AU2015345983A2

AU2015345983A2 - Drive assembly

Info

Publication number: AU2015345983A2
Application number: AU2015345983A
Authority: AU
Inventors: Matthew Raffaele Holden
Original assignee: FCI Holdings Delaware Inc
Current assignee: FCI Holdings Delaware Inc
Priority date: 2014-11-12
Filing date: 2015-11-12
Publication date: 2017-10-12
Anticipated expiration: 2035-11-12
Also published as: EP3218579A4; WO2016074020A1; AU2015345983B2; RU2017120498A; EP3218579A1; AU2015345983A1

Abstract

The disclosure relates generally to drive assemblies for rock bolts and more specifically, but not exclusively, to a dolly for imparting thrust and rotation to a rock bolt and a tensioning device for tensioning a rock bolt.

Description

Drive Assembly Technical Field

The present disclosure relates generally to drive assemblies for rock bolts and more specifically, but not exclusively, to a dolly for imparting thrust and rotation to a rock bolt and a tensioning device for tensioning a rock bolt.

Background Art

Roof and wall support is vital in mining and tunnelling operations. Mine and tunnel walls and roofs consist of rock strata, which must be reinforced to prevent the possibility of collapse. Rock bolts, such as rigid shaft rock bolts and cable bolts are widely used for consolidating the rock strata.

In conventional strata support systems, a bore is drilled into the rock by a drill rod, which is then removed and a rock bolt is then installed in the drilled hole and secured in place typically using a resin or cement based grout. The rock bolt is tensioned which allows consolidation of the adjacent strata by placing that strata in compression.

To allow the rock bolt to be tensioned, the end of the bolt may be anchored mechanically to the rock formation by engagement of an expansion assembly on the end of bolt with the rock formation. Alternatively, the bolt may be adhesively bonded to the rock formation with a resin bonding material inserted into the bore hole. Alternatively, a combination of mechanical anchoring and resin bonding can be employed by using both an expansion assembly and resin bonding material.

When resin bonding material is used, it penetrates the surrounding rock formation to adhesively unite the rock strata and to hold firmly the rock bolt within the bore hole. Resin is typically inserted into the bore hole in the form of a two component plastic cartridge having one component containing a curable resin composition and another component containing a curing agent (catalyst). The two component resin cartridge is inserted into the blind end of the bore hole and the rock bolt is inserted into the bore hole such that the end of the rock bolt ruptures the two component resin cartridge. Upon rotation of the rock bolt about its longitudinal axis, the compartments within the resin cartridge are shredded and the components are mixed. The resin mixture fills the annular area between the bore hole wall and the shaft of the rock bolt. The mixed resin cures and binds the rock bolt to the surrounding rock.

Tension and drive assemblies have been proposed to provide tension along rock bolts, for example, which in turn provides a compressive force on the substrate, usually a mine shaft roof substrate, about the bolt. One such assembly is disclosed in the Applicant’s co-pending patent application AU 2010291865. In this application, a dolly is operative to alternate between a ‘cable drive mode’, whereby rotation of the dolly rotates a shaft of the rock bolt within a bore hole to break a mix the resin cartridge for point anchoring, and ‘tensioning mode’, whereby rotation of the dolly rotates a tensioning device to tension the bolt. In this tension and drive assembly, an outer sheath of the dolly needs to be re-positioned to transition the assembly between cable drive mode and tensioning mode.

Some rock bolts may include passages to allow grout and/or water to be introduced into the bore. During installation resin and debris can infiltrate the passage openings in the bolt. This can make it difficult to fill the bolt with grout following tensioning of the bolt.

The above references to the background art do not constitute an admission that the art forms part of the common general knowledge of a person of ordinary skill in the art. The above references are also not intended to limit the application of the dolly as disclosed herein.

Summary

Disclosed is a dolly for imparting drive to a rock bolt. The dolly may comprise a body having an engagement portion which connects to a tensioning device on the rock bolt, a drive mounted to the body, the drive being operative to rotate the body upon rotation of the drive about a longitudinal axis of the body, and the drive being able to translate axially relative to the body, and biasing device operative to bias the drive into a first position.

In some forms, the biasing device is able to transfer thrust from the drive to the body to insert the rock bolt into a bore.

In some forms, the dolly further comprises a coupling between the drive and the body such that the drive is able to axially translate relative to the body whereas rotation of the drive causes rotation the body.

In some forms, the drive comprises a projection that is able to axially translate within an interior recess of the body.

In some forms, the projection is radially extending from the shaft.

In some forms, the biasing device is in the form of a compression spring that is disposed within the interior recess of the body.

In some forms, the drive is limited to translate relative to the body between the first and a second position.

