Rock Bolt

Abstract

A rock bolt particularly for use in mining, comprising an anchor tube, an anchor nut, an anchor plate supported on the anchor nut. The rock bolt contacts the rock to show sufficient shearing resistance and may be easily cut. The rock bolt preferably includes an anchor tube that is surrounded by a jacket tube.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims priority to German Patent Application DE 10 2011 076 592.1, filed May 27, 2011, and entitled "Gesteinsacker" ("Rock Bolt"), which is hereby incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

[0002] The present invention generally relates to a rock bolt.

[0003] Rock bolts are used in mining and tunnel construction, in order to prevent or slow down any rock movement of the adjacent stone or to ensure against falling adjacent rock to a major extent and thus allow a low-risk operation. Here, two principle functions are known, which are sometimes combined. In mechanical systems anchoring of the bolt occurs through friction-fitting, with mechanical rock and/or stone bolts generally comprising an expanding sleeve and an expanding body. In chemical rock bolts anchor tubes are connected by a curing cement or resin as the fixation element to the underground and/or the adjacent rock by way of material engagement. Here, the rock bolts are installed with or without pre-stressing in the adjacent rock. Rock bolts in mining, e.g., in underground coal mining, contrary to tunnel construction, serve only to temporarily secure the rock, because usually the temporarily secured rock is excavated in a later step and thus the rock bolt is removed again from the rock.

[0004] In mining and tunnel construction rock bolts are used with an anchor tube, particularly embodied as a hollow tube, which are made from fiberglass-reinforced plastic. The fiberglass-reinforced plastic shows only a minor extension under the tensile forces developing at the anchor tube as well as low pressure and shearing resistance. Due to this low expansion of the anchor tube made from fiberglass-reinforced plastic these rock bolts must be placed in large numbers and at short distances in order to prevent any movement of the underground and to reduce the shearing forces developing at each individual bolt. Due to the low pressure and shearing resistance a large number of rock bolts with an anchor tube comprising fiberglass-reinforced plastic are damaged and/or destroyed by the pressure and/or shearing forces developing during installation.

[0005] In coal mining such rock bolts are used with anchor tubes produced from fiberglass-reinforced plastic as anchor tubes in the coalbed in order to secure the approach to a longwall alley. These rock bolts are excavated together with the coal and are not removed from the coal or only with a very high expense. Rock bolts with an anchor tube made from steel are generally not used to secure the coalbed, because they are difficult to cut and/or show very sharp edges after excavation. The rock bolts with an anchor tube made from steel cut the conveyer belts or destroy other installations during the coal mining process and thus cause high costs and malfunctions. The rock bolts used in coal mining comprising an anchor tube made from fiberglass-reinforced plastic preferably cause no damages during the mining process at the conveyer belts or other installations of the mine, because they may easily be cut and thus may be milled by the mining equipment. However, with regards to the mechanic features, particularly with regards the shearing strength, they show only insufficient features.

[0006] WO 2007/059580 A1 shows a self-tapping rock bolt with a cutting head and an anchor tube.

BRIEF SUMMARY OF THE INVENTION

[0007] One or more embodiments of the present invention provide an improved rock bolt and method for its use. The rock bolt is particularly for use in mining. The rock bolt preferably comprises an anchor tube, an anchor nut, and an anchor plate supported on the anchor nut. The rock bolt contacts the rock to show sufficient shearing resistance and may be easily cut. The rock bolt preferably includes an anchor tube that is surrounded by a jacket tube.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] In the following, exemplary embodiments of the invention are described in greater detail with reference to the attached drawings. It shows:

[0009] FIG. 1 shows a longitudinal cross-section of a rock bolt, inserted into a bore in the rock and with the fixation structure not yet inserted into the space between the rock and the anchor tube,

[0010] FIG. 2 shows a longitudinal cross-section of the rock bolt according to FIG. 1, in which the fixation structure is inserted into the space between the rock and the anchor tube,

