EP0366337A1 - Boulon tubulaire d'ancrage de roche - Google Patents

Boulon tubulaire d'ancrage de roche Download PDF

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Publication number
EP0366337A1
EP0366337A1 EP89310689A EP89310689A EP0366337A1 EP 0366337 A1 EP0366337 A1 EP 0366337A1 EP 89310689 A EP89310689 A EP 89310689A EP 89310689 A EP89310689 A EP 89310689A EP 0366337 A1 EP0366337 A1 EP 0366337A1
Authority
EP
European Patent Office
Prior art keywords
bolt
rock
rock bolt
tube
load transfer
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.)
Withdrawn
Application number
EP89310689A
Other languages
German (de)
English (en)
Inventor
Robert B. Brooks
Alan R. Burgess
Allen C. Hunsberger
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Stelco Inc
Original Assignee
Stelco Inc
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Stelco Inc filed Critical Stelco Inc
Publication of EP0366337A1 publication Critical patent/EP0366337A1/fr
Withdrawn legal-status Critical Current

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Classifications

    • E—FIXED CONSTRUCTIONS
    • E21—EARTH 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
    • E21D21/02—Anchoring-bolts for roof, floor in galleries or longwall working, or shaft-lining protection having means for indicating tension
    • E—FIXED CONSTRUCTIONS
    • E21—EARTH 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
    • E21D21/008—Anchoring or tensioning means

