14 of the hole 12 so the expansion shell 122 does not move downwardly but rather is displaced outwardly to engage with the walls 14. Once it is engaged fully and cannot be outwardly displaced any further, the deployment member 128 and hence the rod 102 stops moving and will be considered tensioned (or pre-tensioned if a further tensioning step is envisaged). The first spring 112 will remain at least partially compressed, providing a visual indication that the rod 102 is tensioned and the expansion part 120 is properly deployed to engage the rock bolt assembly 100 in the hole 12 of the rock wall 10. FIG.6 illustrates the wall bolt assembly 300 engaged with sides 14 of the hole 12 of the rock wall 10 in the same way as was discussed with reference to FIG.5, but the channel 311 has been accommodated in an end of the hole 12, creating a live end with a lower profile than that of the rock bolt assembly 100 of FIG.5. This may be suitable were space is at a premium, e.g., in low seam mining. Also, the spring 112 might not be visible, the position of the nut 114 relative to the washer 310 provides a visual indication of tensioning. FIG.7 shows the rock bolt assembly 400 with the wire cable 402 installed in the rock wall 10. The expansion part 420 engages the sides 14 of the hole 12 and tensions the wire cable 402 which maintains the tension just as the rod 102 of FIGS 5–6 did. The spring 112 is compressed between the intermediate nut 411 and the collar 414. FIGS 8–9 illustrate a rock bolt assembly 401 similar to the rock bolt assembly 400, but instead of an expansion part 420 to engage the sides 14, it has an anchoring part comprising an enlarged portion 403 of the wire cable 402 with at least one bulb 404 held captive therein to be anchored in a resin capsule16. This may be attained by using a fast-setting resin capsule 16 at a top of the dead end of the hole 12; the resin sets and causes the spring 112 to tension during the process, e.g., whilst spinning the wire cable 402 into the hole 12, the resin 16 is mixed, and the spring 112 compresses under the compressive load of a roof bolter and once the spring 112 is compressed (indicating that the wire cable 402 is fully inserted) the resin will set and retain most of the pre-tension created by the spring 112 during installation. This may be considered a chemical anchor or adhesive-based anchoring. The spring 112 may have some spring-back once the end adheres and engages, but this can be compensated for by using a slightly longer spring. Thus, the wire cable- based rock bolt assembly 401 may not show a fully compressed spring 112 in most cases, but the spring 112 will nonetheless generate tension. If desired, the rock bolt assemblies 100, 200, 300 could be configured for further tensioning, e.g., using a torque wrench on the rotatable nut 114. Accordingly, a reference to “tension” may include pre-tension or a single step in a multi-step process. The Applicant believes that the invention as exemplified provides an improved rock bolt assembly 100, 200, 300, 400, 401 which can quickly and easily be tensioned or pretensioned. The tensioning may be done either by hand (for a more compliant spring 114) or with basic tools (for a stiffer spring 114). This may not require advanced skills or advanced tools (although the rock bolt assembly 100, 200, 300, 400, 401 could also be used in conjunction with more advanced tensioning techniques, if desired). The rock bolt assembly 100, 200, 300, 400, 401 provides a basic visual indication that the elongate element 102, 402 is tensioned by a visible degree of compression of the spring 112 (or, in the case of the rock bolt assembly 300, a spacing of the nut 114 relative to the washer 310). This is useful as it can provide an immediate and/or ongoing indication of the tension of the elongate element 102, 402. For example, this can immediately indicate if the rock bolt assembly 100, 200, 300, 400, 401 has been installed correctly (if the spring 112 is compressed) and/or can indicate later if some failure has occurred (if the spring 112 becomes uncompressed or loses its initial compression). Again, the rock bolt assembly 100, 200, 300, 400, 401 may be used in conjunction with other load indicators like deformable members or electronic means.