In some forms, the compression spring is disposed about the drive and is adapted to compress between the projection of the drive and the body upon axial translation of the drive from the first position towards the second position.

In some forms, the drive includes a shaft incorporating one or more fluid passages.

In some forms, the shaft includes a single fluid passage extending axially therethough for the introduction of fluid to the rock bolt.

In some forms, the shaft includes opposite driven and sealing ends, and wherein the passage includes a port at the sealing end of the shaft for introducing the water into a passage formed in or on the rock bolt.

In some forms, the sealing end includes in internal cavity adapted to receive an end of the rock bolt therein, and wherein the internal cavity includes a wall about the port of the passage, the wall being configured to provide a sealing surface between the wall and the rock bolt.

In some forms, when the drive is in the first position the sealing surface is arranged to be spaced from the rock bolt, and wherein when the drive is moved to or towards the second position the sealing surface is arranged to move into contact with the rock bolt.

In some forms, when the drive is located between the first and second positions, the sealing surface is spaced from the rock bolt, the space defining a tensioning gap that allows for the rock bolt to move towards the sealing surface under activation of the tensioning device.

In some forms, the engagement potion of the body comprises a profiled end surface that is arranged to engage with cooperating end surface of the tensioning device on the rock bolt.

In some forms, the body comprises an retaining collar disposed adjacent the engagement portion of the body and arranged to capture the compression spring, and wherein the compression spring is adapted to compress between the projection of the drive and the retaining collar upon axial translation of the drive from the first position towards the second position.

Also disclosed is a drive assembly for a rock bolt having a shaft. The drive assembly may comprise; a tensioning device having a coupler that is adapted to be coupled to a dolly, a base member adapted to be fixed to the shaft of the rock bolt, and a torque transfer arrangement that is arranged to allow a threshold torque to be applied to the shaft through the coupler without inducing relative rotation between the coupler and the shaft; the dolly having a body, the body having an engagement portion operative to rotate the coupler; a drive mounted to the body, the drive being operative to rotate the body upon rotation of the drive about a longitudinal axis of the body, and the drive being able to translate axially relative to the body between a first and second position; and biasing device operative to bias the drive into the first position.

Also disclosed is a method of installing a rock bolt into a bore formed in rock strata comprising: connecting a dolly to the rock bolt, imparting thrust to the dolly such that that the thrust is transferred through a biasing device located within the dolly to insert the rock bolt into the bore.

In some forms, the method includes rotating the dolly to rotate the rock bolt within the bore, rotating the dolly to release a torque transfer arrangement, and rotating the drive to tension the rock bolt.

In some forms, the method includes imparting thrust to a shaft of the dolly to axially translate the shaft relative to a body of the dolly such that the shaft engages the rock bolt, maintaining the thrust on the shaft to form a seal between the rock bolt and the shaft, and introducing water to a fluid passage extending through the shaft to flush the rock bolt.

In some forms, the method includes retracting the shaft to break the seal between the rock bolt and the shaft and form a gap between the rock bolt end and the shaft. In some forms the biasing device is operable to maintain the body in engagement with the tensioning device on retracting the shaft.

In some forms, the method includes rotating the shaft whilst in its retracted position to activate the tensioning device to tension the bolt. During tensioning the rock bolt is drawn into the dolly (which movement can be accommodated by the space formed between the end of the bolt and the retracted shaft).

Also disclosed is a tensioning device for a rock bolt having a shaft. The tensioning device may comprise; a base member securable to the shaft so as to be fixed with respect to the shaft; a bearer member moveable with respect to the base member in the direction of a longitudinal axis of the shaft but inhibited from rotating relative to the shaft about that axis; a coupler engageable with the bearer member and the base member so that movement of the coupler with respect to the shaft effects longitudinal movement of the bearer member with respect to the base member which in use allows for tensioning of the rock bolt; and a torque transfer arrangement that is arranged to allow a threshold torque to be applied to the shaft through the coupler without inducing relative rotation between the coupler and the shaft.

In some forms, the torque transfer arrangement is in the form of shear pin.

In some forms, the shear pin extends between the base member and the coupler.

In some forms, the bearer member is inhibited from rotating relative to the shaft by engagement of the bearer member with the base member.

In some forms, the bearer member and the base member have cooperating engaging surfaces that interengage to inhibit rotation of the bearer member relative to the base member.

In some forms, the bearer member is inhibited from rotating about the longitudinal axis during tensioning of the rock bolt.

In some forms, the bearer member has a leading end which is directly or indirectly engageable with a surface of the rock strata in which the rock bolt is installed.

In some forms, engagement of the leading end directly or indirectly with the rock surface inhibits rotational movement of the bearer member about the longitudinal axis.

