NO20240364A1 - Sealing means, rock anchor bolt, and tool - Google Patents

Description

FIELD OF THE INVENTION

The invention relates to a sealing means as defined in the preamble of claim 1 for sealing a borehole, the sealing means being installable to a drawbar of a rock anchor bolt that is installed in the borehole. The invention also relates to the rock anchor bolt and to a tool for installing the sealing means to the rock anchor bolt secured in the borehole, or, for installing the rock anchor bolt in the borehole.

BACKGROUND OF THE INVENTION

A rock anchor bolt is a long rock bolt which is used for reinforcing rock cuts, cavities and walls of tunnels. A variety of structures can also be suspended from a rock anchor bolt installed in place. Typically, when reinforcing a rock, rock anchor bolts are used as an array of several rock anchor bolts installed at a distance from one another. Rock anchor bolts function by binding the rock mass, which is present in the vicinity of the surface of the rock and which may include cracks and boulders, to the firmer and more solid internal part of the rock, thus preventing rockfall.

Typically, the rock anchor bolt is a so-called expansion shell bolt having a drawbar which is made of reinforcing steel and which has a mechanical expansion member at its end. The expansion of the expansion member is induced by a tightening nut which is disposed at the end of the drawbar extending out from the borehole and during the tightening of which the drawbar will move and draw a wedge or the like into the expansion member, making the expansion member expand and adhere to the wall of the borehole. The installation of the rock anchor bolt is effected by boring, for each bolt, a long dead hole in the wall of the rock to be reinforced. The rock anchor bolt is inserted into the dead hole down to a desired depth. Then, the rock anchor bolt is secured in place by expanding the expansion member at the inner end, i.e. the tip thereof so as to press the expansion member against the wall of the borehole. Finally, grouting paste, such as cement or resin, is injected around the anchor bolt in the borehole so as to grout the anchor bolt. When grouted, it becomes a firmer reinforcement.

The advantages of the rock anchor bolt include immediate readiness right after installation, good corrosion resistance when grouted and easy installation. Without grouting, the bolt is easily subjected to corrosion. By grouting it is also possible to ensure that the bolt will work, even if the anchorage at the end of the hole fails.

Water leaking into the borehole from fine cracks in the rock makes it significantly more difficult to install the anchor bolt and to inject the grouting paste. The water may pour out from the borehole as a continuous stream. The problem is that grouting paste is washed away with the water. In addition, the water may remain as pockets in the borehole and within the grouting paste, thus weakening the reinforcement and causing corrosion. Therefore, according to regulations, leaking boreholes must not be grouted.

In order to seal leaking boreholes, it is possible to provide a rock anchor bolt with a sealing means fitted around the outer end of a tube surrounding the drawbar in the borehole. The sealing means seals the space between the tube and the borehole in the vicinity of the mouth of the borehole. The rock anchor bolt comprises a drainage pipe provided in the grouting space between the tube and the drawbar to drain the leakage water while injecting the grouting paste. As a result, as the grouting paste is injected, the grouting paste fills the grouting space between the tube and the drawbar, as well as the space between the borehole and the tube, from the outer end towards the inner end, so that the leakage water is pushed, in front of the grouting paste, to the inner end of the drainage pipe and then out through the drainage pipe.

The rock anchor bolt of this type suffers from the problem that the sealing means is located in the vicinity of the mouth of the borehole. Often, the rock layer in the vicinity of the mouth of the borehole is brittle, not allowing the sealing means to seal the borehole well enough. Besides, in tunnels, for example, a layer of more brittle sprayed concrete can be present on the surface of the rock, having a thickness of more than 10 cm, up to 60 cm. It would be preferable to place the sealing means above the sprayed concrete layer, where the rock layer is located, which is not possible with the current rock anchor bolts.

OBJECTIVE OF THE INVENTION

The invention aims at providing a solution that allows the above-described drawbacks to the alleviated.

SUMMARY OF THE INVENTION

The objective of the invention is achieved by a sealing means as defined in claim 1, by a rock anchor bolt as defined in claim 5, by a tool as defined in claim 9 and by a method as defined in claim 14.

