US20120070234A1 - Rock Bolt - Google Patents
Rock Bolt Download PDFInfo
- Publication number
- US20120070234A1 US20120070234A1 US13/306,313 US201113306313A US2012070234A1 US 20120070234 A1 US20120070234 A1 US 20120070234A1 US 201113306313 A US201113306313 A US 201113306313A US 2012070234 A1 US2012070234 A1 US 2012070234A1
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- US
- United States
- Prior art keywords
- rock bolt
- chuck
- expansion shell
- bolt
- rock
- 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
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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
- E21D21/0026—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 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
- E21D21/0053—Anchoring-bolts in the form of lost drilling rods
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- 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
- the present invention relates to a rock bolt and particularly, but not exclusively, to rock bolts which may be used in mining applications.
- rock bolts for supporting structures e.g. roofs of passageways in mines are well known.
- a rock bolt generally consists of an elongate shank (length will generally depend upon the material which the rock bolt is intended to secure) having a distal end (the end which in use is fixed furthest within the rock), or “head end”, and a proximal end (the end, in use, which is closest to the surface of a rock and, in many cases, may actually project from the rock surface), or “tail end”.
- Rock bolts are fixed in elongate boreholes (not much wider or even slightly less in width than the rock bolt) which is drilled in the rock.
- a bearing plate is secured at the tail end of a rock bolt fast against the rock surface.
- the rock bolt and bearing plate assembly operate to support the rock.
- Many rock bolts may be used to support structures. For example, in mines rock bolts may be used to support passageways.
- Installation usually requires drilling of the borehole by using a drill rig and a drill steel (a long steel rod with a drill bit on the end). The drill steel is then removed from the borehole. Resin (or “grout”) is inserted into the borehole, then the rock bolt itself is inserted and tightened up against the bearing plate.
- rock bolts incorporate point anchoring mechanisms, which can be manipulated post insertion of the rock bolt to mechanically interfere with walls of the borehole in order to firmly secure the rock bolt.
- the conventional procedure for installing rock bolts can be relatively time consuming in the context of efficient mine operation. It requires a number of separate tasks (affixing the drill steel, drilling the borehole, removing the drill steel, inserting the resin and rock bolt, securing the rock bolt) which require time and a significant amount of labour. In a mining situation, where it is important that mining shafts, passageways, etc be created quickly (as this directly affects the economic operation of the mine), this is a disadvantage. Further, the drill steel and drill bit are consumables which add to the cost of installing rock bolts.
- “Self drilling” rock bolts are known. These generally incorporate a drill bit as part of or connected to the head end of the rock bolt, the tail end being attachable to a drill rig in order to drill the borehole. Once the hole is drilled, the rock bolt is retained in the hole. Whilst self drilling rock bolts have the advantage of speed of application, grouting can be difficult and there are no provisions for any point anchoring mechanism to firmly secure the rock bolt.
- the present invention provides a rock bolt, the rock bolt including a mechanical anchoring arrangement and a drill bit to enable self drilling.
- An advantage of at least an embodiment of the invention is that a self drilling rock bolt is provided which can also be mechanically point anchored.
- the mechanical anchoring arrangement and drill bit are arranged such that rotation of the rock bolt about an axis of the rock bolt in a first direction causes the drill bit to drill into rock (or other substrate) and create a borehole to receive the rock bolt. Subsequently, rotation in the opposite direction actuates the mechanical anchoring arrangement to anchor the rock bolt.
- a tail end of the rock bolt is formed with an end fitting which is moveable axially with respect to the rock bolt after the rock bolt has been secured in the borehole, in order to allow for further take up.
- the end fitting provides an engagement surface for a drill rig and is not axially moveable with respect to the rock bolt during drilling.
- the end fitting may include a break out mechanism which breaks when the rock bolt is secured in the borehole, subsequently enabling axial movement.
- the end fitting may be a threaded nut mounted on a co-operating threaded tail end of the rock bolt.
- a fixed stop or thread deformation may prevent rotation of a nut when the borehole is being drilled.
- the mechanical anchoring arrangement includes an expansion assembly including an expansion shell and a co-operating chuck.
- the chuck and expansion shell are arranged to move relative to each other, co-operating surfaces sliding over each other and resulting in expansion of the expansion shell so that walls of the expansion shell abut against walls of the borehole and secure the rock bolt mechanically.
- the expansion shell is arranged to rotate with the rock bolt during the drilling operation.
- outer walls of the expansion shell include protrusions to aid mechanical interference with the borehole walls.
- the protrusions are arranged in spiral formation to facilitate fluid and leavings flow during drilling.
