CA2244617A1 - A rock bolt assembly - Google Patents
A rock bolt assembly Download PDFInfo
- Publication number
- CA2244617A1 CA2244617A1 CA002244617A CA2244617A CA2244617A1 CA 2244617 A1 CA2244617 A1 CA 2244617A1 CA 002244617 A CA002244617 A CA 002244617A CA 2244617 A CA2244617 A CA 2244617A CA 2244617 A1 CA2244617 A1 CA 2244617A1
- Authority
- CA
- Canada
- Prior art keywords
- rock bolt
- nut
- rock
- barrier
- bolt assembly
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
- 239000011435 rock Substances 0.000 title claims abstract description 136
- 230000004888 barrier function Effects 0.000 claims abstract description 33
- 239000011347 resin Substances 0.000 claims abstract description 12
- 229920005989 resin Polymers 0.000 claims abstract description 12
- 238000000034 method Methods 0.000 claims abstract description 8
- 230000003019 stabilising effect Effects 0.000 claims abstract 4
- 230000000717 retained effect Effects 0.000 claims description 4
- 238000005553 drilling Methods 0.000 description 4
- 239000000463 material Substances 0.000 description 4
- 229910000831 Steel Inorganic materials 0.000 description 2
- 230000008901 benefit Effects 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000005755 formation reaction Methods 0.000 description 2
- 230000007246 mechanism Effects 0.000 description 2
- 238000005065 mining Methods 0.000 description 2
- 239000010959 steel Substances 0.000 description 2
- 241000534944 Thia Species 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 239000004568 cement Substances 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 239000003245 coal Substances 0.000 description 1
- 230000002844 continuous effect Effects 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 239000011440 grout Substances 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 235000012976 tarts Nutrition 0.000 description 1
Classifications
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21D—SHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
- E21D21/00—Anchoring-bolts for roof, floor in galleries or longwall working, or shaft-lining protection
- E21D21/0026—Anchoring-bolts for roof, floor in galleries or longwall working, or shaft-lining protection characterised by constructional features of the bolts
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21D—SHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
- E21D20/00—Setting anchoring-bolts
- E21D20/02—Setting anchoring-bolts with provisions for grouting
Landscapes
- Engineering & Computer Science (AREA)
- Mining & Mineral Resources (AREA)
- Structural Engineering (AREA)
- Life Sciences & Earth Sciences (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Geochemistry & Mineralogy (AREA)
- Geology (AREA)
- Earth Drilling (AREA)
Abstract
A rock bolt assembly and a method of stabilising a rock mass by means of the rock bolt assembly is disclosed. The rock bolt assembly comprises a rock bolt (3), a nut (5) on a threaded section (9) of the rock bolt, and a barrier (41), such as a washer, which prevents removal of the nut. The method includes the steps of:
(i) rotating the nut (5) in a first direction against the barrier and thereafter rotating the nut and the rock bolt (3) and mixing resin in a drilled hole (11) in the rock mass; and (ii) after the resin has set, rotating the nut (5) in the opposite direction (away from the barrier) against the rock mass and thereby tensioning the rock bolt (3).
(i) rotating the nut (5) in a first direction against the barrier and thereafter rotating the nut and the rock bolt (3) and mixing resin in a drilled hole (11) in the rock mass; and (ii) after the resin has set, rotating the nut (5) in the opposite direction (away from the barrier) against the rock mass and thereby tensioning the rock bolt (3).
Description
A ROCR BOLT ASSEMBLY
The ~reaent invention relates to an assembly of a rock bolt and a nut.
The ~resent invention relates particularly, although by no mean~ exclu~ively, to an assembly of a rock bolt and a nut that i~ ada~ted to form part of a rock bolt system in which:
(i) the rock bolt is anchored by means of a cement grout or a chemical resin (hereinafter referred to as "re~in") in a hole drilled in a rock formation; and (ii) the nut tension~ the rock bolt and ~ro~ides the end restraint on one end of the bolt to retain bearing plates, strap~, mesh etc.