The sealing means according to the invention is installable to an external thread of a drawbar of a rock anchor bolt that is installed in a borehole. The sealing means comprises a sliding tube fittable around the drawbar of the rock anchor bolt, a sealing member fitted around the sliding tube and comprising material, such as rubber, that can be shaped by pressing, a countermember and a locking member between which the sealing member is fitted in the longitudinal direction of the sliding tube. The sealing member can be pressed against the countermember and locked around the sliding tube in its pressed state. In addition, the sealing means, such as the sliding tube, is equipped with an internal thread to enable the sealing means to be screwed onto the external thread of the drawbar of the rock anchor bolt.

The rock anchor bolt according to the invention comprises a drawbar equipped with an external thread and having an inner end that can be inserted into the borehole and an outer end that protrudes out of the borehole, as well as tightening members provided at the outer end of the drawbar for drawing the drawbar outwards with respect to the borehole in order to tighten the rock anchor bolt in place. In addition, the rock anchor bolt comprises the above-described sealing means having its internal thread screwed onto the external thread of the drawbar and its sliding tube fitted around the drawbar.

The tool according to the invention is suitable for installing the rock anchor bolt according to the invention in a borehole, or, for installing the sealing means according to the invention to the drawbar of the rock anchor bolt equipped with an external thread, the rock anchor bolt being secured in the borehole.

The tool according to the invention comprises an inner insertion tube fittable around the drawbar of the rock anchor bolt and adapted to engage the sealing means for screwing the sealing means along the external thread of the drawbar, an outer insertion tube fitted around the inner insertion tube for pressing the sealing member of the sealing means against the countermember, the outer insertion tube being movable in the axial, i.e. longitudinal, direction with respect to the inner insertion tube, a tightening member for moving the outer insertion tube in the axial direction with respect to the inner insertion tube and for pressing the tightening member against the countermember. Further, the tool comprises an end sleeve provided at the outer end of the inner insertion tube, the end sleeve having a first internal thread screwable onto the external thread of the outer end of the drawbar, and a support surface against which the outer end of the drawbar is adapted to be supported.

In the method according to the invention, a sealing means according to the invention is installed to a rock anchor bolt fitted in a borehole, or, a rock anchor bolt according to the invention is installed in the borehole, the rock anchor bolt comprising a drawbar equipped with an external thread. The sealing means is screwed along the external thread of the drawbar by a tool according the invention or by any appropriate tool, once the drawbar is fitted in the borehole, the sealing member of the sealing means is pressed against the wall of the borehole by the tool, the sealing member is locked in place in its pressed state, and the tool is taken out of the borehole.

Significant advantages can be achieved by means of the invention.

The sealing means according to the invention can be screwed, along the external thread of the drawbar of rock anchor bolt, to a desired depth in the borehole. Consequently, the sealing means can be placed deeper from the mouth of the borehole, at a point where the wall of the borehole is not as brittle as at the mouth, or above the sprayed concrete layer. The sealing means according to the invention can also be installed to rock anchor bolts that are already secured in a borehole, if they comprise a drawbar equipped with an external thread onto which the internal thread of the sealing means can be screwed by means of the tool.

In this disclosure, the terms "inner" and “internal” refer to a part which is located deeper inside the rock in the borehole than another part referred to by the term "outer" and “external”.

LIST OF FIGURES

In the following, the invention will be explained in detail by means of embodiment examples with reference to the accompanying drawings where

figure 1 is a cross-sectional view of a rock anchor bolt according to an embodiment of the invention, after been inserted into a borehole,

figure 2 is a cross-sectional view of the rock anchor bolt of Fig. 1, having a tool according to an embodiment of the invention connected to it,

figure 3a shows a sealing means according to an embodiment of the invention,

figure 3a is a cross-sectional view of the sealing means of Figure 3A,

figure 4a shows a tool according to an embodiment of the invention, and

figure 4b is a cross-sectional view of the tool of figure 4a.

DETAILED DESCRIPTION OF THE INVENTION

Figure 1 shows a rock anchor bolt 1 according to an embodiment of the invention which has been inserted into a borehole 12 bored in a rock and which is intended to be tightened in place.

The rock anchor bolt 1 comprises a drawbar 2 equipped with an external thread, such as a drawtube equipped with an external thread, having an inner end 3 to be inserted into a borehole 12 and an outer end 4 to protrude out of the borehole. A flow channel 5 for grouting paste is provided inside the drawbar 2. In figure 1, the flow channel 5 is denoted by a dashed line. The grouting paste is injected into the borehole 12 through the flow channel 5, the grouting paste being injected from the outer end 4 of the drawbar 2, and the grouting paste is removed from the flow channel into the borehole 12 at the inner end 3 of the drawbar 5. The flow channel 5 extends over the entire length of the drawbar 2. The external thread extends over the entire length of the drawbar 2.

