WO2005047653A1

WO2005047653A1 - Modular rock bolt system

Info

Publication number: WO2005047653A1
Application number: PCT/SE2004/001537
Authority: WO
Inventors: Fredrik ÖBERG; Morgan Kanflod
Original assignee: Atlas Copco Rock Drills Ab
Priority date: 2003-11-13
Filing date: 2004-10-22
Publication date: 2005-05-26
Also published as: SE0302996L; SE0302996D0; SE526972C2

Abstract

The invention relates to a modular rock bolt system, where a rock bolt (2) comprises at least one rock bolt section (4, 6, 8), where each rock bolt section (4; 6; 8) comprises in series a first end module (10; 20; 30) and an intermediate module (14; 24; 34) and a second end module (18; 28; 38) joined together, and where said first end module (10; 20; 30) abuts and is joined against the first axial end surface of said intermediate module (14; 24; 34) thereby forming a first contact region (13; 23; 33) and that said second end module (18; 28; 38) abuts and is joined against the second axial end surface of said intermediate module (14; 24; 34) thereby forming a second contact region (19; 29; 39), and where said first contact region (13; 23; 33) and said second contact region (19; 29; 39) both have cross-sections that substantially overlap each other when seen axially along said rock bolt (2).

Description

MODULAR ROCK BOLT SYSTEM

Technical area

The present invention relates to a modular rock bolt system.

Background of the invention

Different types of rock bolts, for example for supporting of the rock in order to increase its stability or for anchorage of suspension hooks or the like to the rock, are used for different types of rock.

If the rock is solid, then a hole is usually drilled into the rock using a rock drill. Thereafter, the rock drill is removed from the hole and a rock bolt is subsequently inserted into the hole. If a very long rock bolt is needed, jointed rock bolts comprising several sections can be used.

If the rock is non-solid, i.e. it comprises a multitude of cracks and the like, the hole will not remain fully open when the rock drill is removed, thereby making it impossible to insert a rock bolt into the hole due to blocking rock material . In order to be able to arrange a rock bolt in non- solid rock usually a rock: bolt of the self-drilling type is used, i.e. a rock bolt comprising a drill bit mounted thereon which drill bit is left in the rock together with the rock bolt, whereby the hole will remain free from blocking rock material due to the fact that no removal of the drill bit takes place. One example of a self-drilling rock bolt is shown in the Japanese patent application No. 2000-373505, which rock bolt comprises, in series, a rod for connecting the self- drilling rock bolt to a drilling apparatus, an expandable bolt part, and a drill bit unit comprising a holder for a drill bit and a drill bit, respectively. A drilling water supply pipe with a first end opening in the centre of rotation of the connector rod and a second opening on the surface of the drill bit extends from the connector rod, through the inside the expandable part and to the drill bit unit .

A drawback with rock bolts as they have been manufactured up until now, is that all the different types of rock bolts are manufactured in different ways making it necessary to have a great flexibility within a production unit which is intended to manufacture all types of rock bolts. This in turn requires complex and expensive manufacturing systems which can be reprogrammed for each type of rock bolt, and a complex logistic system for delivering different components for the respective types of rock bolts. The operators of the manufacturing systems also need to keep track of which preparations has to be made to which components depending of the type of rock bolt to be manufactured and what components are to be attached to each end of the rock bolt. All in all, this results in high production costs .

Summary of the invention

It is an object of this invention to simplify the manufacture of different types of rock bolts in a manufacturing system by arranging a modular rock bolt system where a rock bolt comprises at least one rock bolt section, where each rock bolt section comprises in series a first end module and an intermediate module and a second end module joined together, and where said first end module abuts and is joined against the first axial end surface of said intermediate module thereby forming a first contact region and where said second end module abuts and is joined against the second axial end surface of said intermediate module thereby forming a second contact region, and where said first contact region and said second contact region both have cross-sections that substantially overlap each other when seen axially along said rock bolt .

By arranging a modular rock bolt system comprising the features in independent claim 1, it is possible to apply the same joining process to all the joints between said intermediate and end modules regardless of the type of end modules, thus making it possible to manufacture different types of rock bolts using the same manufacturing system without having to reprogram the manufacturing system for each type of rock bolt.

Further preferred features are included in the dependent claims .

By arranging a self-drilling rock bolt comprising the features in dependent claims, drilling fluid is delivered without difficulty to the drill bit unit, and expanding fluid to the parts that are to be expanded.

List of figures

The invention is now described by way of a preferred non- limiting example with reference to the appended drawings, wherein:

Figure 1 shows a longitudinal section of a jointed self- drilling rock bolt comprising three rock bolt sections, together comprising nine rock bolt modules.