In some forms, a rotation of the coupler about the longitudinal axis relative to the bearer member is able to effect the longitudinal movement of the bearer member relative to the base member.

In some forms, the coupler and the bearer member are threadingly coupled to one another.

In some forms, the bearer member includes an external thread which engages an internal thread formed on the coupler.

In some forms, the coupler is caused to bear against the base member during activation of the assembly so that movement of the coupler in a direction towards a proximal end of rock bolt is inhibited.

In some forms, the coupler and base member have cooperating abutment shoulders that engage during activation of the assembly.

In some forms, the base member includes one part that forms a barrel and wedge assembly that fixes the base member to the shaft.

In some forms, the base member includes a stem portion that extends along the shaft and the bearer member locates over the stem portion and has an inner surface that incorporates the engaging surface that cooperates with the engaging surface of the base member which is disposed on an exterior surface of the stem portion.

Also disclosed is a rock bolt comprising a shaft and a tensioning assembly mounted on that shaft.

Brief Description of the Drawings

Embodiments will now be described by way of example only, with reference to the accompanying drawings in which

Fig· 1 shows a side view of a tensioning device;

Fig. 2 shows a cross sectional view of the tensioning device of Fig. 1;

Fig. 3 shows a side view of a dolly for use with the tensioning device of Fig. 1;

Fig. 4 shows an exploded view of the dolly of Fig. 3;

Fig. 5 shows a cross sectional view through the dolly shown in Fig. 4;

Fig. 6 shows a cross-section through the connection between the dolly Fig. 3 and the tensioning device Fig. 1 in the first position;

Fig. 7 shows another cross-section through the connection between the dolly Fig. 3 and the tensioning device Fig. 1 in the first position;

Fig. 8 shows a cross-section through the connection between the dolly of Fig. 3 and the tensioning device of Fig. 1 in the second position;

Fig. 9 shows a side view of the dolly of Fig. 3 disconnected from the tensioning device of Fig 1;

Fig. 10a and 10b show a side view (7a) and cross-sectional view of the dolly of Fig. 3 connected to the tensioning device of Fig. 1;

Fig. 11 shows a perspective view of the dolly of Fig. 3 and tensioning device of Fig. 1 being thrust towards the rock strata;

Fig. 12 shows a perspective view of the dolly of Fig. 3 and tensioning device of Fig. 1 whereby the rock bolt is inserted into the rock strata;

Fig. 13a and 13b show cross-sectional views of the dolly of Fig. 3 being thrust from the first (10a) towards the second (10b) positions;

Fig. 14a and 14b show cross-sectional views through the dolly of Fig. 3 and tensioning device of Fig. 1 in the second potion;

Fig. 15a and 15b show cross-sectional views through the dolly of Fig. 3 and tensioning device of Fig. 1 in the second potion whilst the rock bolt is flushed with water;

Fig. 16 shows a cross-sectional view of the dolly of Fig. 3 and tensioning device of Fig. 1 following tensioning of the rock bolt.

Detailed Description

In the following detailed description, reference is made to accompanying drawings which form a part of the detailed description. The illustrative embodiments described in the detailed description, depicted in the drawings and defined in the claims, are not intended to be limiting. Other embodiments may be utilised and other changes may be made without departing from the spirit or scope of the subject matter presented. It will be readily understood that the aspects of the present disclosure, as generally described herein and illustrated in the drawings can be arranged, substituted, combined, separated and designed in a wide variety of different configurations, all of which are contemplated in this disclosure.

Rock Bolts

Rock bolts are often used to reinforce walls and roofs of tunnels in mining operations to prevent the possibility of collapse. Rock bolts include both rigid shaft rock bolts and flexible cable bolts. Cable bolts provide advantages when used in confined spaces, as they can be fed into a bore hole within the rock substrate at an angle. This allows an extended length of cable to be inserted into the rock substrate without the requirement of extensive excavation. Numerous cable bolts are available to reinforce walls and roofs of tunnels. One such cable bolt is manufactured from high strength flexible steel wire strands that are wound to form a single flexible stand. Another cable bolt is also manufactured from high strength flexible steel wire strands that are wound to form a single flexible stand but also includes a corrosion protected flexible central steel hollow tube for grout injection. In the following description reference is made to cable bolt 100 of this latter type that includes a shaft 101 formed of multiple steel strands 102 that are wound around a central steel hollow tube 103 for fluid injection into the bore. The tube 103 of the cable bolt includes a fitting 104 disposed at a proximal end 105 of the cable bolt 100 which is arranged to receive a fluid coupling as will be described in more detail below.

