SE542178C2 - Apparatus for supporting a rock body - Google Patents

Abstract

A ground support apparatus comprising a first portion comprising elongate friction means for substantially anchoring the apparatus in a bore hole formed within a rock body, a second portion disposed substantially towards a front end of the apparatus and which abuts the first portion, a localised anchor means disposed at a junction between the first portion and the second portion and a yielding mechanism. In use, a movement of the rock body engages the yielding mechanism thereby governing the rock body movement.

Description

APPARATUS FOR SUPPORTING A ROCK BODY FIELD OF INVENTION [1] The present invention relates to a ground support apparatus for use in ground support in mining, tunneling and civil engineering operations. More particularly, the present invention relates to a dynamic friction rock bolt having yielding means, elongate anchor means and localised anchor means.

BACKGROUND ART [2] It is known to use a ground support apparatus, such as a rock bolt, for reinforcing a rock body in an underground or civil engineering operation for improving safety of personnel located in nearby environments. Known rock bolts come in many different forms and are chosen based on various factors including the material and quality of the rock body to be reinforced and the amount of geological stress and movement common to particular rock bodies. [3] Known rock bolts consist of an elongate member that is placed into a bore hole predrilled into the rock body to be reinforced. The rock bolt is fitted with one end protruding from a rock face of the rock body. A thrust plate can then be mounted to the protruding end. The thrust plate is often used in combination with a support mesh and/or a spray concrete that forms a net across the rock face so as to constrain or limit movement of the rock face in the event of a movement or failure of the rock body. [4] In order to reinforce the rock body, known rock bolts are required to be anchored deep within the rock body so that the rock bolt can effectively support the rock and limit the movement of the rock face. [5] Known rock bolts anchor the rock face by a mechanical means of anchoring such as a rock bolt having a friction bolt configuration or using a wedge member for example. Other means of anchoring a rock face can be used by more securely mounting the rock bolt in the bore hole and thereby increasing a pull out force. These other means include use of chemical adhesion by the provision of a grout or resin which is applied to a bore hole which is fitted with a rock bolt. The resin/grout is then cured and encases the rock bolt within the resin/grout within the bore hole. [6] Installation of known rock bolts can be costly and time consuming, particularly in the case of rock bolts having chemical means of anchoring as the rock bolt must be installed into the bore hole, the resin or grout applied and then left for a period of time before the rock bolt can be tensioned after the chemical means have cured sufficiently. These types of installation require multiple passes for a complete installation of a rock bolt. [7] Problems arise in practise given the often large number of individual rock bolts fitted to any particular length of a rock body due to the duplication of time and expense of fitting rock bolts that require multiple passes for installation. Additional costs associated with resin cartridges or grout compounds these expenses. [8] Further problems arise in dynamic rock conditions. Seismic and other earth movements, which may frequently take place during underground tunnelling and mining operations, may cause the rock face of a tunnel or excavated region to move and become less stable, thus placing significant load on rock bolts installed in the rock face. Known rock bolts are not able to adaptively withstand and support rock bodies that have experienced such failures. Rock failures may cause bolts to undergo substantial tension, bend or twist, substantially reducing their load bearing strength, and in extreme cases snap. [9] The present invention attempts to overcome at least in part the aforementioned disadvantages of previous ground support apparatus and methods.

SUMMARY OF INVENTION

[10] In accordance with the present invention there is provided a ground support apparatus for use in supporting a rock body, the apparatus comprising friction means arranged to substantially anchor the apparatus in a bore hole formed within the rock body, a first portion and a second portion wherein the second portion is disposed substantially towards a front end of the apparatus abutting the first portion, an elongate support member disposed substantially through and along a complete lengthwise axis of the apparatus, and yielding means arranged to govern a relative movement between the elongate support member and the rock body, the elongate support member comprising a peripheral end arranged for supporting the rock face, wherein in use the first portion is disposed between the rock face and the second portion, wherein installing the apparatus within a bore hole provided in a rock face of the rock body the first portion substantially restrains the apparatus within the bore hole and the second portion substantially supports the rock face, and wherein in use a movement of the rock face is substantially limited by a yielding of the second portion.