[0011] FIG. 3 shows a longitudinal cross-section of an anchor tube with a jacket tube of the rock bolt according to FIG. 1,

[0012] FIG. 4 shows a longitudinal cross-section of a component comprising metal and plastic of the anchor tube without any metal tube according to FIG. 3 with a connection of the two components in a first embodiment,

[0013] FIG. 5 shows a longitudinal cross-section of the component comprising metal and plastic of the anchor tube without any jacket tube according to FIG. 3 with the connection of the two components in a second exemplary embodiment,

[0014] FIG. 6 shows a longitudinal cross-section of the component comprising metal and plastic of the anchor tube without any jacket tube according to FIG. 3 with the connection of the two components in a third exemplary embodiment,

[0015] FIG. 7 shows a longitudinal cross-section of the component comprising metal and plastic of the anchor tube without any jacket tube according to FIG. 3 with the connection of the two components in a fourth exemplary embodiment, and

[0016] FIG. 8 shows a longitudinal cross-section of the components comprising metal and plastic of the anchor tube without a jacket tube according to FIG. 3 with the connection of the two components in a fifth exemplary embodiment.

DETAILED DESCRIPTION OF THE INVENTION

[0017] One or more embodiments of the present invention therefore provide a rock bolt showing sufficient shearing strength and allowing easy cutting.

[0018] This is attained in a rock bolt, particularly for the application in mining, comprising an anchor tube, an anchor nut, an anchor plate supported by the anchor nut to contact the rock, with the anchor tube being surrounded by a jacket tube. The jacket tube may compensate shearing forces and thus the load capacity of the rock bolt may be considerably improved. The failure of the rock bolt due to stronger shearing forces to be compensated may here be preferably excluded.

[0019] In another embodiment the jacket tube is made from metal, particularly steel, at least partially and particularly entirely, and/or the jacket tube rests on the anchor tube, particularly completely circumferential in the cross-section. The jacket tube made from metal shows a low thickness, e.g., less than 3, 2, or 1 mm, and thus it may easily be cut and milled in coal mining by a shearer or a coal plane so that the rock bolt in coal mining cannot cause any considerable damages in the mining equipment.

[0020] In a variant, the jacket tube comprises ribs and/or a folding. The ribs and/or the folding increase the mechanic stiffness of the jacket tube and preferably in an embodiment at the exterior of the jacket tube the material engagement between the fixation structure and the jacket tube may also be improved.

[0021] In an additional embodiment the ribs and/or the folding are embodied axially or helically.

[0022] In another embodiment the jacket tube is embodied as a fibrous winding around the anchor tube, particularly comprising carbon and/or aramide fibers.

[0023] The fibrous winding is beneficially embodied as a helical or a cross winding to compensate shearing forces by the fiber winding.

[0024] In another embodiment the jacket tube is connected using the anchor tube by way of material engagement.

[0025] In an additional embodiment the jacket tube is connected to a connection device, e.g. a drill head, an expanded cross-section, or a connection ring, to the anchor tube, particularly in the axial direction and/or no material engagement exists in the connection of the anchor tube to the jacket tube. A rock bolt without any jacket tube may be connected to the connection device using the jacket tube. For this purpose, the jacket tube is to be pushed onto the anchor tube and subsequently the jacket tube is to be connected to the anchor tube via the connection device.

[0026] Beneficially the exterior diameter of the anchor tube is preferably equivalent to the interior diameter of the jacket tube.

[0027] In another embodiment the axial extension of the jacket tube amounts to at least 50%, 70%, 80%, 90%, or 95% of the axial extension of the anchor tube.

