A rock bolt assembly and associated installation

Abstract

A rock bolt assembly (100) includes a ground support element (102) to be anchored in a borehole (180). The ground support element has an elongate body (104) longitudinally extending between a leading end (104a) and a trailing end (104b). The body provides a hollow interior (114) for receiving a settable material to be dispensed from the body under application of pressure to anchor the ground support element in the borehole, and a sidewall (116) surrounding the hollow interior. The trailing end of the body includes an opening (120) to receive an injection nozzle (208) for supplying fluid under pressure to the hollow interior of the body to dispense the settable material. The rock bolt assembly also includes a sealing member (162) arranged within the hollow interior of the body to provide a seal between the injection nozzle and the sidewall of the body during pressurisation of the hollow interior. The sealing member is displaceable relative to the sidewall of the body to facilitate tensioning of the ground support element.

Description

A ROCK BOLT ASSEMBLY AND ASSOCIATED INSTALLATIONField

[0001] The present invention relates to strata control in civil engineering and mining operations, and in particular relates to a rock bolt assembly and the installation of the rock bolt assembly for securing the roof or wall of a mine, tunnel or other ground excavation.Background

[0002] Hollow rock bolts may contain a pre-installed resin cartridge which is configured to dispense and flow down the borehole annulus to provide anchoring of the bolt.

[0003] Hollow rock bolts may also be self-drilling, allowing the bolts to be installed in a more efficient process. In such single pass self-drilling rock bolt systems, water pressure is introduced through a first water circuit of the rock bolt for flushing drill cuttings during the drilling operation. After the hole boring has been completed, water is injected through a second water circuit of the rock bolt containing the resin cartridge. The water pressure ruptures the resin cartridge under a compressive action, forcing resin through a hole in the tip of the rock bolt to the annulus of the borehole to anchor the bolt. Upon curing of the resin, the bolt is pretensioned in the ground by tightening the nut.

[0004] In such single stage self-drilling rock bolt systems, the nut fits into a drive dolly which rotates the bolt in one direction to drill the borehole, then in the opposite direction to tension the bolt. Incorporated within the drive dolly may be a high-pressure pin to supply the water under pressure for flushing drill cuttings and rupturing the cartridge. Disadvantageously, in such systems, the ability of the drive dolly to advance during pretensioning of the bolt is often constrained, resulting in the nut slipping out of full engagement with the drive dolly, thereby making installation of the bolt difficult, time-consuming and / or cumbersome.Summary of Invention

[0005] In one aspect, the present invention provides a rock bolt assembly including: a ground support element to be anchored in a borehole, the ground support element having an elongate body longitudinally extending between a leading end and a trailing end, the bodyproviding a hollow interior for receiving a settable material to be dispensed from the body under application of pressure to anchor the ground support element in the borehole, and a sidewall surrounding the hollow interior, the trailing end of the body including an opening to receive an injection nozzle for supplying fluid under pressure to the hollow interior of the body to dispense the settable material; and a sealing member arranged within the hollow interior of the body to provide a seal between the injection nozzle and the sidewall of the body during pressurisation of the hollow interior, with the sealing member being displaceable relative to the sidewall of the body to facilitate tensioning of the ground support element.

[0006] In one or more embodiments, the sealing member is displaceable in a direction toward the leading end of the body upon application of a displacing force provided by the injection nozzle.

[0007] In one or more embodiments, the sealing member includes a tubular body defining a central aperture via which the injection nozzle is insertable, with the tubular body being sized relative to the hollow interior to establish an interference fit therewith.

[0008] In one or more embodiments, the sealing member includes a collar projecting partially into the central aperture, with the collar defining a mouth via which a portion of the injection nozzle is insertable.

[0009] In one or more embodiments, the collar includes a lip surrounding the mouth to sealingly interface with the portion of the injection nozzle.

[0010] In one or more embodiments, the tubular body of the sealing member includes a sidewall surrounding the central aperture to sealingly interface with the sidewall of the body of the ground support element.

[0011] In one or more embodiments, the sidewall of the sealing member includes one or more deformable joints to form a fluid seal at the interface with the sidewall of the body of the ground support element, with the one or more joints being configured for sliding engagement with the sidewall of the body of the ground support element upon application of the displacing force.

[0012] In one or more embodiments, the one or more deformable joints includes a gasket formed of an elastomeric material.

[0013] In one or more embodiments, the sealing member includes a trailing end provided by the tubular body for engagement with the injection nozzle via which the displacing force is applied.

[0014] In one or more embodiments, the sealing member is deformable to form a fluid seal between the injection nozzle and the sidewall of the body of the ground support element while permitting sliding engagement with the sidewall of the body.

[0015] In one or more embodiments, the sealing member is formed of plastics.

[0016] In another aspect, the present invention provides a fitting to operatively connect a rock bolt assembly to an installation rig for installing the rock bolt assembly in a borehole, the rock bolt assembly including a tubular bar defining open leading and trailing ends and a threaded trailing end portion for receipt of a nut for tensioning the bar, the bar providing a hollow interior and a sidewall surrounding the hollow interior, the rock bolt assembly further including a sealing member arranged within the hollow interior for displaceable sealing engagement with the sidewall of the bar, the fitting including: a hollow drive body to transmit torque to the nut for tensioning the bar; and an injection nozzle coupled to the drive body for supplying fluid under pressure to the hollow interior via the open trailing end of the bar, the injection nozzle being sealingly engageable with the sealing member during pressurisation of the hollow interior, the injection nozzle including a seat for supporting the sealing member as the hollow interior is pressurised and displacing the sealing member relative to the sidewall of the bar as the bar is tensioned.