Rock bolt sy~tems are used to stabilise rock formations in a wide range of ~ituation~, such a~
underground and surface mines, tunnel~ and cuttings, and rock bolt~ have achieved a high acce~tance in both the mining and civil engineering indu~tries.
In any given a~plication, the ~urpo~e of a resin anchored rock bolt ~y~tem i~ to apply a clam~ing or confining action to a rock ma~s to control deformation of the rock mass and to enh~nce the atrength of the rock mass.
In other words, the ~ur~ose of a rock bolt system is to allow load to be tran~ferred from a rock mass, through the resin, to the rock bolt.
A conventional procedure for installing a rock bolt assembly com~rise~ the following ste~s:
(1) Drill a hole in a rock mas~ to a required de~th.
The ~reaent invention relates to an assembly of a rock bolt and a nut.
The ~resent invention relates particularly, although by no mean~ exclu~ively, to an assembly of a rock bolt and a nut that i~ ada~ted to form part of a rock bolt system in which:
(i) the rock bolt is anchored by means of a cement grout or a chemical resin (hereinafter referred to as "re~in") in a hole drilled in a rock formation; and (ii) the nut tension~ the rock bolt and ~ro~ides the end restraint on one end of the bolt to retain bearing plates, strap~, mesh etc.
Rock bolt sy~tems are used to stabilise rock formations in a wide range of ~ituation~, such a~
underground and surface mines, tunnel~ and cuttings, and rock bolt~ have achieved a high acce~tance in both the mining and civil engineering indu~tries.
In any given a~plication, the ~urpo~e of a resin anchored rock bolt ~y~tem i~ to apply a clam~ing or confining action to a rock ma~s to control deformation of the rock mass and to enh~nce the atrength of the rock mass.
In other words, the ~ur~ose of a rock bolt system is to allow load to be tran~ferred from a rock mass, through the resin, to the rock bolt.
A conventional procedure for installing a rock bolt assembly com~rise~ the following ste~s:
(1) Drill a hole in a rock mas~ to a required de~th.
(2) Pu~h a cartridge of re~in into the drilled hole with the rock bolt until the cartridge reaches the end of the hole and the rock bolt ~enetrate~
the cartridge and relea~e~ the re~in.
the cartridge and relea~e~ the re~in.
(3) Rotate the rock bolt to mix the re~in.
(4) After the re~in ~et~, typically within a minute, rotate the nut on the rock bolt until the nut i8 tight up again t a bearing plate against the rock mas~ and a tension i~ generated in the rock bolt.
There are a number of known option~ for cau~ing rotation of the rock bolt in the re~in mixing step (3).
The options are ba~ed on the use of a drilling mach;ne and on providing some mean~ on or associated with the rock bolt that can be received in a drive ~ocket of the drilling mach;ne. The known "means~ include:
(i) a forged nut on the end of the rock bolt;
(ii) a forged drive square on the end of the rock bolt;
(iii) a crimped section of thread on the end of the nut, ~uch that a threshold breakout torque i~ required to break through the crim~ed section of thread and release the nut for rotation, and whereby ~o~itioning a drive aocket to receive the nut and o~erating at torques les~ than the threshold torque cau~e~ rotation of the rock bolt with the nut;
(iv) a washer tack welded on the end of the nut which, as with (iii) above, requires a threshold breakout torque to release the nut;
(v) a resin or ~lastic plug inserted into the end of the nut which, as with (iii) and (iv) above, requires a threshold breakout torque to release the nut;
(vi) a small steel roll pin inserted into a hole drilled through a side of the nut and into the threaded section of the rock bolt which, as with (iii) to (v) above, requires a threshold breakout torque to release the nut;
(vii) a washer located in a recessed section in a nut and retained by "crimps" at the end of the recessed section and, as with (iii) and (iv) above, requires a threshold breakout torque to release the nut;
(viii) double lock nuts which, as with (iii), (iv) and (vii) above, requires a threshold breakout torque to release the nut; and (ix) an increased diameter of the rock bolt immediately above the nut which requires a threshold breakout torque to screw the nut past the increased diameter section of the rock bolt.
