WO2004055326A1

WO2004055326A1 - An apparatus and method to anchor a rock bolt

Info

Publication number: WO2004055326A1
Application number: PCT/AU2003/001670
Authority: WO
Inventors: Dale Anthony Luke; Adele Jeannette Luke
Original assignee: Lms Geotechnical Pty Ltd
Priority date: 2002-12-17
Filing date: 2003-12-16
Publication date: 2004-07-01
Also published as: AU2002953376A0; WO2004055326A8

Abstract

An apparatus and method to anchor a chemical rock bolt uses parts of an existing percussion hammer and drill, but modifies it by attaching a small fluid pump to the front. A hollow tubular rock bolt containing in internal grout cartridge and sliding plunger is fitted to the pump outlet. The percussion hammer and drill operates the pump which pumps fluid (typically water) into the rock bolt, causing the plunger to move forward and push the grout cartridge to the end of the rock bolt where the grout sets to cement the bolt in place.

Description

ANAPPARATUSANDMETHOD TOANCHORAROCKBOLT

FIELD OF THE INVENTION This invention is directed to an apparatus and a method to anchor a rock bolt into a substrate. The invention will be described with reference to the use of a rock bolt in an underground environment but it should be appreciated that no limitation is meant thereby. Although the invention will be described with reference to a rock bolt, the term rock bolt is to be construed broadly and may include any type of anchor member, and the term rock can include softer materials, coal, sandstone, and the like. BACKGROUND ART

In a mineshaft or underground tunnel, it is often necessary to stabilise unstable areas or zones in the tunnel wall. These zones may comprise loose rock or loose material, rock which is under stress and the like. One known technique comprises the use of rock bolts. Typically, a hole is drilled into the wall face and usually at right angles to the wall face. The hole can have a length of between 1-3 m and a diameter of between 20-60 mm. The hole is formed using a rotating percussion hammer which is attached to a drill rod. The end of the drill rod has a drill bit. Once the hole is formed, the drill rod is removed. There are various known ways to anchor a bolt into the formed hole.

The rock bolt typically comprises a tubular member having a length of between 1-3 m and a diameter to allow it to fit into the formed hole.

One way to fit the rock bolt is using a friction fit. Such a bolt is called a friction bolt. The friction bolt typically comprises a split tube which has an outer diameter which is slightly larger than the diameter of the hole. As the tube is forced into the hole, it will compress to provide a friction fit in the hole. A problem with this type of bolt is that it relies upon compression to provide the friction fit. Thus, if the hole is larger than it should be, the friction engagement will be dramatically reduced and the rock bolt may come loose. It is often difficult to drill a hole of the right diameter as sometimes the drill bit is worn, the drill rod can sometimes be slightly bent and there are many other reasons which can result in the hole being of larger diameter than appropriate or not being entirely straight.

For this reason, it is also known to provide a bolt which uses a settable material to anchor the bolt in the hole [hereinafter called a chemical bolt]. A chemical bolt has a much higher load transfer capacity and can be up to five times more effective than a friction bolt. By chemical bolt is meant a bolt that is anchored using a settable material such as a grout, a cementitous material, or other settable/curable or hardenable material.

There are some different ways to anchor a chemical bolt in a hole. Usually, the hole is formed in the conventional manner (that is the same as for a friction bolt).

