WO2016029266A1

WO2016029266A1 - Rock bolt and method of stabilizing excavations

Info

Publication number: WO2016029266A1
Application number: PCT/AU2015/050497
Authority: WO
Inventors: Kevin Frank STACEY
Original assignee: Stacey Kevin Frank
Priority date: 2014-08-28
Filing date: 2015-08-27
Publication date: 2016-03-03
Also published as: AU2015309690A1

Abstract

A rock bolt assembly having a collapsible resin reservoir and a resin passage means which allows uncured resin to pass to the distal end unobstructed. The invention also relates to a rock bolt which has a predetermined amount of axial displacement when installed and to a rock bolt assembly suitable for one pass installation. The invention also provides methods of stabilization of an excavation or unstable ground.

Description

Title: Rock Bolt and Method of Stabilizing Excavations

Field of Invention

[0001 ] The present invention relates to the use of rock bolts in mining, civil tunnelling or stabilisation of rock slopes.

Background

[0002] Rock bolts are long bolts which function as anchors to stabilize rock excavations and ground.

[0003] There are a great number of rock bolts and stabilizers described in the patent literature.

[0004] These include hollow rock bolts, solid rock bolts and various methods of mixing the adhesive compounds used to secure some rock bolts.

[0005] Some proposals are concerned with obtaining better adhesion or friction and to some extent better responses to seismic events or deformation.

[0006] For example, Australian patent application 2010237600 in the name of Gazmick discloses a method of installing a hollow stabilizer sheathed in a load transfer medium optionally with a cover, wherein the medium is formed by casting or molding. The method is directed at providing an improved system for installation of stabilizers using a load transfer medium made up of a material that is essentially non-compressible.

[0007] Australian patent application number 2001246246 in the name of Gazmick discloses a method of installing a solid or other single material tendon stabilizer by providing filler which enables frictional engagement of the stabilizer with the surrounding environment, the filler having less strength than the tensile strength of the stabilizer. The stabilizer may have a deformable additive such as particulate material including polyurethanes.

[0008] Other proposals include W0 2014/071442 in the name of Rise Mining Developments Proprietary Limited which relates to a sheathed hollow rock bolt having an elongated body made of resilient material with high tensile strength and US patent 7465128 in the name of Bruneau which discloses a solid bolt with an elastically deformable expansion sheath operated by wedges. [0009] Some proposals are concern with resin deployment. For example, US patent 4263832 in the name of Lang discloses a solid rock bolt with a resin cartridges deployed on the end of the bolt.

[0010] PCT/AU 2013/001287 in the name of Gazmick discloses a device for installing resin or grout comprising a chamber and a plunger like thrust member which is fitted on the end of the rock bolt. The chamber and thrust member have aligned central passages through which the rock bolt is pushed and which fractures a frangible part to allow further passage of the rock bolt into the borehole.

[001 1 ] US patent 4607984 in the name of Cassidy discloses a rock bolt comprising a solid bar which is a complex structure with a threaded sleeve that rotates together with the bar to obtain mixing of the resin.

[0012] US patent 6033153 in the name of Fergusson discloses a plastically deformable sleeve fitted over a resin cartridge at the end of a hollow rock bolt.

[0013] While the above proposals may have merit there is still a need for a solid rock bolt which may be produced economically, is practical to install and optionally has good energy absorbing characteristics. The present inventor aims to ameliorate at least some of the problems with prior art rock bolts.

[0014] The above references to and descriptions of prior proposals or products are not intended to be, and are not to be construed as, statements or admissions of common general knowledge in the art.

Summary

[0015] In one aspect the present invention provides a rock bolt assembly comprising: a) a rock bolt with a solid shaft having an outer surface along its length and a distal end portion with a suitable distal end for insertion into a borehole and a proximal end portion with a suitable proximal end for engaging an opening of a borehole; b) at least one collapsible resin reservoir associated with said shaft; c) a resin passage means adjacent said outer surface which runs between said portions and allows uncured resin to travel from said reservoir to the distal end portion and; d) an adjacent passage shielding means; wherein b), c) and d) are arranged such that, in use when said resin reservoir is collapsed uncured resin can pass unobstructed to said distal end portion.

[0016] The term "a rock bolt" refers to a bolt inserted into a borehole to promote stability in a rock mass in the vicinity of an excavation or other disturbance.