- the mechanical anchoring arrangement is provided at one end (the head end) of the rock bolt.
- a mechanical anchoring arrangement includes a sleeve extending nearly the entire length of the rock bolt. This is not the case with this embodiment of the present invention, which only requires the head end of the rock bolt to mount a mechanical anchoring arrangement.
- the mechanical anchoring arrangement includes an expansion shell, the expansion shell is mounted at the head end of the rock bolt.
- the drill bit is mounted to an end of the rock bolt and operates as a stop to prevent the chuck and expansion shell from moving off the rock bolt end.
- the stop may comprise a surface which facilitates non seizure of the chuck.
- a co-operating surface (with the stop) of the chuck may also be arranged to facilitate non-seizure.
- the drill bit is mounted by the chuck of the mechanical anchoring arrangement.
- the chuck in this embodiment includes a recess within which is seated the end of the rock bolt, for relative axial motion with respect to the chuck. A stop on the end of the rock bolt prevents the chuck from moving off the rock bolt during drilling.
- an axially extending central passageway is provided through the rock bolt to enable introduction of a cementatious material to the borehole, for grouting.
- the present invention provides a method of installing a rock bolt in accordance with a first aspect of the invention, including the steps of:
- the method includes the further step of post grouting by injecting cementatious material into the borehole.
- the cementatious material may be injected by way of the axial passageway.
- FIG. 1 is a view from one side of a rock bolt in accordance with a first embodiment of the present invention
- FIG. 2 is a detail of a head end of the rock bolt of FIG. 1 ;
- FIG. 3 is a detail of a tail end of the rock bolt of FIG. 1 ;
- FIG. 4 is a side view of a rock bolt in accordance with a second embodiment of the present invention.
- FIG. 5 is a detail of a head end of the rock bolt of FIG. 4 ;
- FIG. 6 is an exploded view from the side of a rock bolt in accordance with the embodiment of FIGS. 1 to 3 ;
- FIG. 7 is an exploded view from the side of the head end of the rock bolt of the embodiment of FIGS. 4 and 5 ;
- FIG. 8A and FIG. 8B are details of an alternative embodiment of a tail end arrangement for the rock bolt in accordance with an embodiment of the present invention.
- FIG. 9 is a detail of a head end for a rock bolt in accordance with an embodiment of the present invention.
- FIGS. 1 to 3 A first embodiment of the present invention will now be described with reference to FIGS. 1 to 3 .
- a rock bolt, generally designated by reference numeral 1 includes a distal, head end 2 , and a proximal, tail end 3 .
- a shank 4 extends between the head end 2 and tail end 3 .
- the head end 2 includes a mechanical anchoring arrangement 5 which, in this example embodiment, includes a co-operating chuck 6 and expansion shell 7 .
- the head end 2 is also provided with a drill bit 8 to enable self drilling.
- the drill bit 8 is mounted at the distal end of the rock bolt 1 .
- the mechanical anchoring arrangement 5 will now be described in more detail.
- a shank 4 of rock bolt 1 is threaded with screw threads 9 .
- the threaded portion 9 extends up to the drill bit 8 .
- the drill bit 8 comprises a drilling tip 10 at the distal end of the rock bolt and a base forming a stop 11 where the threaded portion 9 meets the drill bit 8 .
- the mechanical anchoring arrangement 5 includes an expansion shell 7 and chuck 6 .
- the expansion shell 7 in this example, has longitudinally extending leaves 12 , 13 (note only two are shown in the drawings but there are three leaves). Note that the number of leaves on the expansion shell 7 could vary. For example, the leaves could vary from two to four or more.
- the leaves 12 , 13 are arranged to move outwardly on expansion of the expansion shell 7 and are formed with a plurality of external protrusions 14 which assist in gripping the sides of the borehole to secure the rock bolt 1 in place.
- the expansion shell 7 also includes a bore 15 for sliding engagement with the threaded portion 9 .
- An abutment member in the form of a threaded nut 16 is mounted on the threaded portion 9 and operates to prevent the expansion shell 7 from sliding further towards the tail end 3 .
- the chuck 6 has a threaded bore (not shown) for threaded engagement with the threaded portion 9 . Rotation of the rock bolt 1 relative to the chuck 6 thus causes axial motion of the chuck 6 along the threaded portion 9 .
- the chuck 6 includes tapered surfaces in sliding keying engagement with complementary surfaces on the extension leaves 12 , 13 , such that axial motion of the chuck 6 towards the tail end 3 relative to the expansion shell 7 will cause the leaves 12 , 13 to diverge outwardly and grip the walls of the borehole.