The above-described known o~tions have a range of disadvantages including, inconvenience, high cost, residual material left in the drive aocket which accumulates with each rock bolt assembly, and residual tor~ue - the nut~ are not free r~nn;ng once the breakout torque has been overcome.
An object of the present invention i~ to provide an o~tion for causing rotation of a rock bolt in the re~in mixing ste~ (3) which alleviate~ the disadvantage~ of the known o~tions described above.
According to the ~re~ent invention there is ~rovided a method of ~tabili~ing a rock mas~ by means of a rock bolt as~embly located in a drilled hole in the rock ma~ and retained in the hole by resin, the rock bolt as~embly comDrising a rock bolt having a threaded ~ection, a tensioning nut on the threaded ~ection, and a barrier for ~reventing removal of the nut from a rearward end of the rock bolt, the method being characterised by:
(i) locating the rock bolt of the rock bolt a~embly and a cartridge of re~in in the hole;
(ii) rotating the nut of the rock bolt assembly in a first direction against the barrier and thereby causing rotation of the rock bolt with the nut and thereby mixing the re~in in the hole; and (iii)after the re~in has ~et, rotating the nut in the op~osite direction to tighten the nut directly or indirectly against the rock ma~ and thereby tensioning the rock bolt.
According to the pre~ent invention there is al~o provided a rock bolt as~embly for tabilising a rock ma~, which rock bolt as~embly com~ri~es:
(i) a rock bolt having a forward end, a rearward end, and a threaded section;
(ii) a nut on the threaded section; and (iii)a barrier which preventa remo~al of the nut from the rearward end of the rock bolt.
The rock bolt may be formed from any suitable material. By way of exam~le, the rock bolt may be formed from steel. By way of further exam~le, the rock bolt may be formed from a plastic~ material.
The barrier may be formed from any ~uitable material and be of any ~uitable shape.
By way of exam~le, the barrier may be a deformation of the rearward end of the rock bolt which disru~ts the thread or alter~ the cross-section of the end.
By way of further exam~le, the barrier may be a sto~
de~ice welded, forged, glued or otherwi~e co~nected to the rearward end of the rock bolt.
Preferably, the main criteria for the ~hape of the barrier are that:
(a) the barrier be formed to contact a rearward face of the nut and thereby ~revent the nut being screwed off the rearward end of the rock bolt;
(b) the nut doe~ not become locked on the barrier; in other words, the torque required to enable the nut to be screwed away from the barrier (ie, the relea~e torque) should be les~ than that a~lied to rotate the nut and the rock bolt in ste~ (ii) (ie, the mixing torque); and .
(c) the barrier ~hould not damage the thread of the nut ~o that the nut ia free to rotate during tightening.
Preferably the barrier i~ a washer welded to the rock bolt.
It iR ~referred ~articularly that the maximum width dimension of the barrier be less that that of the nut so that the barrier doe~ not prevent altogether or restrict a drive ~ocket of a drill mean~ engaging the nut.
The a~licant has found in a ~eries of laboratory te~t~ that wa~her~ welded onto rock bolt~ are an effective barrier. S~ecifically, the a~licant found that the relea~e torque required to relea~e nuts from contact with washer~ welded on rock bolt~ waR 23 to 28% less than the mixing torque a~plied in the fir~t instance to rotate the nut~ against the wa hers and thereafter to rotate the nutc and the rock bolts. This mean~ that there is minimal if any ri~k of locking nut~ on the wa hers after rotating the - nuts in the first direction de~cribed above.
The rock bolt may be of any suitable configuration.
Preferably the rock bolt com~ri~e~ a continuous or di~continuou~ rib exten~;ng along at least ~art of the length of the rock bolt.
The present invention i~ de~cribed further by way of example with reference to the accompanying drawing which is a partially ~ectional side elevation of a ~referred embodiment of a rock bolt a~embly of the ~resent invention re~in anchored in a drilled hole 11 in a mine roof 13.
The rock bolt a~embly of the ~re~ent invention is ~articularly although by no means exclusively ada~ted for u~e in coal or metalliferous mines.