Definitions

  • This invention is directed to a rock bolt system, and embraces the process of manufacture of the rock bolt, the improved rock bolt thus produced, including a Ground Movement Indicator embodiment and the method of use of the system.
  • Rock bolting is practiced in many areas of civil engineering ranging from excavating and tunnelling, to the attachment by anchoring back of fabricated structures to rock masses, and to the use of rock bolts in mining.
  • rock bolts A wide range of rock bolts are known.
  • hollow rock bolts are known, such as: Canadian Patent 999 762 Williams Nov. 16, 1976 Swiss Patent 631 782 Belloli Aug. 31, 1982 WO 86/02/25 Velikov April 10, 1986
  • this hollow rock bolt is manufactured by the pierce-billet method, being a thick walled structure, and initial cost is up to about ten times that of a plain, mechanical rock bolt.
  • the Williams rock bolt is used for specialty bolting, such as anchoring a machine to a cement floor or to rock.
  • rock bolts One of the dominant factors in selecting rock bolts is that of cost.
  • One of the most commonly used underground bolts are mechanical rock bolts, made from solid bar and used in conjunction with an anchoring shell.
  • Rock bolts having expansible shell anchors set into the remote end of a rock bore are anchored within the extended bores, at the back, the wall or the rock face, and a bearing plate and tensioning nut applied the outer end of the bolt for the purpose of compressing an adjacent strata of the rock so as to enhance its strength and stability and to collectively create a virtual rock beam.
  • Rock bolts also are used for the attachment of mine screening mesh in area covering relation primarily with the rock back, for safety purposes, by containment of loose rock.
  • rock bolts are grouted into their respective bores. Grouting is costly, but enhances the security of the rock bolt, and diminishes movement in the strata by filling the residual bore space or a selected portion, with cement or epoxy cement, thus also providing direct load transfer between the full length of the rock bolt and the adjoined strata, so as to more completely stabilize the strata.
  • Grouting is not generally carried out in the working area of a normal stope. However, in areas where acid ground water is encountered, so that rapid bolt deterioration can ensue grouting also affords significant corrosion protection to the rock bolts, to prolong their working life.
  • rock bolts One characteristic of all known prior use rock bolts is a total inability for an observer to ascertain from the stope floor what is taking place in terms of loading and displacements behind the rock face.
  • the present invention provides a tubular rock bolt that is particularly suited for grouting installations either at the time of installation, or subsequently.
  • the presently disclosed tubular rock bolt construction lends itself to a family of tubular rock bolts most of which have a nominal load rating closely approximating the load ratings of existing mechanical rock bolts.
  • the subject tubular rock bolt incorporates standard rolled threads to enable use thereof with standard sizes of nuts and more particularly, with substantially standard shells.
  • the subject tubular rock bolt makes possible the adoption of a visible projecting rod-like ground movement indicator (GMI) for installation with the TRB when in a non-grouted condition, to provide a readily seen visual indicator for indicating relative condition changes having taken place between the TRB and its associated strata subsequent to the placement of the TRB.
  • GMI visible projecting rod-like ground movement indicator
  • TRB a TRB incorporating the foregoing enumerated advantages can be manufactured at an acceptable increase in cost over that of existing mechanical rock bolts, using fabricated cold drawn mechanical steel tube.
  • the fabricated tube can be cold drawn, within very close tolerances, to an outside diameter (O.D.) particularly suited to the formation of rolled threads thereon, for use with existing standard nuts and shells presently used in rock bolting.
  • O.D. outside diameter
  • tubular rock bolts having a range of wall thicknesses
  • the subject tubular rock bolts have a selected tube O.D. to facilitate the rolling of a predetermined standard thread thereon, and a selected wall thickness, as a function of the tensile strength of the fabricated steel tube, to provide an as-installed load bearing capacity equivalent to that of a respective one of the existing equivalent standard mechanical rock bolts.
  • the subject tubular rock bolt demonstrates great axial resilience and a capacity for extension under cold working, such that effective longitudinal bolt extensions under working tensile loads are readily achieved.
  • the strength and ductility of the TRB are significant in maintaining the compression load in the rock strata in the event of strata disturbance, such as blasting in the vicinity of the installed bolt, thereby providing acceptable performance, in use.
  • tubular rock bolt (TRB)
  • TTB tubular rock bolt
  • the required volume of grout on the basis of a standard bored rock hole, is significantly less for grouting a subject 23.4mm (.920") diameter tubular rock bolt than for grouting a 19mm (3/4") diameter, equivalent strength plain rock bolt; and is much less for grouting a subject tubular rock bolt than for grouting 15.9mm (5/8") diameter plain rock bolt.
  • the subject TRB no longer requires the provision of an air vent tube, being self venting through its centre, thereby assuring more reliable grouting, by avoidance of the air locks frequently experienced with vent tubes, in the prior art. It also makes it possible to retroactively grout a bolt zone, subsequent to bolt installation.
  • the present invention thus provides a tubular rock bolt having a Predetermined outside tubular diameter to accept a predetermined rolled thread form.
  • the subject tubular rock bolt has a wall of predetermined thickness, to afford an initial tensile load capacity substantially equal to that of an existing solid section mechanical rock bolt, wherein the subject tubular rock bolt has a comparable extensibility to that of the referenced solid section mechanical rock bolt, and provides a similar ability of maintaining an effective load and reliability, in use.
  • Manufacture of the subject cold drawn tube bolt is effected by first manufacturing a larger diameter steel tube.
  • the tube being fabricated by: electric resistance welding the edges of a roll formed steel strip; by welding the strip edges by airjet or oxyjet heating, or by forming a seamless tube by the pierce billet and cold draw methods.
  • a strip of steel is prepared having its width equal to the perimeter of the tube to be formed.
  • the strip is roll formed to the required circular section and the abutting edges welded, using low or high frequency power through electrode wheels, or sliding contacts or by way of an induction coil.