[0017] The term "assembly" refers to the rock bolt and optionally additional items components required for installation to the rock face such as resin cartridges, bolt plates and the like.

[0018] The term "a solid shaft" refers to a solid mass of material making up the bolt.

[0019] The term "distal end portion" refers to an end portion of the rock bolt which is furthest away from the user.

[0020] The term "a suitable distal end" refers to the end being wider than the remainder of the bolt or having some other stop means to prevent the bolt from pulling out of the borehole or through the passage shielding means.

[0021 ] The term "proximal end portion" refers to an end portion of the rock bolt nearest to the borehole opening in use.

[0022] The term "suitable proximal end" refers to an end being engageable with a bolt plate or the like.

[0023] The term "collapsible resin reservoir" refers to a reservoir or a part of a reservoir which is collapsible or compressible such that its contents can be squeezed out. The reservoir is suitable for delivering resin, or resin precursors and includes a two-part reservoir (one for part A and one for part B) where a two pack resin is utilized. The resin used has a suitably low viscosity to be squeezed out of the reservoir.

[0024] Preferably the resin reservoir is of suitable shape and dimensions to be disposed coaxially on the shaft. The resin reservoir may be a two part reservoir. More preferably the resin reservoir comprises two half cylinders each with a hollow section which are disposed on said passage shielding means. [0025] The term "resin passage means" refers to a means for allowing the uncured resin to travel along a length of the shaft. This will generally be a void, a tube or lumen. The resin passage means has an opening, aperture or gland which allows resin from the reservoir to enter the passage means and an opening or openings at the distal end to allow resin to exit.

[0026] The term "passage shielding means" refers to means such as a shield, sheath, casing or barrier which protects the resin passage means, optionally in cooperation with other members from ingress or impingement of rocks and other debris which may be present in the borehole. In addition it also assists in protecting the shaft from corrosion.

[0027] Preferably the passage shielding means is a sheath of suitable material and said resin passage means is at its simplest an opening or gap between the shaft and the sheath.

Alternatively it may be a lumen formed in the sheath or a tube disposed between the shaft and the sheath.

[0028] More preferably the passage shielding means is a sheath of suitable material. More preferably the passage shielding means is high density polyethylene (HDPE).

[0029] The rock bolt assembly preferably includes e) a resin mixing means associated with the resin reservoir.

[0030] The term "a resin mixing means" refers to a space, chamber or cavity for mixing the components and optionally includes static or moveable elements such as paddles or fins for mixing.

[0031 ] In another aspect the present invention provides a rock bolt which allows a

predetermined amount of axial displacement when installed in a borehole, said rock bolt comprising: a) a solid shaft; b) an adjacent first zone which encases or partly encases said shaft; c) and associated second zone engageable with an anchoring compound said second zone encasing or partially encasing said shaft and/or said first zone; d) wherein said first zone is capable of absorbing more energy than said second zone; e) wherein when appropriately installed and a suitable load is applied the bolt is capable of absorbing energy by moving through said first zone until it reaches said second zone and; f) wherein the shaft is adapted to retard movement through said zones and said predetermined amount of axial displacement is related to the size of the first zone.

[0032] The term "predetermined amount of axial displacement when installed in a borehole" refers to a desired distance the bolt moves along its long axis in relation to the anchoring compound.

[0033] The term "first zone" refers to a zone of suitable material adjacent the shaft which is capable of absorbing more energy than the material of the second zone. Energy is absorbed via non-elastic deformation of the first zone such as being able to be compressed or collapsed.

[0034] The term "encases" refers to the shaft are being enclosed, sheathed or covered or partly enclosed, sheathed or covered by the first zone.

[0035] The term "second zone" refers to the zone where the materials are located which will primarily anchor the bolt to the borehole in cooperation with the anchoring compound. This will commonly comprise a high strength material which can form high bond strength with a chemical anchoring compound such as cured resin thus providing a rigid zone. Material for the second zone may be for example suitable polyolefins, HDPE, polyurethane foam and the like optionally with raised or corrugated profile to increase bond strength with the anchoring compound. The second zone may comprise the sheath described earlier.

[0036] The term "engageable with an anchoring compound" refers to the zone being able to cooperate with the anchoring compound to form suitable frictional engagement with the borehole.