[11] Preferably, the friction means comprises an elongate anchor means and a localised anchor means. Preferably, the localised anchor means is disposed at a junction between the first portion and the second portion of the apparatus, and comprises a point anchor activated upon a tensioning of the apparatus after installation into the bore hole.

[12] Preferably, the elongate anchor means comprises a body having an outer portion arranged to engage an inner surface of the bore hole.

[13] Preferably, the localised anchor means comprises a resilient wedge member, whereupon during tensioning of the apparatus the wedge member acts to displace an outer portion of the first portion of the apparatus for improving a frictional communication between the outer portion of the body and the inner surface of the bore hole. An anchor means comprising a wedge member is advantageous in soft rock environments, in particular, where an increased frictional communication between the outer portion of the body and the inner surface of the bore hole is required to anchor the bolt apparatus effectively.

[14] Preferably, the elongate anchor means comprises a front end and a back end, the front and back ends being spaced apart by a body having a longitudinal axis and contoured outer portion arranged to be forcibly received into the bore hole for substantially engaging the inner surface of the borehole.

[15] Preferably, the yielding means comprises a resilient collar arranged to receive and yieldingly engage the elongate support member.

[16] Preferably, a relative movement between the rock face and the resilient collar urges the elongate support member to undergo a substantial yielding process as it travels through the resilient collar, thereby governing a movement of the rock face and supporting the rock body.

[17] Preferably, the back end of the elongate support member comprises a threaded portion complementary with a fastener for use in installing and tensioning the apparatus.

DRAWINGS

[18] The foregoing summary, as well as the following detailed description of the illustrated embodiments, is better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention, there is shown in the drawings several exemplary embodiments which illustrate what is currently considered to be the best mode for carrying out the invention, it being understood, however, that the invention is not limited to the specific instruments disclosed. In the drawings: Figures 1(a) and 1(b) show a first preferred embodiment of a ground support apparatus in accordance with the present invention; Figures 2(a) and 2(b) show a second preferred embodiment of the present invention which comprises the ground support apparatus shown in Figures 1(a) and 1(b) with alternate friction means; Figure 3 shows an enlarged schematic view of the yielding mechanism used in the embodiments shown in Figures 1 and 2; Figures 4(a) and 4(b) show a third preferred embodiment of the present invention which comprises the ground support apparatus shown in Figures 1(a) and 1(b) with an alternate second portion and resilient collar and having a tapered cylindrical seat disposed towards a back end of the elongate support member of the apparatus; Figures 5(a) and 5(b) show enlarged views of the back end of the ground support apparatus shown in Figures 4(a) and 4(b); Figure 6(a) shows an alternate localised anchor means comprising a wedge member apparatus having two portions that may be used in embodiments of the present invention, the wedge member apparatus being partially fitted in a rock bolt; Figure 6(b) shows the alternate localised anchor means and wedge member apparatus shown in Figure 6(a) fitted in a rock bolt; Figure 7(a) shows an outer side view of a first portion of the wedge member apparatus shown in Figure 6(a); and Figure 7(b) shows an inner side view of the first portion shown in Figure 7(a).

[19] Referring to Figure 1, there is shown a ground support apparatus 10 according to a first preferred embodiment of the present invention. The apparatus comprises a first portion 12 and a second portion 14.

[20] The first portion 12 comprises an elongate body 20 having an outer portion 17 defining a lumen 19 passing therethrough along a longitudinal axis disposed between a back end 22 and a front end 24 of the elongate body 20. The first portion 12 further comprises friction means and, as can be seen in Figure 1 , the friction means is defined, at least in part, by the outer portion 17.