  • a steel ribbon is roll formed at high temperature into a tube formation, and the closure edges thereof compressed together, generally under airjet or oxyjet heating, to form a continuous butt welded tube wall, to provide a high quality continuous butt jointed seamed tube, at comparatively low cost.
  • a heated cylindrical billet is subjected to being pierced axially, and subsequently rolled to produce an intermediate thick walled tube.
  • the tubes thus formed by the respective processes are then cold mandrel-drawn through sizing dies until the required outer diameter (O.D.) and wall thickness are achieved, by cold working.
  • Selection of the initial tube forming process is based primarily upon the cost factors involved, which also are influenced by the scale of the operation.
  • TRB 1, 2, 3, 4, 5 and 6 have been evolved to-date and are in course of development:
  • Adoption of a 6.6mm (.26”) wall thickness with the large 23.4mm (.92”) diameter tube provides a high initial load capacity tubular bolt having substantially the same initial load bearing capacity as a 19mm (3/4") solid bar mechanical rock bolt, while accommodating standard rolled threads to receive a standard 25.4mm (1") threaded rock bolt shell, for anchoring purposes.
  • a further embodiment of the 23.4mm (.920”) diameter tubular bolt having a thinner wall, namely of 5mm (0.195”) thickness, provides an initial applied load bearing capacity approaching that of a 15.9mm (5/8") diameter solid rock bolt.
  • This tube size also accepts a nominal 25.4mm (1") rolled thread, and exhibits characteristic extensibility under load.
  • an end of a tubular rock bolt such as the 23.4mm (0.92") tube
  • a tubular rock bolt such as the 23.4mm (0.92") tube
  • a further aspect of the present invention is the incorporation, with a tubular rock bolt, of a low cost, effective Ground Movement Indicator (GMI).
  • GMI Ground Movement Indicator
  • an elongated rod-like GMI having the rod portion thereof freely suspended within the bore of the tubular rock bolt has the remote distal end thereof independently secured within the distal end of the strata bore, and the free proximal end of the rod portion initially extending outwardly from the bolt proximal end, as the visible GMI.
  • a viewable portion of the GMI rod can be left projecting at the proximal end.
  • the projecting length of the GMI rod becomes sensibly and substantially proportionately diminished, to provide visual indication of significant change in the condition of the rock bolt relative to its strata, in its position at the rock back, wall or face, with a corresponding indication of a possible significant change having taken place in the related rock strata.
  • the extent or degree of disappearance of the GMI rods in a given area of a stope could indicate to some extent the probable degree of danger of a rock fall occurring.
  • the GMI includes an indicator rod having its own anchor located above the shell to optimize its integrity, by enabling the rod to be independently anchored in the strata.
  • the bridge portion of the bail of the shell is recessed to accommodate the distal bolt end of the TRB, and has a central aperture therein through which the GMI rod extends, when installed.
  • the apertured bail bridge serves a valuable purpose in facilitating rupture of the bail in the event that the TRB tube is accidentally screwed upwardly through the shell, so as to rupture the bridge.
  • Rock bolts are provided in a range of lengths and sizes, and 1.5m (5ft) and 1.8m (6ft) rock bolts are generally considered standard production bolts.
  • the subject GMI rods can be provided as a standard item, having a rod size, diametrically compatible with a range of tube bolt ID's and, being readily shortenable by a simple clipping operation, can be provided in a standard length, such as a 2.7m (9ft) or longer GMI rod, suitable for use with a 1.8m (6ft) or longer bolt, and then shortened, if required to be used with 1.5m (5ft) or shorter bolts.
  • the GMI rods is 0.9m (3ft) or 1.2m (4ft) longer than the tube bolt with which it is used.
  • stope roof heights in the range of 3.65m to 6m (12-20ft) are commonplace, it will be understood that to be effective the protruding rod end of a GMI rod must be clearly visible, and a significant relative displacement thereof must be plainly evident, preferably when viewed from stope floor level, by suitable colouration, such as fluorescent paint.
  • the distal end of the GMI rod can be threadedly disengaged by unscrewing it from its anchor portion, to permit withdrawal of the GMI rod from an installed TRB, so that grouting of the TRB can then proceed without any impedence.
  • the rock bolt assembly 10 comprises a cold drawn tube portion 12 having threaded end portions 14, 16 with rolled threads 18 thereon, and an axial through passage 19.
  • a standard type of shell 20 has leaves portions 22, having serrated gripping surfaces 24 on the exterior thereof.
  • Shell wedge body portion 26 is threadedly mounted at the distal end, on the rolled threads 18 of the tube end 16.
  • the bottom tensioning nut 32 bears against the hardened round washer 34 and bearing plate 36, to draw the tube portion 12 axially outwardly in anchor loading relation.
  • the tube portion 12 is tensioned, while the associated surrounding rock portion is compressed, and thereby stabilized.
  • grout may be injected upwardly through the bore 19 of tube 12, and the GMI 40 is not present.
  • the elements of the shell 20 are referred to above.
  • the rod 40 of GMI 54 having a cruciform anchor portion 60 secured to the rod 40 by threads 58 is inserted downwardly into passage 19 of bolt 12.
  • the bail portion 28 of shell 20 has a central aperture 29 therein, for passage of rod 40 therethrough.
  • the surface 40′ of bail portion 28 is recessed to received the distal end 16 of tubular bolt 12, in the event of misadvertant rotation of bolt 12 causing the bolt 12 to advance axially through wedge body 26 of shell 20.
  • the bail portion 40′ ruptures readily, adjacent to aperture 29, to save dislodgement of the leaves 22.
  • the GMI rod retaining thread 58 being formed in GMI anchor portion 60, is secured against rotation, and it is possible to unscrew and withdraw the GMI rod portion 40 from out of an installed TRB, so that initial non-grouted installation of a TRB incorporating a GMI can be followed by removal of the GMI rod 40, and carrying out of normal grouting procedures.
  • the proximal ends of the GMI rods 40 can be clipped off at a standard exposed length, on initial installation, subsequent to the tubular rock bolt 12 being tensioned by application of a predetermined torque on nut 32 to the desired initial value of working load.
  • the GMI rod 40 has the inner end portion 42 thereof supported independently above the distal end 16 of tube portion 12 by way of cruciform spring clip 60 which engages the rock bore 30. This has the benefit of optimizing the independence of GMI 54.
EP89310689A 1988-10-19 1989-10-18 Boulon tubulaire d'ancrage de roche Withdrawn EP0366337A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US25988088A 1988-10-19 1988-10-19
US259880 1988-10-19