[0017] In one or more embodiments, the drive body includes an elongate shank to be rotated, and wherein the injection nozzle includes an elongate nozzle body extending through an interior of the shank to define an annular void extending longitudinally between the shank and the elongate body of the injection nozzle for accommodating the trailing end portion of the bar as the bar is tensioned.

[0018] In one or more embodiments, the injection nozzle includes a nozzle tip section joined with the nozzle body at an intersection thereof, with the nozzle tip section having a reducedthickness relative to the nozzle body to define a shoulder at the intersection, with the shoulder providing the seat.

[0019] In one or more embodiments, the seat is configured to sealingly engage the sealing member as the hollow interior is pressurised.

[0020] In one or more embodiments, the injection nozzle includes a fluid passage communicable with a fluid circuit of the installation rig for supplying the fluid under pressure, the fluid circuit including a relief valve to relieve the fluid in the fluid passage following pressurisation of the hollow interior.

[0021] An aspect of the present disclosure provides a rock bolt assembly including: a ground support element to be anchored in a borehole, the ground support element having an elongate body longitudinally extending between a leading end and a trailing end, the body providing a hollow interior for receiving a cartridge containing a settable material to be dispensed from the body under application of pressure to anchor the ground support element in the borehole, the leading end of the body including an opening via which the settable material is dispensable; and a plug mountable to the leading end of the body to partially close the opening for regulating flow of the settable material when dispensed from the body, the plug being releasably mountable to the leading end to permit removal of the cartridge from the body via the opening.Brief Description of Drawings

[0022] Exemplary embodiments of the present disclosure will now be described, by way of examples only, with reference to the accompanying description and drawings in which:

[0023] FIG. 1 is a longitudinally cross-sectioned, fragmentary, front elevation view of an incomplete rock bolt installation utilising a rock bolt assembly according to a first embodiment;

[0024] FIG. 2 is an enlarged detail view of portion A of the rock bolt installation of FIG. 1;

[0025] FIG. 3 is a longitudinally cross-sectioned, fragmentary, front elevation view of a partially completed rock bolt installation utilising the rock bolt assembly of FIG. 1, shown with a cartridge of the rock bolt assembly in a dispensed state;

[0026] FIG. 4 is an enlarged detail view of portion B of the rock bolt installation of FIG. 3;

[0027] FIG. 4A is a longitudinally cross-sectioned, fragmentary, front elevation view of a partially completed rock bolt installation utilising a rock bolt assembly according to another embodiment of the subject disclosure, shown with a cartridge of the rock bolt assembly in a dispensed state;

[0028] FIG. 4B is an enlarged detail view of portion Bi of the rock bolt installation of FIG. 4 A;

[0029] FIG. 4C is a longitudinally cross-sectioned, fragmentary, front elevation view of a partially completed rock bolt installation utilising a rock bolt assembly according to a further embodiment of the subject disclosure, shown with a cartridge of the rock bolt assembly in a dispensed state;

[0030] FIG. 4D is an enlarged detail view of portion B2 of the rock bolt installation of FIG. 4C;

[0031] FIG. 5 is a longitudinally cross-sectioned, fragmentary, front elevation view of a partially completed rock bolt installation utilising the rock bolt assembly of FIG. 1, shown with a bar of the rock bolt assembly in a tensioned state;

[0032] FIG. 6 is an enlarged detail view of portion C of the rock bolt installation of FIG. 5;

[0033] FIG. 7 is an enlarged detail view of portion D of the rock bolt installation of FIG. 5;

[0034] FIG. 8 is a longitudinally cross-sectioned, fragmentary, front elevation view of a completed rock bolt installation utilising the rock bolt assembly of FIG. 1;

[0035] FIG. 9 is an enlarged detail view of portion E of the rock bolt installation of FIG. 8;

[0036] FIG. 10 is an enlarged detail view of portion F of the rock bolt installation of FIG. 8;

[0037] FIG. 11 is a longitudinally cross-sectioned, fragmentary, front elevation view of a completed rock bolt installation utilising a rock bolt assembly according to a second embodiment; and

[0038] FIG. 12 is an enlarged detail view of portion G of the rock bolt installation of FIG. 11.Description of Embodiments

[0039] Referring firstly to FIG. 1 of the accompanying drawings, a rock bolt assembly 100 according to a first embodiment is depicted. The rock bolt assembly 100 is configured to be installed in a pre-drilled borehole 180 (see FIG. 2) using an installation rig (not shown) to secure the roof or wall of a mine, tunnel or other ground excavation, as will be described in detail below.

[0040] The rock bolt assembly 100 includes a ground support element in the form of a rock bolt 102 to be anchored in the borehole 180. The rock bolt 102 includes an elongate body in the form of a rigid tubular shaft, rod or bar 104. The tubular bar 104 has a length longitudinally extending between leading and trailing ends 104a, 104b of the tubular bar 104. The tubular bar 104 has a leading end portion 106 terminating in the leading end 104a of the tubular bar 104, and a trailing end portion 108 terminating in the trailing end 104b of the tubular bar 104. The trailing end portion 108 of the tubular bar 104 is externally threaded for receipt of a drive nut 110 provided with a corresponding thread for tensioning of the rock bolt 102, as will be described below. In the arrangement depicted, the external thread on the tubular bar 104 is a right-handed thread extending along the full length of the tubular bar 104. In alternative embodiments, the external thread may not extend along the full length of the tubular bar 104 but rather may extend along the trailing end portion 108 to define a threaded trailing end portion of the tubular bar 104. In such alternative embodiments, the threaded trailing end portion may include a finer pitch thread to facilitate tensioning of the tubular bar 104, and the tubular bar 104 may further include a coarse thread form extending along the leading end portion 106 to facilitate mixing of resin and load transfer. In other embodiments, the tubular bar 104 may include any deformation pattern extending at least partially along the full length of the tubular bar 104, in addition to the threaded trailing end portion 108 which may define a different thread form to the deformation pattern. In some embodiments, the external thread at the trailing end 104b of the tubular bar 104 may include a thread stopper (not shown), such as a thread runout portion, shear pin, welded bead, threaded ring or additional nut, to engage the drive nut 110, preventing the drive nut 110 from “running off’ the thread of the trailing end portion 108 of the tubular bar 104 under lefthanded rotation. In some embodiments, the drive nut 110 may be provided with a shear pin (not shown) which fixes the drive nut 110 onto the thread of the trailing end portion 108 up to a threshold torque at which the shear pin fails, enabling the drive nut 110 to be threadingly advanced along the thread of the trailing end portion 108.