One known way is to initially fill the hole with a grout which needs to be pumped into the hole using a pump. Thus, a separate pumping device is required in the mine tunnel. This arrangement is quite labour-intensive and the person pumping the grout into the hole needs to be in the unsupported ground environment which is a safety concern. It is also known to push the grout into the hole using a stick. It is also known to shoot the grout into the hole using an air cannon. A problem with filling the hole with grout using the above methods is that the grout is usually provided in a capsule form. The capsule contains the grout and a hardener such that if the capsule is mixed the grout will set. Therefore, it is important that the capsule does not rupture before it can be positioned at the bottom or end of the hole. Typically, the capsule will rupture when used with an air cannon. Another way to place the grout in the hole is to provide a plastic holding sleeve on the end of the tubular bolt and to position the grout capsule (which is usually quite flexible) in the plastic holding sleeve. The bolt is then pushed into the hole and it is hoped that the capsule will not rupture until the bolt has been pushed all the way to the end of the hole. Often, the capsule does rupture prematurely. Also, it is quite difficult or tricky to align the end of the bolt with the beginning of the hole. This is because the bolt can be several metres long, and the hole can be in the tunnel ceiling. A person needs to carefully align the end of the bolt with the beginning of the hole and this becomes more difficult if the end of the bolt is provided with a flexible sleeve containing the grout capsule. Another known way to anchor a bolt is to push the grout capsule through the inside of the tubular member. Typically, a steel push stick is used to push the grout capsule to the end of the tubular bolt. Conventionally, the tubular bolt is first rammed into the hole and the grout capsule is then pushed along the inside of the tube. This arrangement requires a long steel push stick. It should be appreciated that the diameter of a tunnel may only be between 4-5 m and if the hole is some metres long, it becomes quite difficult to use a push stick of suitable length in the confined space in the workings. Another difficulty with using a push stick is that the hole is not always straight which means that the push stick cannot effectively and efficiently push the grout capsule to the end of the tubular rock bolt.

To provide a good load transfer capacity, it is essential that the grout makes good contact between the outer wall of the tubular member and the wall of the hole. Therefore, it is essential that the grout extends along the small space between the outside wall of the tubular member and the inside wall of the hole. It is found that a push stick etc does not provided consistent and reliable results.

Another known device uses a tubular rock bolt and positions a grout cartridge inside the tubular rock bolt. A movable plunger is positioned behind the grout cartridge and some distance in the bolt. The plunger is designed to tightly engage the inside wall of the tubular bolt. A push stick is then pushed into the tubular rock bolt and engages with the plunger. The entire arrangement is then lifted and pushed into the hole. The reason that the plunger must tightly engage with the inside wall of the tubular bolt is that pushing of the push stick against the plunger must do two things, firstly it must push the tubular rock bolt into the hole, and secondly it must slowly push the plunger forwardly thereby pushing the grout capsule towards the end of the hole. It can be appreciated that this does not always work especially if the hole is rather tight.

Another common disadvantage with installation of chemical anchors is the amount of ancillary equipment which is required and therefore must be in the confined spaces of the tunnel. The ancillary equipment may include quite long lengths of push sticks, air cannons, pumping devices and the like.

One piece of equipment which is common in the tunnel workings is the percussion hammer and drill which is used to form the holes irrespective of whether the hole is fitted with a friction bolt or a chemical bolt and irrespective of how the chemical bolt is attached. Therefore, there would be an enormous advantage if this piece of existing equipment could be used to install the rock bolt instead of needing push sticks, air cannons, pumping equipment and the like.

It will be clearly understood that, if a prior art publication is referred to herein, this reference does not constitute an admission that the publication forms part of the common general knowledge in the art in Australia or in any other country.

OBJECT OF THE INVENTION The present invention is directed to an apparatus and method to install a chemical anchor and which can use existing equipment.

It is an object of the invention to provide an apparatus and a method which may at least partially overcome the above-mentioned disadvantages or provide the consumer with useful or commercial choice

In one form, the invention resides in a method for inserting a chemical anchor into a substrate, the method comprising:

1. Forming a hole in the substrate,

2. Providing an anchor which comprises a tubular member having an open inner end and an open outer end

3. Placing a settable material inside the tubular member, 4. Placing a plunger in the tubular member and between the settable material and the open outer end of the tubular member,

5. Using fluid pressure to push the plunger along the tubular member towards the inner end thereby pushing the grout towards the inner end, and,

6. Maintaining the fluid pressure until substantially all the grout has been pushed through the inner end.

In this manner, there is no need to provide push sticks or other cumbersome devices.

The term fluid pressure includes water pressure, pneumatic pressure, hydraulic pressure and the like. The term fluid pressure will be described with reference to water pressure, but no limitation is meant thereby.