Further, the rock anchor bolt 1 comprises tightening means 7 for tightening the anchor bolt in place. The tightening means 7 comprise a support plate 8 for supporting the outer end 4 of the rock anchor bolt against the surface of the rock around the mouth of the borehole 12. The support plate 8 has a center hole.

Further, the tightening means 7 may comprise a centering member 9 provided at the outer end 4 of the drawbar 2, in the center hole of the support plate 8. The centering member 9 has a central hole through which the outer end 4 of the drawbar 2 is adapted to extend. Further, the tightening means 7 comprise a nut (not shown) screwed onto the outer end 4 of the drawbar 2, against the centering member 9, to draw the drawbar 2 outwards with respect to the borehole 12, for the purpose of tightening the rock anchor bolt 1 in place.

In order to lock the rock anchor bolt 1 in place in the borehole 12, the rock anchor bolt 1 may comprise a conical wedge anchoring mechanism at the inner end 3 of the drawbar 2 or in the vicinity of the inner end 3. The anchoring mechanism comprises an expansion member 10 enclosing a conical member 11. The anchoring mechanism may comprise two conical members 11 or just one conical member 11.

A thread connects the conical member 11 to the drawbar 2 at the inner end 3 of the drawbar 2 or in the vicinity of the inner end 3. The conical member 11 is provided within the expansion member 10. The expansion member 13 expands and adheres to wall of the borehole as the drawbar 2 is screwed inwards in the borehole 12 by the tool 20. The rock anchor bolt 1 does not necessarily need to be equipped with the conical member 11 and the expansion member 10 but it can be secured in the borehole 12 by a sealing means 13 according to the invention.

The rock anchor bolt 1 comprises a sealing means 13 according to an embodiment of the invention to seal the borehole 12. The structure of the sealing means 13 is described in more detail in figures 3a and 3b. The sealing means 13 is installable/installed to the external thread of the drawbar 2 of the rock anchor bolt 1. The sealing means 13 comprises a sliding tube 14 equipped with an internal thread and adaptable/adapted around the drawbar 2 and screwable/screwed onto the external thread of the drawbar. The sliding tube 14 may comprise a tip sleeve 15 equipped with an internal thread, or the internal thread is provided on the inner surface of the sliding tube 14. The clearance between the external thread of the drawbar 2 and the internal thread of the sliding tube 14 is chosen to allow water and air to exit on the side of the inner end of the borehole 12, along the clearance.

A clearance can be provided between the inner surface of the sliding tube 14 and the outer surface of the drawbar 2 along which water and air can exit the borehole. If the sliding tube 14 comprises the tip sleeve 15, the tip sleeve 15 is provided at the inner end of the sliding tube 14.

The sealing means 13 includes a sealing member 17 surrounding the sliding tube 14 and comprising or being made of material, such as rubber, that can be shaped by pressing. The sealing member 17 can be a rubber sleeve. The sealing member 17 is placed on the outer surface of the sliding tube 14. The sealing member also comprises a countermember 18 and a locking member 19 between which the sealing member 17 is provided in the axial, i.e. longitudinal direction of the sliding tube. The sealing member 17 can be pressed against the countermember 18 and locked, by the locking member 19, around the sliding tube 14, against the countermember 18, in its pressed state. When pressed in the radial direction of the borehole 12, the sealing member 17 expands and seals against the wall of the borehole 12.

The sliding tube 14 may comprise one or more lateral holes 16 extending from the outer surface of the sliding tube 14 to the inner surface thereof and located between the sealing member 17 and the inner end of the sliding tube 14. It is possible to remove water and air through the lateral hole(s) 16.

The countermember 18 can be constituted by an annular shoulder surrounding the outer surface 14 of the sliding tube 14, or by the outer end of the tip sleeve 15 having a larger outer diameter than the point on the sliding tube 14 where the sealing member 17 is located. The locking member 19 may comprise one or more lock rings adapted to attach to the outer surface of the sliding tube 14 in such a way that any movement of the lock ring towards the outer end of the sliding tube 14 is hindered. The locking member 19 may also comprise a washer between the lock ring and the sealing member 17.

