HK1006868B - Rock stabilizer - Google Patents

Description

The present invention is related to a rock stabilizer and a method for inserting such a rock stabilizer into a bore formed in an earth formation for stabilizing the formation in the vicinity of where the stabilizer is located in the earth formation.

From an advertisement in the "Mining Magazine", February 1988, page 104, the so-calles "Split Set" (registered trademark) rock stabilizer, manufactured by Ingersoll Rand Mining Machinery, has become known. This stabilizer has the shape of a straight tube which comprises a slot along its entire length which allows the tube to be compressed when driven into a drilled hole. The tube further has a roof plate fastened at its rear end. However, this stabilizer suffers from the main disadvantage that the circumferential elastic forces are inherently low. Furthermore, the inside of the tube can only be sealed by full grouting.

The document AU-B-51667/79 discloses a tubular friction stabilizer for insertion in a bore, such as a bore of a mine shaft, which does not present a slot and which has a substantially one cross-sectional configuration along its full length. This stabilizer is foreseen to be plastically deformed during its installation in a pre-drilled bore. Due to this plastic deformation, satisfactory frictional anchoring in the bore cannot be achieved.

Starting from this prior art, it is the first objective of the present invention to provide a rock stabilizer whose manufacturing costs are lowered and its field of application extended and which affords a better and stronger contact to the wall of the bore where it is installed. Such a rock stabilizer is defined in first independent claim 1; special embodiments thereof are made the subject of dependent claims.

The rock stabilizer of the invention comprises a hinge-like arrangement of tubular walls. Of course, the strength of the tube which forms the stabilizer of the invention should be selected such that the restoring force provided by the hinge-like arrangement formed by the inwardly disposed side wall portions will hold the tube in the bore.

The present invention further aims at providing a method for inserting said new rock stabilizer into a bore formed in an earth formation for stabilizing said formation in the vicinity of the location of the stabilizer. This method is defined in the second independent claim 13.

Typically, one end of the tube is provided with a tapered portion for facilitating entry of the tube into a bore drilled into a rock formation or similar. Typically, the tapered portion is a truncated conical section located at the forward end of the stabilizer in use. Typically, the flute means extends along the side wall of the truncated conical tip portion.

Typically, one end of the tube is provided with a fastening means for fastening roof plates or other fittings to the end of the tube. Typically, the fastening means comprises a ring fixedly secured to the end of the tube by welding or other similar means. Typically, the ring is discontinuous having a portion which is removed. Typically, the removed portion is aligned to correspond to the position of the flute in the side wall of the tube. In one embodiment the tube, ring and roof plate are formed integrally whereas in another embodiment the tube and ring are integral and the roof plate separate or in a still further embodiment, the tube, ring and roof plate are all separate components which can be assembled together into a single unit prior to use of the tube.

The present invention will now be described by way of example with reference to the accompanying drawings in which:

• Figure 1 is a perspective view of one end of one embodiment of the rock stabilizer;
• Figure 2 is a perspective view of the other end of the embodiment of Figure 1;
• Figure 3 is a perspective view of the first end of a second embodiment of the present invention provided with a roof plate; and
• Figure 4 is a perspective view of one form of the roof plate for use with the rock stabilizer of the present invention.

In Figures 1 and 2 there is shown a rock stabilizer according to the present invention generally denoted as 2. The rock stabilizer 2 is in the form of an elongate hollow circular cross-sectional tube having a flute 4 provided in the side wall of tube 2 extending along the lengthwise extending axis almost to the entire length of tube 2. It is to be noted that in some embodiments flute 4 may extend only partially along the entire length of tube 2.

Flute 4 comprises a pair of opposed wall portions 6, 8 joined together at their respective inboard ends 10 along the respective entire lengths. Join 10 is located internally within tube 2 and extends radially inwards towards the central axis of tube 2. Flute 4 acts as a hinge since opposed wall portions 6, 8 are able to deform or otherwise flex with respect to each other depending on the compressive loads applied radially to the rock stabilizer when in a bore in use. It is to be noted that wall portions 6, 8 are free to deform and flex in response to loads applied longitudinally and transversely to the tube as well as radially.

Flute 4 is typically formed integrally with tube 2 such as at the rolling stage of tube 2. The amount that flute 4 extends radially internally within tube 2 can vary from being almost as large as the diameter of the tube to being quite small depending upon the rock formation in which it is to be used. Additionally, the radial extent of flute 4 may vary over its length.

Tube 2 is provided at one end with a fastening means, such as for example a fastening ring 20 which is securely attached to tube 2, such as by welding. In one embodiment ring 20 may be continuous to completely surround tube 2 whereas in another embodiment ring 20 is provided with a portion removed such as at location 22. If ring 20 is discontinuous, the omitted part is aligned with the position of flute 4 as shown in Figure 1. It is to be noted that the end of tube 2 having ring 20 is not received in the bore of the rock formation but rather extends outwardly therefrom in use and accordingly there is no requirement for that end portion of tube 2 to be able to flex.