Tensioning Device

Tensioning devices are used to tension rock bolts to provide a compressive force on the substrate. Figs. 1 and 2 show a side view and sectional view respectively of a tensioning device 10 which in the illustrated form is connected to the cable bolt 100 adjacent its proximal end 105. The tensioning device comprises four primary components; a coupler, in the form of a rotatable outer sheath 12, a base member 14 that is adapted to be fixed to the shaft 101 of the rock bolt 101, a torque transfer arrangement 16 that is arranged to allow a threshold torque to be applied the shaft 101 of the rock bolt 100 through the outer sheath 12 without inducing relative rotation between the outer sheath 12 and the shaft 101, and a bearer member 18 which is movable relative to the base member 14 and which is arranged to abut either directly or indirectly the rock strata.

The base member 14 comprises a first part that forms a barrel 20, a second part that forms a stem 24, and tension wedges 22 which are located within the barrel 20 which in use secure the base member 14 with respect to the rock bolt 100. The tension wedges 22 receive the bolt shaft 101 in use and fix the bolt 100 to the base member 14. The tension wedges 22 are forced into engagement with the rock bolt under loading of the barrel. Further the barrel 20 and wedges 22 have sufficient strength to prevent shear stress failure to ensure that the rock bolt 100 is held in place by the tension wedges 22 within the barrel 20 under this loading.

The stem 24 of the base member 14 extends from the barrel 20 and along the rock bolt 100. The stem 24 is cylindrical and merges with the barrel to form an annular shoulder 26. An interior passage is provided through the barrel 20 and stem 24 to allow the rock bolt shaft 101 to be inserted through the stem.

In the illustrated embodiment, the torque transfer arrangement is in the form of a shear pin 16 that extends between the sheath 12 and the base member 14. It is understood that the torque transfer arrangement may also be in the form of a stop, or an adhesive (e.g., adhesive sold under the trade name LOCTITE), or any other suitable form of arrangement which prevents relative rotation between the coupler and the shaft up to a threshold loading. The torque transfer arrangement is able to break out when torque is applied to the outer sheath that exceeds that threshold torque such that the outer sheath is able to rotate relative to the shaft of the rock bolt.

The bearer member 18 is mounted on, and moveable with respect to, the stem 24. The bearer member 18 comprises an externally threaded body 28 and a dome head 30 at one end of the body. The body 28 has an internal cavity, the walls of which are complementary to the exterior of the stem 24 and include internal keyed sections. The internal keyed sections are located within the cavity such that when the bearer member 18 locates over the base member 14 (such that stem 24 extends into the cavity in bearer member 18), the external keyed sections on the stem 24 engage with the internal keyed sections on the bearer member 18 thereby inhibiting the rotation of the bearer member 18 with respect to the base member 14 about the longitudinal axis of the rock bolt 100. However, the bearer member 18 is movable along the stem 24 in the direction of the axis of the rock bolt.

The bearer member 18 is arranged so that the dome head 30 engages directly or indirectly with the rock surface into which the rock bolt extends. The head 30 which incorporates an opening to allow passage of the rock bolt shaft 101 through the bearer member, may be shaped other than a dome (for example being flattened to form a plate like appearance) so that it is engageable directly with the rock surface. However, in the illustrated forms, the dome head 30 is arranged to engage a separate rock bolt bearer plate which in use is positioned between the rock surface and the bearer member 18.

The dome head 30 is hemispherical and engages with an inner edge of the plate. This direct contact is arranged to provide sufficient frictional resistance so that in tensioning of the device 10 the engagement between the plate and the head 30 inhibits rotation of the head relative to the plate. Further the use of a generally hemispherical head 30 allows the head to remain engaged (and thereby provide the rotational resistance) with the plate when the bearer member 18 is tilted at an angle with respect to the bearing plate, allowing for the axis of the rock bolt to be tilted with respect to the bearing plate, which may occur in use. The inhibiting of the rotation of the bearer member assists in preventing twisting of the rock bolt during tensioning.

The outer sheath 12 is arranged to receive the body 28 of the bearer member 18 and extend partially over the base member 14. The outer sheath 12 is internally threaded 37 so as to engage with the externally threaded body 28 of the bearer member 18 and includes a shoulder 32 which is adapted to engage with the shoulder 26 formed on the base member 14 at the junction between the barrel part 53 and the stem 24. In this way, the sheath 12 engages both the base member 14 (through abutment of the shoulders 32 and 26) and the bearer member 18 (through engagement of the cooperating threads on those members).

Rotation of the outer sheath 12 in one direction allows for both rotation of the bolt (when the shear pin is intact) by the sheath and base member rotating together, and tensioning of the rock bolt (after the shear pin has failed) by causing relative rotation between the outer sheath and the base member. The outer sheath 12 is adapted to engage with a dolly that imparts this rotation so as to transmit that rotational force. This may be by making an external surface of the outer sheath 12 non-circular (such as a hexagonal or other polygonal profile) so that it can engage a dolly that incorporates a complementary shape and which locates over the outer sheath 12. In the following illustrated embodiments, the engagement is via teeth 11 formed on along an edge of the outer sheath 12 of the tensioning device 10.