Publications (1)

Publication Number Publication Date
EP0366337A1 true EP0366337A1 (fr) 1990-05-02

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Family Applications (1)

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EP89310689A Withdrawn EP0366337A1 (fr) 1988-10-19 1989-10-18 Boulon tubulaire d'ancrage de roche

Country Status (3)

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EP (1) EP0366337A1 (fr)
AU (1) AU626111B2 (fr)
ZA (1) ZA897909B (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2003093644A1 (fr) * 2002-04-29 2003-11-13 Welser Profile Ag Procede de fabrication d'une cheville metallique pour exploitation miniere
CN114922178A (zh) * 2022-06-28 2022-08-19 兰州理工大学 一种地下土遗址坑壁裂隙加固装置及其使用方法

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN109750664B (zh) * 2019-01-28 2020-10-30 中国矿业大学(北京) 一种新型双极恒阻大变形锚杆构件

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2696137A (en) * 1949-10-15 1954-12-07 Super Grip Anchor Bolt Company Multicontact roof reinforcer or anchor
US2804797A (en) * 1954-06-23 1957-09-03 Super Grip Anchor Bolt Company Tubular, pronged reinforcing member for rock strata
GB1025729A (en) * 1963-11-06 1966-04-14 Chester Irving Williams Rock bolt assembly
GB1164007A (en) * 1967-01-30 1969-09-10 William Ellis Worley Bolts
GB2199952A (en) * 1987-01-16 1988-07-20 Coal Ind Method and apparatus for measuring load on a rock bolt

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CA1286129C (fr) * 1986-06-24 1991-07-16 Inco Limited Boulon d'ancrage dans le roc pris dans un materiau durci, et dispositif servant a son implantation

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2696137A (en) * 1949-10-15 1954-12-07 Super Grip Anchor Bolt Company Multicontact roof reinforcer or anchor
US2804797A (en) * 1954-06-23 1957-09-03 Super Grip Anchor Bolt Company Tubular, pronged reinforcing member for rock strata
GB1025729A (en) * 1963-11-06 1966-04-14 Chester Irving Williams Rock bolt assembly
GB1164007A (en) * 1967-01-30 1969-09-10 William Ellis Worley Bolts
GB2199952A (en) * 1987-01-16 1988-07-20 Coal Ind Method and apparatus for measuring load on a rock bolt

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2003093644A1 (fr) * 2002-04-29 2003-11-13 Welser Profile Ag Procede de fabrication d'une cheville metallique pour exploitation miniere
CN114922178A (zh) * 2022-06-28 2022-08-19 兰州理工大学 一种地下土遗址坑壁裂隙加固装置及其使用方法
CN114922178B (zh) * 2022-06-28 2023-01-24 兰州理工大学 一种地下土遗址坑壁裂隙加固装置及其使用方法

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Publication number Publication date
AU626111B2 (en) 1992-07-23
ZA897909B (en) 1990-09-26
AU4282389A (en) 1990-04-26

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