Figure 2 shows a cross-section of an intermediate rock bolt module according to one embodiment of the invention.

Figure 3 shows a longitudinal section of an alternative intermediate rock bolt module. Detailed description of preferred embodiments

The invention relates to a modular rock bolt system where a rock bolt comprises at least one rock bolt section, where each rock bolt section comprises in series a first end module and an intermediate module and a second end module joined together, and where said first end module abuts and is joined against the first axial end surface of said intermediate module thereby forming a first contact region and where said second end module abuts and is joined against the second axial end surface of said intermediate module thereby forming a second contact region, and where said first contact region and said second contact region both have cross-sections that substantially overlap each other when seen axially along said rock bolt .

Figure 1 shows a longitudinal section of a jointed self- drilling rock bolt 2 according to one embodiment of the invention comprising three rock bolt sections 4,6,8, preferably joined together by threads, together comprising nine rock bolt modules 10, 14, 18;20, 24, 28 ; 30, 34, 38. In this embodiment, the front section 4 comprises at least three main modules: firstly, a drill bit unit module 10; secondly, an intermediate module 14, preferably comprising an expandable part intended to be expanded after the rock bolt 2 has been fully inserted in position within a rock 42 in order to lock said rock bolt 2 mechanically to the internal radial surface 44 of a hole 46 drilled into the rock 42; and thirdly, a connector module 18 intended for connecting the rear end 17 of the front section 4 of the rock bolt 2 to a front end of another section of said rock bolt 2. The drill bit unit module 10 may comprise a drill bit 50 intended to be used for drilling a hole 46 into a rock 42, or a holder 52 for a drill bit 50 and a drill bit 50, respectively. The rear section 8 also comprises at least three main modules: firstly, a connector module 30 intended for connecting the front end of the rear section 8 of the rock bolt 2 to a rear end of another section of said rock bolt 2; secondly, an intermediate module 34; and thirdly, a connector module 38 intended for connecting the rear end 37 of the rear section 8 of the rock bolt 2 to a drilling apparatus 60. Said intermediate module 34 may comprise an expandable part of the same type as mentioned in the front section 4 of the rock bolt 2, but it may also be a non-expandable part intended to convey drilling fluid, percussion force, rotation and expanding fluid, respectively, from the drilling apparatus 60 or another fluid source to the front section 4 of the rock bolt 2.

The self-drilling rock bolt 2 may further comprise one or more intermediate sections 6, where said intermediate section (s) also comprise at least three main modules: firstly, a connector module 20 intended for connecting the front end of the intermediate section 6 of the rock bolt 2 to a rear end (e.g. 17) of another section (e.g. 4) of said rock bolt 2 ; secondly, an intermediate module 24; and thirdly, a connector module 28 intended for connecting the rear end 27 of the intermediate section 6 of the rock bolt 2 to a front end of another section (e.g. 8) of said rock bolt 2. Said intermediate module may comprise an expandable part of the same type as mentioned in the front section 4 of the rock bolt 2, but it may also be a non-expandable part intended to convey expanding fluid 62, and in some embodiments also drilling fluid 64, from the drilling apparatus 60 or another fluid source to the front section 4 of the rock bolt 2.

In the following description of this embodiment of the invention, the drill bit unit module 10 comprises a holder 52 for a drill bit 50 and a drill bit 50, respectively, where the front end of said intermediate module 14 of said front section 4 of the rock bolt 2 is joined to the holder 52.

In order to be able to transport drilling fluid 64, usually water, from said drilling apparatus 60, or any other fluid source, to the holder 52 for the drill bit 50, and from there on right through the drill bit 50, each of the sections 4; 6; 8 in the rock bolt 2 preferably also comprise a drilling fluid supply pipe 66; 68; 70 located along the axis of rotation X of the rock bolt 2. Said fluid supply pipes 66;68;70 together with a rear opening 72 in the connector module 38 intended for connecting the rear end 37 of the rear section 8 of the rock bolt 2 to a drilling apparatus 60 and a front opening 74 in the drill bit 50, form a channel for drilling fluid 64 extending from said connector module 38 surface to said drill bit 50 surface when the rock bolt 2 is in its assembled state as shown in figure 1.