[0037] The term "wherein the shaft is adapted to retard movement through said zones" refers to a physical feature of the shaft such as a flared toe end, a thread and nut arrangement at the toe end or a high pitched thread or knurling or other deformations along the outside of the shaft which create friction as the shaft moves through the zones.

[0038] The term "said predetermined amount of axial displacement is related to the size of the first zone" refers to the distance or length of travel of the bolt in an axial direction as a function of the distance or width of the first zone. [0039] The first zone and the second zone may be disposed in a coaxial arrangement along the length of the bar. Alternatively these zones may be disposed in a linear arrangement with the first zone having the energy absorbing properties located at the toe end of the bar.

[0040] In yet another aspect the invention provides a rock bolt assembly suitable for one pass installation comprising: a) a rock bolt with a solid shaft; said rock bolt comprising: i) a suitable distal end for insertion into a borehole; ii) a suitable proximal end for engaging an opening of a borehole; iii) a distal portion located at said distal end and a proximal portion located at said proximal end; iv) an intermediate portion located between said ends; v) said distal portion at least partially encased in a relatively soft deformable material; vi) said intermediate and proximal portions at least partially encased in a relatively non-deformable material or a precursor thereof; b) an associated resin extrusion means comprising a collapsible resin reservoir said resin extrusion means enabling resin to be extruded through or past said non-deformable material; d) wherein when appropriately installed and a suitable load is applied the bolt is capable of absorbing energy by moving through said relatively soft deformable material until it reaches said relatively non-deformable material and; e) wherein application of the rock bolt into a suitable borehole and extrusion of resin can be performed simultaneously or in rapid succession by collapsing said resin reservoir and allowing uncured resin to the pass unobstructed to said distal end portion.

[0041 ] The term "one pass installation" refers to the operation of drilling a borehole and installing a bolt being performed by one crew/machine.

[0042] The term "at least partially encased" means that the surface of the bolt is at least partly enclosed or covered by the relatively soft deformable material.

[0043] The term "deformable material" refers to material which can compress or collapse. The term "relatively soft" means that the material is comparatively easier to deform (i.e. absorbs more energy) than the "relatively non-deformable material". The relatively non-deformable material is resistant to deformation and is relatively more rigid.

[0044] The term "resin extrusion means" refers to a means for obtaining extrusion or dispensing of resin along the bolt. Preferably the resin extrusion means includes cylinders or half cylinders with hollow sections suitable for mounting concentrically adjacent said proximal end. In addition, preferably the assembly also comprises a resin passage means and a passage shielding means. [0045] In yet another aspect the present invention provides a system for installing a rock bolt for stabilising excavations or unstable ground, said system comprising providing: i) a rock bolt with a solid shaft having an outer surface along its length and a distal end portion with a suitable distal end for insertion into a borehole and a proximal end portion with a suitable proximal end for engaging an opening of a borehole; ii) a resin passage means engageable with a resin reservoir, said resin passage means adjacent said outer surface, running between said portions and able to allow uncured resin to travel to the distal end portion; iii) an adjacent passage shielding means; and iv) at least one collapsible resin reservoir adjacent said shaft; wherein ii), iii), and iv) are arranged such that, in use when said resin reservoir is collapsed uncured resin can pass unobstructed to said distal end portion.

[0046] In a further aspect the invention provides a method of manufacturing a rock bolt assembly said method comprising the steps of: i) providing a rock bolt with a solid shaft having an outer surface along its length and a distal end portion with a suitable distal end for insertion into a borehole and a proximal end portion with a suitable proximal end for engaging an opening of a borehole; ii) applying to said rock bolt a passage shielding means to form a resin passage means or otherwise providing a passage shielding means and associated resin passage means; wherein said resin passage means is adjacent said outer surface and runs between said portions, and is engageable with a suitable resin reservoir and in use allows uncured resin to travel to the distal end portion.

[0047] In yet a further aspect the present invention provides method of manufacturing a rock bolt which in use allows a predetermined amount of axial displacement when installed in a borehole said method comprising the steps of: i) applying to a suitable shaft a first zone which encases or partially encases the shaft, and; ii) applying a second zone engageable with an anchoring compound which encases or partially encases said shaft and/or said first zone wherein said first zone is capable of absorbing more energy than said second zone; wherein when appropriately installed and a suitable load is applied the bolt is capable of absorbing energy by moving through said first zone until it reaches said second zone and; wherein the shaft is adapted to retard movement through said zones and said predetermined amount of axial displacement is related to the size of the first zone.