[21] The outer portion 17 comprises a resilient material shaped complementary to a bore hole into which, in use, the apparatus 10 is to be installed. In the first embodiment shown in Figures 1(a) and (b), the elongate body 20 comprises a friction rock bolt configuration wherein the outer portion 17 is defined, at least in part, by a substantially arcuate wall 26 substantially formed about the lumen 19. In this first embodiment of the invention a gap 28 is formed between opposed edges 30, 32 of the arcuate wall 26 and disposed substantially along the longitudinal axis of the first portion 12.

[22] It will be understood that the gap 28 provides for an amount of flexure of the arcuate wall 26 such that the edges 30, 32 may be moved closer to one another during a radial compression of the elongate body 20. A variation in the gap 28 corresponds with a change in an outer dimension of the arcuate wall 26 during fitting of the apparatus 10 into a bore hole which has a smaller internal diameter than a free standing outer dimension of the body 20, for example.

[23] The resilient nature of the arcuate wall 26 ensures that the body 20 is biased toward an expanded position thereby urging the outer portion 17 into a radial expansion after a compressive installation process and thereby provides a source of frictional communication between the arcuate wall 26 and an inner surface of a bore hole.

[24] The elongate body 20 of the preferred embodiment of the present invention may comprise any dimension of length and/or free standing outer diameter, however it will be appreciated that the dimensions of the apparatus 10 will be substantially complementary to a receiving rock body bore hole such that the first portion 12 may be forcefully inserted into the bore hole. During the forceful insertion the arcuate wall 26 of the body 20 is compressed such that the opposed edges 30, 32 move closer to one another thereby yielding the gap 28. The resilient and tensile character of the first portion 12 results in an internally generated radially expanding force acting along the length of the elongate body 20 and urging the elongate body 20 into an interference fit with the bore hole. It will be understood that a force acting in an orientation generally parallel with the longitudinal axis upon the first portion 12 of an installed apparatus 10 will be opposed by frictional force generated by the resultant radially expanding force.

[25] It is also an advantage of the present invention that no pull ring is required on the elongate body 20. Known friction rock bolts comprise a pull ring welded to a peripheral end of the rock bolt for limiting travel of the rock bolt into the bore hole and for assisting in removing the rock bolt from the bore hole. Known pull rings are welded about a circumference of the rock bolt and can be counterproductive to the function of the rock bolt in that they operate to resist compressive or expansive urges developed in the bolt.

[26] Referring to Figure 2, there is shown a second alternative embodiment of the present invention. In the figure, the ground support apparatus 10 comprises an elongate body 20 having an outer portion 17 having a clover leaf configuration comprising one or more resilient longitudinal lobes 27 running along the substantial length of the first portion 12. Each lobe 27 is arranged to have a peripheral surface which, in use, abuts with an inner surface of a bore hole in which the apparatus 10 is installed, and each lobe 27 is connected with an adjacent lobe via a junction 29. The first portion 12 of the apparatus 10 in this embodiment is also configured to have an outer dimension substantially greater than an inner dimension of the bore hole such that an interference fit is achieved upon a forceful installation of the apparatus 10. A radially compressive force is imposed by the inner surface of the bore hole upon the peripheral surface of each lobe 27. The compressive force acting on the lobes 27 urges a displacement at the junctions 29 which effectively spring loads the elongate body 20 thereby providing an outward bias for restraining the elongate body 20 in the bore hole.

[27] As with the first embodiment, after a forceful installation into a bore hole the resilient and tensile material of the elongate body 20 generates a resultant radially expanding force along the length of the elongate body 20 and maintains a frictional communication with the bore hole. It will be understood that a force acting upon the first portion 12 in an orientation generally parallel with the longitudinal axis of an installed apparatus 10 will be opposed by the friction generated by the radially expanding force.