The expanding fluid 62 is preferably conveyed from a fluid source 76, via a pipe 77 and through an inlet 78 in the connector module 38 intended for connecting the rear end 37 of the rear section 8 of the rock bolt 2 to a drilling apparatus 60, through the intermediate modules 34,24,14 thereby reaching those of the intermediate modules 34,24,14 that are to be expanded after the rock bolt 2 has been fully inserted in position within a rock 42 in order to lock said rock bolt 2 mechanically to the internal radial surface 44 of a hole 46 drilled into the rock 42. Joints 80,81 comprising at least one fluid passage 82 , 84 , 86; 88, 90 , 92 are arranged between said intermediate modules 34,24,14 in order for the expanding fluid 62 to be able to flow through the joints 80,81. It is possible to let the drilling fluid 64 use the intermediate modules 34,24,14 as a pipe, in the same way as the expanding fluid 62. In this case some means for closing off the fluid opening in the drill bit unit module 10 must be arranged. Otherwise, expanding those of the intermediate modules 34,24,14 that are to be expanded will be difficult as the expanding fluid 62 will continuously keep leaking out through the opening 74 in the drill bit unit module 10 thus making it difficult to build up a preferred expanding pressure in the expanding fluid 62 situated within those of the intermediate modules 34,24,14 that comprise a part that is to be expanded. The pressure in the drilling fluid 64 is much lower than that in the expanding fluid 62. Therefore, the closing off of said opening may for example be executed using a pressure or rotation controlled vent (not shown) in the opening 74 which vent closes when the pressure in the expanding fluid 62 exceeds a threshold. Thus, when the expanding fluid 62 is conveyed at a high pressure into the opening, said vent closes thus expanding the walls of those of the parts of the intermediate modules 34,24,14 that are to be expanded until they come into contact with the radial surface 44 inside the drill hole 46. The expanding fluid 62 and the drilling fluid 64 may be the same fluid such as water fed from the same fluid source and through the same opening or two different fluids such as liquid concrete and water fed from two different fluid sources.

Figure 2 shows a cross-section of an intermediate module 14,24,34 in a section 4,6,8 of a rock bolt 2. In this embodiment, both the outer periphery 100 and the inner periphery 102 of said intermediate module has a symmetrical cross-section forming a cross-like shape having an inner channel 104 also with a cross-like shape as shown in figure 2. The wall thickness between the inner periphery 102 and the outer periphery 100 is preferably equal throughout said cross- section. Said part thus forms a pipe-like device preferably with room for a drilling fluid supply pipe 66; 68; 70 in the centre. When using an intermediate module having a symmetrical profile as described above, the inner channel can always be accessed through a hole in the axis of rotation of an end module 10 , 18 ; 20 , 28 ; 30 , 38 of a section 4,6,8 in a rock bolt 2. All the intermediate modules 14,24,34 may have a similar construction regarding the cross-section. The intermediate module may also be expandable when using a profile as shown in figure 2.

Fig. 3 shows a expanding rock bolt 3 according to prior art, e.g. a "SWELLEX^®" type of rock bolt from Atlas Copco, Sweden. This type of rock bolt 3 may alternatively be used as an intermediate module 14,24,34 instead of a profile as described in figure 2. This prior art rock bolt 3 comprises and intermediate expandable part 5 welded (at 55 and 57) to two non-expandable end parts 7,9, where the respective non- expandable end parts 7,9 will be joined to two end modules (e.g. 10 and 18) .

Symmetrical cross-sections for the intermediate modules 14,24,34 of the rock bolt 2 other than the one shown in figure 2 are also possible to use preferably with room for a drilling fluid supply pipe 66,68,70 located along the axis X of rotation of the intermediate rock bolt modules 14,24,34. Although symmetrical cross-sections are preferred, non- symmetrical cross-sections are also possible to use, preferably with room for a drilling fluid supply pipe 66,68,70 located along the axis X of rotation of the intermediate rock bolt module 14,24,34. When using an intermediate module having a symmetrical cross- section the three modules 10, 14, 18 ;20, 24, 28 ; 30, 34, 38 of a section 4,6,8 in a rock bolt 2 may be aligned and joined together in a way that allows the axial forces F during a hammer drilling operation to propagate in an essentially axial direction A through said three modules

10, 14, 18; 20, 24, 28; 30, 34,38, thus maximizing the stability of said section 4,6,8. This will be explained below for the first section 4, but joining of modules 10, 1 , 18 ;20, 24, 28;30 , 34 , 38 in a section may be done in a similar way for all sections 4,6,8, thereby forming first contact regions 13,23,33 and second contact regions 19,29,39.

