Hydraulic and earth engineering – Earth treatment or control – Rock or earth bolt or anchor
Patent
1996-11-25
1998-06-16
Graysay, Tamara L.
Hydraulic and earth engineering
Earth treatment or control
Rock or earth bolt or anchor
4052591, 411 19, E21D 2000
Patent
active
057659699
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a tubeformed rock bolt with closed cross section. The rock bolt according to the invention is intended to be expanded into contact with the rock by means of cement or other comparatively viscous material.
It has for a long time been a desire to expand tubeformed rock bolts with cement in order to achieve a bolt which can stand higher shearing forces. With a prior art tubeformed rock bolt, see U.S. Pat. No. 4,423,986, it has turned out to be difficult to use cement for expansion of the bolt since one gets cement about the bolt end so that difficulties arise when taking away the setting tool after the bolt has been set. Furthermore, one has obtained an entrapped air volume which after the bolt has been set has pressed out a part of the cement which was used at the expansion of the bolt.
SUMMARY OF THE INVENTION
The present invention, which is defined in the appended claims, aims at solving the above mentioned problems by forming the rock bolt so that one avoids that the cement accumulates about the bolt end and by seeing to it that the cement is not pressed out from the rock bolt when it is set.
A further advantage with the present invention is that the protection against corrosion of the bolt is improved because cement during expansion of the bolt forces its way out through a venting hole near the end of the rock bolt being innermost in the bore hole so that a plug of cement is created about the top of the bolt. This considerably decreases, or prevents, the amount of water that trickles along the outside of the bolt.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a tubeformed rock bolt according to the invention;
FIG. 2 shows a section as seen along directional arrows 2--2 of FIG. 1;
FIG. 3 shows a section through the rock bolt after expansion in a bore hole;
FIG. 4 shows a section through part of the rock bolt and part of a tool for setting the bolt;
FIG. 5 shows a view taken along directional arrows 5--5 of FIG. 4;
FIG. 6 shows the manner in which a tool and the rock bolt cooperate during expansion of the rock bolt; and
FIG. 7 shows the manner in which a tool and the rock bolt cooperate after the expansion of the rock bolt has been completed.
DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION
The tubeformed rock bolt 10 shown in FIGS. 1-3 comprises a tube 11 which in the manufacturing has been provided with a longitudinal depression 12 along a part of its length, preferably along all the length. The bolt has a first end 21 which is surrounded by a first sleeve 14 and a second end 22 which is surrounded by a second sleeve 13. The sleeves 13 and 14 are welded to the tube 11 so that an enclosed room 23 is created. A hole 18 connecting the room 23 with the surroundings extends through the second sleeve 13 and the tube 11. The tube 11 is furthermore provided with a second hole 19 near the first end 21 of the tube 11. This hole, which is a venting hole for letting our air from the room 23 when the bolt is expanded, is suitably arranged in the tube 11 at some distance from the sleeve 14. The sleeve 13 is provided with a flange 15 which forms a support for a washer 16 which is intended for contacting the rock when the bolt has been set. The washer 16 is provided with a hole 17 which has a larger diameter than the sleeve 14 but a smaller diameter than the flange 15 so that the washer can be mounted on the bolt before the setting of the bolt. The sleeve 13 is provided with orientation means in form of a radial groove 20 by means of which the rock bolt is given a defined angular position in a tool for setting the bolt.
The tool shown in FIGS. 4-7 for setting the rock bolt 10 comprises a housing 31 provided with a cover 35 screwed to the housing. The housing 31 comprises a dolly 32 against which the rock bolt 10 can be pressed. The dolly 32 is provided with a support 33 for the rock bolt. The support 33 is provided with a projection 34 for cooperation with the groove 20 in the sleeve 13 on the rock bolt. Two pistons 36 and 37 are slidably ar
REFERENCES:
patent: 4139323 (1979-02-01), Brandstetter
patent: 4423986 (1984-01-01), Skogberg
patent: 4459067 (1984-07-01), Skogberg et al.
patent: 4511289 (1985-04-01), Herron
patent: 4954017 (1990-09-01), Davis et al.
K.ang.reby Bjorn
Mandal Anita
Atlas Copco Rock Drill AB
Graysay Tamara L.
Lagman Frederick L.
Stone Mark P.
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