[28] As seen in both Figures 1 and 2, the apparatus 10 further comprises a second portion 14 which is arranged to at least abut and preferably engage the first portion 12. The second portion 14 comprises a yielding anchor means which comprises a resilient collar 42. As is most clearly seen in the enlarged view in Figure 3, the resilient collar 42 has an interior wall 43 that defines a substantially contoured lumen 44 passing through a longitudinal axis of the resilient collar 42. The resilient collar lumen 44 is arranged to receive a support means therethrough. The support means preferably comprises an elongate support member 50 capable of being received by the resilient collar 42 and extending substantially through the first portion 12 of the elongate body 20 for supporting the rock face. In the preferred embodiments shown in Figures 1 and 2, the resilient collar 42 may comprise a tapered nose or wedge portion 46 and tail portion 48. The elongate support member 50 preferably comprises a solid and continuous length of resilient metallic material that is capable of undergoing a distortion as it passes through the lumen 44 of resilient collar 42.

[29] The resilient collar 42 and the elongate support member 50 are preferably arranged such that the frictional communication between the elongate support member 50 and the lumen 44 of the resilient collar 42 is substantial, thereby providing that the elongate support member 50 may only travel through and along the lumen 44 if a considerable force is applied to the elongate support member 50 relative to the resilient collar 42. Further, the lumen 44 may comprise one or more sections in which the diameter of the lumen 44 is less than other sections of the lumen 44 thereby serving to increase the frictional communication between the elongate support member 50 and the lumen 44. As shown in Figure 3, the interior wall 43 that defines the lumen 44 may have a section preferably comprising a raised circumferential ring 47 that reduces the diameter of the lumen 44 and forms a stricture point 49. In this arrangement, a very high frictional co-efficient exists between the elongate support member 50 and the lumen 44 at the stricture point 49.

[30] As shown in Figures 1 and 2, a back end 52 of the elongate support member 50 comprises a threaded portion 53, or other known means, for use in attaching and/or restraining a press plate 60, which is used to assist with the installation of the apparatus 10, and/or a thrust plate 62 for engaging with and supporting the rock face. The threaded portion 53 will typically receive a nut 55 dimensioned to be complementary to installation equipment such as a jumbo rig, for example.

[31] An opposed peripheral front end 54 of the elongate support member 50 substantially extends from the tail portion 48 of resilient collar 42 for providing a travel length available for undergoing distortion when the elongate support member 50 travels through and along the lumen 44 of the resilient collar 42. A terminal portion of the peripheral front end 54 preferably comprises stop means for limiting the travel length of the elongate support member 50 through the lumen 44. In the preferred embodiment of the present invention, the stop means comprises a raised resilient portion having a dimension greater than that of the resilient collar 42 lumen 44, such as a weld ring 56 for example. In alternative embodiments, the stop means may comprise a pin, nut or endplate for example, disposed at the peripheral front end 54.

[32] After a pre-defined travel length of the elongate support member 50 through the resilient collar 42 lumen 44, the stop means is arranged to abut a surface of the resilient collar 42 thereby halting the relative movement of the elongate support member 50 through the lumen 44. It should be understood that once the stop means has been activated, the apparatus 10 has reached the full extent of its working range and can no longer provide a controlled dynamic yielding of the elongate support member 50 for governing a movement of the rock face.

[33] The front end 24 of the first portion 12 may comprise a tapered periphery and be arranged to receive at least the wedge portion 46 therein such that the first and second portions 12, 14 are orientated to be substantially co-axial. It should be understood that the wedge portion 46 engages with the first portion 12 so as to develop a point anchor 18 as the apparatus 10 is pretensioned during the installation process.

[34] The present invention further discloses friction means used in combination with yielding means for supporting a rock face of a rock body by providing a travel length of governed movement between the rock face and the rock body.

[35] In use, the present invention relates to an apparatus 10 providing a friction anchored dynamic yielding rock bolt 10 having dual anchor means comprising a length of friction bolt defined by the body 20 of the first portion 12 and a point anchor 18 generated at a junction 57 between the first and second portions 12,14.

[36] The apparatus 10 may be fitted to a bore hole using known forceful means, such as those provided by underground equipment including jumbo rigs and/or production drills, for example. The apparatus 10 is arranged with the thrust plate 62 fitted over the elongate support member 50 and with a nut 55 fitted to the threaded portion 53 of the back end 52.