[0041] The tubular bar 104 will typically be formed of steel but other suitable materials may be utilised such as fibre reinforced polymers. The tubular bar 104 may have any of various lengths and diameters selected to suit the reinforcement or performance requirements for the particular borehole in which the rock bolt 102 is to be installed.

[0042] With particular reference to FIGs. 2 and 4, the tubular bar 104 has a central bore 112 defining an internal channel 114 of the tubular bar 104, and a generally cylindrical sidewall 116 surrounding the internal channel 114. The internal channel 114 extends longitudinally along the length of the tubular bar 104 and terminates in first and second openings 118, 120 formed, respectively, at the leading and trailing ends 104a, 104b of the tubular bar 104. Insertable within the internal channel 114 is a frangible cartridge 122 containing a settable or hardenable material to be released or dispensed from the cartridge 122 to anchor the rock bolt 102 in the borehole 180. In the embodiment depicted, the cartridge 122 contains a two-speed, two-component (that is, a mastic and a catalyst) resin with a relatively fast setting resin at the bottom or trailing portion 124 (see FIG. 1) of the cartridge 122 used to encapsulate the leading end portion 106 of the tubular bar 104, and a slower setting resin at the top or leading portion 126 of the cartridge 122 used to encapsulate a portion of the rock bolt 102 towards the trailing end portion 108 of the tubular bar 104. The cartridge 122 is of a slightly reduced thickness compared to the diameter of the central bore 112 to provide clearance with the sidewall 116 of the tubular bar 104, permitting movement of the cartridge 122 along the internal channel 114 with minimal frictional interference with the sidewall 116.

[0043] With particular reference to FIG. 4, the rock bolt assembly 100 includes an optional end cap or closure plug 128 mountable to the leading end portion 106 of the tubular bar 104 to regulate flow of the hardenable material when dispensed from the cartridge 122. In the embodiment depicted, the closure plug 128 includes a discharging head portion 130 and a shank-like sleeve portion 132 trailing the head portion 130. In the arrangement depicted, the sleeve portion 132 is integrally formed with the head portion 130. In other embodiments, the head portion 130 and the sleeve portion 132 may be formed as separate components and joined to form a two-piece assembly of the closure plug 128. In such other embodiments, the head portion 130 may be releasably mounted to the sleeve portion 132 (such as via threaded engagement) to facilitate removal or replacement of the cartridge 122 within the internal channel 114 of the tubular bar 104, if required.

[0044] The sleeve portion 132 is of a generally hollow cylindrical form defining a central passageway 134 (see FIG. 1) for fluid communication with the internal channel 114 of the tubular bar 104 and which is sized for insertion through the first opening 118 formed at the leading end 104a of the tubular bar 104. The sleeve portion 132 may have an interference fit with the sidewall 116 such that the closure plug 128 may be mounted to the leading end portion 106 of the tubular bar 104 by press fitting the sleeve portion 132 with the sidewall 116 of the tubular bar 104. In some embodiments, the sleeve portion 132 may be tapered to provide a tapered interference fit with the sidewall 116 to secure the closure plug 128 with respect to the tubular bar 104. Alternatively, the sleeve portion 132 may have a clearance fit with the sidewall 116 and be secured to the leading end portion 106 of the tubular bar 104 via welding, an adhesive or other means which is additionally adapted to form a fluid seal between the sidewall 116 of the tubular bar 104 and the sleeve portion 132. In other embodiments, the sleeve portion 132 may be externally threaded, and the leading end portion 106 of the tubular bar 104 may be internally threaded so that the closure plug 128 can be releasably secured to the leading end portion 106 of the tubular bar 104 via threaded engagement between the external and internal threads. In the arrangement of the rock bolt assembly 100' shown in FIGs. 4A and 4B, the sleeve portion 132' includes a plurality of discharge holes, ports or slots 133 via which the hardenable material may dispense. Each of the slots 133 is formed laterally through a sidewall of the sleeve portion 132' such that advancement of the sleeve portion 132' relative to the tubular bar 104 exposes the discharge slots 133 to the exterior of the tubular bar 104, permitting the hardenable material to flow from the internal channel 114 to the exterior of the tubular bar 104. In this way, the sidewall of the sleeve portion 132' has a length sufficient to permit advancement of the sleeve portion 132' relative to the tubular bar 104 to expose the discharge slots 133 whilst still enabling secure engagement with the sidewall 116 of the leading end portion 106. Whilst a plurality of discharge slots 133 are shown, in other embodiments there may only be one discharge slot formed through the sidewall of the sleeve portion.