- the chuck also includes projections 17 which extend into slots 18 formed between the leaves 12 , 13 and prevent relative rotation of the chuck 6 and expansion shell 7 with respect to each other.
- Stop 11 formed by the base of the drill bit 8 prevents chuck 6 and expansion shell 7 from moving over the head end of the rock bolt 1 .
- the protrusions 14 are in a spiral formation, to assist with the flow of fluid during drilling, and aid in clearance of filings/cuttings.
- the spiral runs in the opposite direction to the thread form i.e. right hand spiral for left hand thread.
- the tail end 3 of the bolt 1 will now be described in more detail with reference in particular to FIGS. 1 and 3 .
- the tail end includes a further threaded portion 19 which, in this embodiment, is threaded in the same direction (left hand) as the threaded portion 9 .
- a ball washer 20 , washer 21 and threaded nut 22 are mounted on the further threaded portion 19 . In use, the ball washer abuts a mounting plate (not shown), which, when the rock bolt is installed, is hard up against the rock face.
- the nut includes a torque break out mechanism 23 .
- the nut 22 is therefore initially fixed relative to the threaded portion 19 and can be gripped by the spanner of a drill rig for rotation of the rock bolt for installation. Subsequently, when the mechanical anchoring arrangement is anchored, the torque break out mechanism 23 may be broken to allow the nut 22 to rotate relative to the threaded portion 19 to enable additional thread take up, for example, in heavily fractured rock which can therefore be compressed and partings closed.
- a drill rig and spanner is attached to the rock bolt by way of the tensionable nut 22 .
- Drilling into the rock substrate is implemented by rotating the rock bolt in the clockwise direction (in this embodiment. It will be appreciated that a reverse threaded arrangement may be rotated in the anticlockwise direction).
- the expansion shell 7 may resist rotation as it abuts the walls of the borehole, and this will result in relative anticlockwise rotation of the expansion shell 7 and chuck 6 relative to the rock bolt 1 . This will cause the chuck 6 to travel along the threaded portion 9 towards the head end of the rock bolt where it will abut the flat 11 . Once flat 11 is engaged by the chuck 6 then the expansion shell 7 and chuck 6 will continue to rotate in the drilling direction with the rock bolt 1 .
- a grout hose for injecting cementateous material may then be placed over the threaded end 24 so that cementateous material can be injected via the passageway 25 extending axially in the rock bolt 1 . Holes (not shown) in the chuck 6 allow the cementateous material to flow into the borehole and down to the plate.
- grout can be pumped up between the section between the borehole and the outer circumference of the rock bolt.
- the hollow centre of the bolt is used as a breather tube to allow air to escape as grout fills the voids.
- the rock bolt 100 includes some features which are the same as the rock bolt of FIGS. 1 to 3 . These features have been allocated the same reference numerals and no further description will be given. The main differences between the embodiment of FIGS. 4 and 5 and embodiment of FIGS. 1 to 3 , is in the head end 2 and tail end 3 of the rock bolt 100 .
- the chuck 101 is of a different configuration.
- the chuck 101 directly mounts the drill tip 102 on the periphery of a extension portion 103 of the chuck 101 .
- the extension portion 103 surrounds a centre hole 104 extending within the chuck 101 .
- the chuck 101 includes tapered surfaces in sliding key engagement with complementary surfaces of the extension leaves 12 , 13 , and also includes projections 17 which extend into slots 18 formed between the leaves 12 , 13 and prevent relevant rotation of the chuck 101 and expansion shell 7 with respect to each other.
- threaded portion 9 does not end in a stop supporting a drill bit. Instead, a fixed stop 105 is mounted at the end 106 of the threaded portion 9 extending within the centre hole 104 . During drilling operation, this prevents the chuck 101 from moving off the end of the threaded portion 9 . A shoulder 107 formed at the base of the centre hole 104 abuts the fixed stop 105 to prevent movement of the chuck 101 past the stop.
- the tail end 3 of the rock bolt 100 is formed without any threaded portion. Instead, the tail end 3 includes a drive end in the form of a forged end portion 108 for engagement by the drill rig for drilling. Washer 21 and Ball washer 20 are slideably mounted on the shank 4 of the rock bolt 100 . A hole (not shown) to suit a water spickett is also provided in the forged end 108 .
- drill rig engages the forged end 108 and rotates the rock bolt 100 in the drilling direction (in this case clockwise).
- the drill tip 102 is larger than the expansion shell diameter and operates directionally opposite to what is required to expand the shell.
- the chuck 101 On commencement of rotation in the clockwise direction, the chuck 101 will rotate relative to the threaded end 9 and will move along the threaded end 9 until the shoulder 107 meets the fixed stop 105 .