[0048] The present invention also relates to a method of installing a rock bolt according to the invention and methods of stabilizing excavations comprising installing a plurality of the rock bolts. Detailed Description of Illustrative Embodiments of the Invention

[0049] The invention will now be described with reference to the following non limiting illustrative drawings.

[0050] Figure 1 a is a side view of the full-length rock bolt assembly of one embodiment of the present invention with bolt plate shown in ghost lines and positioned prior to installation of the bolt.

[0051 ] Figures 1 b to 1 e are cross sections through the rock bolt assembly of figure 1 a from the distal end to the proximal end respectively.

[0052] Figure 2 is a compressed side view of the embodiment of the rock bolt assembly shown in figure 1 which includes a resin deployment system.

[0053] Figure 3 is a compressed side view of another embodiment of a rock bolt of the present invention without a resin deployment system.

[0054] Figure 4a is a side view of a full length rock bolt assembly of another embodiment of the present invention.

[0055] Figure 4b is a detailed view of part of the proximal end portion and associated resin extrusion means of the rock bolt assembly of figure 4a.

[0056] Figure 4c is a cross section through the proximal end portion and associated resin extrusion means.

[0057] Figure 5 is a side view of a jumbo boom and drilling module loaded with a rock bolt assembly of the present invention ready for installation.

[0058] Before describing the preferred embodiments of the present invention it would be useful to outline current procedures. Current resin bolt installation involves: drilling a hole, inserting a long resin sausage into a plastic tube attached to the drill, attempting to push the plastic tube into the hole, pushing the bolt into the hole, rotating the bolt to break the resin sausage and mix the two parts of the resin. In practice it is fiddly, very time consuming, and not possible if the ground is broken as the hole blocks up. The time consuming part is what costs huge amounts to the company installing the bolts. It is this aspect that is the most important to rectify. The other problem with resin bolts is that they are very rigid and do not respond well to seismic conditions or other circumstances where the bolt is caused to slip.

[0059] Figure 1 shows rock bolt assembly 100 including rock bolt 10 having shaft 15 with intermediate portion 20 which lies between distal end portion 30 at one end and proximal end portion 40 at the other end. Resin extrusion means 70 is located at proximal end portion 40.

[0060] Rock bolt assembly 100 shown in Figure 2 comprises rock bolt 10, protective casing sheath 55, cushioning sheath 85, two part resin reservoir 73 and combined nut/dome ball washer 46.

[0061 ] Rock bolt 10 comprises at its core solid shaft 15 made of steel with outer surface 15a. Rock bolt 10 runs between distal end 35 and proximal end 45. Flared toe 37 at distal end 35 is designed to go to the back of a borehole while proximal end 45 and combined nut/dome ball washer 46 is suitable for attachment of plate 47 adjacent the opening on the rock face when the bolt is installed.

[0062] Passage shielding means 50 in the form of sheath 55 is made of high density polyethylene (HDPE) which is adjacent shaft 15 and encases most of the length of bolt 10 except for distal end portion 30 and a small section of proximal end portion 40. Sheath 55 is substantially static in relation to (i.e. moves in unison with) shaft 15 when being installed. Sheath 50 is also relatively rigid so as to avoid impingement from rocks or debris in the borehole. Sheath 55 has resin passage means 60 in the form of conduits 67 through which resin can be dispensed.

Sheath 55 also has flared ring 56 near proximal end 45 for sealing mixing cavity 78. Sheath 55 may be made of any suitable compression resistant material such as polyurethane or

polyethylene or another material which may be slid onto, moulded or extruded around shaft 15.

[0063] Resin passage means 60 in the form of conduits 67 are formed of suitable plastic tubing. Conduits 67 run either side of shaft 15 from near proximal end 45 to near distal end portion 30 and have openings at each end. While in the embodiment shown conduits 67 are separate structures, resin passage means 60 may be lumens formed in protective sheath 55 or may comprise a generally annular void or gap between sheath 55 and shaft 15. [0064] Resin extrusion means 70 comprises collapsible two part resin reservoirs/cartridges in the form of half cylinders 73, and resin mixing means provided by mixing fins 75 and mixing chamber 78.