[0045] In the arrangement depicted in FIG. 4, the head portion 130 of the closure plug 128 extends radially beyond the sleeve portion 132 to define a circumferential flange 136 having a maximum diameter which is greater than the diameter of the central bore 112 but slightly less than, or the same as, the maximum diameter of the rock bolt 102. The flange 136 has a shoulder surface 138 for mating with the leading end 104a of the tubular bar 104. In use, the shoulder surface 138 may engage the leading end 104a of the tubular bar 104, preventing movement of the head portion 130 into the internal channel 114 of the tubular bar 104. As shown in FIG. 4,the head portion 130 has an internal cavity 140 in fluid communication with the central passageway 134 of the sleeve portion 132. Formed through the flange 136 is at least one port or exit hole 142 via which the hardenable material may dispense. The exit hole 142 communicates the exterior of the head portion 130 with the internal cavity 140 thereof and, in turn, the central passageway 134 and internal channel 114 of the tubular bar 104 when the closure plug 128 is fitted to the leading end portion 106 of the tubular bar 104. In the arrangement of the rock bolt assembly 100" shown in FIGs. 4C and 4D, there are an opposing pair of exit holes 142" formed through the flange 136" of the closure plug 128", although the arrangement and / or number of exit holes may be varied depending on the intended application. The head portion 130 terminates in a generally conical nose portion 144 defining a leading end tip 146. In some embodiments, the head portion 130 may include an integrated static mixer (not shown) to facilitate processing and mixing of the hardenable material following dispensation from the cartridge 122.

[0046] In some embodiments, the closure plug may be partly or entirely formed of plastics, as opposed to metal, which may reduce the strength of the compressive fit with the sidewall 116 of the leading end portion 106, facilitating insertion and / or removal of the closure plug with respect to the tubular bar 104 to in turn ease recharging of the cartridge 122, negating the need to replace the entire rock bolt assembly. The strength of the compressive fit may be designed to achieve a secure engagement whilst still permitting advancement of the closure plug relative to the tubular bar 104 under a predetermined hydraulic pressure, enabling controlled dispensation of the hardenable material from the internal channel 114 to the exterior of the tubular bar 104.

[0047] In an alternative embodiment, the closure plug 128 may be omitted and the leading end portion 106 of the tubular bar 104 may instead include one or more discharge ports (not shown), via which the hardenable material may flow, formed through the sidewall 116 of the tubular bar 104 communicating the exterior of the tubular bar 104 with the internal channel 114. In other embodiments, the leading end 104a of the tubular bar 104 may be swaged entirely closed with one or more discharge ports or holes drilled therethrough, or swaged partially closed whilst retaining a gap, via which the hardenable material may flow.

[0048] With particular reference to FIG. 2, the rock bolt assembly 100 also includes a resin dispensing member in the form of a plunger or piston 148 slidably arranged within the internal channel 114 to facilitate release of the hardenable material from the cartridge 122. The piston148 divides the internal channel 114 into a trailing chamber 150 which trails the piston 148, and a leading chamber 152 (see FIG. 1) which leads the piston 148. Each of the trailing and leading chambers 150, 152 occupies a variable volume of the internal channel 114 such that the total volume of the trailing and leading chambers 150, 152 is constant. That is, as the volume of the trailing chamber 150 increases, the volume of the leading chamber 152 correspondingly decreases, as will be described below.

[0049] The piston 148 includes a body 154 of a generally solid cylindrical form having a slightly reduced diameter compared to the diameter of the central bore 112 to provide clearance with the sidewall 116 of the tubular bar 104, permitting movement of the body 154 of the piston 148 along the internal channel 114 with minimal frictional interference with the sidewall 116. The body 154 of the piston 148 terminates in leading and trailing rims 156, 158 of the piston 148. Each of the leading and trailing rims 156, 158 is flared so as to project radially outwardly from the body 154 to sealingly interface with the sidewall 116 of the tubular bar 104 while being uniformly slidable thereagainst, permitting the piston 148 to move along the internal channel 114 in response to an increase in pressure in the trailing chamber 150 above a threshold pressure. In this way, the piston 148 acts as a fluid seal which is moveable to reduce the volume occupied by the leading chamber 152 of the internal channel 114 of the tubular bar 104. The piston 148 is moveable in a direction toward the first opening 118 of the tubular bar 104 from a rest, or home, position to a deployed position in which the piston 148 has advanced along the internal channel 114 of the tubular bar 104, reducing the volume of the leading chamber 152. In the embodiment depicted, in which the cartridge 122 is inserted within the leading chamber 152 between the piston 148 and the closure plug 128, the leading rim 156 of the piston 148 surrounds a cradle 160 of the piston 148 for engaging the cartridge 122 as the piston 148 moves to the deployed position. The cradle 160 is shaped for supporting conformity with the trailing end 125 of the cartridge 122 to facilitate pushing the cartridge 122 towards the first opening 118 of the tubular bar 104 and in turn against the head portion 130 of the closure plug 128, causing the cartridge 122 to be crushed or compressed against the head portion 130 to dispense the hardenable material from the cartridge 122. In the arrangement depicted, the piston 148 is initially arranged within the internal channel 114 so that the home position of the piston 148 is adjacent, but spaced from, the trailing end 104b of the tubular bar 104 to minimise the volume of the trailing chamber 150 relative to the leading chamber 152. In this way, the home position of the piston 148 may at least aid in reducing the air void in the trailing chamber 150 which may otherwise impede pressurisation of the trailing chamber 150. In an alternative embodiment, thepiston 148 may be initially arranged within the internal channel 114 so that the home position of the piston 148 is adjacent, but spaced from, the leading end 104a of the tubular bar 104 to maximise the volume of the trailing chamber 150 relative to the leading chamber 152, thereby minimising installation time to advance the cartridge 122 relative to the internal channel 114. In other embodiments, the piston 148 may be omitted and the internal channel 114 instead defines a single working chamber between the first and second openings 118, 120 of the tubular bar 104 along which the cartridge 122 is movably arranged. In such embodiments, sufficient pressure may be applied directly to the trailing end 125 of the cartridge 122 to push the cartridge 122 towards the first opening 118 against the head portion 130 to dispense the hardenable material from the cartridge 122.

