WO2012023101A1

WO2012023101A1 - Anchoring device

Info

Publication number: WO2012023101A1
Application number: PCT/IB2011/053617
Authority: WO
Inventors: Martin Cawood
Original assignee: Anglogold Ashanti Limited
Priority date: 2010-08-16
Filing date: 2011-08-16
Publication date: 2012-02-23
Also published as: US20130294844A1; ZA201105990B; CN103299034A; AU2011292797A1; CL2013000472A1

Abstract

This invention relates to an anchoring device and more particularly but not exclusively, to a rock anchor for use in a mining environment, and which combines the functionality of a split set and an attachment anchor. The anchoring device includes a tubular body having a longitudinal slot provided therein, and an elongate anchoring element locatable inside the tubular body. The anchoring element is displaceable between a retracted position in which an end of the anchoring element is located inside the tubular body, and a protruding position, in which at least part of the elongate element protrudes from the tubular element.

Description

ANCHORING DEVICE

BACKGROUND TO THE INVENTION

THIS invention relates to an anchoring device and more particularly but not exclusively, to a rock anchor for use in a mining environment, and which combines the functionality of a split set and an attachment anchor.

Anchoring devices, generally known as anchor bolts or rock bolts in the industry, are ubiquitous in mining and excavation applications, and are used for stabilizing a rock mass where excavation or mining has taken or is taking place. In particular, the anchor bolts assist in transferring loads from unstable surface zones to more stable interior zones of a rock body in question. Many different types of anchor bolts are used in industry, and the anchor bolt designs vary from simple to very complex designs.

One type of frictional anchor bolt is commonly referred to as a 'split set' in industry. Split sets are anchors that comprise of an elongated high strength steel tube which is slotted along its length. One end of the tube is of a slightly tapered configuration for easy insertion into a drill hole, whilst the other end may include a welded ring-flange for holding a bearing plate. In use, the slotted tube is driven into a slightly smaller hole, by applying an insertion force with a hammer drill, which is typically the same drill used to drill the hole. As the tube is forced into the hole, outer surfaces of the tube engages an inner surface of the hole, which causes the slot and thus the tube, to be compressed. The tube therefore exerts an opposing radially outwardly directed force onto the walls of the hole, thus resulting in secure engagement between the tube and the hole. Equally common to the anchoring devices referred to above, are anchors used to secure meshing, pipes or other utilities relative to a rock body. In this case the purpose of the anchoring device is to provide an attachment point for some external article, rather than reinforcing the rock body, and these anchors are, in this specification, generally referred to as attachment anchors.

In practice, separate holes are drilled into the rock body for receiving the reinforcing anchors / tendons and the attachment anchors (which may for example be anchor bolt eyes, Pigtail eyebolts, or many other configurations). It will be appreciated that this result in duplication of work, as separate holes needs to be drilled, often in close proximity of one another. This is not an ideal solution, as it results in inefficiency, duplication of costs, and may also pose safety risks. If one tries to insert an attachment anchor into a bore of a friction anchor which has already been installed, it is common for the bore to be distorted or blocked to such an extent that it is not possible to insert the attachment anchor therein. Space and practical constraints further exacerbates retrofitting of the attachment anchor inside the friction anchor. It is accordingly an object of the invention to provide an anchoring device that will, at least partially, alleviate the above disadvantages.

It is also an object of the invention to provide an anchoring device which will be a useful alternative to existing anchoring devices. SU ARY OF THE INVENTION

According to the invention there is provided an anchoring device, suitable for being installed inside a drilled hole, the anchoring device including: a tubular body having a longitudinal slot provided in a sidewall thereof, the body being displaceable between a tensioned position and a relaxed position, with a diameter of the tube being smaller in the tensioned position than in the relaxed position, and with the tubular body being biased towards the relaxed position so as to in use engage sidewalls of a hole in which it is installed; and an elongate anchoring element locatable inside the tubular body, the anchoring element being displaceable between a retracted position in which an end of the anchoring element is located inside the tubular body, and a protruding position, in which at least the end of the elongate element protrudes from the tubular element.

There is provided for the anchoring device to include a displacement limitation means configuration for limiting the displacement of the elongate anchor element relative to the tubular body.

In one embodiment there is provided for the elongate anchoring element to be slideably secured to the tubular body.