[0028] Beneficially the anchor tube is preferably made in its entirety from fiber-reinforced plastic or the anchor tube comprises at least partially, particularly entirely metal and plastic and at least one component of the anchor tube made from metal and plastic serves to compensate tensile forces and in particular at an inner section of the anchor tube said anchor tube comprises at least partially, particularly entirely metal and plastic, and in particular the anchor tube shows a frontal end and a rear end and the inner section shows a distance of at least 5%, 10%, or 20% of the overall length of the anchor tube from the frontal and rear end. The embodiment of the anchor tube made from metal and plastic therefore relates preferably not to an embodiment comprising metal and plastic at an area of the anchor tube in the proximity of the frontal and rear end. When the anchor tube comprises fiber-reinforced, e.g., fiberglass-reinforced plastic, particularly entirely, the fibers of the anchor tube are aligned preferably in the axial direction in order to compensate tensile forces and in the lateral direction or in a helical or cross-wise winding to compensate torque.

[0029] The anchor tube of the rock bolt therefore comprises metal, particularly steel, and plastic. This way, in case of tensile forces occurring the anchor tube may perform greater extensions in the longitudinal direction so that this way the rock bolt is also embodied as a gliding anchor and thus motions of the secured rock occurring may be better secured. Further, extraction devices in mining, particularly in coal mining, may easily cut and/or separate the anchor tube of the rock bolt so that this way damages of technical mining equipment may preferably be avoided.

[0030] In a complementary embodiment the anchor tube is designed in several parts comprising plastic and metal components. At least one plastic component and at least one metal component of the anchor tube are first be produced separately and connected to each other during the production of the anchor tube.

[0031] Preferably, alternating one metal component and one plastic component are arranged at the anchor tube in a longitudinal direction of said anchor tube and/or the anchor tube comprising metal, particularly at the inner section, shows no plastic cover, in particular at least one plastic component represents no cover of at least one metal component.

[0032] In one variant, the plastic represents fiber-reinforced plastic, particularly fiberglass-reinforced plastic, and the metal represents steel.

[0033] Beneficially at least one plastic component is made from at least 50%, 70%, or 90% plastic, particularly entirely, and/or at least one metal component is made from at least 50%, 70% or 90% metal, particularly entirely.

[0034] In another embodiment, in a fist cross-section, particularly at the inner section, perpendicular in reference to the longitudinal axis of the anchor tube, said anchor tube is made by at least 50%, 70%, or 90% from plastic, particularly entirely, and in a second cross-section, particularly at the inner section, perpendicularly in reference to the longitudinal axis of the anchor tube, the anchor tube comprises metal, at least by 50%, 70%, or 90%, particularly entirely.

[0035] In particular, the components are connected to each other by an inner or outer plastic sheath and/or fibers of the fiber-reinforced plastic are arranged on the metal component, in particular the fibers are saturated with a matrix material and cured, and together with the fibers the plastic component is connected to the metal component and/or the inner diameter of a component is preferably equivalent to the outer diameter of another component so that the other component is axially arranged inside the component and the two components are connected to each other by way of adhesion and/or a component comprises an internal thread and another component shows an external thread so that both components are screwed to each other at the internal and external threads and/or the exterior diameter of a component and preferably partially the interior diameter of the other component are preferably equivalent and the other components are partially pushed onto the component at an overlapping section and at the outside the two components are connected to each other at the overlapping area with the sheath pressed thereupon, particularly comprising metal, e.g., steel.

[0036] In another embodiment the anchor tube is embodied as a hollow tube.

[0037] In a complementary variant the anchor tube encases an interior space, the rock bolt comprises a fixation structure arranged inside the interior space for a material engaging fixation of the anchor tube to the rock, a mobile piston arranged inside the interior space to convey the fixation structure outside the anchor tube in an arrangement of the anchor tube in a bore in the rock and at least one structure to move the piston. The rock bolt is therefore a chemical rock bolt.

[0038] In another variant a rear end of the anchor tube is closed by a cap and the anchor tube and/or the cap comprises at least one opening to conduct the fixation structure out of the interior space encased by the anchor tube.

[0039] In another embodiment a mixer is arranged between the fixation structure and at least one opening to mix the fixation structure, particularly the two components, prior to the emission of the fixation structure from at least one opening.