[37] In a preferred embodiment the press plate 60 comprises a seating recess 60a complementary to the back end 22 of the first portion 12 thereby ensuring the first portion 12 and the elongate support member 50 remain substantially coaxial before, during and after installation.

[38] To install the apparatus 10, the apparatus 10 is positioned adjacent a bore hole such that the elongate support member 50 front end 54 is in the bore hole and the preferably tapered tail portion 48 of the resilient collar 42 is arranged to be received into the bore hole. A force is applied to the apparatus 10, preferably via the press plate 60 and/or nut 55 thereby urging the apparatus 10 into the bore hole and compressing the friction means of the first portion 12. The apparatus 10 is urged into the bore hole until the body 20 is substantially received therein and the back end 52 of the elongate support member 50 substantially protrudes from the rock face.

[39] A pre-tensioning step is then applied to the apparatus 10 for activating the point anchor 18 between the first and second portions 12, 14. The pre-tensioning step involves tightening the nut 55 to a predefined tension thereby urging the first and second portions 12, 14 to engage one another at the junction 57. Due to the tapered nose 45 or wedge portion 46, the second portion 14 can be drawn into the lumen 19 simultaneously urging the outer portion 17 outwardly and developing the point anchor 18 with the bore hole at the junction 57.

[40] A thrust plate 62 is then fitted and secured to the back end 52 of the elongate support member 50 by known means for substantially engaging and supporting the rock face. Mesh and spray concrete or similar means may also be used as known In the art.

[41] In a further aspect of the present invention the nut 55 preferably comprises a lock nut (not shown) for use with the ground support apparatus 10. The lock nut is dimensioned to be complementary to the threaded portion 53 of the back end 52 of the elongate support member 50 and is threadedly attached thereto for restraining the thrust plate 62 in position securely against the rock face. It will be appreciated that problems arise in the art of ground support wherein vibrations caused by mining practices and associated machinery and explosions can, for example, expose a supported rock body to substantial vibrations. Such vibrations are known to loosen prior art rock bolt nuts and, as a result, the thrust plate of an installed rock bolt can work loose and compromise the efficiency of the rock bolt and thrust plate in respect to supporting a rock face.

[42] The lock nut used in the present invention may, therefore, comprise vibration damping means for minimizing relative movement between the threaded portion 53 of the elongate support member 50 and the lock nut itself. In a preferred embodiment, the lock nut will comprise a polymer portion that is arranged to engage the elongate support member 50 and/or the threaded portion 53 of the elongate support member 50. The polymer portion may be arranged as an insert proximal to a traditional metallic thread of the nut 55 such that both the metallic thread of the nut 55, and the proximal polymer portion, engage with the threaded portion 53 of the elongate support member 50.

[43] Small fluctuations or movements of the thrust plate 62, nut 55 or elongate support member 50 caused by vibrations in the rock body are absorbed through a substantially elastic deformation of the polymer portion. The polymer portion may provide a compressive force against the elongate support member 50 for limiting undesired movement of the nut 55. The polymer portion preferably comprises a nylon or rubber material. Because the conditions in an underground environment can be corrosive, the material used in the vibration damping means will preferable be substantially resistant to corrosion.

[44] It is to be understood that the friction means of the first portion 12 substantially restrains the apparatus 10 within the bore hole and anchors the second portion 14 resilient collar 42 in position. Upon a rock body failure, creep or similar geological event whereby the rock face loses support and can move, a weight of the rock face is transferred to the elongate support member 50 via the thrust plate 62. Movement of the thrust plate 62 is limited by the yielding action of the elongate support member 50 as it passes through the resilient collar 42 and the rock face is thereby supported. Yielding of the elongate support member 50 can continue to occur over the travel length until the stop means 56 abuts the resilient collar 42 at which point the apparatus 10 can no longer provide a governed movement of the rock face and the apparatus 10 thereafter acts as a solid whole.