Dolly

Figs. 3 illustrates a drive dolly which is suitable for use with the tensioning device 10 described above. It is to be appreciated that the drive dolly may be advantageously used with the tensioning device 10, but is not limited to that use and may be adapted (with for example different drive ends) to be used in other applications where rotational drive is required to be imparted to a device. The dolly may also be used with rigid and flexible bolts.

The dolly 1 comprises two primary components; a body, in the form of a casing 5, and a drive, in the form of shaft 13 that is mounted to the casing 5 and operative to rotate the casing 5 upon rotation of the shaft 13 about a longitudinal axis A of the casing.. The casing 5 has an engagement portion and its leading end, in the form of teeth 7, which connects to the tensioning device 10 on the rock bolt 100 (which in the illustrated embodiment is via the complementary teeth 11 formed on the outer sheath 12 of the tensioning device 10) to impart rotation to the sheath 12.

Fig. 4 shows an exploded view of the dolly 1. In use, in addition to being able to impart rotation to the casing, the shaft 13 is designed to be captured within the casing 5 and movable in an axial direction of the dolly 1 between first and second positions.

To provide this restricted axial movement, the shaft 13 includes an enlarged portion 17 which is designed to be captured within the casing 5. This enlarged portion 17 is disposed intermediate a first (or sealing) end 31 of the shaft and a second (driven) end 29 of the shaft. A retaining collar 39 is fitted within the casing 5 (typically by a circlip 40, although any other suitable fastening arrangement may be used) to limit movement of the enlarged portion in the casing in one direction, whereas an end fitting 42 is fitted on the casing to capture the enlarged head within the casing and limit axial movement of the shaft in the casing in the other direction. A biasing arrangement (which in the illustrated form comprises a compression spring 15) is disposed within the casing and locates around the shaft proximate the sealing end 31. The spring 15 bears against the enlarged portion 17 and the retaining collar so as to bias the engaging portion 17 into the first position wherein it abuts end fitting 42. In this first positon the shaft is retracted within the casing (relative to the leading end 7 of the casing 7). A drive receiving portion 43, which is adapted to fit into the chuck of a drilling rig, is provided adjacent the drive end to allow drive to be imparted to the shaft from a drilling rig.

Fig. 5 shows a sectional view of the dolly 1 when in the first position. To transfer rotation from the shaft 13 to the casing 5, the internal surface 41 of the casing 5 is noncircular in cross section and the external surface of the enlarged portion 17 is of a complementary non circular shape. In the illustrated form, these components are hexagonally shaped. With this arrangement, the torque is able to be transferred from the shaft to the casing whilst allowing the axial movement of the shaft relative to the casing between the first and second positions. As will be apparent to the skilled addressee, the coupling between the shaft 13 and the casing 5 that allows the shaft 13 to axially translate within the casing 5 and is able to cause rotation of the casing 5 upon rotation of the shaft 13 could be other than the disclosed hex arrangement and may be configured as any keyway configuration between the shaft and casing.

The shaft 13 is also provided with at least one fluid passage 27 that extends through the shaft to the sealing end 27. In the illustrated form, a single central passage is provided but it will be appreciated that other arrangements, such as an offset passage or multiple passages may be provided. The passage 27 opens to the sealing end 31 which is shaped to fit against fitting 104 formed on the cable bolt 100 to allow the fluid communication between the shaft passage 27 and the cable passage 101.

The dolly 1 is configured so that, whilst the casing 5 is connected to the tensioning device 10 (through the complementary engaging teeth 11,7), the sealing end 31 of the dolly shaft is able to move into and out of engagement with the end fitting 104 by axial movement of the shaft in the casing from the first position to, or towards, the second position.

Figs. 6 and 7 show cross-section views through the connection between the dolly and the tensioning device when the shaft is in the first (retracted) position. In this position, the sealing end 31 of the shaft 13 is spaced from the end fitting 104 of the shaft. This space (indicated by letter “S”) provides a gap into which the end 105 of the shaft 101 can move on tensioning of the bolt 100 by the tensioning device (as will be described in more detail below).

Furthermore, as best shown in Fig. 6, the sealing end 31 includes in internal cavity 35 that is adapted to receive the end fitting 104 therein. The internal cavity 35 includes a sealing surface 37. The sealing surface 37 configured to provide a sealing contact surface between the sealing end 31 of the shaft 13 when inserted therein. The internal cavity also includes a radial recess 34 that can receive the O-ring to further seal the shaft 13 to the rock bolt if required.