The fluid pressure may be provided by a pump. The pump may comprise any suitable type of pump. It is preferred that the pump is a water pump fitted to the existing percussive hammer and drill assembly which is widely used to form the hole. In another form, the invention resides in an apparatus to chemically anchor a bolt into a substrate, the apparatus comprising a pump adapted to be fitted to the front of a percussion hammer and drill, the pump comprising an elongate pump body having a forward end and a rear end, a piston adapted for reciprocal movement in the pump body, the piston being moved by operable association with the reciprocating hammer of the percussion device, a one-way valve in the pump body and which allows fluid to enter into the pump body upon the reverse stroke of the piston, the forward end of the pump body adapted for contact with the open outer end of the tubular anchor.

In this manner, a specially designed pump can be simply attached to the front of the hammer assembly (which is used to form the hole) and which functions to pump pressurised fluid ( typically water) against the plunger in the tubular anchor to push the plunger forwardly towards the inner end of the tubular assembly. Thus, the only extra piece of equipment required in the workings is a relatively small pump as opposed to long lengths of push stick, an air cannon etc.

The settable material may comprise a grout. The grout is typically a cementitious grout but may also comprise a resin grout. Other types of settable materials are envisaged. The settable material may comprise a known and well used cartridge of grout. The cartridge is typically fairly flexible and contains the settable material together with a setting agent such that mixing of the grout cartridge causes the material to set. This is known.

In the method, the hole can be formed in a conventional manner. A conventional manner uses a percussion hammer and drill which is hydraulically or pneumatically powered. This apparatus can be quite large and is moved forwardly on a feed rail. The front of the apparatus is provided with a hydraulically powered reciprocating hammer. Attached to the front of the reciprocating hammer is a sacrificial shank. The front of the shank is threadingly connected to a long drill rod. The front of the drill rod is connected to a drill bit. The shank or hammer is caused to rotate using a gear arrangement which is well known and which is powered by a hydraulic motor. Thus, the shank rotates causing rotation of the drill rod, and the entire apparatus is can be moved forwardly on the feed rail. The reciprocating hammer improves the cutting efficiency of the drill bit as is quite well known.

Water is used to flush the hole and to clean the drill bit as the hole is formed. Water under pressure passes through the head/shank and through the hollow drill rod to the drill head. As mentioned above, this apparatus is known and is widely used in the mining industry to form holes for rock bolt.

The present invention takes advantage of the known apparatus. The bolt typically comprises an elongate tubular member. This type of bolt is known. The elongate tubular member can have a length of between 1-4 m and typically has a diameter of between 20-50 mm, but in any event should have a diameter which is slightly smaller than the hole diameter. The tubular member has an inner end which extends into the hole and which is open and has an opposite outer end. The open inner end preferably has an opening size which is less than the diameter of the main body of the tubular member such that the opening creates a throttle or a narrowing. The reason for this is that as the grout capsule is squeezed through the opening, the contents will become mixed and the grout will begin to set. Another advantageous reason for having the narrowed opening is that the plunger is prevented from passing through the narrow opening. The reason for this will be described in greater detail below.

The open outer end is typically formed with a small rib or collar which allows a bearing plate to be attached about the outer end to transmit the forces more equally. The use of a bearing plate is known.

The plunger may be of any suitable shape and size and manufactured of any suitable material. Typically, the plunger will have a length of between 10-100 mm. It is preferred that the plunger engages with the sidewall of the tubular member but in such a manner that the plunger can move forwardly relatively easily while still retaining a sealed fit between the fluid pressure and the settable material. The plunger may be made of plastics, rubber, composite materials or any other suitable material. BRIEF DESCRIPTION OF THE DRAWINGS An embodiment of the invention will be described with reference to the following drawings in which: Figure 1 and 2. Illustrates a PRIOR ART conventional apparatus for forming a hole in a tunnel wall in rock.

Figure 3. Illustrates a PRIOR ART hydraulic drill forming a bolt hole in a tunnel wall. Figure 4. Illustrates an exploded view of an embodiment of the apparatus. Figure 5. Illustrates an exploded schematic view of the various internal components of the apparatus.