The rock bolt assembly com~ri~e~ a rock bolt 3 having a forward end 17, a rearward end 19, a generally cylindrical core 7, a continuous rib 21 exten~;ng along a ~ub tantial part of the length of the core 7, and a single ~tart left hand thread 9 formed on a lower ~ection of the core 7.
The rock bolt assembly further comprise~ a nut 5 threaded on the rock bolt 3.
The rock bolt as~embly i8 characteri~ed by a barrier 41 connected to the rearward end 19 of the rock bolt 3 which in u~e can contact a rearward face 43 of the nut 5 and thereby prevent removal of the nut 5 from the rearward end 19.
The barrier 41 may be any ~uitable form of barrier.
Ty~ically, the barrier 41 comprises a ~top device, such a~
a wa~her (a~ shown in the figure), welded or forged onto the rock bolt 3. Alternatively, the barrier 41 is a deformed section of the rock bolt 3 formed by hammering or otherwise a~plying a force to the rearward end 19 of the rock bolt 3 to di~ru~t the thread on the ~ection of the rock bolt 3 or to change the cro~ ection of the end.
In u~e of the rock bolt a~sembly, the hole 11 is drilled in the roof 13 of a mine, a bearing ~late a~embly 15 is pre-a~embled on the rock bolt a~sembly, and a cartridge (not ~hown) of resin and the rock bolt 3 are inserted into the hole 11 until the rock bolt 3 penetrate~
the cartridge and relea~e~ the re~in. Thereafter, a drive ~ocket (not ~hown) of a drill meanq i~ po~itioned to receive the nut 5 and i~ operated to drive the nut 5 in a clockwi~e direction. Thia rotation ha~ the effect of moving the nut 5 relative to the rock bolt 3 until the nut 5 contacts the barrier 41 on the rearward end 19 of the rock bolt 3. Thereafter, continued rotation of the nut 5 in the clockwi~e direction al~o rotate~ the rock bolt 3, and this ha~ the effect of mixing the re~in in the hole 11.
After the reain sets, the drilling machine is o~erated to rotate the nut 5 in the anti-clockwi~e direction, and thi~
rotation screw~ the nut 5 away from the barrier 41 and into contact with the bearinq ~late assembly to tension the rock bolt 3.
It is noted that the nut 5 would be rotated in the op~osite direction to that indicated above in situations where the thread 9 i~ a right hand thread rather than a left hand thread as shown in the drawing.
In laboratory te~ts on the above-described rock bolt as~embly the a~plicant was able to operate with mixing torques of 280 Nm with hydraulic bolting equi~ment and 120 Nm with hand-held bolting equipment without break-out and thread damage. Moreover, as indicated above, the applicant found that the relea~e torque~ were 23 to 28% less than that of the mixing torque~. In addition, the applicant applied torque~ of u~ to 500 Nm without severing the wa~hers and breAk;ng out the nut~ from the rearward end~ of the rock bolts. The laboratory te~t~ were carried out on the above-de~cribed rock bolt assembly with rock bolts having nominal diameters of 21.7mm and 25.8mm and with wa~her~ having a nominal thickness of 4mm, central hole diameters of 24mm and 25mm, and outer diameter~ of 36mm and 40mm welded to the rock bolts. The weld~ connecting the washers to the rock bolt~ extended around a~proximately one half of the circumference of the central hole of washer on both faces of each wa~her.
The above-described rock bolt a~sembly ha~ a number of advantages over conventional o~tion~.
By way of example, the ~re~ent invention makes it possible to ensure a high level of control over the extent to which the nuts 5 are retained on the rock bolts 3 - this level of consiAtency is im~ortant in mining o~erations.
Furthermore, the ~resent invention ensures that nuts will never experience ~remature breakout.
Furthermore, the rock bolt 3 and the nut 5 can be assembled together off-site and thi~ reducea handling difficulties on-site and the number of component~ that must be handled on-site.
Furthermore, the present invention enable~ one breakout ~ystem to be used for all different rock bolt lengths and for all different drilling m~h;ne~ compared to having up to 5 different breakout nuts all with different breakout torque~.