[0065] Half cylinders 73 comprise a hollow section so that they can snugly fit around the periphery of sheath 55 and when fitted come together to form a casing at proximal end portion 40.

[0066] Each half cylinder 73 comprises curved wall 73a, sloped end wall 73b and flat end wall 73c adjacent mixing chamber 78. Curved wall 73a is made from vinyl or other suitably compressible/collapsible plastic whereas sloped end wall 73b and flat end wall 73c are made of rigid PVC. Sloped end wall 73b designed to minimize premature compression of the cartridges as they pass through the first centralizer in the Jumbo boom 300.

[0067] Mixing chamber 78 is essentially a short open cylinder (which is an extension of flat end walls 73c) which mates with rubber covered head of dome ball washer 46 to form a pressure tight seal. Mixing chamber 78 contains tapered mixing fins 75 made from the poly vinyl chloride (PVC) and pressure release valves 79.

[0068] In use cylinder walls 73b jam up against bolt plate 47; continued pushing of bolt assembly 100 into borehole (not shown) causes curved wall 73a to start to collapse and resin components to be squeezed from cartridges 73 through pressure release valves 79 into mixing chamber 78. Resin is mixed by mixing fins 75 and then pushed into conduit 67 along and out near distal end 35 via openings and once cured, resin will grip inside and outside sheath 55 thus forming a rigid structure. Although the mixing fins starts the mixing process as the resin is pushed through the pipe or lumen there will be some amount of turbulent flow which also mixes the two resin parts. Optionally flexible netting in the form of plastic spider 87 covers end of cushioning sheath 85 may be employed. This can best be seen in figure 1 b. Plastic spider 87 is to help to avoid waste by preventing resin from going past distal end 35. To some extent cushioning sheath 85 also provides a plug at the end of the borehole.

[0069] It will be appreciated that such a resin deployment system which is physically confined within the length of the bolt does not add to the length of the bolt in the restricted spaces encountered below ground. It will also be recognized that such a resin deployment system which is external to the bolt and has resin parts separate until installation allows economical manufacture of the bolt. Further the resin deployment system enables resin to be reliably delivered to the distal end of the bolt.

[0070] The rock bolt assembly and associated resin deployment system of the present invention is in contrast to that disclosed in PCT/AU2013/001287 (Gazmick). The Gazmick system involves a device which is loaded onto the end of the rock bolt therefore increasing the overall length of the apparatus limits the length of the bolt able to be installed given the amount of room adjacent the opening is typically strictly limited. In addition, deployment of fixative using the Gazmick plunger system (thrusting mechanism) into the hole would appear to generate air pressure build up (which would force resin to be blown back out). Further the in the Gazmick system the shaft moves through the resin reservoir during installation. In contrast the present invention provides a protected passage (shielded by a sheath) for the resin from the reservoir to travel the toe end of the rock bolt. The sheath is substantially static with respect to the shaft during installation.

[0071 ] In the second aspect the invention relates to a rock bolt without an associated resin deployment system. This is shown in Figure 3, where rock bolt 10a has a first zone 80 which is an energy absorbing zone in the form of cushioning sheath 85 which encases a small length of shaft 15 at distal end portion 30 adjacent flared toe 37. Cushioning sheath 85 is made of soft deformable material such as medium to high density rubber or any suitable synthetic elastomeric compound such as hollow HDPE or polyvinyl chloride (PVC) or polyurethane (PU) (memory foam).

[0072] Second zone/less energy absorbent zone 90 corresponds to sheath 55 and is made of non-deformable relatively rigid material such as suitable HDPE which becomes even more rigid when filled and encapsulated with resin.

[0073] The idea of the two zones is that sheath 55 is non deformable and is stuck to the borehole with cured resin. Because the distal end is deformable, the solid shaft of the bar can slide axially with respect to the sheath as far as the deformable section deforms (by absorbing energy). The flared end of the bolt then hits the non deformable material (sheath 55) and stops sliding. The solid metal shaft of the bolt will then start to stretch and ultimately snap if enough force is applied. This means that the bolt can be axially displaced a predetermined amount; that amount being predetermined by the length and material properties of cushioning sheath 85. It is anticipated that this allows for the bolt to respond to seismic events or stress damage better than most currently available rock bolts. [0074] It will be understood that where axial movement of shaft 15 is required after installation of rock bolt such as in the second aspect of the invention, shaft 15 should not adhere to the resin. This means that upon installation the sheath/resin composite will be firmly adhered to the borehole but shaft 15 will be able to move axially in relation to the bonded sheath/resin/borehole. To achieve this outer surface of shaft 15 is either smooth or coated with a membrane of thin plastic, beeswax or another barrier substance to prevent the resin inside the sheath 55 from bonding to shaft 15.