Fig. 8 shows a cross-sectional view through the connection between the dolly and the tensioning device when the sealing end 31 has the end fitting 104 received therein. In use, this will occur when the shaft is moved from its first retracted position towards, or at, its second position against the bias of the spring 15. When in this position, the contact between the end fitting 104 and the shaft provides a seal such that, in this position, water (or another fluid) introduced into the shaft passes through to an internal passage of the rock bolt without escaping into the internal recess 25 of the dolly.

Operation

Operation of the dolly 1 and tensioning device 10 will be described in detail with reference to Figs. 9 to 16.

In a first step, shown in Fig. 9, the tensioning device 10 is brought into contact with the end 105 of the cable bolt 100 (which has previously been placed in rock strata together with a resin cartridge). The dolly 1 is then attached to the tensioning device 10 by connecting the teeth 7 of the casing 5 to the corresponding teeth 11 on the tensioning device 10. When initially attached, the shaft 13 is in a first position (under the influence of the biasing spring 15). This is shown in Figs. 10a and 10b.

When in said first position, a mining drilling rig (not shown) is attached to the driven end 19 of the dolly. Fig. 11 shows a perspective view of the dolly and tensioning device and, as represented by the arrows, the mining drilling rig is able to impart thrust to insert the cable bolt fully in the rock strata 200 and rotation to install the bolt (as will be described in more detail below). Under the trust of the drilling rig, the bolt is moved from the position as shown in Fig. 11 to the position shown in Fig. 12, whereby the tension device is located against an abutment plate 39 mounted on the rock bolt 100 and disposed against the rock strata 200. In this position the resin cartridge inserted in the bore of the strata 200 is forced against the blind end of the bore by the rock bolt 100 and caused to burst. The thrust applied to the shaft 13 is transferred through the compression spring 15 to the bolt 100 (through the tensioning device 10). Typically the thrust applied is insufficient to compress the spring 15 to any great extent so that the shaft 13 remains at or close to the first (retracted) position. As such, the space “S” substantially remains between the shaft 13 and the end fitting 104 of the rock bolt 100.

When inserted into the rock strata 200 as shown in Fig. 12, the shaft 13 is rotated (under operation of the drill rig) to spin the rock bolt 100 in the bore hole to mix the resin. After adequate mixing time, the rotation of the bolt then stops.

In the next step as shown in Figs. 13a and 13b additional thrust is applied to the shaft 13 to cause it to move from its first position (as shown in Fig. 13 a) towards its second position until the sealing end of the shaft moves into engagement with the end fitting 104 on the rock bolt (as shown in Fig. 13b). Under this movement, there is translation of the enlarged portion 17 of the shaft 13 within the internal recess 19 to compress the internal compression spring 15 When the end fitting 104 on the rock bolt 100 is coupled with the sealing end 31 of the shaft 13, axial loading is maintained on the shaft 13 to ensure a sufficient water tight seal is maintained between the end fitting 104 and the sealing surface 37 of the shaft 13.

As the connection is made between the shaft 13 and the rock bolt 100, fluid can be introduced into the rock bolt passage via the shaft passage. This step is shown in Figs. 14 and 15 (note, the water is not shown in the Figs.). Flushing the rock bolt 100 with water, or another fluid, clears the rock bolt 100 of resin or debris that may have infiltrated the rock bolt 100 when it is inserted and rotated in the rock strata. Such debris can impede subsequent grouting of the rock bolt. Whilst maintaining thrust on the shaft 13 to ensure a sufficient water tight seal is maintained between the grout adaptor 43 and the sealing end 31 of the shaft 13, the flushing fluid is introduced into the fluid passage 27 via the driven end 29 of the shaft 13 (or via another port if provided). Fluid is pumped through the fluid passage 27 in the direction of the outlet 33 such that the fluid then passes into the rock bolt 100 for flushing of the rock bolt.

Following flushing of the rock bolt 100, the thrust on the shaft 13 is released and the shaft is retracted by pulling back the drill rig. Upon this withdrawal of the shaft, the compression spring biases the casing 5 to remain in engagement with the tensioning device 10 so that the shaft 13 will adopt the first position relative to the casing 5. This retracting movement of the shaft creates the space “S” between the sealing end 31 and the rock bolt end 105 such that the bolt can be tensioned by further rotation of the drive shaft 13 once the resin has set. This will now be described with reference to Fig. 16, which shows a cross-sectional view of the dolly and tensioning device following tensioning of the rock bolt.