[0040] In particular, the rock bolt comprises an expanding sleeve and an expanding body. The rock bolt therefore represents a mechanical rock bolt.

[0041] Preferably the rock bolt is also a stone bolt.

[0042] In the supplementary embodiment the fixation structure, particularly a resin or cement, comprises two components, e.g., an adhesive component and a curing component.

[0043] Preferably the two components are arranged separated from each other in bags. Any device to store the two separate components is considered a bag, here, for example also a cartridge or any other container.

[0044] In another embodiment the rock bolt comprises a drilling head, particularly in the area of the frontal end or at the frontal end of the anchor tube. The rock bolt is therefore a self-tapping rock bolt.

[0045] A rock bolt 1 embodied as a gliding anchor 2 is used in mining for the temporary securing of rock in galleries. The rock bolt 1 comprises an anchor tube 3, which encases an interior space 4. The anchor tube 3 is encased by a jacket tube 22. The jacket tube 22 is connected by a connection ring 39 as the connection device 49 to an anchor tube 3 and no material-engaging connection exists between the anchor tube 3 and the jacket tube 22. An inner side of the jacket tube 22 contacts an exterior of the anchor tube 3. The rock bolt 1 is a chemical rock bolt 1; this structure a fixation structure 5 arranged in the interior space 4 may connect the jacket tube 22 to the rock 28 in a material-engaging fashion. For this purpose, a bore 29 must be inserted into the rock 28 and subsequently the rock bolt 1 is to be inserted into the bore 29. This status is shown in FIG. 1, prior to the expression of the fixation structure 5 into a space between the anchor tube 3 and the rock 28. FIG. 2 shows the rock bolt 1 fastened to the rock 28 by material-engagement. The fixation structure 5 is here a resin 6, which comprises an adhesive component 7 and a curing component 8. The adhesive component 7 is stored in a first bag 9 and the curing component 8 in a second bag 10. The two bags 9, 10 are stored in the interior space 4.

[0046] The interior space 4 comprises a hydraulic chamber 17, which is closed by an annular part 20 in the area of the exterior, rear end 37 of the anchor tube 3. The annular part 20 comprises a hydraulic bore 19. The hydraulic chamber 17 is further limited by a piston 11 in the area of another, interior, frontal end 36. The inner, frontal end 36 of the anchor tube 3 is closed by a cap 23 having an opening 24. The fixation structure 5 may pass from the interior chamber 4 of the anchor tube 3 through the opening 24 towards the outside into the space, particularly the annular chamber between the anchor tube 3 and the rock 28. Here, a mixture 25 is arranged at the opening 24, through which due to the geometric arrangement of the mixer 25 the fixation structure 5 must mandatorily flow from the two bags 9, 10 first through the mixer 25 and subsequently from the opening 24 out into the interior chamber 4. Here, the mixer 25 comprises devices, such as an appropriate geometry, such that the fixation structure 5 flows meandering or in the form of a hose through the mixer 25 and thus mixing occurs of the adhesive component 7 with the curing component 8 of the resin 6 prior to flowing out of the opening 24.

[0047] In the area of the outer, exterior rear end 37 of the jacket tube 22, comprising an external thread 18, an anchor nut 14 is screwed onto the jacket tube 22 comprising an internal thread and an anchor plate 15 rests on the anchor nut 14. Here, the anchor plate 15 comprises a plate bore 13 without an internal thread, arranged inside the anchor tube 3. This way, pressure may be applied by the rock 28 onto the anchor plate 15, according to the illustration in FIG. 2. This pressure is transferred from the anchor plate 15 to the anchor nut 14 and from the anchor nut 14 to the anchor tube 3 so that a tensile force is applied at the anchor tube 3. This tensile force is transferred from the anchor tube 3 at the outside to the rock 28 in a material engaging fashion using the fixation structure 5.