[0075] In the embodiment shown in figure 4 bolt 210 of assembly 200 is the same as in the first embodiment, however resin extrusion means 270 comprises shorter and wider half cylinders 273 with similarly arranged mixing fins 275 in mixing chamber 278. Each half cylinder 273 with a hollow section comprises curved wall 273a, front flat wall 273b and back flat wall 273c. The resin cartridges in this embodiment will not pass through the centralisers of the jumbo boom 300. Therefore the resin cartridges need to be connected around the bolt in between the centralisers. The resin cartridges will lock into place as the bolt is inserted into the hole. The resin is expelled from the cartridges through a pressure valve when the front wall hits the end centraliser of the jumbo boom. This arrangement of resin cartridge may be more economical to produce and will not suffer from premature compression.

[0076] It should be appreciated that in this invention the resin reservoir could be positioned in a variety of locations relative to the bolt at the start of the installation process: at the proximal end of the bolt, around the shaft of the bolt between the proximal and distal ends, or at the distal end of the bolt near the plate. The design of the reservoir would be slightly different in all three cases. The drawings show some of these possible arrangements but not all.

[0077] An alternative arrangement (not shown) is to locate the resin cartridges past the end centraliser of the boom at the distal end of the bolt prior to bolt installation (either above or below the plate).

[0078] Example 1 : Use of embodiment shown in Figure 1

The embodiment shown in Figure 1 is installed via the following steps:

1 . Drill hole of required diameter (typical diameter 43-45mm but hole diameter could vary) to required depth with boom of jumbo chosen to drill holes. 2. Attach the two half cylinder resin cartridges 73 to each other at proximal end 45 of bolt 10. Mixing chamber 78 of cartridge half cylinders 73 form a pressure tight seal with the dome ball washer 46 when pressure is applied.

3. Feed bolt through centralisers of boom chosen to install the bolt and place nut 46 into the dolly (standard bolt dolly).

4. Place a standard bolt plate 47 over the toe end 35 of the bolt and run down bolt to rest on the end of the boom.

5. Lift boom to hole.

6. Inset bolt into hole until dome ball washer 46 presses on the plate 47 firmly. As the resin cartridges pass through bolt plate 47 the outer wall 73 b of the resin cartridges are squeezed in towards the inner walls 73c forcing the resin into the mixing cavity 78 and then into the open ends of the resin pipe 67 within the polyurethane sheath 55 of bolt 10. Plastic/rubber fin arrangement 75 aids mixing of the resin parts.

7. After the resin has been forced through bolt 10 the dome ball washer 47 will crush the plastic shells that form the pressure tight cavity.

8. Hold the bolt firmly against the bolt plate for 15 seconds.

9. Apply left rotation to tighten the nut against the plate.

[0079] Example 2: Use of embodiment shown in Figure 4

The embodiment shown in Figure 4 is installed via the following steps:

1 . Drill hole of required diameter to required depth with boom of jumbo.

2. Feed bolt 210 through centralisers of boom chosen to install the bolt and place nut 246 into the dolly (standard bolt dolly).

3. Attach the two half cylinder resin cartridges 270 to each other around the bolt 210 in between the two centralisers of the boom.

4. Place a bolt plate 247 over the toe end of the bolt and run down bolt to rest on the end of the boom.

5. Lift boom to hole.

6. Inset bolt into hole.

7. When the proximal end 245 of the bolt passes then through the first centraliser of the boom the half cylinder resin cartridges 273 is lifted up with the bolt until the cartridges hit the end centraliser of the boom.

8. When the upper plastic wall 273b of the resin half cylinders 273 hit the end centraliser, the flared end of the polyurethane sheath 256 is forced to click into place and form a pressure tight cavity 278 with the plastic shells of the resin cartridges and the dome ball washer 246. The upper and lower plastic walls of the resin cartridges are squeezed together forcing the resin into the mixing cavity 278 and then into the open ends of the resin pipe 257 within the polyurethane sheath/casing 255 of the bolt 210. A plastic/rubber fin arrangement 275 aid mixing of the resin parts.