No rotation or thrust is applied to the rock bolt 100 for a period of time that is sufficient to allow the resin to set, thereby anchoring the rock bolt 100 within the bore hole. After the resin has set, the shaft 13 is again rotated. As the rock bolt is now anchored within the bolt it is not free to spin. As a result there is a large increase in torque applied to the casing 5. This exceeds the threshold torque of the shear pin to cause break-out of the shear pin 16. Breaking the shear pin allows the outer sheath 12 to then rotate relative to the base member 14 (see Figs. 1 & 2), bearer 18 and rock bolt 100 such that engagement between the shoulders 47 and 49 forces the base member 14, and with it the end of the rock bolt captured within the base member 14, to move down the bearer 18 and away from the rock strata.

The space “S” (or stand-off distance) between the sealing surface 37 and the rock bolt 100 allows the rock bolt to move towards the sealing surface 37 during tensioning of the rock bolt. With the space, the shaft (and therefore the drilling rig) does not need to move axially (relative to the shaft axis) during tensioning. In the described embodiment, the space “S” is typically 45mm in the first position. This distance has been found to be adequate for the thread extension 79 of the rock bolt 100 that occurs during tensioning of the rock bolt. However, depending on the application, this distance can be varied. Fig. 16 shows the tensioning device 10 in the tensioned configuration with the head of the bearing member spaced from the end of the outer sheath.

After tensioning of the rock bolt 100, the dolly 1 is released from the tensioning device 10. At a later stage, the passage of the rock bolt is filled with grout.

An advantage of the disclosed drive assembly is that a single direction of rotation is used to both insert the rock bolt and tension the rock bolt. Additionally, the dolly can remain attached to the tensioning device during insertion, flushing and tensioning of the rock bolt.

In the claims which follow and in the preceding summary except where the context requires otherwise due to express language or necessary implication, the word “comprising” is used in the sense of “including”, that is, the features as above may be associated with further features in various embodiments.

Variations and modifications may be made to the parts previously described without departing from the spirit or ambit of the disclosure.