- the drill bit 102 will then rotate with the drill rig, resulting in drilling of a borehole for the rock bolt 100 .
- drill rotation is then applied in an anticlockwise direction. This causes the chuck 101 to move along the threaded end 9 away from the fixed stop 105 and causes expansion of the expansion shell 7 until the protrusions 14 grip the sides of the borehole and the rock bolt 100 is fixed in place.
- the centre hole 104 in the chuck 101 allows the bolt end 106 to move into the void during tightening, and provides over drill. This allows tightening of end 108 compressing the rock, closing partings in the ground, etc. This allows tightening of the bolt without any tails left hanging from the wall. This is an important feature for bolting in the ribs/wall where personnel can walk and machines often hit and damage bolt tails.
- post grouting can be implemented utilising the axial passageway 25 .
- FIGS. 8A and 8B an arrangement such as that shown in FIGS. 8A and 8B may be utilised at the tail end of the rock bolts in accordance with the embodiments described above.
- a threaded nut 200 is mounted at the tail end of the rock bolt. On rotation in a drilling direction, the nut 200 rotates towards the proximal end of the rock bolt where a press deformation 201 prevents travel passed the deformation 201 . On completion of drilling of the borehole, and on reverse rotation of the rock bolt, the nut disengages from the deformation end and operates as discussed in relation to the embodiment of FIG. 1 .
- a welded ring may provide a stop to prevent the nut 200 from moving off the rock bolt during drilling.
- the nut 200 is a reversing nut.
- the surfaces of the stop 11 and 105 are planar, as are corresponding abutting surfaces of the chucks in those embodiments. In some circumstances, this could potentially lead to seizure, as drilling forces may cause seizing of the chuck against the stop which would prevent opening of the expansion shell during reverse rotation, or make it more difficult.
- FIG. 9 in a further embodiment, in arrangement where the abutting chuck surface 210 and stop surface 211 do not make planar contact, but instead contact only particular areas (e.g. 212 ) may be utilised in order to facilitate non seizure. Other arrangements of surfaces may be utilised to facilitate non seizure and this embodiment is not limited to the arrangement shown in FIG. 9 .
- the projections which interfere with the walls of the boreholes ( 14 ) are arranged in spiral formation.
- the present invention is not limited to spiral formation projections.
- the projections may be non-spiral.
- the projections may be in any form which engages with the walls of the borehole.
Abstract
Description
- This application is a divisional of U.S. application Ser. No. 11/880,468 filed on Jul. 20, 2007, which claims priority to Australian Application No. 2006903922 filed on Jul. 20, 2006.
- 1. Field of the Invention
- The present invention relates to a rock bolt and particularly, but not exclusively, to rock bolts which may be used in mining applications.
- 2. Background of the Invention
- Rock bolts for supporting structures e.g. roofs of passageways in mines are well known. There are many different types of rock bolts. A rock bolt generally consists of an elongate shank (length will generally depend upon the material which the rock bolt is intended to secure) having a distal end (the end which in use is fixed furthest within the rock), or “head end”, and a proximal end (the end, in use, which is closest to the surface of a rock and, in many cases, may actually project from the rock surface), or “tail end”.
- Rock bolts are fixed in elongate boreholes (not much wider or even slightly less in width than the rock bolt) which is drilled in the rock. In use, a bearing plate is secured at the tail end of a rock bolt fast against the rock surface. The rock bolt and bearing plate assembly operate to support the rock. Many rock bolts may be used to support structures. For example, in mines rock bolts may be used to support passageways.
- Installation usually requires drilling of the borehole by using a drill rig and a drill steel (a long steel rod with a drill bit on the end). The drill steel is then removed from the borehole. Resin (or “grout”) is inserted into the borehole, then the rock bolt itself is inserted and tightened up against the bearing plate.
- Some rock bolts incorporate point anchoring mechanisms, which can be manipulated post insertion of the rock bolt to mechanically interfere with walls of the borehole in order to firmly secure the rock bolt.
- The conventional procedure for installing rock bolts can be relatively time consuming in the context of efficient mine operation. It requires a number of separate tasks (affixing the drill steel, drilling the borehole, removing the drill steel, inserting the resin and rock bolt, securing the rock bolt) which require time and a significant amount of labour. In a mining situation, where it is important that mining shafts, passageways, etc be created quickly (as this directly affects the economic operation of the mine), this is a disadvantage. Further, the drill steel and drill bit are consumables which add to the cost of installing rock bolts.