9. As the bolt is continuously pushed into the hole by the drifter in one steady motion, and after the resin has been forced into the bolt, the dome ball washer 246 crushes the plastic shells that form the pressure tight cavity.

10. The proximal end of the bolt passes through the end centraliser of the boom.

1 1 . Prior to the dome ball washer 246 pressing against the bolt plate, the remains of the resin in the resin cartridges will be expelled into the bolt as it is pressed against the bolt plate.

12. Hold the bolt firmly against the bolt plate for 15 seconds.

13. Apply left rotation to tighten the nut against the plate.

[0080] Most current resin bolt installation still involves inserting the resin sausage into the hole then inserting the bolt into the hole. It will be appreciated by those skilled in the art that the present invention is truly one pass as the resin is forced to the end of the bolt as the bolt is pushed to the end of the hole.

[0081 ] From the foregoing, it will be observed that numerous modifications and variations can be effected without departing from the true spi t and scope of the novel concept of the present invention. It is to be understood that no limitation with respect to the specific embodiment illustrated herein is intended or should be inferred. The disclosure is intended to cover, by the appended claims, all such modifications as fall within the scope of the claims.

[0082] Throughout this specification and the claims that follow, unless the context requires otherwise the words "comprise", "comprises", "comprising" will be understood to mean the inclusion of the stated integer, step or group of integers or steps but not the exclusion of any of other integer, step or group of integers or steps.

Table 1 : Figure Legend

Reference numeral/letter Feature

10 rock bolt of figure 1

10a Rock bolt without resin deployment system

15 solid shaft

15a Outer surface of solid shaft

20 Intermediate portion

30 distal end portion

35 distal end

37 flared toe proximal end portion

proximal end

Nut/dome ball washer

Bolt plate

Passage shielding means

Casing/sheath of HDPE

Flared ring to seal mixing chamber 78

Resin passage means

Conduit in casing/sheath 55

Resin extrusion means

Two part resin reservoir Half cylindersa Curved wall of half cylinder

b Sloped front end wall of half cylinderc Straight back end wall of half cylinder

Mixing fins

Mixing chamber

Pressure release valves

First zone/Energy absorbing zone

Cushioning sheath

Plastic netting/spider

Second zone/Less energy absorbent zone0 Rock bolt assembly of figure 1

0 Rock bolt assembly of figure 4

0 Rock bolt of figure 4

0 Resin extrusion means

5 Casing/sheath of polyurethane

6 Flared ring of sheath to seal mixing chamber 2783 Half cylinders

3a Curved wall of half cylinder

3b Front end wall of half cylinder

3c Back end wall of half cylinder

5 Mixing fins

8 Mixing chamber

0 Jumbo Boom

Claims

The claims defining the invention are as follows:

1 . A rock bolt assembly comprising:

a) a rock bolt with a solid shaft having an outer surface along its length and a distal end portion with a suitable distal end for insertion into a borehole and a proximal end portion with a suitable proximal end for engaging an opening of a borehole;

b) at least one collapsible resin reservoir associated with said shaft;

c) a resin passage means adjacent said outer surface which runs between said portions and allows uncured resin to travel from said reservoir to the distal end portion; and;

d) an adjacent passage shielding means;

wherein b), c) and d) are arranged such that, in use when said resin reservoir is collapsed uncured resin can pass unobstructed to said distal end portion.

2. The assembly of claim 1 wherein the passage shielding means is a sheath and said resin passage means is a gap between said shaft and said sheath, a tube located between said sheath and said outer surface or a lumen formed within said sheath.

3. The assembly of claim 1 or claim 2 wherein said resin reservoir is disposed between said proximal end and said distal end thereby not extending the length of the rock bolt.

4. The assembly of any one of claims 1 to 3 wherein said reservoir comprises a cylinder like arrangement made of one or two parts and is disposed coaxially on a part of said sheath.

5. The rock bolt assembly of any one of claims 1 to 4 which includes a resin mixing means associated with said resin reservoir.