There is provided for the displacement limitation configuration to comprise a sleeve formation located inside the tubular element, and a stopper secured to the anchoring element, the configuration being such that a body of the anchoring element is displaceable relative to a bore of the sleeve formation, but that the stopper is of a larger diameter than the bore of the sleeve formation, and therefore not displaceable beyond the sleeve formation. The sleeve formation may be in the form of a body having a bore provided therethrough, which body is welded to the tubular body. Alternatively, there is provided for the sleeve formation to be in the form of an eye or eyelet formed by punching a depression into a sidewall of the tubular body.

In another embodiment of the invention there is provided for the displacement limitation configuration to be in the form of complementary tapering formations provided on the tubular body and on the anchoring element.

The tubular body is preferably in the form of a split set as is known in the art. The elongate anchoring element may be in the form of a steel eye bolt, a steel cable, or alternatively any other suitable elongate element that terminates in a suitable attachment formation.

According to a further aspect of the invention there is provided a tubular body having a longitudinal slot provided therein, the tubular body being displaceable between a tensioned position and a relaxed position, with a diameter of the tube being smaller in the tensioned position than in the relaxed position, the tubular body being biased towards the relaxed position, characterized in that a sleeve formation is provided inside the tubular body.

The sleeve formation may be in the form of a body having a bore provided therethrough, with the body being welded to the tubular body. Alternatively, there is provided for the sleeve formation to be in the form of an eye or eyelet formed by punching a depression into a sidewall of the tubular body. Preferably, the tubular body is in the form of a split set.

According to a still further feature of the invention there is provided a method of installing an anchoring device in a hole drilled in a rock body, the method including the step of:

providing an anchoring device as described above;

inserting the anchoring device into the hole; and

displacing the anchoring element from the retracted position to the protruding position.

The method may include the further step of securing the anchoring element relative to the tubular body in the protruding position.

The step of securing the anchoring element in the protruding position may entail injecting a settable fluid in a cavity formed between the tubular body and the anchoring element.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention are described by way of non-limiting examples, and with reference to the accompanying drawings in which:

Figure 1 is a cross-sectional side view of an anchoring device in accordance with a first embodiment of the invention, and with the anchoring element in a retracted position;

Figure 2 shows the anchoring device of Figure 1 with the anchoring element in a protruding position; and Figure 3 is a cross-sectional side view of an anchoring device in accordance with a first embodiment of the invention, and with the anchoring element in a retracted position.

DETAILED DESCRIPTION OF INVENTION

Referring to the drawings, in which like numerals indicate like features, a non-limiting example of an anchoring device in accordance with the invention is generally indicated by reference numeral 10.

The anchoring device essentially combines two different existing devices in a novel and inventive manner so as to achieve unexpected benefits. To this extent, the anchoring device 10 comprises a frictional anchor in the form of a split set 20, as well as an attachment anchor 20 which may take many different forms. The purpose of the frictional anchor 30 is to transfer loads from unstable surface regions to more stable interior zones of a rock body. The purpose of the attachment anchor 30 is to provide attachment formations suitable for receiving pipes, cable, meshing or any other utility required in the mining environment.

The frictional anchor 20, or split set, is in the form of an elongate tubular body having a longitudinal slot (not shown) provided therein. The tubular body terminates in a tapered end 21 , and an opposing end terminates in a flange formation 22. The use and advantages of a split set is well known, and does not require further explanation. Suffice it to say that the inherent outward bias of the walls of the tubular body causes the split set to engage the walls of the hole in which it is secured, thus resulting in a rigid interface between the tubular body and the rock body, and therefore also in an efficient transfer of loads. The attachment anchor 30 can take many different forms, and the one in the specific example is in the form of a cable anchor, comprising an elongate body 31 , having a first end 32 terminating in a loop formation, and a second end 33 that is in use located inside the hole provided in the rock body.

The attachment anchor 30 is furthermore configured and dimensioned to fit inside the split set 20. It will however be appreciated that it would be advisable for the attachment anchor 30, and in particular the first end 32 of the attachment anchor, only to protrude from the split set when it is actually required for use. This would simplify installation of the split set, and will also ensure that the attachment anchor 30 is only used once properly secured relative to the split set. For this reason the attachment anchor 30 is displaceable between a retracted position (Figure 1) in which in which the first end 32 of the anchoring element 30 is located inside the tubular body of the split set 20, and a protruding position (Figure 2), in which at least part of the elongate element protrudes from the tubular body of the split set 20.