- “Self drilling” rock bolts are known. These generally incorporate a drill bit as part of or connected to the head end of the rock bolt, the tail end being attachable to a drill rig in order to drill the borehole. Once the hole is drilled, the rock bolt is retained in the hole. Whilst self drilling rock bolts have the advantage of speed of application, grouting can be difficult and there are no provisions for any point anchoring mechanism to firmly secure the rock bolt.
- In accordance with a first aspect, the present invention provides a rock bolt, the rock bolt including a mechanical anchoring arrangement and a drill bit to enable self drilling.
- An advantage of at least an embodiment of the invention is that a self drilling rock bolt is provided which can also be mechanically point anchored.
- In an embodiment, the mechanical anchoring arrangement and drill bit are arranged such that rotation of the rock bolt about an axis of the rock bolt in a first direction causes the drill bit to drill into rock (or other substrate) and create a borehole to receive the rock bolt. Subsequently, rotation in the opposite direction actuates the mechanical anchoring arrangement to anchor the rock bolt.
- In an embodiment, a tail end of the rock bolt is formed with an end fitting which is moveable axially with respect to the rock bolt after the rock bolt has been secured in the borehole, in order to allow for further take up. This may be useful in heavily fractured rock which can be compressed, for example. In an embodiment, the end fitting provides an engagement surface for a drill rig and is not axially moveable with respect to the rock bolt during drilling. In this embodiment, the end fitting may include a break out mechanism which breaks when the rock bolt is secured in the borehole, subsequently enabling axial movement. The end fitting may be a threaded nut mounted on a co-operating threaded tail end of the rock bolt. In an embodiment, instead of a break out mechanism, a fixed stop or thread deformation may prevent rotation of a nut when the borehole is being drilled.
- In an embodiment, the mechanical anchoring arrangement includes an expansion assembly including an expansion shell and a co-operating chuck. In operation, the chuck and expansion shell are arranged to move relative to each other, co-operating surfaces sliding over each other and resulting in expansion of the expansion shell so that walls of the expansion shell abut against walls of the borehole and secure the rock bolt mechanically. In an embodiment, the expansion shell is arranged to rotate with the rock bolt during the drilling operation. In an embodiment, outer walls of the expansion shell include protrusions to aid mechanical interference with the borehole walls. In an embodiment, the protrusions are arranged in spiral formation to facilitate fluid and leavings flow during drilling.
- In an embodiment, the mechanical anchoring arrangement is provided at one end (the head end) of the rock bolt. In some prior art, a mechanical anchoring arrangement includes a sleeve extending nearly the entire length of the rock bolt. This is not the case with this embodiment of the present invention, which only requires the head end of the rock bolt to mount a mechanical anchoring arrangement. In an embodiment where the mechanical anchoring arrangement includes an expansion shell, the expansion shell is mounted at the head end of the rock bolt.
- In an embodiment, the drill bit is mounted to an end of the rock bolt and operates as a stop to prevent the chuck and expansion shell from moving off the rock bolt end. In an embodiment, the stop may comprise a surface which facilitates non seizure of the chuck. A co-operating surface (with the stop) of the chuck may also be arranged to facilitate non-seizure.
- In an alternative embodiment, the drill bit is mounted by the chuck of the mechanical anchoring arrangement. The chuck in this embodiment includes a recess within which is seated the end of the rock bolt, for relative axial motion with respect to the chuck. A stop on the end of the rock bolt prevents the chuck from moving off the rock bolt during drilling.
- In an embodiment, an axially extending central passageway is provided through the rock bolt to enable introduction of a cementatious material to the borehole, for grouting.
- In accordance with a second aspect, the present invention provides a method of installing a rock bolt in accordance with a first aspect of the invention, including the steps of:
- rotating the rock bolt in a first direction to drill a borehole in a substrate in a self drilling operation; and
- rotating the rock bolt in a second, opposite direction, in order to secure the mechanical anchoring arrangement in the borehole.
- In an embodiment, the method includes the further step of post grouting by injecting cementatious material into the borehole. In an embodiment, where the rock bolt has an axial passageway extending within it, the cementatious material may be injected by way of the axial passageway.
