WO2016019402A2

WO2016019402A2 - A jointed rock anchor

Info

Publication number: WO2016019402A2
Application number: PCT/ZA2015/000039
Authority: WO
Inventors: Brendan Robert Crompton; Paolo Ettore Pastorino; James William Sheppard; Schalk BURGER
Original assignee: Ncm Innovations (Pty) Ltd
Priority date: 2014-07-31
Filing date: 2015-05-27
Publication date: 2016-02-04
Also published as: WO2016019402A3

Abstract

The invention provides a jointed rock anchor which includes a elongate body comprising a first section, a second section and a joining part connectedly interposed between respective ends of each section to allow relative movement of the sections about the joining part.

Description

A JOINTED ROCK ANCHOR

BACKGROUND OF THE INVENTION

[0001] The invention relates to a rock anchor for supporting a wall, and more particularly to a flexible anchor for use in support of a hanging or side wall in an underground excavation.

[0002] In excavations such as in underground mining, hanging and side rock walls of a mine shaft or stope must be supported behind an advance face which is being actively mined. Support is typically done through inserting and securing elongate rock anchors within pre-drilled bores in the walls, thereby transferring peripheral stresses on the walls to a more stable interior of the rock.

[0003] In some mining environments, especially those found in South Africa, the stopes are narrow in that the space between a foot wall and a hanging wall is often less than 900mm. As most rock anchors used in this environment are over 900mm in length, it becomes difficult or near impossible to insert a rock anchor into a bore.

[0004] One solution to this problem is to use multiple anchor parts of a shortened length, which are coupled together to provide the anchor once inserted into the bore A problem exists in that an insufficient number of shortened anchors can be inserted into the bore, giving the appearance of a correct installation, whereas the full length on the bore has not been supported which can result in collapse or failure of the wall. [0005] It is an objective of the invention to at least partially address the above problems.

SUMMARY OF INVENTION

[0006] The invention provides a jointed rock anchor which includes a elongate body comprising a first section, a second section and a joining part connectedly interposed between respective ends of each section to allow relative movement of the sections about the joining part.

[0007] The joining part may be a joint which will allow limited relative movement of the sections.

[0008] The joint may be any one of the following: a universal joint, a ball and socket joint, a saddle joint, a knuckle joint and a hinge joint.

[0009] Alternatively, the joining part may be a flexible member.

[0010] The flexible member may be a length of wire rope or tendon.

[0011] The flexible member may include, at each of its ends, a connector element which is adapted to connectedly receive a respective end of a respective section.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The invention is described with reference to the following drawings in which:

Figure 1 shows, in perspective, a jointed rock anchor in accordance with the invention; Figure 2 shows, in perspective, an enlarged view of a joint of the rock anchor of Figure 1 ;

Figure 3 shows, in perspective, a jointed rock anchor according to an additional embodiment of the invention; Figure 4 shows, in perspective, an enlarged view of a joint of the rock anchor of

Figure 3; and

Figure 5 diagrammatically illustrates the jointed rock anchor of either embodiment in use in an underground excavation.

DESCRIPTION OF PREFERRED EMBODIMENTS [0013] Figure 1 shows, in perspective, a jointed rock anchor 10 in accordance with a first embodiment of the invention. The anchor includes a composite elongate body consisting of a first rigid part 12 and a second rigid part 14 which are connected at one another by a joint 16.

[0014] The first part 12 includes a leading end 18, a mechanical anchor 20 positioned toward the leading end 18, and an opposing first connecting end 22 (see

Figure 1 ). The second part 14 includes a trailing end 24 to which a face plate 26 is engaged. Opposing the trailing end is a second connecting end 30 (see Figure 2).

[0015] The joint 16 is connectedly interposed between first and second connecting ends (22 and 30). [0016] Figure 2 is an enlarged view of the joint 16 of Figure 1 illustrating, in greater detail, the rigid composition of the joint 16 which, in this example, is a ball 32 and socket 34 joint. Both the ball 32 and the socket 34 parts of the joint have coupling formations, respectively designated 36 and 38 (see Figure 2).

[0017] Each coupling formation (36 and 38) is complementarily recessed to receive ends 22 and 30 of parts 12 and 14 respectively, in frictional fit. Alternatively or additionally, to ensure fixed engagement, the ends can be adhered, crimped, welded or swaged to or within the coupling formations.

[0018] The ball and socket joint 16 is of rigid construct, adapted to provide only limited relative movement by allowing the parts to pivot relatively to one another within a single plane.