Furthermore, the problem of debri~ accumulating in the drill ~ocket from the break-out mechanisms in the nut i~
overcome.
The prior art ~roblem of high residual torque required to turn nut~ after the breakout "mechani~mn ha~ been broken is avoided by the ~re~ent invention.
Furthermore, the pre~ent invention make~ it ~o~ible to de~ign the thread form on the rock bolt pecifically to im~rove the mechanical advantage of the nut - rather than to trigger the breakout mechanism.
Many modification~ may be made to the ~referred embodiment of the rock bolt a~embly described above without de~arting from the s~irit and ~co~e of the ~re~ent invention.
By way of exam~le, whilst the preferred embodiment described above com~rises a rock bolt 3 of a ~articular configuration, it is noted that the ~resent invention is not 80 limited and extends to any suitable form of rock bolt 3.
There are a number of known option~ for cau~ing rotation of the rock bolt in the re~in mixing step (3).
The options are ba~ed on the use of a drilling mach;ne and on providing some mean~ on or associated with the rock bolt that can be received in a drive ~ocket of the drilling mach;ne. The known "means~ include:
(i) a forged nut on the end of the rock bolt;
(ii) a forged drive square on the end of the rock bolt;
(iii) a crimped section of thread on the end of the nut, ~uch that a threshold breakout torque i~ required to break through the crim~ed section of thread and release the nut for rotation, and whereby ~o~itioning a drive aocket to receive the nut and o~erating at torques les~ than the threshold torque cau~e~ rotation of the rock bolt with the nut;
(iv) a washer tack welded on the end of the nut which, as with (iii) above, requires a threshold breakout torque to release the nut;
(v) a resin or ~lastic plug inserted into the end of the nut which, as with (iii) and (iv) above, requires a threshold breakout torque to release the nut;
(vi) a small steel roll pin inserted into a hole drilled through a side of the nut and into the threaded section of the rock bolt which, as with (iii) to (v) above, requires a threshold breakout torque to release the nut;
(vii) a washer located in a recessed section in a nut and retained by "crimps" at the end of the recessed section and, as with (iii) and (iv) above, requires a threshold breakout torque to release the nut;
(viii) double lock nuts which, as with (iii), (iv) and (vii) above, requires a threshold breakout torque to release the nut; and (ix) an increased diameter of the rock bolt immediately above the nut which requires a threshold breakout torque to screw the nut past the increased diameter section of the rock bolt.
The above-described known o~tions have a range of disadvantages including, inconvenience, high cost, residual material left in the drive aocket which accumulates with each rock bolt assembly, and residual tor~ue - the nut~ are not free r~nn;ng once the breakout torque has been overcome.
An object of the present invention i~ to provide an o~tion for causing rotation of a rock bolt in the re~in mixing ste~ (3) which alleviate~ the disadvantage~ of the known o~tions described above.
According to the ~re~ent invention there is ~rovided a method of ~tabili~ing a rock mas~ by means of a rock bolt as~embly located in a drilled hole in the rock ma~ and retained in the hole by resin, the rock bolt as~embly comDrising a rock bolt having a threaded ~ection, a tensioning nut on the threaded ~ection, and a barrier for ~reventing removal of the nut from a rearward end of the rock bolt, the method being characterised by:
(i) locating the rock bolt of the rock bolt a~embly and a cartridge of re~in in the hole;
(ii) rotating the nut of the rock bolt assembly in a first direction against the barrier and thereby causing rotation of the rock bolt with the nut and thereby mixing the re~in in the hole; and (iii)after the re~in has ~et, rotating the nut in the op~osite direction to tighten the nut directly or indirectly against the rock ma~ and thereby tensioning the rock bolt.
According to the pre~ent invention there is al~o provided a rock bolt as~embly for tabilising a rock ma~, which rock bolt as~embly com~ri~es:
(i) a rock bolt having a forward end, a rearward end, and a threaded section;
(ii) a nut on the threaded section; and (iii)a barrier which preventa remo~al of the nut from the rearward end of the rock bolt.