The rock anchor bolt 1 comprising the sealing means 13 can be installed in the borehole by means of the tool 20 according to the invention, an embodiment thereof being depicted in figures 4a and 4b. The tool 20 also allows the sealing means 13 to be installed to a rock anchor bolt 1 that already is secured in the borehole 12, in case any water is leaking from the borehole 12, for example. The tools 20 can be provided in two or more different lengths, for example, to allow the sealing means 13 to be installed at different depths in the borehole 12.

The tool 20 comprises an inner insertion tube 21 fittable around the drawbar 2 and against the sealing means 13, such as against the sliding tube 14 or the outer end of the sliding tube 14. The inner insertion tube 21 is adapted to engage the sealing means 13, such as the sliding tube 14 or the outer end of the sliding tube 14, to screw the sealing means 13 along the external thread of the drawbar 2 as the inner insertion tube 21 is rotated. This allows the sealing means 13 to be screwed to a desired point on the external thread of the drawbar 2.

The inner insertion tube 21 comprises engaging members 22 adapted to engage the sliding tube 14 of the sealing means 13, such as the outer end of the sliding tube 14, to screw the sealing means 13 along the external thread of the drawbar 2 by the tool 20. The engaging members 22 may comprise an inner bevel at the inner end of the inner insertion tube 21, the inner diameter of the inner insertion tube 21 thus increasing towards its inner end. The inner bevel allows the inner insertion tube 21 to be connected to the outer end of the sliding tube 14 in such a way that the sealing means 13 can be screwed along the external thread of the drawbar 2 by the tool 20. The outer surface of the inner insertion tube 21 can be equipped with an external thread 23 extending from the outer end of the inner insertion tube 21 towards its inner end. The pitch of the external thread of the drawbar 2 is larger than the pitch of the external thread 23 of the inner insertion tube 21.

The tool 20 also comprises an outer insertion tube 24 to press the sealing member 17 against the countermember 18, once the sealing means 13 has been screwed down to a desired point on the external thread of the drawbar 2. The outer insertion tube 24 is fitted around the inner insertion tube 21. The outer insertion tube 24 extends to the front of the inner end of the insertion tube 21. The outer insertion tube 24 can be fitted around the sliding tube 14. The outer insertion tube 24 is movable with respect to the inner insertion tube 21 in the axial, i.e. longitudinal direction thereof. The inner end of the outer insertion tube 24 can be equipped with a support sleeve 25 whose outer diameter is larger than the outer diameter of the outer insertion tube 24. The outer portion of the support sleeve 25 is located inside the outer insertion tube 24. The support sleeve 25 allows the insertion force of the outer insertion tube 24 to be more evenly applied to the sealing member 17.

The tool 20 also comprises a tightening means to move the outer insertion tube 24 with respect to the inner insertion tube 21 in the axial direction thereof and to press the sealing member 17 against the countermember 18. The tightening means may comprise a tightening nut 26 screwed onto the external thread 23 of the inner insertion tube and fitted against the outer end of the outer insertion tube 24. As the tightening nut 26 is screwed, the outer insertion tube 24 presses the sealing member 17 against the countermember 18, the sealing member 17 thus expanding against the wall of the borehole 12 and sealing the borehole 12. A hexagonal tube extending towards the outer end of the tool 20 can be connected to the tightening nut 26. The hexagonal tube makes it easier to screw the tightening nut 26.

The outer end of the tool 20 comprises an end sleeve 27 having a first internal thread 28 that can be screwed onto the external thread of the drawbar 2. The inner end of the end sleeve 27 may have a second internal thread 29 that can be screwed onto the external thread 23 of the inner insertion tube 21 to connect the end sleeve 27 to the inner insertion tube 21. Alternatively, the end sleeve 27 can be connected to the inner insertion tube 21 in another way, such as by welding. Besides, the outer end of the end sleeve 27 may have a third internal thread 30, such as an end nut 34 equipped with an internal thread and located at the outer end of the end sleeve 27.

The end sleeve 27 may comprise a support surface 31 that can be fitted against the outer end of the drawbar 2 while screwing the end sleeve 27 along the external thread of the drawbar 2. As the outer end 4 of the drawbar 2 is supported against the support surface 31 and the end sleeve 27 is screwed, the drawbar 2, the sealing means 13 and the inner insertion tube 21 are rotated inwards in the borehole 12, with the result that the conical member 11 expands the expansion member 10, making the expansion member 10 to adhere to the wall of the borehole 12.

