Classifications

• • E—FIXED CONSTRUCTIONS
  • E21—EARTH OR ROCK DRILLING; MINING
  • E21D—SHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
  • E21D20/00—Setting anchoring-bolts
• • 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 and a device for rock bolting according to the preambles of claims 1 and 11 respectively.
• Pre-stressed wire bolts for rock enforcement are installed by grouting the wire bolt in a bore hole in the rock to be reinforced.
• cement concrete or any other binding agent is used as cement.
• the pre-tension will occur only along the part of the wire which is pulled free from the set binding agent.
• the length of the part being pulled free from binding agent is undefined which is a problem regarding the security of the fastener.
• pre-tension can be applied to the bolt before grouting thereof with a settable agent, which result in that the pre-tension will be well defined along a complete length of an element of the bolt and that the security of the installation is increased.
• the same channel for transmitting the said settable agent provides means which open for communication with the outside of the tension element through pressurizing to a certain pressure level
• the same channel may be used for transmitting expansion medium and settable medium.
• the said pressure level is set such that the channel opens at a pressure increase with a certain ⁇ -pressure above the expansion pressure.
• the tension element is used for transmission of medium for expanding the tubular bolt, wherefore the tension element comprises a through channel for transmission of pressure water or the like.
• the settable medium is transmitted through a channel in the tension element, wherein in particular it is preferred that it is this channel which can be opened through pressurizing to a certain pressure level which exceeds a certain predetermined threshold value.
• the bursting plate can be an integral part of the material in the tension element, for example a drilled-out or milled-out portion having a certain remaining material thickness, which allows shearing of the material when said pressure level is reached.
• Fig 1 shows a disassembled perspective view of a device for rock bolting according to the invention
• Fig 2 shows, partly in section, the device in Fig 1, assembled and inserted into a bore hole
• Fig 3 shows a detail of the device in Fig 1 and 2 with a bursting plate
• Fig 4 shows diagrammatically a block diagram of steps included in a method according to the invention
• Figs 5 and 6 show diagrammatically alternative devices according to the invention.
• numeral 1 generally denotes a device for rock bolting including pre-stressing a rock bolt and with a tubular expandable rock bolt, essentially of the kind which is described in US-A-4459067 (Atlas Copco AB) .
• the tubular bolt includes in general an expandable portion 5 and a fastening portion 6, into which is attachable a tubular tension element 3 including an inner portion 7 having a thread for cooperation with the fastening portion 6 and a female thread for cooperation with a tension section 8, which in turn over a joining element 9 is arranged to be threaded to one further tension section 8.
• the parts included in the tension element 3 are standard components, which can be combined as desired, for example for adjustment to the depth of a bore hole wherein the device 1 is intended to be inserted.
• An abutment element 4 includes an abutment plate 10 and a tension nut 11, which cooperates with an outside tension section 8, is arranged outside an insertion opening of said bore hole.
• Fig 2 shows the device in Fig 1 in an assembled state and inserted into a bore hole 12, which is drilled in a rock structure 20.
• the bore hole 12 provides an insertion opening 13, an outer. portion 14 and an inner portion 15.
• the outside end 29 of the outermost tension section 8 is after insertion of the device into the bore hole 12 connected to a pressure water source or the like for transmitting a pressure of as an example 300 bar to the expandable portion 5.
• This expandable portion 5 will thereby be brought to firm anchoring against the inside of the inner portion 15 of the bore hole 12 so that already in this step a considerable anchoring of the complete rock bolt will occur.
• the tension element consisting of the parts 7, 8 and 9 may now be pre-stressed, which is made in such a way that the abutment plate 10 is pressed against the rock face 20 around the insertion opening 13 with the aid of the tension nut 11, which is tightened to a predetermined torque value.
• the device is now grouted-in in order to reinforce the anchoring as well as for assistance against corrosion, by injecting a settable medium into the space 27 between the tension element and the wall of the bore hole 12.
• this is achieved in such a way that the channel inside the tension element is pressurized with a pressure which exceeds the pressure for expanding the expandable portion 5 and which is chosen to such a level that a bursting plate ⁇ , which is positioned in the inner part 7 of the tension element, bursts so that an open channel is formed between this channel 19 and said space 27.
• the device is connected at its end portion 29 to a cement pump or any other source of a suitable settable medium.
• Fig 3 shows a detail of an inner portion 7 of a tension element with a bursting plate 16, which in this case is integrated in the material of the portion 7 in such a way that a milling operation 17 has been made so that the surrounding portion 18 of the bursting plate 6 provides a material thickness that can be sheared off at a certain pressurizing level.
• Position 21 denotes the start of the sequence
• Position 22 concerns assembling a device for rock bolting and inserting thereof into a bore hole
• Position 23 concerns expansion of a tubular bolt
• Position 24 concerns pre-stressing of a tension element
• Position 25 grouting of settable material
• Position 26 end of the sequence
• the invention can be modified within the scope of the following claims, and as an example a device for rock bolting can be used, wherein medium for expanding the tubular bolt as well as settable medium is transmitted otherwise than through the tension element, for example through separate inserted and removable element (28 in Fig 5), wherein in that case the tension element can be made homogenous.
• the bursting plate can be a separate element inserted inside the tension element and also other means for establishing a channel for transmitting the settable medium can be used, for example an element having a valve function may be used.
• a further example is the use of a break-pin which is sheared off at a certain pressure and fixes a potentially movable valve element .
• the tension element as an example can be anchored in a way that is shown in Fig 6, through clamping of a tension element 29 between an expandable bolt 2 and the wall of the bore hole, wherein the tension element in that case can be formed of a wire, which then can be pre-tensioned and anchored and be secured against corrosion through injection of cement or any other binding agent according to the above.

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)
• Piles And Underground Anchors (AREA)
• On-Site Construction Work That Accompanies The Preparation And Application Of Concrete (AREA)
• Dowels (AREA)
• Joining Of Building Structures In Genera (AREA)
• Control Of Metal Rolling (AREA)

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Citations (3)

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• 2003
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• 2008
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