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
  • E21D21/02—Anchoring-bolts for roof, floor in galleries or longwall working, or shaft-lining protection having means for indicating tension
• • E—FIXED CONSTRUCTIONS
  • E21—EARTH 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
  • E21D21/0046—Anchoring-bolts for roof, floor in galleries or longwall working, or shaft-lining protection characterised by constructional features of the bolts formed by a plurality of elements arranged longitudinally
• • 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
  • E21D21/0073—Anchoring-bolts having an inflatable sleeve, e.g. hollow sleeve expanded by a fluid

Definitions

• This invention concerns a method in rock bolting according to the preamble of claim 1.
• the invention also concerns a rock bolt according to the preamble of claim 6.
• the previously known rock bolt is capable of supporting loads in order to i.a. stabilize a rock face belonging to a rock structure in connection. with tunnelling, mining, drifting and the like.
• a rock bolt having a tubular bolt portion can be manufactured and dimensioned such that great pulling forces, which a rock bolt typically can be subjected to at powerful but in space limited movements in the rock structure it is intended to stabilize, does not cause breakage of the rock bolt but instead results in controlled sliding of the tubular bolt portion, a limited distance inside the bore hole, whereupon the rock bolt is again capable of resisting essentially the same load as prior to the sliding, so that such movements in the rock structure will be tolerable.
• the advantages of the invention are besides that rock bolt failure is avoided also that the number of rock bolts per surface unit can be reduced, and that the dimensions of rock bolts that are used can be reduced, since the intended and resulting yielding thus allows rock movements in a controlled manner. Thereby the rock structure does not have to be stabilized in an exaggerated and a more costly manner.
• the length of the tubular bolt portion is determined as the result of at least one measurement, preformed during pulling of at least one rock bolt having a tubular bolt portion of a predetermined in at least one bore hole in the same or in a corresponding rock structure.
• the rock bolts to be used at the stabilization can thereupon be produced and adequately dimensioned with respect to the length of the tubular bolt portion, so that the intended sliding at intended loads is achieved.
• said predetermined value is the yield point load for the tubular bolt portion, which means that the material is optimized to the existing conditions in an advantageous way.
• the yield point load for the tubular bolt portion of a rock bolt intended here can be determined by a person skilled in the art through in per se previously known load tests.
• a number of drawing tests as for example 5 - 10 drawing tests, are performed, in order to obtain more reliable values for dimensioning.
• the distribution in the results is considered in order to determine the marginal to the yield point when the length of a tubular bolt portion which is to be used for each rock bolt, is to determine.
• the length of the tubular bolt portion is determined and dimensioned such that said frictional force exceeds a predetermined minimum value in order to avoid unnecessary sliding movements at less powerful rock movements.
• a device for performing said method includes means for engagement with a rock bolt having a tubular bolt portion inserted into and expanded inside a bore hole, means for applying a pulling force to said rock bolt, means for detecting sliding of said rock bolt as a result of application of said pulling force and means for detecting and measuring the pulling force that corresponds to the detected sliding.
• This device allows effective determining of the effective length of a rock bolt which has the ability of yielding through sliding at greater movements in the rock structure.
• Fig. 1 shows a section through a rock structure with a rock bolt according to the invention
• Fig. 2 shows a device for performing a method according to the invention in connection with a rock bolt
• Fig. 3 shows a sequence in order to illustrate the method in rock bolting according to the invention.
• reference number 1 relates to a rock structure, wherein a rock bolt 2 is inserted inside a bore hole, the inner wall of which is referenced 3.
• the rock bolt 2 includes a tubular expandable bolt portion 4 and a tension rod 5 which adjoins to the tubular bolt portion 4 over an adapter sleeve 6.
• a tension rod in the form of a number of tubular sections 5', in pairs joined with the aid of a joining sleeve 5". This arrangement allows the use of rock bolts having a great total length also in narrow drifts, which otherwise would limit the length of a tension rod in one piece.
• the tubular bolt portion 4 is completed with a terminal sleeve 7.
• a rock plate 8 is as usually applied, which through preloading of the tension rod 5 exerts an inwardly directed stabilizing pressing force against an outer part of the rock structure 1.
• Fig. 1 9 indicates a crevice in the rock structure in order to somewhat illustrate the inherent instability of the rock structure 1.
• movements in the rock structure which tend to displace the rock plate 8 axially outwards, that is to the right in Fig. 1, and that subject the rock bolt to a sufficiently high force, result in a sliding of the tubular bolt portion 4 against the inner wall of the bore hole 3. In particular this occurs if the force exerted on the rock bolt by the moveable portion of the rock structure, exceeds a minimum value.
• a device 14 for measuring frictional forces that are present in a certain type of expandable rock bolts in connection with a certain contracture is shown.
• This device is intended for dimensioning of rock bolts according to the invention and in particular the length of the tubular bolt portion.
• a process is undertaken in order to determine the effective length of a tubular bolt portion of a rock bolt before the positioning of a number of rock bolts in a rock structure in order to stabilize the rock face, as an example in tunnelling or drifting in mining.
• the measurement is made such that a test specimen in the form of a rock bolt 10 having a tubular bolt portion of a predetermined length is inserted inside a bore hole 12 in the rock structuring 13 in question.
• the length of the tubular bolt portion is suitably chosen such that sliding of the rock bolt is safely achieved at a force that is below the yield point of the tubular bolt portion. If the yield point would be reached before sliding is obtained, a new rock bolt with a shorter tubular bolt portion 11 will be selected.
• the device for measuring 14 includes a tension rod 15 for adjoining to the expandable tubular bolt portion, a supporting portion 16 for applying against the side of the rock structure, an engagement portion 17 for the engagement with the tension rod 15 and a pulling mechanism 18 which, for example with hydraulic means, applies a pulling force to the rock bolt 9.
• a control unit 19 senses the applied pulling force and detects when sliding occurs, and at which pulling force this occurs.
• rock bolts can be dimensioned with adequate length of tubular bolt portion so that a pulling force corresponding to sliding for the chosen rock bolt with a tubular bolt portion of selected length as an example corresponds to about 60 - about 90% of said yield point load. Selection of an adequate length can as an example be made practically through lists, diagrams or the like.
• Fig. 3 is illustrated a sequence for carrying out the method according to the invention.
• Position 20 indicates the start of the sequence.
• Position 21 concerns inserting and expanding a tubular rock bolt having a certain predetermined length in a predrilled bore hole in a rock structure.
• Position 22 concerns axially pulling of the rock bolt in a direction outwardly.
• Position 23 concerns detecting of sliding of the rock bolt and the pulling force, at which sliding occurs.
• Position 24 concerns calculating of the length of the tubular bolt portion for a rock bolt, either through manual control in tables, diagrams etc. or automatically through a circuit which is connected to the control unit. This is performed starting from the drawing test or the drawing tests and associated detections performed in positions 22 - 24.
• Position 25 concerns termination of the sequence.
• the device for performing the method can be. designed otherwise as long as it includes means for exerting a pulling force, detecting sliding and measuring pulling force at sliding.
• the yield point is used as reference when dimensioning of rock bolts according to the invention. It is, however, not excluded that also other values that are significant for a rock bolt can be used for dimensioning. As an example the break load of the rock bolt could be used, wherein the tubular portion of the rock bolt could be dimensioned to have a length corresponding to a frictional force which is a certain determined part of the break load. It is also not excluded that dimensioning starts from the fact that the fictional force is to comprise a certain determined part of a significant value of the strength of the rock.
• rock bolt according to the invention could be of different embodiments. It is for example not excluded that a rock bolt according to the invention includes more than one tubular bolt portion arranged one after the other.