The support surface 31 can be a bolt 32 screwed into the third internal thread 30 of the end sleeve 27. The outer end of the end sleeve 27 can be equipped with a coupling member 33, such as a bushing, to which an installation tool for screwing the end sleeve 27 can be coupled. The coupling member 33 is connected to the outer end of the bolt 32 comprising the support surface 31, for example, or the outer end of the bolt 32 is provided with a nut head having the coupling member 33 connected to its outer surface. The installation tool can be a batterypowered nut driver. The inner end of the bolt 32 may comprise a stopper to prevent the bolt from being removed from the third internal thread 30. The stopper can be a threadless part provided at the inner end of the bolt 32 and having a diameter larger than the thread of the bolt 32.

Once the rock anchor bolt 1 is fitted in the borehole 12 and the outer end of the drawbar 2 is supported against the support surface 31 of the end sleeve 27, and as the end sleeve 27 is rotated, the drawbar 2 rotates inwards in the borehole 12 and the conical member 11 expands the expansion member 10, making the expansion member 10 adhere to the wall of the borehole 12. Thereafter, the tightening nut 26 is screwed towards the inner surface of the tool 20, resulting in that the tightening nut 26 pushes the outer insertion tube 24 towards the sealing member 17, thus pressing the sealing member 17 and expanding it against the wall of the borehole 12 to seal the borehole 12.

A borehole 12 leaking water and having a rock anchor bolt equipped with an external thread already installed therein can be sealed by means of the sealing means 13 according to the invention in the following way. The tightening means 7 for the rock anchor bolt, i.e. the nut, the centering member 9 and the support plate 8, are removed from the outer end 4 of the drawbar 2. The sliding tube 14 of the sealing means 13 is fitted inside the outer insertion tube 24, and the inner end of the outer insertion tube 24 is fitted against the sealing means 13, such as a lock ring. The sealing means 13 is screwed along the external thread of the drawbar 2 by the tool 20. The inner end of the inner insertion tube 21 of the tool 20, such as the inner bevel of the inner end, is fitted against the sealing means 13, such as the outer end of the sliding tube 14. The tool 20 can be rotated by the end sleeve 27, such as the coupling member 33.

The sealing means 13 is screwed along the external thread of the drawbar 2 by rotating the tool 20. The outer end of the drawbar 2 is supported onto the support surface 31 of the end sleeve 27. As the tool 20 is rotated further, the drawbar 2 is screwed inwards in the borehole 12 and the expansion member 10 is tightened against the wall of the borehole 12 by the conical member 11.

Thereafter, the tightening nut 26 is screwed along the external thread 23 of the inner insertion tube 21, resulting in that the sealing member 17 is pressed against the countermember 18 by the outer insertion tube 24 and the sealing means 17 is pressed against the wall of the borehole 12. The sealing member 17 seals the space between the outer surface of the sliding tube 14 and the inner surface of the borehole 12 in the borehole 12. The locking member 19 locks the sealing member 17, which is in its pressed state, in place.

The tool 20 is removed by rotating the tool 20, for example, by the end sleeve 27, such as the coupling member 33, in the opposite direction. If the end sleeve 27 comprises an end nut 34 and a bolt 32 screwed into it, the bolt 32 is first screwed outwards within the end nut 34. If necessary, the drawbar 2 is prevented from rotating by keeping the end nut 34 in place by an openend spanner, for example, while the bolt 32 is screwed outwards. Thereafter, the tool 20 can be removed from the external thread of the drawbar 2 by rotating and taken out of the borehole 12.

Thereafter, the tightening means 7 are installed in place, i.e. the support plate 8 and the centering member 9 are installed in place at the outer end 4 of the drawbar 2 and the nut is screwed onto the outer end 4 of the drawbar 2, against the centering member 9, in order to tighten the rock anchor bolt 1 in place. Water and air can exit the borehole 12, from between the internal thread of the sliding tube 14 and/or the external thread of the drawbar 2, or, through the lateral hole(s) and along the clearance between the inner surface of the sliding tube 14 and the outer surface of the drawbar 2.

A grouting hose (not shown) is connected to the outer end 4 of the drawbar 2 through which grouting paste, such as cement or resin, is injected into the flow channel 5 of the drawbar 2, in order to grout the rock anchor bolt 1 in place. The grouting paste flows from the inner end of the flow channel 5 into the borehole 12 and fills the space between the borehole 12 and the rock anchor bolt 1. Further, the grouting paste pushes the water and air in front of it and out of the borehole 12, from between the threads of the sealing means 13 and the drawbar 2, and/or through the lateral hole(s) 16 and, further, along the play between the inner surface of the sliding tube 14 and the outer surface of the drawbar 2.