[0048] In order to insert the fixation structure 5 into the space between the anchor tube 3 and the rock 28 a piston 11 is moved inwardly, e.g., upwards according to the illustration in FIG. 1. This way, the piston 11 destroys the first and second bag 9, 10 so that the adhesive component 7 and the curing component 8 move and, due to the reducing volume of the interior space 4 between the piston 11 and the cap 23, the fixation structure 5 is impressed through the mixer 25 and the opening 24 into the space between the anchor tube 4 and the rock 28 and subsequently cured. For this purpose, hydraulic fluid, e.g., water, is pumped under high pressure through the hydraulic bore 19 into the hydraulic chamber 17 and thus the piston 11 is moved. The hydraulic chamber 17 and the hydraulic bore 19 are therefore structure 12 to move the piston 11.

[0049] In FIG. 2 the fixation structure 5 has already been impressed into the space between the anchor tube 3 and the rock 28 in its entirety, e.g., the jacket tube 22 is fastened to the rock 28 in a material-engaging fashion, particularly by adhesion. Here, in the installed condition of the anchor tube 3 and the jacket tube 22 shown in FIG. 2, they are preferably arranged entirely inside the bore 29, e.g., only a small portion of the anchor tube 3 and the jacket tube 22, for example less than 10% or 5%, are located outside the bore 29. This way, only very little operating space is required at an operating location 30 in the mining gallery in the installed state of the rock bolt 1. In the installed state according to FIG. 2 the anchor plate 15 contacts the rock 28 and thus it may compensate pressures. Further, greater shearing forces upon the rock bolt 1 perpendicular in reference to a longitudinal axis 38 of the anchor tube 3 may overwhelmingly be compensated by the jacket tube 22 and to a lesser extent by the anchor tube 3 and thus the rock 28 may be additionally secured.

[0050] FIG. 3 shows a detail of the anchor tube 3 in a longitudinal cross-section as a hollow tube and the jacket tube 22. The anchor tube 3 comprises components 26 made from metal, particularly steel or a steel alloy, and components 27 made from plastic, particularly fiberglass-reinforced plastic. Here, these components 26, 27 comprising metal and plastic are arranged alternating in the direction of the longitudinal axis 38 of the anchor tube 3. The type of connection between the components 26, 27 is not shown in FIG. 3. The fibers 32, not shown here, of the fiberglass-reinforced plastic of the components 27 include fibers 32, which are aligned in the direction of the longitudinal axis 38 to compensate tensile forces at the anchor tube 3 and fibers 32, which are aligned at an angle in reference to the longitudinal axis 38, for example perpendicularly thereto in a lateral direction or at an angle amounting to about 45° in reference to the direction of the longitudinal axis 38. The latter mentioned fibers 32 represent lateral fibers and may compensate torque at the anchor tube 3.

[0051] FIGS. 4 through 8 show various exemplary embodiments to connect the components 26, 27. In the first exemplary embodiment according to FIG. 4 a plastic sheath 31 is applied by injection molding upon both the component 26 made from metal as well as upon the component 27 made from plastic and thus the two components 26, 27 are connected to each other.

[0052] In the second exemplary embodiment according to FIG. 5 fibers 32 of the fiberglass-reinforced plastic of the component 27 are applied at the outside of the component 26 made from metal. Here, these fibers 32 are saturated and cured with a matrix material, e.g., resin, and therefore they may create a supporting connection with the component 26 made from metal, e.g., a steel part. Here, these fibers 32 are aligned both as longitudinal fibers as well as lateral fibers.

[0053] FIG. 6 shows a third exemplary embodiment to connect the components 26, 27. The interior diameter of the component 26 is here preferably equivalent to an exterior diameter of another component 27. Here it is preferable that the interior diameter and the exterior diameter show a difference of less than 10%, 5%, 2% or 1%. This way, the component 27 may be inserted coaxially into the component 26, embodied as a steel part, and a material-engaging connection between the components 26, 27 may be created by an adhesion 33 as well as by a form-fitting connection.