- Features and advantages of the present invention will become apparent from the following description of embodiments thereof, by way of example only, with reference to the accompanying drawings, in which:
-
FIG. 1 is a view from one side of a rock bolt in accordance with a first embodiment of the present invention; -
FIG. 2 is a detail of a head end of the rock bolt ofFIG. 1 ; -
FIG. 3 is a detail of a tail end of the rock bolt ofFIG. 1 ; -
FIG. 4 is a side view of a rock bolt in accordance with a second embodiment of the present invention; -
FIG. 5 is a detail of a head end of the rock bolt ofFIG. 4 ; -
FIG. 6 is an exploded view from the side of a rock bolt in accordance with the embodiment ofFIGS. 1 to 3 ; -
FIG. 7 is an exploded view from the side of the head end of the rock bolt of the embodiment ofFIGS. 4 and 5 ; -
FIG. 8A andFIG. 8B are details of an alternative embodiment of a tail end arrangement for the rock bolt in accordance with an embodiment of the present invention, and -
FIG. 9 is a detail of a head end for a rock bolt in accordance with an embodiment of the present invention. - A first embodiment of the present invention will now be described with reference to
FIGS. 1 to 3 . - A rock bolt, generally designated by reference numeral 1 includes a distal,
head end 2, and a proximal,tail end 3. Ashank 4 extends between thehead end 2 andtail end 3. Thehead end 2 includes amechanical anchoring arrangement 5 which, in this example embodiment, includes aco-operating chuck 6 andexpansion shell 7. Thehead end 2 is also provided with adrill bit 8 to enable self drilling. In this example embodiment, thedrill bit 8 is mounted at the distal end of the rock bolt 1. - The
mechanical anchoring arrangement 5 will now be described in more detail. Towards thehead end 2, ashank 4 of rock bolt 1 is threaded withscrew threads 9. The threadedportion 9 extends up to thedrill bit 8. Thedrill bit 8 comprises adrilling tip 10 at the distal end of the rock bolt and a base forming astop 11 where the threadedportion 9 meets thedrill bit 8. - The
mechanical anchoring arrangement 5 includes anexpansion shell 7 andchuck 6. Theexpansion shell 7 in this example, has longitudinally extendingleaves 12, 13 (note only two are shown in the drawings but there are three leaves). Note that the number of leaves on theexpansion shell 7 could vary. For example, the leaves could vary from two to four or more. The leaves 12, 13 are arranged to move outwardly on expansion of theexpansion shell 7 and are formed with a plurality ofexternal protrusions 14 which assist in gripping the sides of the borehole to secure the rock bolt 1 in place. Theexpansion shell 7 also includes abore 15 for sliding engagement with the threadedportion 9. An abutment member in the form of a threadednut 16 is mounted on the threadedportion 9 and operates to prevent theexpansion shell 7 from sliding further towards thetail end 3. - The
chuck 6 has a threaded bore (not shown) for threaded engagement with the threadedportion 9. Rotation of the rock bolt 1 relative to thechuck 6 thus causes axial motion of thechuck 6 along the threadedportion 9. Thechuck 6 includes tapered surfaces in sliding keying engagement with complementary surfaces on the extension leaves 12, 13, such that axial motion of thechuck 6 towards thetail end 3 relative to theexpansion shell 7 will cause theleaves projections 17 which extend intoslots 18 formed between theleaves chuck 6 andexpansion shell 7 with respect to each other. -
Stop 11 formed by the base of thedrill bit 8 preventschuck 6 andexpansion shell 7 from moving over the head end of the rock bolt 1. - The
protrusions 14 are in a spiral formation, to assist with the flow of fluid during drilling, and aid in clearance of filings/cuttings. The spiral runs in the opposite direction to the thread form i.e. right hand spiral for left hand thread. - The
tail end 3 of the bolt 1 will now be described in more detail with reference in particular toFIGS. 1 and 3 . The tail end includes a further threadedportion 19 which, in this embodiment, is threaded in the same direction (left hand) as the threadedportion 9. Aball washer 20,washer 21 and threadednut 22 are mounted on the further threadedportion 19. In use, the ball washer abuts a mounting plate (not shown), which, when the rock bolt is installed, is hard up against the rock face. - The nut includes a torque break out
mechanism 23. Thenut 22 is therefore initially fixed relative to the threadedportion 19 and can be gripped by the spanner of a drill rig for rotation of the rock bolt for installation. Subsequently, when the mechanical anchoring arrangement is anchored, the torque break outmechanism 23 may be broken to allow thenut 22 to rotate relative to the threadedportion 19 to enable additional thread take up, for example, in heavily fractured rock which can therefore be compressed and partings closed. - Installation of a rock bolt 1 in accordance with the embodiment of
FIGS. 1 to 3 will now be described. - A drill rig and spanner is attached to the rock bolt by way of the
tensionable nut 22. Drilling into the rock substrate is implemented by rotating the rock bolt in the clockwise direction (in this embodiment. It will be appreciated that a reverse threaded arrangement may be rotated in the anticlockwise direction). As drilling proceeds, theexpansion shell 7 may resist rotation as it abuts the walls of the borehole, and this will result in relative anticlockwise rotation of theexpansion shell 7 andchuck 6 relative to the rock bolt 1. This will cause thechuck 6 to travel along the threadedportion 9 towards the head end of the rock bolt where it will abut the flat 11. Once flat 11 is engaged by thechuck 6 then theexpansion shell 7 andchuck 6 will continue to rotate in the drilling direction with the rock bolt 1. - Once the rock bolt 1 has created a borehole of the desired length, drilling in the forward direction is ceased and rotation in the reverse direction (anticlockwise in this embodiment) is applied by the drill rig. By virtue of the anticlockwise motion of the threaded