Figures 6-10. Illustrate the stroke operation of the pump. Figure 11. Illustrates a rock bolt (tubular member) attached to the dolly and containing the settable material. Figure 12. Illustrates an alternative embodiment.

Figure 13. Illustrate the relative sizes of the devices according to the invention and the prior art. Figure 14. Illustrates the formed hole with the drill rod and drill bit removed and replaced.

Figure 15. Illustrates the removal of the drill rod and drill bit and attachment of the pump. Figure 16. Illustrates the arrangement of Figure 12 pushed into the formed hole. Figure 17. Illustrates the forward most position of the plunger in the rock bolt.

Figure 18. Illustrates the completed installation of the rock bolt and retraction of the dolly and feed rail.

BEST MODE Referring to figure 1-18, the following reference numerals are used: 12 hammer reciprocating direction arrow, 15 tunnel wall, 16 feed rail, 17 shank, 19 shank profiled end, 21 drill rod, 22 drill rod fluid passageway, 23 drill bit, 24 rock bolt tubular, 25 rock bolt open inner end, 26 rock bolt open outer end, 27 rock bolt bearing plate, 28 hammer assembly, 29 feed ram, 31 pump apparatus, 32 drill flushing head, 33 drill flushing head water inlet, 34 pressure seals, 35 shank, 36 piston, 37 piston fluid passageway, 39 outer pump housing, 40 pump housing anti-rotation recess, 41 piston anti-rotation ribs, 42 one-way valve, 43 ball valve, 44 ball valve socket, 45 ball valve seal, 46 ball valve biasing spring, 47 piston return spring, 48 fluid outlet, 49 pressure relief valve, 50 outlet seal, 51 grout capsule, 52 plunger seal, 55 grout, expelled, mixed, set, 56 pressure relief valve discharge, 57 steel tube partially collapsed, 58 steel tube closed end, 59 steel tube fluid cavity.

Referring initially to figure 1, this illustrates a conventional motorised hydraulic drill for drilling a hole in the wall 15 of a tunnel. The apparatus comprises a hydraulic reciprocating hammer assembly 28. The hammer assembly 28 slides along a feed rail 16 which is better illustrated in figures 2 and 3. A rotating drill rod 21 is attached to the hammer assembly. A drill bit 23 is attached to the end of the drill rod

21. The hammer assembly has a reciprocating hammer which reciprocates in the direction of arrow 12 (see fig 3). A drill flushing head 32 passes pressurised water through the hollow drill rod 21 to flush cuttings away from the drill bit 23. A water inlet 33 allows water to pass into the drill flushing head 32.

Referring to figures 4 and 5, there is illustrated an embodiment of the invention. The embodiment basically comprises a fluid pump attachment that is powered by the hammer assembly and which can use fluid power to push a settable grout through a hollow rock bolt.

Referring to figures 4 and 5, the hammer assembly 28 is conventional and has a forwardly mounted drill flushing head 32 having a water inlet 33. The water passes through the passageway in the reciprocating hammer shank 17 which has a profiled outer end 19. Shank 17 is caused to reciprocate by a hydraulic/pneumatic motor and gear assembly which is not illustrated but which is conventional. In the conventional use to drill a hole, a drill rod is attached to the profiled outer end 19 of the shank (see figure 3). However, in the embodiment the drill rod is removed and a pump apparatus 31 is attached.

Apparatus 31 is best illustrated in figure 4 and figure 5. Apparatus 31 is attached to the drill flushing head 32 on the known percussion hammer and drill apparatus. Head 32 contains a pressurised water inlet 33 which communicates with a reciprocating member which is shank 17. Shank pressure seals 9 are provided to prevent leakage of water. Reciprocating member [shank] 17 is operated by the hammer. The device housing is attached to the flushing head housing 33 by means of a locking mechanism 61 between the feed thrust plate and flushing head.