[0050] With particular reference to FIGs. 2 and 9, the rock bolt assembly 100 further includes a sealing member in the form of a connector seal 162 arranged within the internal channel 114 of the tubular bar 104 to sealingly connect an injection nozzle 208 of the installation rig to the sidewall 116 of the tubular bar 104. The connector seal 162 includes a tubular body 164 longitudinally extending between leading and trailing ends of the connector seal 162 and which defines a central aperture 166 (see FIG. 9) extending therethrough. The central aperture 166 communicates the trailing chamber 150 of the internal channel 114 with the second opening 120 formed at the trailing end 104b of the tubular bar 104. The body 164 of the connector seal 162 has a sidewall 168 surrounding the central aperture 166 and which is dimensioned relative to the internal channel 114 to establish an interference fit therebetween such that the sidewall 168 of the connector seal 162 sealingly interfaces with the sidewall 116 of the tubular bar 104. The ‘tightness’ of fit or amount of interference between the sidewall 168 of the body 164 of the connector seal 162 and the sidewall 116 of the tubular bar 104 is engineered to permit displacement of the connector seal 162 within the internal channel 114 of the tubular bar 104 upon application of a displacing force to the connector seal 162. The displacing force acts in the direction toward the first opening 118 of the tubular bar 104 and has a magnitude sufficient to overcome static friction at the interface between the sidewall 168 of the body 164 of the connector seal 162 and the sidewall 116 of the tubular bar 104.

[0051] To facilitate engineering of the interference fit, the sidewall 168 of the body 164 of the connector seal 162 includes a plurality of toric joints 170 circumferentially arranged around, and integrally formed with, the outer surface of the sidewall 168 of the body 164. Each of the toric joints 170 are designed to form a fluid seal at the interface between the sidewall 168 of the body164 of the connector seal 162 and the sidewall 116 of the tubular bar 104 while permitting sliding engagement with the sidewall 116 of the tubular bar 104 upon application of the displacing force. In some embodiments, each of the toric joints 170, and thus the sidewall 168 of the body 164 of the connector seal 162, is formed of a deformable material, such as plastics, so as to plastically deform to form the fluid seal at the interface while permitting sliding engagement with the sidewall 116 of the tubular bar 104. In other embodiments, each of the toric joints 170 may not be integrally formed with the sidewall 168 of the body 164 of the connector seal 162 but instead be a separate component for mounting thereto. For example, each of the toric joints 170 may be in the form of an elastomeric gasket (such as an O-ring) which may be seated in corresponding grooves formed in the outer surface of the sidewall 168 of the body 164.

[0052] The connector seal 162 also includes an annular collar 172 integrally formed with the sidewall 168 of the body 164 of the connector seal 162 and which projects partially into the central aperture 166, effectively narrowing a portion of the central aperture 166. The collar 172 defines a mouth 174 for releasably coupling the injection nozzle 208 to the connector seal 162. Surrounding the mouth 174 is a lip 176 to sealingly interface with a sidewall of the injection nozzle 208. In some embodiments, the lip 176 may include a deformable gasket, or may otherwise be urged toward the sidewall of the injection nozzle 208, to facilitate sealing the interface between the lip 176 and the sidewall of the injection nozzle 208.

[0053] Optionally, the connector seal 162 includes an inner sleeve-like insert 178 retained by the body 164 of the connector seal 162 and which trails the collar 172. The insert 178 may be formed of a polymer exhibiting a hardness greater than the hardness of the body 164 of the connector seal 162 to facilitate sliding engagement with the injection nozzle 208.

[0054] Installation of the rock bolt assembly 100 utilising the installation rig will now be described with reference to FIGs. 1 to 10.

[0055] Initially, a borehole 180 (see FIG. 2) is first drilled through a rock face 182 into a strata 184 to be stabilised by the rock bolt assembly 100. The borehole 180 has a blind end 186 and a cylindrical borehole wall 188. The borehole 180 is drilled with a slightly oversized diameter for accommodation of the rock bolt 102 such that an annulus 190 is defined between the tubular bar 104 and the borehole wall 188.

[0056] The rock bolt assembly 100 may be pre-assembled by threadingly engaging the drive nut 110 with the thread of the trailing end portion 108 of the tubular bar 104, inserting the cartridge 122, the piston and the connector seal 162 within the internal channel 114 of the tubular bar 104 adjacent the trailing end portion 108, and fitting the closure plug 128 to the leading end portion 106 of the tubular bar 104. The rock bolt assembly 100 is then loaded on to a drive assembly 192 of the installation rig. Prior to or following loading of the rock bolt assembly 100 onto the drive assembly 192, a standard plate washer 194 and ball washer 196 is mounted onto the rock bolt assembly 100 adjacent the drive nut 110 to transfer loads to the rock face 182. An optional anti-friction washer 198 may also be provided between the drive nut 110 and the ball washer 196.