[45] Referring to Figure 4, there is shown a third preferred embodiment of the present invention which substantially comprises the ground support apparatus shown in Figure 1 with an alternate second portion 14 and resilient collar 42. The resilient collar 42 comprises a substantially tapered nose portion 45 and tail portion 48 and has a substantially contoured lumen 44 passing there through. Further, the resilient collar 42 comprises a gripping section 15 having a series of indentations or protuberances on the surface of the gripping section 15, produced by knurling or a similar manufacturing process. The gripping section 15 provides additional friction torque between the surface of the resilient collar 42 and the inner surface of the elongate support member 50 lumen 19 at the junction 57 when the nut 55 is tightened during the installation process. This friction torque impedes rotation of the resilient collar 42 as the nut 55 is tightened, thereby facilitating the pre-tensioning of the apparatus 10 during installation. In contrast to the embodiments of the invention illustrated in Figures 1 and 2, the resilient collar 42 in the third embodiment disclosed does not comprise a wedge portion 46. Instead, the tapered nose 45 acts to outwardly displace the outer portion 17 at the junction 57, thus developing the point anchor 18 with the bore hole at the junction 57 when the apparatus 10 is pre-tensioned during installation.

[46] As shown in Figure 4 and, more particularly, in Figure 5, the ground support apparatus 10 that is the subject of the present invention may additionally comprise a floating tapered cylindrical seat 61 disposed between the thrust plate 62 and the nut 55. As is most clearly shown in Figure 5(b), a top end 61a of the cylindrical seat 61 is preferably tapered providing a substantially rounded surface that abuts a curved lower surface 64 of the thrust plate 62. In use, when the nut 55 is tightened during installation of the apparatus 10, the cylindrical seat 61 may freely rotate about, and travel along, the longitudinal axis of the elongate support member 50. The cylindrical seat 61 serves to evenly distribute and spread the load that would otherwise be placed on the thrust plate 62 by the nut 55 when it is tightened. In this arrangement, the thrust plate 62 may move more easily along the longitudinal axis of the elongate support member 50 as the nut 55 is tightened during installation. Further, the tapered top end 61a of the cylindrical seat 61 enables the thrust plate 62 to be secured to a rock face effectively in situations where the length of the elongate body 20 is aligned at an angle that is not substantially perpendicular to the rock face surface - for example, because the apparatus 10 has been driven into a bore hole in the rock face at an angle. The rounded surface of the cylindrical seat 61 at its tapered top end 61a ensures that a uniform, evenly distributed force is applied to the thrust plate 62 thereby allowing the apparatus 10 to support the rock face effectively in such situations.

[47] It will be appreciated that the second portion 14 and localised anchor means used in accordance with the present invention will not be limited to the resilient collar 42 and/or wedge member 46 designs shown in Figures 1 , 2 and 4. Referring to Figures 6 and 7, there is shown a further alternate anchoring apparatus 200 that may be used to facilitate the localized anchor used in accordance with the present invention. The anchoring apparatus 200 comprises a split wedge apparatus comprising a plurality of complementary portions 220 each disposed about a longitudinal axis, the split wedge apparatus comprising a substantially tapered inner lumen 265 arranged to receive at least a portion of a resilient wedge member 300, and an outer portion arranged to engage with a peripheral end of elongate anchor means used in the ground support apparatus 10.

[48] In the exemplary embodiment shown in Figure 6, the anchoring apparatus 200 comprises a plurality of complementary portions 220, where each portion comprises a half section of the anchoring apparatus 200. It will, however, be understood by a skilled addressee that alternate embodiments of the anchoring apparatus 200 may comprise a varied number of portions 220, including three, four, etc., which are also encompassed within the scope of the anchoring apparatus 200 disclosed.

[49] As shown in Figure 7, each portion 220 comprises an elongate body 230 spaced between peripheral ends 202,204. The body 230 preferably comprises a substantially resilient material, typically a metallic material, however other resilient materials such as a polymer material may be used. The body 230 comprises a profiled inner surface 260 and a profiled outer surface 280 that are spaced apart at least in part by a longitudinal edge surface 235. As is most clearly shown in Figure 6(a), the outer surface 280 is arranged to be complementary to the inner surface of the lumen 19 at the junction 57 between the first portion 12 and second portion 14 of the ground support apparatus 10.