The front of shank 17 is profiled 19 and grips a formed cavity 41 in the rear of a piston 36. Piston 36 forms part of the pump apparatus according to an embodiment of the invention. Piston 36 is a reciprocating member (as it is attached to the reciprocating shank 17) and contains an internal water passageway to allow water passing through inlet 33 to pass through piston 36. The pump apparatus 31 comprises an outer pump housing 39 which is roughly tubular in shape. The inside passageway of pump housing 39 contains recesses 40 which capture extending ribs/splines 41 on piston 36 to function as an anti rotational mechanism for piston 36. Thus, piston 36 can reciprocate in pump housing 39 but cannot rotate relative to pump housing 39. A one-way valve arrangement is provided adjacent the front of piston

36. The valve arrangement comprises a ball valve 43 which sits partially within a socket 44 on the front of piston 36. Socket 44 is lined with a seal 45. A small spring 46 biases ball valve 43 into engagement with seal 45 which means that the valve is naturally in the closed position. Inside pump housing 39 is a larger piston return spring 47. The arrangement is such that when the piston 36 moves forwardly, it pumps water in housing 39 through the front outlet 48. When piston 36 moves in the opposite direction, water can pass into pump housing 39 through passageways 37 and inlet 33. A check valve assembly 60 prevents fluid from re-entering the outer end of the pump housing 39. A pressure relief valve 49 is provided in pump housing 39 the reason for which will be described in greater detail below.

Outlet 48 is necked and is designed to fit into a seal 50. Seal 50 seals against the outer open end 26 of tubular member 24 (see fig 4). Therefore, in use, once the hole has been formed, the drilling apparatus is retracted and drill rod 21 is removed. A rock bolt in the form of a tubular member 24 is inserted into the hole. The pump apparatus 31 is attached to the front of the apparatus, the water flow is switched on, and the reciprocating hammer is activated to reciprocate piston 36 in the pump to cause the pump to pump water into tubular member 24.

Referring to figure 6-10 there is illustrated operation of the apparatus. A rock bolt in the form of a steel tubular member 24 (fig 4, 7 and 9) contains a grout capsule 51. In front of grout capsule 51 is a plunger 52. Plunger 52 is designed to seal against the inside wall of tubular member 24 but still able to slide along the tubular member. In use, the percussion device containing the attached pump apparatus 31 is positioned such that outlet 48 extends partially into the outer open end of tubular member 24 and is sealed thereto via seal 50. Operation of the pump apparatus pumps pressurised water into the tubular member 24 and the pressurised water pushes seal 52 towards the end of the member 24. This action also pushes the grout capsule 51 to the end of member 24. As the grout capsule 51 contacts the narrower opening 25 (see fig 4), it will compress and the contents of the grout capsule will mix to cause the setting action to begin. Further forward movement of plunger 52 will cause the grout to be squeezed between the outer wall of tubular member 24 and the inner wall of the hole, this being best illustrated in figure 9. In figure 9, plunger 52 has now moved entirely along the tubular member and towards the narrowed inner end 25. Plunger 52 is designed such that it cannot pass through end 25. Thus, as the plunger reaches the end of the tubular member as illustrated in figure 5, further operation of the pump apparatus 31 will cause an increase in the water pressure in the tubular member and therefore in the pump housing. At some stage, the increase is sufficient to activate the pressure release valve 49 in the pump housing 39 (see fig 10). Thus, in use, an operator will operate the pump apparatus until such time as the operator sees water squirting out of the pressure release valve at which stage the operator will know the plunger 52 is at the end of tubular member 24. The pump apparatus can then be switched off (by switching off the reciprocating hammer).

Specifically referring to figures 6-10, in figure 6, the pump piston 36 is being pulled back by the shank and water passes into the pump housing 39 (by passing about ball 42. In the forward stroke illustrated in fig 8, water is forced through outlet 48 to push the plunger 52 (see fig 7). When the plunger reaches the end of the rock bolt (tubular member 24) ( see fig 9), a back pressure builds up which causes the relief valve 49 to open ( see fig 10).

Referring to figure 11, there is illustrated the apparatus with the rock anchor ( containing the plunger and grout) attached to the front of the pump apparatus 31 and ready to be inserted into the pre drilled hole.

The pump apparatus is relatively small and uses the existing percussion device to ensure that the grout properly anchors the bolt (tubular member) in the hole.