Claims

CLAIMS 1. A rock bolt assembly (100; 200; 300; 400; 401) for engaging a hole (12) in a rock wall (10), the rock bolt assembly (100; 200; 300; 400; 401) comprising: an elongate element (102; 402) having a dead end, which is intended to be inserted into the hole (12) in the rock wall (10), and a live end, which is intended to be at or outside the hole (12); an anchoring part (120; 420; 403, 404) provided at the dead end of the elongate element (102; 402), the anchoring part (120; 420; 403, 404) being configured to engage with the rock wall (10) in response to tensioning of the elongate element (102; 402); a washer or rock plate (110; 210; 310; 410) at the live end of the elongate element (102; 402), the washer or rock plate (110; 210; 310; 410) configured to bear directly against the rock wall (10); characterised in that the rock bolt assembly (100; 200; 300; 400; 401) comprises: a flange or end stop (114; 414) provided on the elongate element (102; 402) outwardly of the washer or rock plate (110; 210; 310; 410); and a spring (112) provided around the elongate element (102; 402) between the flange (114; 414) and the washer or rock plate (110; 210; 310; 410), the spring (112) being configured to urge the flange (114; 414) and the washer or rock plate (110; 210; 310; 410) apart, wherein when the elongate element (102; 402) is installed in the hole (12) and the spring (112) is compressed against its bias by displacing the flange (114; 414) towards the washer or rock plate (110; 210; 310; 410), the spring (112) is configured to urge the flange (114; 414), and hence the elongate element (102; 402), outwardly thereby tensioning the elongate element (102; 402) and deploying the anchoring part (120; 420; 403, 404).

2. The rock bolt assembly (100; 200; 300; 400; 401) as claimed in claim 1, in which the elongate element (102; 402) is one of: a rigid shank or rod (102); or a flexible cable (402).

3. The rock bolt (100; 200; 300) assembly as claimed in any one of claims 1–2, in which the flange is a nut (114).

4. The rock bolt assembly (100; 200; 300) as claimed in claim 3, in which the nut (114) is threadedly engaged with the elongate element (102) and is rotatable to displace the nut (114) inwardly or outwardly along the elongate element (102).

5. The rock bolt assembly (100; 200; 300) as claimed in claim 4, in which the nut (112) is configured to be rotated to displace it inwardly towards the washer or rock plate (110; 210; 310) , thereby to compress the spring (112) against its bias and further tension the elongate element (102).

6. The rock bolt assembly (400; 401) as claimed in any one of claims 1–3, in which the flange (414) is fixed to the elongate element (402).

7. The rock bolt assembly (100; 200; 300; 400) as claimed in any one of claims 1– 6, in which the anchoring part (120; 420) is an expansion part (120; 420) comprising an expansion shell (122; 422), wherein the expansion part (120; 420) is configured to deploy the expansion shell (122; 422) to engage with the rock wall (10) in response to tensioning of the elongate element (102; 402).

8. The rock bolt assembly (100; 200; 300; 400) as claimed in claim 7, in which the spring (112) is a first spring (112) and the expansion part (120; 420) comprises a second spring (126, 426), wherein compression of the second spring (126, 426) against its bias causes the expansion part (120; 420) to deploy the expansion shell (122; 422), in which a compliance of the first spring (122) is lower than a compliance of the second spring (126, 426).

9. The rock bolt assembly (300) as claimed in any one of claims 1–8, in which the washer or rock plate (310) defines an inwardly projecting channel (311) to accommodate at least a portion of the spring (112).

10. The rock bolt assembly as claimed in any one of claims 1–9, which additionally includes load indicator provided at the head outwardly of the washer or rock plate.

11. The rock bolt assembly (100; 200; 300; 400; 401) as claimed in any one of claims 1–10, in which a degree of compression of the spring (112) after tensioning the elongate element (102; 402) provides a visual indication of the tensioning of the elongate element (102; 402).

12. The rock bolt assembly (401) as claimed in any one of claims 1–11, in which the anchoring part (403, 404) is configured to interact with an adhesive (16) to adhere the elongate element (402) to the rock wall (10).

13. A method of installing a rock bolt assembly (100; 200; 300; 400; 401) as claimed in any one of claims 1–12, the method including: inserting the rock bolt assembly (100; 200; 300; 400; 401) in the hole (120) in the rock wall (10), such that the washer or rock plate (110; 210; 310; 410) abuts the rock wall (10) around the hole (12); urging the live end of the elongate element (102; 402) inwardly against the bias of the spring (112), thereby to compress the spring (112); and releasing the live end of the elongate element (102; 402) such that the spring (112) urges the elongate element outwardly (102; 402) relative to the washer or rock plate (110; 210; 310; 410), thereby tensioning the elongate element (102; 402) and deploying the anchoring part (120; 420; 403, 404).

14. The method as claimed in claim 13, in which a compression force of the spring (112) is 45–100 kg, the urging of the live end of the elongate element (102) inwardly against the bias of the spring being done by hand.

15. The method as claimed in claim 13, in which a compression force of the spring (112) is over 100 kg, the urging of the live end of the elongate element (102; 402) inwardly against the bias of the spring (112) being done by a tool.

16. The method as claimed in any one of claims 13–15, in which the steps of urging and releasing may be repeated until the elongate element (102; 402) is tensioned.