6. A rock bolt which allows a predetermined amount of axial displacement when installed in a borehole, said rock bolt comprising:

a) a solid shaft;

b) an adjacent first zone which encases or partly encases said shaft;

c) and associated second zone engageable with an anchoring compound said second zone encasing or partially encasing said shaft and/or said first zone;

d) wherein said first zone is capable of absorbing more energy than said second zone;

e) wherein when appropriately installed and a suitable load is applied the bolt is capable of absorbing energy by moving through said first zone until it reaches said second zone and;

f) wherein the shaft is adapted to retard movement through said zones and said predetermined amount of axial displacement is related to the size of the first zone.

7. The rock bolt of claim 6 wherein said first and second zones are disposed coaxially in relation to the shaft.

8. The rock bolt of claim 7 wherein said first and second zones are disposed side by side along the shaft.

9. The rock bolt of claim 7 wherein the shaft comprises a high pitched thread or knurls to retard movement through said zones.

10. The rock bolt of claim 8 wherein a distal end of the shaft comprises a flared toe to retard movement through said zones.

1 1 . A rock bolt assembly suitable for one pass installation comprising:

a) a rock bolt with a solid shaft; said rock bolt comprising:

i) a suitable distal end for insertion into a borehole;

ii) a suitable proximal end for engaging an opening of a borehole;

iii) a distal portion located at said distal end and a proximal portion located at said proximal end; iv) an intermediate portion located between said ends;

v) said distal portion at least partially encased in a relatively soft deformable material;

vi) said intermediate and proximal portions at least partially encased in a relatively non- deformable material or a precursor thereof;

b) an associated resin extrusion means comprising a collapsible resin reservoir said resin extrusion means enabling resin to be extruded through or past said non-deformable material; d) wherein when appropriately installed and a suitable load is applied the bolt is capable of absorbing energy by moving through said relatively soft deformable material until it reaches said relatively non-deformable material and;

e) wherein application of the rock bolt into a suitable borehole and extrusion of resin can be performed simultaneously or in rapid succession by collapsing said resin reservoir and allowing uncured resin to the pass unobstructed to said distal end portion.

12. The assembly of claim 1 1 wherein said relatively non-deformable material comprises a sheath which forms a gap between said sheath and said shaft.

13. A method of stabilizing an excavation in rock or unstable ground comprising installing a plurality of the rock bolt assembly of claim 1 or claim 1 1 into said rock face or unstable ground.

14. A system for installing a rock bolt for stabilising excavations or unstable ground, said system comprising providing:

i) a rock bolt with a solid shaft having an outer surface along its length and a distal end portion with a suitable distal end for insertion into a borehole and a proximal end portion with a suitable proximal end for engaging an opening of a borehole;

ii) a resin passage means engageable with a resin reservoir, said resin passage means adjacent said outer surface, running between said portions and able to allow uncured resin to travel to the distal end portion;

iii) an adjacent passage shielding means; and

iv) at least one collapsible resin reservoir adjacent said shaft; wherein ii), iii), and iv) are arranged such that, in use when said resin reservoir is collapsed uncured resin passes unobstructed to said distal end portion.

15. A method of manufacturing a rock bolt assembly said method comprising the steps of: i) providing a rock bolt with a solid shaft having an outer surface along its length and a distal end portion with a suitable distal end for insertion into a borehole and a proximal end portion with a suitable proximal end for engaging an opening of a borehole;

ii) applying to said rock bolt a rigid passage shielding means to form a resin passage means or otherwise providing a passage shielding means and associated resin passage means; wherein said resin passage means is adjacent said outer surface and runs between said portions, and is engageable with a suitable collapsible resin reservoir and in use allows uncured resin to travel to the distal end portion.

16. A method of manufacturing a rock bolt which in use allows a predetermined amount of axial displacement when installed in a borehole said method comprising the steps of:

i) applying to a suitable shaft a first zone which encases or partially encases the shaft, and; ii) applying a second zone engageable with an anchoring compound which encases or partially encases said shaft and/or said first zone wherein said first zone is capable of absorbing more energy than said second zone; wherein when appropriately installed and a suitable load is applied the bolt is capable of absorbing energy by moving through said first zone until it reaches said second zone and; wherein the shaft is adapted to retard movement through said zones and said predetermined amount of axial displacement is related to the size of the first zone.

17. A rock bolt, rock bolt assembly, collapsible resin reservoir, method of use or system substantially as hereinbefore described with reference to the examples and/or drawings.