[0057] In the embodiment depicted, the drive assembly is in the form of a fitting or drive dolly 192 to be operatively connected to a rotary drive motor (not shown) of the installation rig. In an alternative embodiment, the drive dolly 192 may be integrated with the output of the rotary drive motor. The drive dolly 192 includes a hollow shank 200 to be rotated, and a hollow drive body 202 integrally formed with the shank 200. In other embodiments, the drive body 202 and the shank 200 may be formed as two separate components and joined together. The drive body 202 has an interior 204 (see FIG. 8) terminating in a leading open end of the drive dolly 192, and an interior face surrounding the interior 204 of the drive body 202. The interior face of the drive body 202 is configured as a square sectioned drive socket 206 sized to engage the drive faces of the drive nut 110 of the rock bolt assembly 100. In some embodiments, the interior face of the drive body 202 may define a hexagonal or other polygonal profile for mating with the drive faces of the drive nut 110.

[0058] With particular reference to FIG. 8, the drive dolly 192 further includes an injection nozzle 208 fixed or rotatably coupled to the shank 200 at a base 208a thereof to supply water under pressure to the internal channel 114 of the tubular bar 104 (see FIG. 1) from an external source. The injection nozzle 208 includes an elongate nozzle body 210 providing an inlet 212, a pin-like nozzle tip section 214 integrally formed with the nozzle body 210 and providing an outlet 216, and a central water passage 218 extending between the inlet 212 and the outlet 216 for fluid communication with a water circuit of the installation rig, providing the external source of water. In other embodiments, the nozzle tip section 214 and the nozzle body 210 may be formed as two separate components. In some embodiments, the injection nozzle 208 may supplyother pressurising agents to the internal channel 114 of the tubular bar 104 such as compressed air, hydraulic oil and the like.

[0059] The nozzle body 210 extends through the interior of the shank 200 and is spaced therefrom to form an annular slot or void 220 between the nozzle body 210 and the shank 200 and which communicates with the leading open end of the drive body 202. The annular void 220 is sized to accommodate the trailing end portion 108 of the tubular bar 104 as the rock bolt 102 is pretensioned, as will be described below. A flange 222 is formed at a trailing end portion of the nozzle body 210 to engage the base 208a of the shank 200, preventing rearward travel of the shank 200 relative to the injection nozzle 208. In some embodiments, the injection nozzle 208 may be welded to the shank 200 via the flange 222.

[0060] A step or shoulder 224 is provided at the junction of the nozzle body 210 and the nozzle tip section 214 by virtue of the reduced thickness or diameter of the nozzle tip section 214 relative to the diameter of the nozzle body 210. The shoulder 224 provides a step or seat 226 to engage the trailing end 164b (see FIG. 9) of the connector seal 162 to apply the displacing force to the connector seal 162, as will be described below. In some embodiments, the seat 226 may be configured to sealingly interface with the trailing end of the connector seal 162.

[0061] The rock bolt assembly 100 is loaded on to the drive dolly 192 via mating of the drive surfaces of the drive nut 110 with the drive socket 206 of the drive body 202. In this mating position, the nozzle tip section 214 protrudes through the central aperture 166 of the connector seal 162 via the second opening 120 formed at the trailing end 104b of the tubular bar 104 and sealingly interfaces with the lip 176 of the collar 172. In this position, the outlet 216 of the injection nozzle 208 is fluidly communicable with the trailing chamber 150.

[0062] As shown in FIG. 1, once the leading end portion 106 of the tubular bar 104 is guided into the borehole 180, the installation rig is operated by thrusting the rock bolt assembly 100 toward the blind end 186 of the borehole 180 via the drive dolly 192, such that the leading end tip 146 of the head portion 130 is adjacent to, or bears against, the blind end 186 of the borehole 180. During this step, the leading end of the drive nut 110 is also engaged with the radially protruding portion of the anti -friction washer 198 which in turn is engaged with the trailing face of the ball washer 196, pushing the ball washer 196 and plate washer 194 against the rock face 182.

[0063] In a first stage of operation, the drive dolly 192 supplies water under pressure to the trailing chamber 150 of the internal channel 114 via the injection nozzle 208. In this way, water under pressure flows from the water circuit of the installation rig through the inlet 212 of the nozzle body 210, along the central water passage 218 and exits the nozzle tip section 214 via the outlet 216. By virtue of the fluid seals formed between 1) the lip 176 of the collar 172 and the sidewall of the nozzle tip section 214, 2) the sidewall 168 of the body 164 of the connector seal 162 and the sidewall 116 of the tubular bar 104, and 3) the trailing rim 158 of the piston 148 and the sidewall 116 of the tubular bar 104, water is inhibited from escaping the trailing chamber 150 so that a sufficient supply of water to the trailing chamber 150 of the internal channel 114 causes the trailing chamber 150 to pressurise. Continued supply of water causes the pressure in the trailing chamber 150 to reach the threshold pressure which is applied to the piston 148, resulting in movement of the piston 148 from the home position toward the deployed position so that the piston 148 reduces the volume of the leading chamber 152 and pushes the cartridge 122 toward the head portion 130 of the closure plug 128. Further supply of water to the trailing chamber 150 causes the piston 148 to reach the deployed position (see FIGs. 3 and 4) in which the piston 148 has forced the cartridge 122 against the head portion 130 which in turn is forced firmly against the blind end 186 of the borehole 180, causing the cartridge 122 to be crushed or compressed against the head portion 130 which in turn ruptures the cartridge 122, forcing the resin from the cartridge 122 through the exit holes 142 and down the annulus 190 (see FIG. 2) between the tubular bar 104 and the borehole wall 188. Alternatively, if the closure plug 128' is employed, the hydraulic pressure will be sufficient to advance the closure plug 128' relative to the tubular bar 104 until the closure plug 128' bears against the blind end 186 of the borehole 180, thereby exposing the discharge slots 133 and enabling controlled dispensation of the resin. Indeed, in those embodiments in which the closure plug is formed of plastics, the advancement of the closure plug relative to the tubular bar under the application of hydraulic pressure is further promoted, thereby facilitating control over the dispensation of the resin. If a static mixer is employed then the resin will have mixed during dispensation and reaction will have commenced. If a static mixer is not employed then the installation rig may be used to rotate the drive nut 110 which in turn rotates the tubular bar 104, by virtue of the fixed connection therebetween provided by way of the shear pin, to mix and react the resin in the annulus 190, via an Archimedean pumping action, for example.

