Hydraulic and earth engineering – Earth treatment or control – Rock or earth bolt or anchor
Patent
1995-08-31
1997-07-22
Taylor, Dennis L.
Hydraulic and earth engineering
Earth treatment or control
Rock or earth bolt or anchor
52698, E21D 2000
Patent
active
056497890
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a rock bolting apparatus.
The invention has been developed particularly for use in stabilising roofs and sides or ribs in underground mining operations and will be described hereinafter with reference to this application. However, it will be appreciated that the invention is not limited to this field of use.
The conventional prior art technique of fixing bolts in a rock substrate involves first drilling a hole several feet into the rock. The drill shaft and bit are then retracted and a correspondingly sized rock bolt installed in the usual manner.
This operation is relatively labour intensive and time consuming. Furthermore, the rock formation is often inherently unstable in mines and excavations making the drilling operation potentially dangerous. The prior art technique is also difficult and expensive to automate because of the number of separate operations required.
It is an object of the present invention to overcome or at least ameliorate one or more of the above discussed disadvantages of the prior art.
According to the invention there is provided an integrated self drilling rock bolting apparatus comprising: threaded end and a transverse slot extending from the other end thereof and terminating adjacent said threaded end, said slot having a free end and opposed inclined wedge faces adjacent its free end, said drilling element having a proximal end secured in said slot by connection means and having opposed wedge shaped faces forming a wedge shaped section at the proximal end which mates with the wedge faces in said slot, said bolt being connectable at its opposite end to rotational drive means; relative axial displacement between the drilling element and the bolt whereby the drilling element is adapted to bore a hole in a substrate upon conjoined rotation of said bolt by said drive means, said connection means being subsequently operable in an anchoring mode to permit relative axial displacement between the drilling element and the bolt in response to a predetermined threshold axial force component applied to said bolt; and secure said bolt within said hole.
In one preferred form, the retaining means comprises a longitudinally extending slot adapted to divide one end of the bolt into two complimentary halves, and a complementary wedge member associated with the proximal end of the drilling element. In the anchoring mode the wedge member urges the complimentary halves of the bolt outwardly into locking engagement with the surrounding substrate.
In a variation of this embodiment, the drilling element incorporates a multiplicity of interconnected longitudinally extending wedge sections nestingly disposed within correspondingly configured segments defined between the divided end portions of the bolt. In this way, the bolt can be expanded and anchored over its entire length, or over discrete sections of its length to enhance anchorage characteristics.
The bolt and drilling element in a preferred form of the invention are formed integrally and connected by fracturable connection means to temporarily connect these components in the drilling mode. Under the predetermined axial load conditions, the fracturable connections means are subsequently broken to initiate the anchoring mode whereby the so divided bolt portions are driven into expanding engagement with the wedge member, thereby progressively forcing the bolt portions outwardly into engagement with the surrounding substrate.
In a modification an axial bore extends throughout the length of the apparatus and longitudinal grooves extend on either side of the bore in the bolt but spaced therefrom to a fracturable connection.
In a further modification the bolt and drill are formed as separate units and connection by one or more shear pins extending transversely through the wedge member and the surrounding divided bolt portions. The shear pins operate in the same manner as the fracturable connection means described.
In another preferred form, the retaining means comprises a frangible capsule of chemical adhesive adapted to be
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patent: 747219 (1903-12-01), Preslar
patent: 1098250 (1914-05-01), Gonia
patent: 1996121 (1935-04-01), Phillips
patent: 2351449 (1944-06-01), Noble
patent: 2771746 (1956-11-01), Fischer et al.
patent: 4334392 (1982-06-01), Dziedzic
patent: 4946314 (1990-08-01), Gruber
Cutincoal PTY Limited
Taylor Dennis L.
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