Therefore, there is no need to provide lengthy push sticks etc. Using a water column to push plunger 52 also overcomes the problem of a curved hole as the water will still evenly push plunger 52 and therefore the grout cartridge along the tubular member.

In a variation to the invention (see fig 12), it is envisaged that the pump apparatus according to the embodiment, or a different type of pump apparatus can be used together with an inflatable or expandable rock bolt. To explain, it is envisaged that an inflatable tubular member 57 may be used. The tubular member in the deflated state or semi -■<■ deflated state can be placed into the hole. The pump can then be used to inflate the cavity 59 in the tubular member or other type of expandable member to frictionally engage with the wall of the hole.

Figure 13 illustrates the major components of a typical percussion drill and shows the relative sizes of (a) the apparatus according to an embodiment of the invention, (b) a conventional "push stick" dolly, and (c) a drill rod and bit.

Figure 14 illustrates the formed hole, with the drill rod and a drill bit removed and replaced by a conventional "push stick" dolly with a rock bolt attached. The shaded areas 54 cannot be bolted effectively because of the combined length of the dolly and the bolt.

Figure 15 illustrates the removal of the drill rod and drill bit, and attachment of the apparatus according to an embodiment of the invention in place of the conventional "push stick" dolly. Figure 11 illustrates a bolt loaded onto the dolly and the forward feed

(arrow) applied to push the bolt into the hole.

Figure 16 illustrates the bolt inserted into the hole, and the reciprocating action of the drill shank pumping fluid into the bolt. The fluid pressure forces the plunger and grout forward expelling the grout. Figure 17 illustrates the plunger at the end of its stroke fully expelling the grout. No further fluid can enter the rock bolt. The pressure relief valve activates, allowing fluid to exit from the side of the dolly. This provides a visual signal to the operator that installation is complete.

Figure 15 illustrates the completed installation and retraction of the dolly and feed rail.

Claims

CLAIMS:

1. A method for inserting a chemical anchor into a substrate, the method comprising forming a hole in the substrate, providing an anchor which comprises a tubular member having an open inner end and an open outer end, providing a settable material inside the tubular member, providing a plunger in the tubular member and between the settable material and the open outer end of the tubular member, using fluid pressure to push the plunger along the tubular member towards the inner end thereby pushing the grout towards the inner end, and, maintaining the fluid pressure until substantially all the grout has been pushed through the inner end.

2. The method of claim 1, wherein the fluid pressure is provided by a pump.

3. The method of claim 2, wherein the pump is operated by a percussive hammer and drill assembly.

4. The method of claim 3, wherein the fluid is water.

5. The method of claim 4, wherein the settable material is a grout cartridge.

6. An apparatus to chemically anchor a bolt into a substrate, the apparatus comprising a fluid pump adapted to be. fitted to the front of a percussion hammer and drill, a rock bolt comprising a tubular member which is open at both ends, a moveable body of settable material in the rock bolt, and a sliding plunger in the rock bolt and between the settable material and the pump.

7. The apparatus of claim 6, wherein the pump comprises an elongate pump body having a forward end and a rear end, a piston adapted for reciprocal movement in the pump body, the piston being moved by operable association with the reciprocating hammer of the percussion device, a one-way valve in the pump body and which allows fluid to enter into the pump body upon the reverse stroke of the piston, the forward end of the pump body adapted for contact with an open end of the tubular anchor.

8. The apparatus of claim 7, comprising pressure relief means to release fluid pressure when the sliding plunger has moved to the end of the rock bolt.

9. The apparatus of claim 6, wherein one end of the tubular member is necked to cause mixing of the settable material as the material is forced tbrough this end of the tubular member.

10. A pump for use in an apparatus to chemically anchor a bolt into a substrate, the fluid pump adapted to be fitted to the front of a percussion hammer and drill, the fluid pump comprising an elongate pump body having a forward end and a rear end, a piston adapted for reciprocal movement in the pump body, the piston being moved by operable association with the reciprocating hammer of the percussion device, a one-way valve in the pump body and which allows fluid to enter into the pump body upon the reverse stroke of the piston, the forward end of the pump body adapted for contact with an open end of a tubular anchor.