[0064] As the trailing chamber 150 of the internal channel 114 is pressurised, rearward pressure exerted on the connector seal 162, particularly on the collar 172, may be sufficient to overcomestatic friction at the interface between the sidewall 168 of the body 164 of the connector seal 162 and the sidewall 116 of the tubular bar 104, causing the connector seal 162 to displace rearwardly toward the second opening 120 formed at the trailing end 104b of the tubular bar 104. In this instance, while the drive dolly 192 supports the rock bolt assembly 100 against the rock face 182, the trailing end 164b of the connector seal 162 will engage the seat 226 provided by the injection nozzle 208, limiting further rearward travel of the connector seal 162 relative to the tubular bar 104, thereby preventing ejection of the connector seal 162 under pressure from the internal channel 114 of the tubular bar 104. In the embodiment depicted, the body 164 of the connector seal 162 has a thin-walled portion 228 (see FIG. 9) of reduced sidewall thickness at a leading end portion 164a of the connector seal 162 to permit the connector seal 162 to radially expand in the leading end portion 164a under application of pressure, further promoting sealing against the sidewall 116 of the tubular bar 104.

[0065] In a second stage of operation, the drive dolly 192 will be utilised to pretension the rock bolt 102 once the first, faster setting resin has cured, anchoring the leading end portion 106 of the tubular bar 104, but prior to the second, slower setting resin curing (see FIGs. 5 to 7). This enables elongation of the portion of the rock bolt 102 towards the trailing end portion 108 of the tubular bar 104 within the second, slower setting resin during the pretensioning process. If a shear pin is employed (where there is no static mixer present), the shear pin is broken during this action or the drive nut 110 otherwise advances away from the thread stopper.

[0066] To begin the pretensioning operation, the installation rig, without thrust, rotatably drives the drive nut 110 via the drive socket 206 of the drive dolly 192 in the right-handed (or opposite-handed) direction which threads the drive nut 110 along the trailing end portion 108 of the tubular bar 104. Continued driving of the drive nut 110 bears the drive nut 110 against the anti-friction washer 198 which in turn bears the ball washer 196 and plate washer 194 firmly against the rock face. Application of further torque to the drive nut 110 tensions the tubular bar 104, causing the trailing end portion 108 of the tubular bar 104 to relatively displace rearwardly into the annular void 220 of the drive dolly 192 as the drive nut 110 and drive dolly 192 advances, effectively point-anchoring the tubular bar 104 to complete the installation (see FIG. 8). As the trailing end portion 108 of the tubular bar 104 is sufficiently accommodated in the annular void 220, the seat 226 of the injection nozzle 208 engages the trailing end of the connector seal 162, resulting in the displacing force being applied to the connector seal 162 which pushes or displaces the connector seal 162 within the internal channel 114 of the tubularbar 104 relative to the sidewall 116 of the tubular bar 104, permitting advancement of the drive dolly 192 with the drive nut 110 relative to the tubular bar 104. In this manner, the seat 226 of the injection nozzle 208 acts to hold or retain the connector seal 162 in a position relative to the drive nut 110, permitting the sidewall 116 of the tubular bar 104 to move relative to both the connector seal 162 and the drive nut 110 as the trailing end portion 108 of the tubular bar 104 is drawn into the annular void 220 (see FIGs. 5 and 6). In some embodiments, the annular void 220 is sized to permit unconstrained advancement of the drive dolly 192 and the drive nut 110 relative to the tubular bar 104.

[0067] The water circuit of the installation rig may include a relief or switchable valve (not shown), enabling pressure to be relieved from the trailing chamber 150 of the internal channel 114 of the tubular bar 104 (beyond natural leakage) during the pretensioning operation to facilitate advancement of the connector seal 162 within the internal channel 114. In this way, water is permitted to flow in a reverse direction from the trailing chamber 150 to re-enter the water circuit, via the central water passage 218, to be relieved from the water circuit via the valve.

[0068] By virtue of the configuration of the drive dolly 192 and engagement with the connector seal 162 inserted within the internal channel 114 of the tubular bar 104, the injection nozzle 208 can be made geometrically larger in diameter compared to other designs, providing a more robust and rigid construction whilst enabling the injection nozzle 208 and shank 200 to be made proportionally longer to accommodate travel of trailing end portion 108 of the tubular bar 104 and to minimise slenderness ratio concerns associated with other designs thereby being less prone to side-loading risks.