The rock bolt may be formed from any suitable material. By way of exam~le, the rock bolt may be formed from steel. By way of further exam~le, the rock bolt may be formed from a plastic~ material.
The barrier may be formed from any ~uitable material and be of any ~uitable shape.
By way of exam~le, the barrier may be a deformation of the rearward end of the rock bolt which disru~ts the thread or alter~ the cross-section of the end.
By way of further exam~le, the barrier may be a sto~
de~ice welded, forged, glued or otherwi~e co~nected to the rearward end of the rock bolt.
Preferably, the main criteria for the ~hape of the barrier are that:
(a) the barrier be formed to contact a rearward face of the nut and thereby ~revent the nut being screwed off the rearward end of the rock bolt;
(b) the nut doe~ not become locked on the barrier; in other words, the torque required to enable the nut to be screwed away from the barrier (ie, the relea~e torque) should be les~ than that a~lied to rotate the nut and the rock bolt in ste~ (ii) (ie, the mixing torque); and .
(c) the barrier ~hould not damage the thread of the nut ~o that the nut ia free to rotate during tightening.
Preferably the barrier i~ a washer welded to the rock bolt.
It iR ~referred ~articularly that the maximum width dimension of the barrier be less that that of the nut so that the barrier doe~ not prevent altogether or restrict a drive ~ocket of a drill mean~ engaging the nut.
The a~licant has found in a ~eries of laboratory te~t~ that wa~her~ welded onto rock bolt~ are an effective barrier. S~ecifically, the a~licant found that the relea~e torque required to relea~e nuts from contact with washer~ welded on rock bolt~ waR 23 to 28% less than the mixing torque a~plied in the fir~t instance to rotate the nut~ against the wa hers and thereafter to rotate the nutc and the rock bolts. This mean~ that there is minimal if any ri~k of locking nut~ on the wa hers after rotating the - nuts in the first direction de~cribed above.
The rock bolt may be of any suitable configuration.
Preferably the rock bolt com~ri~e~ a continuous or di~continuou~ rib exten~;ng along at least ~art of the length of the rock bolt.
The present invention i~ de~cribed further by way of example with reference to the accompanying drawing which is a partially ~ectional side elevation of a ~referred embodiment of a rock bolt a~embly of the ~resent invention re~in anchored in a drilled hole 11 in a mine roof 13.
The rock bolt a~embly of the ~re~ent invention is ~articularly although by no means exclusively ada~ted for u~e in coal or metalliferous mines.
The rock bolt assembly com~ri~e~ a rock bolt 3 having a forward end 17, a rearward end 19, a generally cylindrical core 7, a continuous rib 21 exten~;ng along a ~ub tantial part of the length of the core 7, and a single ~tart left hand thread 9 formed on a lower ~ection of the core 7.
The rock bolt assembly further comprise~ a nut 5 threaded on the rock bolt 3.
The rock bolt as~embly i8 characteri~ed by a barrier 41 connected to the rearward end 19 of the rock bolt 3 which in u~e can contact a rearward face 43 of the nut 5 and thereby prevent removal of the nut 5 from the rearward end 19.
The barrier 41 may be any ~uitable form of barrier.
Ty~ically, the barrier 41 comprises a ~top device, such a~
a wa~her (a~ shown in the figure), welded or forged onto the rock bolt 3. Alternatively, the barrier 41 is a deformed section of the rock bolt 3 formed by hammering or otherwise a~plying a force to the rearward end 19 of the rock bolt 3 to di~ru~t the thread on the ~ection of the rock bolt 3 or to change the cro~ ection of the end.