portion 9, thechuck 6 will now move towards thetail end 3. As thechuck 6 moves along the threadedportion 9, the tapered surfaces in sliding keying engagement with the complementary surfaces on the extension leaves 12, 13, cause theexpansion shell 7 to expand outwardly. Theprotrusions 14 on the external surfaces of theleaves - Once the expansion shell tightens in the borehole, continued rotation in the anticlockwise direction causes the break out
mechanism 23 to break and thenut 22 to rotate relative to the further threadedportion 19, in order to tighten up against thewasher 21,ball washer 20 and mounting plate (not shown). This is particularly useful where additional thread take up is required in heavily fractured rock which can be compressed and partings closed. The threadedend 24 of the rock bolt 1 remaining provides a protruding section which may be used to allow secure attachment of grout hose for post grouting applications. - A grout hose for injecting cementateous material may then be placed over the threaded
end 24 so that cementateous material can be injected via thepassageway 25 extending axially in the rock bolt 1. Holes (not shown) in thechuck 6 allow the cementateous material to flow into the borehole and down to the plate. - Alternatively, grout can be pumped up between the section between the borehole and the outer circumference of the rock bolt. The hollow centre of the bolt is used as a breather tube to allow air to escape as grout fills the voids.
- A further embodiment of the present invention will now be described with reference to
FIGS. 4 and 5 . Therock bolt 100 includes some features which are the same as the rock bolt ofFIGS. 1 to 3 . These features have been allocated the same reference numerals and no further description will be given. The main differences between the embodiment ofFIGS. 4 and 5 and embodiment ofFIGS. 1 to 3 , is in thehead end 2 andtail end 3 of therock bolt 100. - Referring firstly to the
head end 2 of therock bolt 100, although theexpansion shell 7 is of the same configuration as theexpansion shell 7 of theFIGS. 1 to 3 embodiment, thechuck 101 is of a different configuration. In this embodiment, thechuck 101 directly mounts thedrill tip 102 on the periphery of aextension portion 103 of thechuck 101. Theextension portion 103 surrounds acentre hole 104 extending within thechuck 101. Thechuck 101 includes tapered surfaces in sliding key engagement with complementary surfaces of the extension leaves 12, 13, and also includesprojections 17 which extend intoslots 18 formed between theleaves chuck 101 andexpansion shell 7 with respect to each other. - In this embodiment however, threaded
portion 9 does not end in a stop supporting a drill bit. Instead, afixed stop 105 is mounted at theend 106 of the threadedportion 9 extending within thecentre hole 104. During drilling operation, this prevents thechuck 101 from moving off the end of the threadedportion 9. Ashoulder 107 formed at the base of thecentre hole 104 abuts the fixedstop 105 to prevent movement of thechuck 101 past the stop. - The
tail end 3 of therock bolt 100 is formed without any threaded portion. Instead, thetail end 3 includes a drive end in the form of a forgedend portion 108 for engagement by the drill rig for drilling.Washer 21 andBall washer 20 are slideably mounted on theshank 4 of therock bolt 100. A hole (not shown) to suit a water spickett is also provided in the forgedend 108. - In operation of this embodiment, drill rig engages the forged
end 108 and rotates therock bolt 100 in the drilling direction (in this case clockwise). Thedrill tip 102 is larger than the expansion shell diameter and operates directionally opposite to what is required to expand the shell. - On commencement of rotation in the clockwise direction, the
chuck 101 will rotate relative to the threadedend 9 and will move along the threadedend 9 until theshoulder 107 meets the fixedstop 105. Thedrill bit 102 will then rotate with the drill rig, resulting in drilling of a borehole for therock bolt 100. - On completion of the borehole, drill rotation is then applied in an anticlockwise direction. This causes the
chuck 101 to move along the threadedend 9 away from the fixedstop 105 and causes expansion of theexpansion shell 7 until theprotrusions 14 grip the sides of the borehole and therock bolt 100 is fixed in place. - The
centre hole 104 in thechuck 101 allows thebolt end 106 to move into the void during tightening, and provides over drill. This allows tightening ofend 108 compressing the rock, closing partings in the ground, etc. This allows tightening of the bolt without any tails left hanging from the wall. This is an important feature for bolting in the ribs/wall where personnel can walk and machines often hit and damage bolt tails. - As with the embodiments of
FIGS. 1 to 3 , post grouting can be implemented utilising theaxial passageway 25. - As an alternative to a break out arrangement or forged end of the rock bolt, an arrangement such as that shown in
FIGS. 8A and 8B may be utilised at the tail end of the rock bolts in accordance with the embodiments described above. A threadednut 200 is mounted at the tail end of the rock bolt. On rotation in a drilling direction, thenut 200 rotates towards the proximal end of the rock bolt where apress deformation 201 prevents travel passed thedeformation 201. On completion of drilling of the borehole, and on reverse rotation of the rock bolt, the nut disengages from the deformation end and operates as discussed in relation to the embodiment ofFIG. 1 . - Instead of a crimp deformation, a welded ring may provide a stop to prevent the
nut 200 from moving off the rock bolt during drilling. Thenut 200 is a reversing nut. - Other arrangements for preventing motion of the nut during drilling and allowing motion after drilling may be employed.