The grouting paste reaches the sealing means 13 and clogs the thread between the sealing means 13 and the drawbar 2. Once the grouting paste has hardened, the rock anchor bolt 1 becomes a firmer reinforcement. Finally, the hose is disconnected and the outer end of the flow channel 5 of the drawbar 2 is blocked with a plug, for example.

If the sealing means 13 and the rock anchor bolt 1 are installed in the borehole 12 at the same time, the sealing means 13 is screwed onto the external thread of the drawbar 2. The sliding tube 14 of the sealing means 13 is fitted inside the outer insertion tube 24, and the inner end of the outer insertion tube 24 is fitted against the sealing means 13, such as the lock ring. The rock anchor bolt 1 is inserted into the borehole 12 manually or by using the tool 20. Thereafter, the sealing means 13 is screwed along the thread of the drawbar 2 by means of the tool 20 in such a way that the outer end of the drawbar 2 is supported onto the countersurface 31 of the end sleeve 27. As the end sleeve 27 is screwed further, the drawbar 2 is rotated inwards in the borehole 12 and the conical member 11 expands the expansion member 10, thus securing the expansion member 10 in the borehole 12. The rest of the steps for installing the rock anchor bolt 1 are similar to the installation steps described above where only the sealing means 13 is installed in the borehole 12.

The sliding tube 14 of the sealing means 13 may comprise one or more elongated slots 35 extending through the wall of the sliding tube 14 and from the outer end of the sliding tube 14 to the inner end thereof. The slot 35 allows or the slots 35 allow the inner insertion tube 21 to slide with respect to the sliding tube 14 as the end sleeve 27 starts to screw onto the external thread of the drawbar 2. This makes it possible to align the thread at the outer end of the drawbar 2 and the first thread 28 of the end sleeve 27 at their starting points.

The invention is not merely limited to the embodiment examples set forth above, but many variations are possible within the scope of the inventive idea defined by the claims.

Claims (15)

1. A sealing means (13) for sealing a borehole (12), the sealing means (13) being installable to an external thread of a drawbar (2) of a rock anchor bolt (1) that is installed in the borehole (12), c h a r a c t e r -i z e d in that the sealing means (13) comprises

- a sliding tube (14) fittable around the drawbar (2) of the rock anchor bolt (1),

- a sealing member (17) fitted around the sliding tube (14) and comprising material, such as rubber, that can be shaped by pressing,

- a countermember (18) and a locking member (19) between which the sealing member (17) is fitted in the axial direction of the sliding tube (14), the sealing member (17) being pressable against the countermember (18) and lockable around the sliding tube (14) by the locking member (19) in its pressed state, and

- the sliding tube (14) being equipped with an internal thread (14.1) to allow the sealing means (13) to be screwed onto the external thread of the drawbar (2) of the rock anchor bolt (1).

2. A sealing means (13) as defined in claim 1, c h a r -a c t e r i z e d in that the sliding tube (14) comprises a tip sleeve (15) equipped with an internal thread (14.1), or the internal thread (14.1) is located on the inner surface of the sliding tube (14).

3. A sealing means (13) as defined in claim 1 or 2, c h a r a c t e r i z e d in that the locking member (19) comprises a washer fitted against the sealing member (17) and one or more lock rings fitted against the washer and adapted to lock to the sliding tube (14).

4. A sealing means (13) as defined in any of the preceding claims, c h a r a c t e r i z e d in that the tip sleeve (15) or the sliding tube (14) comprises the countermember (18).

5. A rock anchor bolt (1) to be installed in a borehole (12) bored in a rock, the rock anchor bolt (1) comprising - a drawbar (2) equipped with an external thread and having an inner end (3) to be inserted into the borehole and an outer end (4) to protrude out of the borehole (12), and

- tightening means (7) provided at the outer end (4) of the drawbar (2) to draw the drawbar (2) outwards with respect to the borehole (12) for the purpose of tightening the rock anchor bolt (1) in place, c h a r a c t e r i z e d in that

the rock anchor bolt (1) comprises a sealing means (13) as defined in any the preceding claims 1 to 4, the internal thread (14.1) thereof being screwed onto the external thread of the drawbar (2) and the sliding tube (14) thereof being fitted around the drawbar (2).