It is however important for the degree of displacement to be limited, in order for the attachment anchor only to be displaced to the position in which it will be when it is secured (e.g. by way of grouting) relative to the split set. For this purpose displacement limitation means 40 are provided to limit displacement between the attachment anchor 30 and the split set 20. In the embodiment shown in Figures 1 and 2 the displacement limitations means 40 are in the form of a sleeve 41 secured to the split set, and a stopper 42 secured to the attachment anchor 30. The sleeve 41 and the elongate body 31 of the attachment anchor 30 are configured and dimensioned to allow displacement of the elongate body through a bore of the sleeve. However, the stopper 42 has a larger span than the diameter of the bore of the sleeve 41 , and therefore prevents further displacement of the attachment anchor when the stopper 42 abuts the sleeve 41. At this point the loop of the attachment anchor protrudes beyond the flange 22 of the split set, and the attachment anchor can now be secured relative to the split set by injecting a suitable settable media, such as grouting, into an annulus formed between the tubular body of the split set and the elongate body of the attachment anchor. In another embodiment (not shown) the sleeve is formed by punching an indentation / depression into the sidewall of the tubular body, in order for part of the sidewall to extend radially into the tubular body. In this way an eye or eyelet is formed, edges of which are still secured to the sidewall, thus resulting in the sleeve being integrally formed with the tubular body, and in so doing negating the need for welding.

An alternative embodiment is shown in Figure 3, and in this embodiment the displacement limitation means 40 are in the form of two complementary wedge formations (41 and 42) that will also prevent further movement once a predetermined relative position is reached. This configuration will have the additional benefit of increasing the force exerted by the split set on the walls of the aperture, as the wedge formations will exert a outwardly directed reactive force onto the walls of the tubular body of the split set when the attachment anchor is downwardly displaced.

It will be appreciated that the above are only two embodiments of the invention and that there may be many variations without departing from the spirit and/or the scope of the invention.

Claims

An anchoring device, suitable for being installed inside a drilled hole, the anchoring device including:

a tubular body having a longitudinal slot provided in a sidewall thereof, the body being displaceable between a tensioned position and a relaxed position, with a diameter of the tube being smaller in the tensioned position than in the relaxed position, and with the tubular body being biased towards the relaxed position so as to in use engage sidewalls of a hole in which it is installed; and

an elongate anchoring element locatable inside the tubular body, the anchoring element being displaceable between a retracted position in which an end of the anchoring element is located inside the tubular body, and a protruding position, in which at least the end of the elongate anchoring element protrudes from the tubular element.

The anchoring device of claim 1 including a displacement limitation configuration for limiting the displacement of the elongate anchor element relative to the tubular body.

The anchoring device of claim 2 in which the displacement limitation configuration comprises a sleeve formation located inside the tubular element, and a stopper secured to the anchoring element, the configuration being such that a body of the anchoring element is displaceable relative to a bore of the sleeve formation, but that the stopper is of a larger diameter than the bore of the sleeve formation, and therefore not displaceable beyond the sleeve formation.

4. The anchoring device of claim 3 in which the sleeve formation is in the form of a body having a bore provided therethrough, which body is welded to the tubular body.

5. The anchoring device of claim 3 in which the sleeve formation is in the form of an eye or eyelet formed by punching a depression into a sidewall of the tubular body.

6. The anchoring device of claim 2 in which the displacement limitation configuration is in the form of complementary tapering formations provided on the tubular body and on the anchoring element.

7. The anchoring device of any one of the preceding claims in which the tubular body is a body of a split set.

8. The anchoring device of any one of the preceding claims in which the elongate anchoring element is in the form of a steel eye bolt, a steel cable or any other elongate element that terminates in a suitable attachment formation.

9. A tubular body forming part of a anchoring device, the tubular body having a longitudinal slot provided therein and being displaceable between a tensioned position and a relaxed position, with a diameter of the tube being smaller in the tensioned position than in the relaxed position, the tubular body being biased towards the relaxed position, characterized in that a sleeve formation is provided inside the tubular body.

10. The tubular body of claim 9 in which the sleeve formation is in the form of a body having a bore provided therethrough, with the body being welded to the tubular body.

11. The tubular body of claim 9 in which the sleeve formation is in the form of an eye or eyelet formed by punching a depression into a sidewall of the tubular body.

12. A method of installing an anchoring device in a hole drilled in a rock body, the method including the steps of:

providing an anchoring device as claimed in any one of claims 1 to 8;

inserting the anchoring device into the hole; and displacing the anchoring element from the retracted position to the protruding position.

13. The method of claim 12 including the step of securing the anchoring element relative to the tubular body in the protruding position.

14. The method if claim 13 in which the anchoring element is secured in the protruding position by injecting a settable fluid in a cavity formed between the tubular body and the anchoring element.