Claims

Claims

1. A dolly for imparting drive to a rock bolt, the dolly comprising; a body having an engagement portion which connects to a tensioning device on the rock bolt; a drive mounted to the body, the drive being operative to rotate the body upon rotation of the drive about a longitudinal axis of the body, and the drive being able to translate axially relative to the body; and biasing device operative to bias the drive into a first position.
2. A dolly according to claim 1, wherein the biasing device is able to transfer thrust from the drive to the body to insert the rock bolt into a bore.
3. A dolly according to any one of the preceding claims further comprising a coupling between the drive and the body such that the drive is able to axially translate relative to the body whereas rotation of the drive causes rotation the body.
4. A dolly according to any one of the preceding claims, wherein the drive comprises a projection that is able to axially translate within an interior recess of the body.
5. A dolly according to claim 4, wherein the projection is radially extending from the shaft.
6. A dolly according to claim 4 or claim 5, wherein the biasing device is in the form of a compression spring that is disposed within the interior recess of the body.
7. A dolly according to any one of claims 4 to 6, wherein the drive is limited to translate relative to the body between the first and a second position.
8. A dolly according to claim 7, wherein the compression spring is disposed about the drive and is adapted to compress between the projection of the drive and the body upon axial translation of the drive from the first position towards the second position.
9. A dolly according to any one of the preceding claims, wherein the drive includes a shaft incorporating one or more fluid passages.
10. A dolly according to claim 9, wherein the shaft includes a single fluid passage extending axially therethough for the introduction of water to the rock bolt.
11. A dolly according to claim 10, wherein the shaft includes opposing driven and sealing ends, and wherein the passage includes a port at the sealing end of the shaft for introducing the water into the rock bolt.
12. A dolly according to claim 11, wherein the sealing end includes in internal cavity adapted to receive the rock bolt therein, and wherein the internal cavity includes a wall about the port of the passage, the wall being configured to provide a sealing surface between the wall and the rock bolt.
13. A dolly according to any one of claims 8 to 12, when dependent on claim 7, wherein when the drive is in the first position the sealing surface is spaced from the rock bolt, and wherein when the drive is in the second position the sealing surface is in contact with the rock bolt.
14. A dolly according to claim 13, wherein when the drive is located between the first and second positions, the sealing surface is spaced from the rock bolt, the space defining a tensioning gap that allows for the rock bolt to move towards the sealing surface.
15. A dolly according to any one of the preceding claims, wherein the engagement potion of the body comprises a profiled end surface that is arranged to engage with cooperating end surface of the tensioning device on the rock bolt.
16. A dolly according to any one of claims 8 to 15, when dependent of claim 7, wherein the body comprises an releasable plate disposed adjacent the engagement portion of the body, and wherein the compression spring is adapted to compress between the projection of the drive and the releasable plate upon axial translation of the drive from the first position towards the second position.
17. A drive assembly for a rock bolt having a shaft, the drive assembly comprising: a tensioning device having a coupler that is adapted to be coupled to a dolly, a base member adapted to be fixed to the shaft of the rock bolt, and a torque transfer arrangement that is arranged to allow a threshold torque to be applied to the shaft through the coupler without inducing relative rotation between the coupler and the shaft; the dolly having a body, the body having an engagement portion operative to rotate the coupler; a drive mounted to the body, the drive being operative to rotate the body upon rotation of the drive about a longitudinal axis of the body, and the drive being able to translate axially relative to the body between a first and second position; and biasing device operative to bias the drive into the first position.
18. A drive assembly in accordance with claim 17 wherein the dolly is as defined in any one of claims 1 to 17.
19. A method of installing a rock bolt into a bore formed in rock strata comprising: connecting a dolly to the rock bolt; and imparting thrust to the dolly such that that the thrust is transferred through a biasing device located within the dolly to insert the rock bolt into the bore.
20. A method in accordance with claim 19 further comprising; imparting thrust to a shaft of the dolly to axially translate the shaft relative to a body of the dolly such that the shaft engages the rock bolt; maintaining the thrust on the shaft to form a seal between the rock bolt and the shaft; and introducing water to a fluid passage extending through the shaft to flush the rock bolt.
21. A method in accordance with claim 20 further comprising; releasing the thrust on the shaft such that the biasing device biases the shaft away from the rock bolt to break the seal between the rock bolt and the shaft.
22. A method in accordance with claim 21 further comprising; rotating the shaft such that the rock bolt is drawn into the dolly and thereby tensioned.
23. A tensioning device for a rock bolt having a shaft, the tensioning assembly comprising: a base member securable to the shaft so as to be fixed with respect to the shaft; a bearer member moveable with respect to the base member in the direction of a longitudinal axis of the shaft but inhibited from rotating relative to the shaft about that axis; a coupler engageable with the bearer member and the base member so that movement of the coupler with respect to the shaft effects longitudinal movement of the bearer member with respect to the base member which in use allows for tensioning of the rock bolt; and a torque transfer arrangement that is arranged to allow a threshold torque to be applied to the shaft through the coupler without inducing relative rotation between the coupler and the shaft.
24. A tensioning device according to claim 23, wherein the torque transfer arrangement is in the form of shear pin.
25. A tensioning device according to claim 24, wherein the shear pin extends between the base member and the coupler.
26. A tensioning device as defined in any one of claims 23 to 25, wherein the bearer member is inhibited from rotating relative to the shaft by engagement of the bearer member with the base member.
27. A tensioning device as defined in claim 26, wherein the bearer member and the base member have cooperating engaging surfaces that interengage to inhibit rotation of the bearer member relative to the base member.
28. A tensioning device as defined in any one of claims 23 to 27, wherein the bearer member is inhibited from rotating about the longitudinal axis during tensioning of the rock bolt.
29. A tensioning device as defined in any one of claims 23 to 28, wherein the bearer member has a leading end which is directly or indirectly engageable with a surface of the rock strata in which the rock bolt is installed.
30. A tensioning device as defined in claim 29, wherein engagement of the leading end directly or indirectly with the rock surface inhibits rotational movement of the bearer member about the longitudinal axis.
31. A tensioning device as defined in any one of claims 23 to 30, wherein a rotation of the coupler about the longitudinal axis relative to the bearer member is able to effect the longitudinal movement of the bearer member relative to the base member.
32. A tensioning device as defined in any one of claims 23 to 31, wherein the coupler and the bearer member are threadingly coupled to one another.
33. A tensioning device according to claim 32, wherein the bearer member includes an external thread which engages an internal thread formed on the coupler.
34. A tensioning device as defined in any of claims 23 to 33, wherein the coupler is caused to bear against the base member during activation of the assembly so that movement of the coupler in a direction towards a proximal end of rock bolt is inhibited.
35. A tensioning device as defined in claim 34, wherein the coupler and base member have cooperating abutment shoulders that engage during activation of the assembly.
36. A tensioning device as defined in any one of claims 23 to 35, wherein the base member includes one part that forms a barrel and wedge assembly that fixes the base member to the shaft.
37. A tensioning device as defined in any one of claims 23 to 36, when dependent on claim 27, wherein the base member includes a stem portion that extends along the shaft and the bearer member locates over the stem portion and has an inner surface that incorporates the engaging surface that cooperates with the engaging surface of the base member which is disposed on an exterior surface of the stem portion.
38. A rock bolt comprising a shaft and a tensioning assembly as claimed in any one of claims 23 to 37 mounted on that shaft.