[0069] FIGs. 11 and 12 show a rock bolt assembly 300 according to a second embodiment. The rock bolt assembly 300 of the second embodiment is of an identical construction to the rock bolt assembly 100 of the first embodiment, except that the rock bolt assembly 300 includes a modified form of the drive nut 310 having a leading flange 311 providing increased surface area to force the anti-friction washer 198 against the ball washer 196, permitting a reduced geometry of the drive nut 310 and reduction in overall working diameter of the drive socket 206.Reference Numeral List100 Rock bolt assembly according to a first embodiment102 Rock bolt104 Tubular bar104a Leading end of bar104b Trailing end of bar106 Leading end portion of bar108 Trailing end portion of bar110 Drive nut112 Central bore of bar114 Internal channel of bar116 Sidewall of bar118 First opening of bar120 Second opening of bar122 Cartridge124 Trailing portion of the cartridge125 Trailing end of the cartridge126 Leading portion of the cartridge128 Closure plug130 Head portion of plug132 Sleeve portion of plug133 Discharge slots134 Central passageway136 Flange of head portion138 Shoulder surface of flange140 Internal cavity of head portion142 Exit holes144 Nose portion146 Leading end tip148 Piston150 Trailing chamber152 Leading chamber154 Body of pistonLeading rim of pistonTrailing rim of pistonCradle of pistonConnector sealBody of connector seal a Leading end portion of connector sealb Trailing end of connector sealCentral aperture of body of connector sealSidewall of body of connector sealToric jointsCollarMouthLipInsertBoreholeRock faceStrataBlind end of boreholeBorehole wallAnnulusDrive dollyPlate washerBall washerAnti -friction washerShankDrive bodyInterior of drive bodyDrive socketInjection nozzle a Base of nozzleNozzle bodyInletNozzle tip sectionOutletCentral water passage Annular void Flange of nozzle body Shoulder of inj ection nozzle Seat of shoulder Thin-walled portion Rock bolt assembly according to a second embodiment Drive nut Leading flange of drive nut

Claims

CLAIMS1. A rock bolt assembly including: a ground support element to be anchored in a borehole, the ground support element having an elongate body longitudinally extending between a leading end and a trailing end, the body providing a hollow interior for receiving a settable material to be dispensed from the body under application of pressure to anchor the ground support element in the borehole, and a sidewall surrounding the hollow interior, the trailing end of the body including an opening to receive an injection nozzle for supplying fluid under pressure to the hollow interior of the body to dispense the settable material; and a sealing member arranged within the hollow interior of the body to provide a seal between the injection nozzle and the sidewall of the body during pressurisation of the hollow interior, with the sealing member being displaceable relative to the sidewall of the body to facilitate tensioning of the ground support element.

2. The rock bolt assembly of claim 1, wherein the sealing member is displaceable in a direction toward the leading end of the body upon application of a displacing force provided by the injection nozzle.

3. The rock bolt assembly of claim 2, wherein the sealing member includes a tubular body defining a central aperture via which the injection nozzle is insertable, with the tubular body being sized relative to the hollow interior to establish an interference fit therewith.

4. The rock bolt assembly of claim 3, wherein the sealing member includes a collar projecting partially into the central aperture, with the collar defining a mouth via which a portion of the injection nozzle is insertable.

5. The rock bolt assembly of claim 4, wherein the collar includes a lip surrounding the mouth to sealingly interface with the portion of the injection nozzle.

6. The rock bolt assembly of any one of claims 3 to 5, wherein the tubular body of the sealing member includes a sidewall surrounding the central aperture to sealingly interface with the sidewall of the body of the ground support element.

7. The rock bolt assembly of claim 6, wherein the sidewall of the sealing member includes one or more deformable joints to form a fluid seal at the interface with the sidewall of the body of the ground support element, with the one or more joints being configured for sliding engagement with the sidewall of the body of the ground support element upon application of the displacing force.

8. The rock bolt assembly of claim 7, wherein the one or more deformable joints includes a gasket formed of an elastomeric material.

9. The rock bolt assembly of any one of claims 3 to 8, wherein the sealing member includes a trailing end provided by the tubular body for engagement with the injection nozzle via which the displacing force is applied.

10. The rock bolt assembly of any one of the preceding claims, wherein the sealing member is deformable to form a fluid seal between the injection nozzle and the sidewall of the body of the ground support element while permitting sliding engagement with the sidewall of the body.

11. A fitting to operatively connect a rock bolt assembly to an installation rig for installing the rock bolt assembly in a borehole, the rock bolt assembly including a tubular bar defining open leading and trailing ends and a threaded trailing end portion for receipt of a nut for tensioning the bar, the bar providing a hollow interior and a sidewall surrounding the hollow interior, the rock bolt assembly further including a sealing member arranged within the hollow interior for displaceable sealing engagement with the sidewall of the bar, the fitting including: a hollow drive body to transmit torque to the nut for tensioning the bar; and an injection nozzle coupled to the drive body for supplying fluid under pressure to the hollow interior via the open trailing end of the bar, the injection nozzle being sealingly engageable with the sealing member during pressurisation of the hollow interior, the injection nozzle including a seat for supporting the sealing member as the hollow interior is pressurised and displacing the sealing member relative to the sidewall of the bar as the bar is tensioned.

12. The fitting of claim 11, wherein the drive body includes an elongate shank to be rotated, and wherein the injection nozzle includes an elongate nozzle body extending through an interior of the shank to define an annular void extending longitudinally between the shank and theelongate body of the injection nozzle for accommodating the trailing end portion of the bar as the bar is tensioned.

13. The fitting of claim 12, wherein the injection nozzle includes a nozzle tip section joined with the nozzle body at an intersection thereof, with the nozzle tip section having a reduced thickness relative to the nozzle body to define a shoulder at the intersection, with the shoulder providing the seat.

14. The fitting of any one of claims 11 to 13, wherein the seat is configured to sealingly engage the sealing member as the hollow interior is pressurised.

15. The fitting of any one of claims 11 to 14, wherein the injection nozzle includes a fluid passage communicable with a fluid circuit of the installation rig for supplying the fluid under pressure, the fluid circuit including a relief valve to relieve the fluid in the fluid passage following pressurisation of the hollow interior.

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