[0054] In the fourth exemplary embodiment shown in FIG. 7 the component 26 shows an external thread and the component 27 shows an internal thread, each in the form of the thread 34. This way the two threads 34 may be screwed together and thus create a connection between the two components 26, 27.

[0055] FIG. 8 shows a fifth exemplary embodiment to connect the components 26, 27. The fibers 32, particularly aligned as longitudinal and lateral fibers, are here applied at the outside of the component 26 made from metal. These fibers 32, applied at the outside of the component 26, are compressed with each other or stretched by a sheath 35, particularly a steel sheath 35. The sheath 35 is therefore pressed upon the fibers 32 or is embodied conically and/or allowing a screw-connection, in order to create a radial pressure between the fibers 32 and the outside of the component 26 made from metal.

[0056] The anchor 3 comprises therefore steel parts 26 and/or components 26 made from steel and plastic parts 27 and/or components 27 made from plastic following each other. After the fastening of the rock bolt 1 in the bore 29 and/or at the rock 28 the tensile forces are compensated by the anchor tube 3 and the jacket tube 22. Here, the components 26 made from metal, particularly steel, show a large extension in case of tensile forces applied, so that this way a large overall extension develops at the anchor tube 3 and the jacket tube 22 when high tensile forces are applied, because a portion of the anchor tube 3 is made from the components 26. Here, preferably in the direction of the longitudinal axis 38, the components 26 comprise at least 30%, 50%, or 70% of the entire extension of the anchor tube 3.

[0057] This way, the rock bolt 1 also represents a gliding anchor 2 and thus shows a gliding function, so that minor movements of the secured rock 28 may be compensated due to the changes in length occurring in the form of the anchor tube 3 being stretched. Accordingly the rock bolt 1 allows movements of the rock 28. The jacket tube 22 made from metal, particularly steel, may perform greater extensions so that greater overall extensions occur at the rock bolt 1, both of the anchor tube 3 as well as the jacket tube 22. This way an unpredictable breaking of the anchor tube 3 may preferably be avoided.

[0058] The rock bolt 1 is preferably used in mining, particularly coal mining. When used in mining, the rock bolts 1 are used for the temporary securing of the neighboring rock 28, particularly coal. For the excavation of coal shearers or a coal plows are used. In this type of excavation the rock bolts 1 in the coal and/or in the rock 28 are also excavated and may be cut or dismembered by the shearer or the coal plow and thus removed because the components 27 made from plastic may easily be cut by the shearer or the coal plow. This way, after the excavation only small parts of the anchor tube 3 are present and they may easily be transported in the conveyer system and due to their metal portion in the components 26 they may easily be separated by a magnet. Furthermore, a separation of the anchor parts comprising metal from coal is also possible in the wash plant, because they show a great difference in density. The jacket tube 22 is made from a thin sheet metal, which may also easily be cut into small parts and then easily separated using magnets.

[0059] In another exemplary embodiment the anchor tube 3 is entirely made from fiberglass-reinforced plastic, e.g., not made from components 26 comprising metal and components 27 comprising plastic as a hybrid anchor. The fiberglass of the anchor tube 3 is aligned in the axial direction to compensate tensile forces and in the lateral direction or in the form of helical or cross-wise windings to compensate torque. The jacket tube 22 may compensate strong shearing forces. When the glass fibers of the anchor tube 3 are destroyed the tensile forces may be compensated by the jacket tube 22. The jacket tube 22 made from metal shows great extensions so that the rock bolt 1 as a gliding anchor may compensate greater extensions. Otherwise, this exemplary embodiment, not shown, is preferably equivalent to the exemplary embodiment described above.

