Hydraulic and earth engineering – Earth treatment or control – Rock or earth bolt or anchor
Patent
1991-08-01
1994-03-29
Taylor, Dennis L.
Hydraulic and earth engineering
Earth treatment or control
Rock or earth bolt or anchor
4052591, 411521, E21D 2000
Patent
active
052979008
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to rock stabilizers for use in stabilizing rock formations in mines, tunnels, and the like so as, for example, to make the working conditions in the mine or tunnel safer by providing greater stability for the rock formation. The rock stabilizer is also known under different names such as a rock-bolt, roof-bolt or under other similar names. In particular, the present invention relates to a rock stabilizer of a generally circular cross-section provided with a longitudinally extending deformity or interruption to its curved surface, such as for example a flute. More particularly, the present invention relates to an elongate tube of substantially circular cross-section having a flute, channel or groove extending more or less longitudinally along the entire length of the tube which is located in the side wall of the tube. The flute allows the diameter of the tube to vary within limits in accordance with the stresses and strains imposed thereon the-tube by the rock formation. Additionally, the present invention relates to methods of inserting the fluted stabilizer into earth structures, particularly into bores drilled in the walls of the tunnels, mines and other earth structures.
A particularly preferred form of the present invention relates to a rock stabilizer or rock-bolt in which a lengthwise extending flute is provided in the side wall of the tube which flute has a pair of opposed wall portions deformed inwardly toward the central axis of the tube, the opposed wall portions being joined together over their lengths so as to provide a hinge means to accommodate the changes in external diameter of the tube imposed by the stresses and strains of being tightly located in a bore in a rock formation.
Although the present invention will be described with particular reference to a rock stabilizer or rock-bolt having a flute acting as a hinge, it is to be noted that the scope of the present invention is not limited to the described embodiment but that the rock stabilizer of the present invention may take other forms and be used in other applications.
Rock bolts or stabilizers usually take the form of a solid cylinder or a hollow cylinder.
It is also known to have rock stabilizers of a form in which there is a longitudinally extending slot in the side wall of the hollow rock stabilizer (so-called slotted stabilizers) so that the generally circular cross-section of the stabilizer may be deformed slightly so as to adopt a number of varying diameters and/or configurations depending on the diameter of the bore into which it is received and on the compression forces applied to the stabilizer by the rock formation when received in the bore in use. However, in use of the stabilizers in many cases once the slotted stabilizers have been compressed to a relatively smaller diameter by the side walls being forced together when the compression forces are removed or the bore, because of ground movement, opens up slightly, the slotted stabilizer will not be able to radially expand to a longer diameter to fill the available space because it has been deformed beyond its elastic limit. Furthermore, it is to be noted that the movement of the earth is not constant over the length of the slotted stabilizer thus some parts of the bore within which the stabilizer is received will be of a larger diameter or size than other parts. In extreme cases the slotted stabilizer may De severed at one or more places over its length. Therefore, in many cases, the holding power of the slotted stabilizer is significantly reduced since it is not in full comparision over the entire length of the slotted stabilizer but rather is only in compression at those places where it is in intimate contact with the bore, where the bore has enlarged or the rock stabilizer broken there is only minimal holding power at best and at worst no holding power at all. In this case the earth or rock formation is not being reinforced and thus the chances of the earth or rock formation falling is significantly increased.
The present invention seeks to
REFERENCES:
patent: 4260294 (1981-04-01), Cantrel
patent: 4284379 (1981-08-01), Chaiko
patent: 4407610 (1983-10-01), Elders
patent: 4472087 (1984-09-01), Elders
patent: 4502818 (1985-03-01), Elders
patent: 4636115 (1987-01-01), Davis et al.
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