6. A rock anchor bolt (1) as defined in claim 5, c h a r a c t e r i z e d in that a conical member (11) is secured to the inner end (3) of the drawbar (2) or in the vicinity of the inner end (3), and the rock anchor bolt (1) comprises an expansion member (10) enclosing the conical member (11), the expansion member (10) being adapted to expand and to be secured in the borehole (12) as the drawbar (2) is rotated inwards.

7. A rock anchor bolt (1) as defined in claim 5 or 6, c h a r a c t e r i z e d in that a flow channel (5) is provided within the drawbar (2) which extends from the outer end (4) of the drawbar (2) to the inner end (3) thereof and through which grouting paste can be injected into the borehole (12).

8. A rock anchor bolt (1) as defined in any of claims 5 to 7, c h a r a c t e r i z e d in that a clearance is provided between the external thread of the drawbar (2) and the internal thread (14.1) of the sealing means (13) along which water and air can exit the borehole (12) while the grouting paste is injected into the borehole (12).

9. A tool (20) for installing a rock anchor bolt (1) as defined in claim 5 in a borehole (12) or for installing a sealing means as defined in claim 1 to the drawbar (2) of the rock anchor bolt (1) equipped with an external thread, the rock anchor bolt (1) being secured in the borehole (12), c h a r a c t e r i z e d in that the tool (20) comprises

- an inner insertion tube (21) fittable around the drawbar (2) of the rock anchor bolt (1) and adapted to engage the sealing means (13) in order to screw the sealing means (13) along the external thread of the drawbar (2),

- an outer insertion tube (24) fitted around the inner insertion tube (21) to press the sealing member (17) of the sealing means (13) against the countermember (18), the outer insertion tube (24) being movable with respect to the inner insertion tube (21) in the axial direction,

- a tightening member (26) for moving the outer insertion tube (24) with respect to the inner insertion tube (21) in the axial direction and for pressing the sealing member (17) against the countermember (18), and - an end sleeve (27) provided at the outer end of the inner insertion tube (21), the end sleeve (27) having a first internal thread (28) screwable onto the external thread at the outer end (4) of the drawbar (2), and a support surface (31) against which the outer end of the drawbar (2) is adapted to be supported.

10. A tool (20) as defined in claim 9, c h a r a c t e r -i z e d in that the tightening member comprises a tightening nut (26), and the inner insertion tube (21) has an external thread (23) onto which the tightening nut (26) is screwed and fitted against the outer end of the outer insertion tube (24), the outer insertion tube (24) being adapted to press the sealing member (17) as the tightening nut (26) is screwed.

11. A tool (20) as defined in any of the preceding claims 9 to 10, c h a r a c t e r i z e d in that a third internal thread (30) is provided at the outer end of the end sleeve (27), and the support surface (31) comprises a bolt (32) screwed into the third internal thread (30).

12. A tool (20) as defined in any of the preceding claims 9 to 11, c h a r a c t e r i z e d in that the inner insertion tube (21) comprises engaging means adapted to engage the sliding tube (14) of the sealing means, such as the outer end of the sliding tube (14).

13. A tool (20) as defined in claim 12, c h a r a c -t e r i z e d in that the engaging means comprise, at the inner end of the insertion tube, a bevel (22), such as an inner bevel adapted to engage the outer end of the sliding tube (14).

14. A method of installing a sealing means (13) as defined in claim 1 to a rock anchor bolt (1) fitted in a borehole (12), or of installing a rock anchor bolt (1) as defined in claim 9 in a borehole (12), the rock anchor bolt (1) comprising a drawbar (2) equipped with an external thread, c h a r a c t e r i z e d in that the tightening means (13) is screwed along the external thread of the drawbar (2) by a tool (20), once the drawbar (2) is fitted in the borehole (12), the sealing member (17) of the sealing means (13) is pressed against the wall of the borehole (12) by the tool (20), the sealing member (17) is locked in place in its pressed state, and the tool (20) is taken out of the borehole (12).

15. A method as defined in claim 14, c h a r a c t e r -i z e d in that the rock anchor bolt (1) comprises a conical member (11) secured to the inner end of the drawbar (2) or in the vicinity of the inner end, and an expansion member (10) enclosing the conical member (11), and in that the drawbar (2) is rotated inwards in the borehole (12) by the tool (20), the conical member (11) thus expanding the expansion member (10) and the expansion member (10) thus adhering to the wall of the borehole (12).