In u~e of the rock bolt a~sembly, the hole 11 is drilled in the roof 13 of a mine, a bearing ~late a~embly 15 is pre-a~embled on the rock bolt a~sembly, and a cartridge (not ~hown) of resin and the rock bolt 3 are inserted into the hole 11 until the rock bolt 3 penetrate~
the cartridge and relea~e~ the re~in. Thereafter, a drive ~ocket (not ~hown) of a drill meanq i~ po~itioned to receive the nut 5 and i~ operated to drive the nut 5 in a clockwi~e direction. Thia rotation ha~ the effect of moving the nut 5 relative to the rock bolt 3 until the nut 5 contacts the barrier 41 on the rearward end 19 of the rock bolt 3. Thereafter, continued rotation of the nut 5 in the clockwi~e direction al~o rotate~ the rock bolt 3, and this ha~ the effect of mixing the re~in in the hole 11.
After the reain sets, the drilling machine is o~erated to rotate the nut 5 in the anti-clockwi~e direction, and thi~
rotation screw~ the nut 5 away from the barrier 41 and into contact with the bearinq ~late assembly to tension the rock bolt 3.
It is noted that the nut 5 would be rotated in the op~osite direction to that indicated above in situations where the thread 9 i~ a right hand thread rather than a left hand thread as shown in the drawing.
In laboratory te~ts on the above-described rock bolt as~embly the a~plicant was able to operate with mixing torques of 280 Nm with hydraulic bolting equi~ment and 120 Nm with hand-held bolting equipment without break-out and thread damage. Moreover, as indicated above, the applicant found that the relea~e torque~ were 23 to 28% less than that of the mixing torque~. In addition, the applicant applied torque~ of u~ to 500 Nm without severing the wa~hers and breAk;ng out the nut~ from the rearward end~ of the rock bolts. The laboratory te~t~ were carried out on the above-de~cribed rock bolt assembly with rock bolts having nominal diameters of 21.7mm and 25.8mm and with wa~her~ having a nominal thickness of 4mm, central hole diameters of 24mm and 25mm, and outer diameter~ of 36mm and 40mm welded to the rock bolts. The weld~ connecting the washers to the rock bolt~ extended around a~proximately one half of the circumference of the central hole of washer on both faces of each wa~her.
The above-described rock bolt a~sembly ha~ a number of advantages over conventional o~tion~.
By way of example, the ~re~ent invention makes it possible to ensure a high level of control over the extent to which the nuts 5 are retained on the rock bolts 3 - this level of consiAtency is im~ortant in mining o~erations.
Furthermore, the ~resent invention ensures that nuts will never experience ~remature breakout.
Furthermore, the rock bolt 3 and the nut 5 can be assembled together off-site and thi~ reducea handling difficulties on-site and the number of component~ that must be handled on-site.
Furthermore, the present invention enable~ one breakout ~ystem to be used for all different rock bolt lengths and for all different drilling m~h;ne~ compared to having up to 5 different breakout nuts all with different breakout torque~.
Furthermore, the problem of debri~ accumulating in the drill ~ocket from the break-out mechanisms in the nut i~
overcome.
The prior art ~roblem of high residual torque required to turn nut~ after the breakout "mechani~mn ha~ been broken is avoided by the ~re~ent invention.
Furthermore, the pre~ent invention make~ it ~o~ible to de~ign the thread form on the rock bolt pecifically to im~rove the mechanical advantage of the nut - rather than to trigger the breakout mechanism.
Many modification~ may be made to the ~referred embodiment of the rock bolt a~embly described above without de~arting from the s~irit and ~co~e of the ~re~ent invention.
By way of exam~le, whilst the preferred embodiment described above com~rises a rock bolt 3 of a ~articular configuration, it is noted that the ~resent invention is not 80 limited and extends to any suitable form of rock bolt 3.
Claims (8)
1. A method of stabilising a rock mass by means of a rock bolt assembly located in a drilled hole in the rock mass and retained in the hole by resin, the rock bolt assembly comprising a rock bolt having a threaded section, a tensioning nut on the threaded section, and a barrier for preventing removal of the nut from a rearward end of the rock bolt, the method being characterised by:
(i) locating the rock bolt of the rock bolt assembly and a cartridge of resin in the hole;
(ii) rotating the nut of the rock bolt assembly in a first direction against the barrier and thereby causing rotation of the rock bolt with the nut and thereby mixing the resin in the hole; and (iii) after the resin has set, rotating the nut in the opposite direction to tighten the nut directly or indirectly against the rock mass and thereby tensioning the rock bolt.