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)
• Force Measurement Appropriate To Specific Purposes (AREA)
• Medicines Containing Material From Animals Or Micro-Organisms (AREA)
• Joining Of Building Structures In Genera (AREA)
• Investigating Strength Of Materials By Application Of Mechanical Stress (AREA)
• Flanged Joints, Insulating Joints, And Other Joints (AREA)
• Materials For Medical Uses (AREA)
• Piles And Underground Anchors (AREA)
• Electrical Discharge Machining, Electrochemical Machining, And Combined Machining (AREA)
• Hooks, Suction Cups, And Attachment By Adhesive Means (AREA)
• Medicines Containing Plant Substances (AREA)
• Pharmaceuticals Containing Other Organic And Inorganic Compounds (AREA)
• Saccharide Compounds (AREA)
• Devices Affording Protection Of Roads Or Walls For Sound Insulation (AREA)
• Dowels (AREA)

Priority Applications (12)

Applications Claiming Priority (2)

Publications (1)

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Citations (4)

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• 2004
  • 2004-05-24 SE SE0401317A patent/SE527107C2/sv unknown
• 2005
  • 2005-04-18 ES ES05732230T patent/ES2306132T3/es active Active
  • 2005-04-18 EP EP05732230A patent/EP1749144B1/de active Active
  • 2005-04-18 CA CA002564291A patent/CA2564291A1/en not_active Abandoned
  • 2005-04-18 PL PL05732230T patent/PL1749144T3/pl unknown
  • 2005-04-18 DE DE602005006794T patent/DE602005006794D1/de not_active Expired - Fee Related
  • 2005-04-18 SI SI200530313T patent/SI1749144T1/sl unknown
  • 2005-04-18 JP JP2007514971A patent/JP2008500474A/ja not_active Withdrawn
  • 2005-04-18 WO PCT/SE2005/000555 patent/WO2005113939A1/en active Application Filing
  • 2005-04-18 DK DK05732230T patent/DK1749144T3/da active
  • 2005-04-18 US US11/596,939 patent/US20070253783A1/en not_active Abandoned
  • 2005-04-18 BR BRPI0510935-3A patent/BRPI0510935A/pt not_active IP Right Cessation
  • 2005-04-18 RU RU2006145897/03A patent/RU2006145897A/ru not_active Application Discontinuation
  • 2005-04-18 AU AU2005245752A patent/AU2005245752A1/en not_active Abandoned
  • 2005-04-18 ZA ZA200609069A patent/ZA200609069B/xx unknown
  • 2005-04-18 PT PT05732230T patent/PT1749144E/pt unknown
  • 2005-04-18 CN CNA2005800166010A patent/CN1957159A/zh active Pending
  • 2005-04-18 AT AT05732230T patent/ATE395501T1/de not_active IP Right Cessation
• 2006
  • 2006-10-17 IL IL178669A patent/IL178669A0/en unknown
  • 2006-12-22 NO NO20066000A patent/NO20066000L/no not_active Application Discontinuation
• 2008
  • 2008-07-18 HR HR20080360T patent/HRP20080360T3/xx unknown

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