- In the preceding embodiments, the surfaces of the
stop FIG. 9 , in a further embodiment, in arrangement where theabutting chuck surface 210 and stopsurface 211 do not make planar contact, but instead contact only particular areas (e.g. 212) may be utilised in order to facilitate non seizure. Other arrangements of surfaces may be utilised to facilitate non seizure and this embodiment is not limited to the arrangement shown inFIG. 9 . - In the above embodiments, the projections which interfere with the walls of the boreholes (14) are arranged in spiral formation. Although this is advantageous, the present invention is not limited to spiral formation projections. The projections may be non-spiral. The projections may be in any form which engages with the walls of the borehole.
- It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.
Claims (8)
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US13/306,313 US20120070234A1 (en) | 2006-07-20 | 2011-11-29 | Rock Bolt |
Applications Claiming Priority (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
AU2006903922A AU2006903922A0 (en) | 2006-07-20 | Rock bolt | |
AU2006903922 | 2006-07-20 | ||
US11/880,468 US8087850B2 (en) | 2006-07-20 | 2007-07-20 | Rock bolt |
US13/306,313 US20120070234A1 (en) | 2006-07-20 | 2011-11-29 | Rock Bolt |
Related Parent Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US11/880,468 Division US8087850B2 (en) | 2006-07-20 | 2007-07-20 | Rock bolt |
Publications (1)
Publication Number | Publication Date |
---|---|
US20120070234A1 true US20120070234A1 (en) | 2012-03-22 |
Family
ID=38973764
Family Applications (2)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US11/880,468 Expired - Fee Related US8087850B2 (en) | 2006-07-20 | 2007-07-20 | Rock bolt |
US13/306,313 Abandoned US20120070234A1 (en) | 2006-07-20 | 2011-11-29 | Rock Bolt |
Family Applications Before (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US11/880,468 Expired - Fee Related US8087850B2 (en) | 2006-07-20 | 2007-07-20 | Rock bolt |
Country Status (5)
Country | Link |
---|---|
US (2) | US8087850B2 (en) |
CN (1) | CN101109276B (en) |
AU (2) | AU2007203409B2 (en) |
CA (1) | CA2607850C (en) |
ZA (1) | ZA200706013B (en) |
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- 2007-07-20 US US11/880,468 patent/US8087850B2/en not_active Expired - Fee Related
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US10941657B2 (en) | 2016-07-12 | 2021-03-09 | Fci Holdings Delaware, Inc. | Corrosion resistant yieldable bolt |
CN108412527A (en) * | 2018-05-23 | 2018-08-17 | 向开秀 | A kind of constructing tunnel reinforcing anchor pole |
Also Published As
Publication number | Publication date |
---|---|
AU2007203409B2 (en) | 2009-10-22 |
CN101109276A (en) | 2008-01-23 |
CA2607850C (en) | 2015-01-06 |
AU2010200232B2 (en) | 2014-02-13 |
ZA200706013B (en) | 2010-05-26 |
AU2007203409A1 (en) | 2008-02-07 |
AU2010200232A1 (en) | 2010-02-11 |
US20080038068A1 (en) | 2008-02-14 |
US8087850B2 (en) | 2012-01-03 |
CA2607850A1 (en) | 2008-01-20 |
CN101109276B (en) | 2013-03-06 |
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