[0060] In another exemplary embodiment of the rock bolt, not shown, the rock bolt preferably only comprises the anchor tube 3, the jacket tube 22, the anchor nut 14, and the anchor plate 15. Here, the anchor tube 3 is not embodied as a hollow tube but as a solid profile. When this rock bolt 1 is inserted into a bore hole 29 first a fixation structure 5 is inserted into the bore hole 29 and subsequently the anchor tube 3 is inserted into the bore so that this way the fixation structure 5 is distributed in a space between the anchor tube 3 and the bore hole 29. Here, the fixation structure 5 may also be inserted in at least one bag 9, 10 prior to the insertion of the anchor tube 3 into the bore hole 29.

[0061] Overall, the rock bolt 1 according to the invention shows several advantages. The rock bolt 3 with the anchor tube 3 and the jacket tube 22 may compensate strong tensile, torque, and shearing forces and thus is suitable for a lasting securing of rock 28. When excavating rock 28, particularly coal, the excavating machines may easily cut the anchor tube 3 and the jacket tube 22. This way, damages of the excavating devices for mining may be avoided.

[0062] While particular elements, embodiments, and applications of the present invention have been shown and described, it is understood that the invention is not limited thereto because modifications may be made by those skilled in the art, particularly in light of the foregoing teaching. It is therefore contemplated by the appended claims to cover such modifications and incorporate those features which come within the spirit and scope of the invention.

Claims

1. A rock bolt, particularly for the use in mining, said rock bolt comprising: an anchor tube; an anchor nut; and an anchor plate supported by said anchor nut to contact the rock, wherein the anchor tube is encased by a jacket tube.

2. The rock bolt of claim 1 wherein said jacket tube is made from metal.

3. The rock bolt of claim 1 wherein said jacket tube rests on said anchor tube.

4. The rock bolt of claim 1 wherein said jacket tube includes at least one of a rib or a folding.

5. The rock bolt of claim 4 wherein said at least one of a rib or a folding are embodied at least one of axially and helically.

6. The rock bolt of claim 1 wherein said jacket tube is embodied as a fibrous winding about the anchor tube.

7. The rock bolt of claim 6 wherein said fibrous winding is embodied as a helical or cross-wise winding to compensate shearing forces by the fibrous winding.

8. The rock bolt of claim 1 wherein said jacket tube is connected to the anchor tube in a material-engaging fashion.

9. The rock bolt of claim 1 wherein said jacket tube is connected by a connection device.

10. The rock bolt of claim 9 wherein said connection device is at least one of a drilling head, a cross-sectional expansion, or a connection ring to an anchor tube, particularly in the axial direction.

11. The rock bolt of claim 1 wherein no material-engaging connection exists between the anchor tube and the jacket tube.

12. The rock bolt of claim 1 wherein the axial expansion of the jacket tube amounts to at least 50% of the axial dimension of the anchor tube.

13. The rock bolt of claim 1 wherein the anchor tube comprises fiber-reinforced plastic.

14. The rock bolt of claim 1 wherein the anchor tube at least partially comprises metal and plastic and at least one component of the anchor tube comprising metal and plastic serves to compensate tensile forces.

15. The rock bolt of claim 1 wherein an interior section of the anchor tube is at least partially made from metal and plastic.

16. The rock bolt of claim 1 wherein the anchor tube shows a frontal end and a rear end and the inner section shows a distance of at least 5% of the overall length of the anchor tube from the frontal and rear end.

17. The rock bolt of claim 15 wherein alternating one component made from metal and one component made from plastic are arranged at the anchor tube in the direction of a longitudinal axis of the anchor tube.

18. The rock bolt of claim 15 wherein the plastic is a fiber-reinforced, particularly fiberglass-reinforced plastic and the metal is steel.

19. The rock bolt of claim 15 wherein at least one component comprises plastic by 50% and at least one component comprises metal by at least 50%.

20. The rock bolt of claim 15 wherein in a first cross-section, particularly at the interior section, perpendicularly in reference to the longitudinal axis of the anchor tube the anchor tube is made from at least 50% plastic, and in a second cross-section, particularly at an interior section perpendicular in reference to the longitudinal axis of the anchor tube said anchor tube is made from at least 50% metal.

Images