Roof plate 30 is fitted over tube 2 and is retained on tube 2 by ring 20. Roof plate 30 may take any suitable, convenient or desirable form. Roof plate 30 may be used to stabilize the rock formation into which the rock stabilizer is received or may be used to provide support for further stabilization such as a wire-net or wire-mesh or may be used as an attachment from which other fittings may be suspended such as for conveyors or the like.

The other end of tube 2 is typically tapered 14 in order to facilitate entry of the rock stabilizer into a bore in the earth structure requiring stabilization. Typically, the tapered end 14 is a truncated conical section.

In operation, a bore is drilled in the roof of a mine shaft. The diameter of the bore is slightly smaller than the at-rest diameter of the rock stabilizer of the present invention. Tapered end 14 of tube 2 is inserted into the bore and the other end containing ring 20 is hammered to force tube 2 into the bore. Since the diameter of the bore is slightly less than the at rest diameter of tube 2 the walls of tube 2 are slightly compressed along join 10. The restoring force provided by the hinge means formed by the flute 4 holds tube 2 in the bore. If due to movement in the rock formation, the diameter of the bore increases, the resilient bias provided by the flute forces the side walls of tube 2 to expand against the walls of the bore to securely anchor tube 2 in the bore. On the other hand, if the diameter of the bore decreases the flute means allows the tube to be compressed which means that the stabilizer does not fracture in the bore and may still reinforce the earth formation.

The described arrangement has been advanced by explanation and many modifications may be made without departing from the scope of the invention which includes every novel feature and novel combinations of features hereindisclosed.

One modification is to have two or more flutes arranged around the wall of the tube. The two or more flutes may be arranged in any pattern around the walls. A further modification is that the flute may taken any configuration or shape.

Those skilled in the art will appreciate that the invention described herein is susceptible to variations and modifications other than those specifically described. It is understood that the invention includes all such variations and modifications which fall within its spirit and scope.

Claims (13)

1. A rock stabilizer (2) for being received in a bore of an earth formation for stabilizing the earth formation in the vicinity of the location of the rock stabilizer, the rock stabilizer (2) having a body of a generally hollow tubular configuration intended to be firmly held in said bore by frictional forces, characterised in that said body (2) is a continuous tube provided with an inwardly directed wall arrangement in the form of a flute (4), said flute (4) comprising two opposed side wall portions (6, 8) interconnected at their respective inboard ends (10) to form a hinge arrangement allowing a hinge-like movement of said opposed side wall portions (6, 8) of the flute (4) relative to each other, that said flute (4) extends generally parallel to the central longitudinal axis of said tube over at least part of the tube length, that said tube has at least one open end, and that the said opposed side wall portions (6, 8) extend radially into said body to substantially the central longitudinal axis of said body.
2. A rock stabilizer according to claim 1, characterised in that the tubular body is substantially circular in cross-section and substantially cylindrical in overall shape.
3. A rock stabilizer according to claim 1 or 2, characterised in that one end of the stabilizer is tapered in order to facilitate entry of the tube into the bore.
4. A rock stabilizer according to claim 3, characterised in that the tapered end is in the form of a substantially truncated conical section located at the entry end of the stabilizer in use.
5. A rock stabilizer according to any one of claims 1 - 4, characterised in that the open end is the end protruding from the bore in use.
6. A rock stabilizer according to any one of claims 1 - 5, characterised in that the tube is open at both ends or at least partially open at both ends.
7. A rock stabilizer according to any one of claims 3 - 5, characterised in that the tapered end is substantially closed.
8. A rock stabilizer according to any one of claims 1 - 7, characterised in that the rock stabilizer further comprises a fastening means for fastening roof plates (30) or other fittings to the end of the stabilizer not received in the bore in use.
9. A rock stabilizer according to claim 8, characterised in that the fastening means is a ring (20) fixedly secured to the end of the tube remote from the tapered end.
10. A rock stabilizer according to claim 9, characterised in that the ring (20) is discontinuous and the discontinuity of the ring is in register with the flute means (4).
11. A rock stabilizer according to claim 9 or 10, characterised in that the ring (20) and fitting (30) are integrally formed.
12. A rock stabilizer according to any one of claims 1-11, characterised in that the flute means (4) is substantially of a "V" shape in cross-section.
13. A method of inserting the stabilizer (2) of claim 1 into a bore formed in an earth formation for stabilizing the formation in the vicinity of where the stabilizer (2) is located in the earth formation, characterized in that said opposed side wall portions (6, 8) of the flute means (4) are hingedly moveable relative to each other in order to elastically vary the outside diameter of the tube solely in accordance with the frictional forces imposed upon the tube by the bore when the rock stabilizer (2) is being frictionally inserted into the bore and when in the bore in order to maintain intimate contact between the tube and the wall of the bore in use so as to frictionally retain the rock stabilizer (2) securely in the bore in use, the body having a first, free, relaxed, transverse dimension, adapted to be resiliently compressed, wherein a first end of the stabilizer is placed at the mouth of a bore having a given transverse dimension smaller than said first, free, relaxed, transverse dimension and a force is applied to said stablizer to slidably insert said stabilizer into said bore, resiliently compressing at least a portion of the stabilizer to a second, constrained, transversed dimension slightly less than said given transverse dimension of said bore.