[0019] The fixed coupling of the ends (22, 30) with the respective coupling formation 36 and 38, there is little or no rotation about these points of attachment. Therefore when the projecting part, in use, being the second part 14, is spun about its longitudinal axis, this motion is transmitted to the first part positioned distally within a rock hole in use. This feature is of significance and will be described more fully below.

[0020] Figure 3 is a perspective view of a second embodiment of the invention, which shows a jointed rock anchor 10A. In describing this embodiment, the features bear like designations, with reference to the first embodiment.

[0021] The anchor 10A has a composite body consisting of a first rigid part 12 and a second rigid part 14, connected to one another by a joining section 16A.

[0022] The first part 12 includes a leading end 18, a mechanical anchor 20 positioned towards the leading end, and an opposing first connecting end 22. The second part 14 includes a trailing end 24 to which is attached a face plate 26. Opposing the trailing end 24 is a second connecting end 30 (see Figure 4).

[0023] The joining section 16A is connectedly interposed between the first and second connecting ends (22 and 30). [0024] Figure 4 is an enlarged view of the joining section 16A. The Figure shows the section comprised of a length of wire rope or tendon 40. The tendon 40 is flexible, comprised of a plurality of interwoven wire strands 42. At each end of the tendon, a coupling formation (36 and 38) is provided.

[0025] The ends 22 and 30, of parts 12 and 14 respectively, are frictionally received within recessed ends of the respective connector formation (36 and 38). Alternatively or additionally, to ensure fixed engagement, the ends can be adhered, crimped, welded or swaged to or within the coupling formations.

[0026] Unlike with the restrictive pivotal movement of the parts (14, 16) of bolt 10 imparted by the joint 16, in the current embodiment, the joining section 16A allows for a greater degree of relative movement by allowing the parts to pivot or bend, relatively to one another, along multiple planes.

[0027] As with the bolt 10, little rotational force, imposed on the proximal second part 14, is lost within loose fittings between ends (22, 30) and respective connector formations (36, 38). Spinning of the second part 14 will therefore cause spinning rotation of the first distal part 12, transmitted through the joint 16A. However, as joint

16A is not rigidly constructed as in joint 16, some of the rotational motion will be taken up in twisting the tendon 40. [0028] Figures 5A and 5B illustrate a narrow reef stope 52, typical in the South African mining context, in which a jointed rock anchor of either embodiment (10 or 10A) would be required.

[0029] A rock hole 54 is illustrated, predrilled into a rock face 56 to be supported. Within the stope, a miner 58 is shown, unable to stand upright.

[0030] In Figure 5A, a conventional rock anchor 60 is illustrated only partially inserted into the rock hole, prevented from being fully inserted due to its length and the narrowness of the stope.

[0031] Figure 5B illustrates the use, by way of example, of the jointed rock anchor 10A. Due to the joining section16A, the first part 12 can be fed into the hole, followed by the second part 14, facilitated by the bending of the anchor body about the joining part 16A.

[0032] Once the anchor 0A is fully inserted in the hole 54, with the face plate 26 abutting the rock face 56, the anchor is then fixed within the rock hole. This can be achieved mechanically, by actuating the mechanical anchor 20 to radially expand into contact with the rock hole, and/or chemically wherein the rock anchor is adhered with the rock hole with a grout or resin.

[0033] The rock anchor may need to be spun to actuate the mechanical anchor and/or sever grout capsules, passed in to the rock hole in advance of the anchor. This, of course depends on the type of mechanical anchor used and the type of grout used and the method of introducing the grout into the rock hole. If the rock anchor needs to be spun, the spinning force will be applied to a projecting section of the second part 14 of the composite anchor body, which force will be transferred to the distally positioned first part 12, carrying the anchor 20 or near pre-installed grout capsules. This, of course, will be more efficient if the rock anchor is of the first embodiment 10, with the rigid joint 6.

Claims

1. A jointed rock anchor which includes a elongate body comprising a first section, a second section and a joining part connectedly interposed between respective ends of each section to allow relative movement of the sections about the joining part.

2. A jointed rock anchor according to claim 1 wherein the joining part is a joint.

3. A joining rock anchor according to claim 2 wherein the joint is any one of the following: a universal joint, a ball and socket joint, a saddle joint, a knuckle joint and a hinge joint.

4. A jointed rock anchor according to claim 1 wherein the joining part is a flexible member.

5. A jointed rock anchor according to claim 4 wherein the flexible member includes, at each of its ends, a connector element which is adapted to connectedly receive a respective end of a respective section.

6. A jointed rock anchor according to claim 4 or 5 wherein the flexible member is a length of wire rope or tendon.