(i) locating the rock bolt of the rock bolt assembly and a cartridge of resin in the hole;
(ii) rotating the nut of the rock bolt assembly in a first direction against the barrier and thereby causing rotation of the rock bolt with the nut and thereby mixing the resin in the hole; and (iii) after the resin has set, rotating the nut in the opposite direction to tighten the nut directly or indirectly against the rock mass and thereby tensioning the rock bolt.
2. A rock bolt assembly for stabilising a rock mass, which rock bolt assembly comprises:
(i) a rock bolt having a forward end, a rearward end, and a threaded section;
(ii) a nut on the threaded section; and (iii) a barrier which prevents removal of the nut from the rearward end of the rock bolt.
(i) a rock bolt having a forward end, a rearward end, and a threaded section;
(ii) a nut on the threaded section; and (iii) a barrier which prevents removal of the nut from the rearward end of the rock bolt.
3. The rock bolt assembly defined in claim 2 wherein the barrier is a deformation of the rearward end of the rock bolt which disrupts the thread or alters the cross-section of the end.
4. The rock bolt assembly defined in claim 2 wherein the barrier is a stop device welded or forged or glued onto the rearward end of the rock bolt.
5. The rock bolt assembly defined in claim 4 wherein the barrier is a washer welded to the rock bolt.
6. The rock bolt assembly defined in any one of claims 2 to 5 wherein the maximum width dimension of the barrier is less that that of the nut to that the barrier does not present altogether or restrict a drive socket of a drill means engaging the nut.
7. A method of stabilising a rock mass substantially as hereinbefore described with reference to the accompanying drawing.
8. A rock bolt assembly substantially as hereinbefore described with reference to the accompanying drawing.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| AUPO8456 | 1997-08-08 | ||
| AUPO8456A AUPO845697A0 (en) | 1997-08-08 | 1997-08-08 | A rock bolt assembly |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2244617A1 true CA2244617A1 (en) | 1999-02-08 |
Family
ID=3802745
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002244617A Abandoned CA2244617A1 (en) | 1997-08-08 | 1998-08-10 | A rock bolt assembly |
Country Status (3)
| Country | Link |
|---|---|
| AU (1) | AUPO845697A0 (en) |
| CA (1) | CA2244617A1 (en) |
| ZA (1) | ZA987162B (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| AU2009202450B2 (en) * | 2008-07-17 | 2011-09-01 | Hilti Aktiengesellschaft | Method of setting a self-drilling, chemically anchorable fastening element and a self-drilling chemically anchorable fastening element |
| AU2014203653B2 (en) * | 2009-09-01 | 2016-06-09 | Fci Holdings Delaware, Inc. | Yielding bolt and assembly |
| CN112343635A (en) * | 2020-11-04 | 2021-02-09 | 中铁隆昌铁路器材有限公司 | Mining composite hollow resin anchor rod assembly and mounting method thereof |
-
1997
- 1997-08-08 AU AUPO8456A patent/AUPO845697A0/en not_active Abandoned
-
1998
- 1998-08-10 CA CA002244617A patent/CA2244617A1/en not_active Abandoned
- 1998-08-11 ZA ZA987162A patent/ZA987162B/en unknown
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| AU2009202450B2 (en) * | 2008-07-17 | 2011-09-01 | Hilti Aktiengesellschaft | Method of setting a self-drilling, chemically anchorable fastening element and a self-drilling chemically anchorable fastening element |
| AU2014203653B2 (en) * | 2009-09-01 | 2016-06-09 | Fci Holdings Delaware, Inc. | Yielding bolt and assembly |
| CN112343635A (en) * | 2020-11-04 | 2021-02-09 | 中铁隆昌铁路器材有限公司 | Mining composite hollow resin anchor rod assembly and mounting method thereof |
Also Published As
| Publication number | Publication date |
|---|---|
| AUPO845697A0 (en) | 1997-08-28 |
| ZA987162B (en) | 1999-02-11 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| FZDE | Dead |