As can be seen in figure 1, the intermediate module 14 is joined at a first end to a first end module 10 and at a second end to a second end module 18. Said first end module 10 abuts against the first axial end surface of said intermediate module 14 thereby forming a first contact region 13, and said second end module 18 abuts against the second axial end surface of said intermediate module 14 thereby forming" a second contact region 19. Said intermediate module 14, said first contact region 13, and said second contact region 19 all have cross-sections that at least partly overlap each other when seen axially along said rock bolt 2, thereby allowing axial forces during a hammer drilling operation to propagate in an essentially axial direction from said second end. module 18 via said intermediate module 14 into said first end. module 10, thus improving the axial stability of the rock boLt 2. Said intermediate module 14 is preferably joined to said first end module 10 and said second end module 18, respectively, by welding but it is also possible to use another joining- method, e.g. soldering or an adhesive if the resulting joint becomes sufficiently strong. Welding methods that may be used comprises, but are not limited to, resistance welding, friction welding and electron beam welding.

A jointed self-drilling rock bolt has been used to exemplify the invention in the description above. The invention also relates to other kinds of rock bolts, e.g. jointed rock bolts that are not self-drilling, self-drilling rock bolts that are not jointed, and rock bolts that are neither self-drilling nor jointed. The rock bolts that are self drilling preferably comprise drilling fluid pipes, but this is not mandatory as has been mentioned above. The rock bolts that are not self drilling do preferably not comprise any drilling fluid pipes as they are unnecessary and thus only give rise to unnecessary costs.

The end modules that have been used to exemplify the invention are: a drill bit unit module , comprising a drill bit, or comprising both a drill bit and a holder for a drill bit; a connector module for connecting a rock bolt section to a drilling apparatus; and different connector modules for connecting a rock bolt section to another- rock bolt section. Depending on the intended use of the rock bolt, other end modules are also possible. E.g., if the r-ock bolt is neither self-drilling nor jointed, the front end module may be a cap intended only to seal off the interior of the intermediate module thus preventing leakage of expanding fluid, or a cap with external protrusions intended to prevent a rock bolt inside a drilling hole from falling out. End modules in the form of differently shaped male- or female connectors.

Claims

1. Modular rock bolt system, where a rock bolt (2) comprises at least one rock bolt section (4,6,8), where - each rock bolt section (4,-6; 8) comprises in series a first end module (10;20;30) and an intermediate module (14;24;34) and a second end module (18;28;38) joined together, characterized in, that - said first end module (10; 20; 30) abuts and is joined against the first axial end surface of said intermediate module (14; 24; 34) thereby forming a first contact region (13;23;33) and that said second end module (18; 28; 38) abuts and is joined against the second axial end surface of said intermediate module (14;24; 34) thereby forming a second contact region (19;29;39), and where said first contact region (13; 23; 33) and said second contact region (19; 29; 39) both have cross-sections that substantially overlap each other when seen axially along said rock bolt (2) .

2. Modular rock bolt system according to claim 1, characterized in, that the intermediate module (14; 24; 34) is joined at a first end to the first end module (10;20;30) and at a second end to the second end module (18;28;38), respectively, by welding.

3. Modular rock bolt system according to claim 1 or 2 , characterized in, that at least one intermediate module (14; 24; 34) has a symmetrical cross-section.

4. Modular rock bolt system according to claim 3, characterized in, that said at least one intermediate module (14; 24; 34) has a symmetrical cross-section, and that - said intermediate module (14;24;34), said first contact region (13;23;33), and said second contact region (19; 29; 39) all have cross-sections that at least partly overlap each other when seen axially along said rock bolt (2) , thereby allowing axial orces during a hammer drilling operation to propagate in an essentially axial direction (A) thus improving the axial stability of the rock bolt (2) .

5. Modular rock bolt system according to claim 4, characterized in, that said at least one intermediate module (14,-24,-34) is at least partially expandable.

6. Modular rock bolt system according to one of the preceding claims, characterized in, that the front section (4) comprises a first end module (10) which can be chosen among the group of a drill bit unit module, a sealing cap, or a sealing cap with external protrusions, and a second end module (18) which can be chosen among the group of a male connector or a female connector.

7. Modular rock bolt system according to one of the preceding claims, characterized in, that the rear section (6) comprises a second end module (38) which can be chosen among the group of: a drilling apparatus connector, a female connector, or a male connector, and a first end module (30) which can be chosen among the group of a male connector or a female connector.

8. Modular rock bolt system according to one of the preceding claims, characterized in, that the intermediate section (6) comprises a first end module (20) which can be chosen among the group of a male connector or a female connector, and a second end module

(28) which can be chosen among the group of a female connector, or a male connector.

Modular rock bolt system according to one of claims 1 to 5, characterized in, that the rock bolt (2) comprises one rock bolt section (4; 6; 8) only, and that the section (4; 6; 8) comprises a first end module (10;20;30) which can be chosen among the group of a drill bit unit module, a sealing cap, or a sealing cap with external protrusions, and a second end module (18; 28; 38) which can be chosen among the group of a drilling apparatus connector, a female connector or a male connector.