[50] As shown in Figure 6(a), a first peripheral end 202 of the anchoring apparatus 200 is arranged to be substantially received into the lumen 19 of the ground support apparatus 10. As shown in Figures 7(a) and 7(b), preferably the outer surface 280 of each portion 220 comprises a raised portion 210 defining a face 215. As shown in Figure 6(a), the face 215 is arranged to abut an end of a wall 216 of the first portion 12 for limiting a travel of the anchoring apparatus 200 into the lumen 19 of the first portion 12. Further, the raised portion 210 preferably comprises a tapered nose 212 for assisting the installation process during which a ground support apparatus 10 fitted with the anchoring apparatus 200 is inserted into a bore hole using known means.

[51] It will be understood that the portions 220 are configured to be used in plural and, collectively, they form the anchoring apparatus 200. The anchoring apparatus 200 comprises a generally tubular configuration that defines a lumen 265 which extends between the peripheral ends 202,204. As seen in Figure 6(a), the edge surface 235 of a respective portion 220 is arranged to abut the edge surface 235 of an adjacent portion 220 when the apparatus 200 is in a first compact position as seen in the figure.

[52] As shown in Figures 7(a) and 7(b), each portion 220 preferably comprises a recess 270 running radially about an outer surface 280 of the portion 220. The recess 270 may be disposed at any point along the anchoring apparatus 200 and is dimensioned to provides a protected space in which a biasing means (not shown) may be disposed for biasing the anchoring apparatus 200 in the compact first position (as shown in Figure 6(a)) during installation such that the edge surfaces 235 of adjacent portions 220 abut one another along a substantial length of the apparatus 200. The biasing means may comprise any known means including, but not limited to, a spring, rubber band, wire, cable tie, etc. In alternative embodiments of the anchoring apparatus 200, when it is arranged in the first compact position the edge surfaces 235 may be adhered to one another using a relatively weak adhesive in lieu of biasing means.

[53] It is to be understood that, in use, the anchoring apparatus 200 may be moved from the first compact position (as shown in Figure 6(a)) to a second expanded position (as shown in Figure 6(b)). Therefore, the biasing means that is used must be able to be overcome when activating the anchoring apparatus 200 to move from the first position to the second position to provide a point anchor.

[54] As can also be seen in Figure 7(b), the inner surface 260 of a portion 220 is not parallel with the outer surface 280. Instead, the shape of the inner surface 260 forms a tapered lumen 265 when the portion 220 is arranged adjacent to a complementary portion 220. When the apparatus 200 is in the first compact position, the tapered lumen 265 has a diameter at the first peripheral end 202 that is substantially smaller than a diameter at the second peripheral end 204.

[55] The anchoring apparatus 200 is designed to be used with expansion means for overcoming the biasing means and urging the portions 220 apart to provide the point anchor. The expansion means preferably comprises a wedge member 300, as illustrated in Figure 6(b). The wedge member 300 is preferably substantially non-compressible and will preferably comprise a configuration of a known wedge that is complementary to the tapered lumen 265 into which the wedge member 300 is received. However, it should be understood that because the lumen 265 of the anchoring apparatus 200 is tapered, it is not necessarily required that the wedge member 300 be tapered.

[56] The wedge member 300 is arranged to be in rigid communication with the elongate support member 50 of the ground support apparatus 10. In order to activate the anchoring apparatus 200, an operator may selectively apply a tensile load to the elongate support member 50 by known means thereby drawing the wedge member 300 into the lumen 265, overcoming the biasing means and urging the portions 220 apart into the second expanded position as shown in Figure 6(b). It will be understood that the anchoring apparatus 200 may be selectively tensioned at periodic intervals thereby re-tensioning the point anchor and accounting for creep or other movement of the rock body.

[57] Modifications and variations as would be apparent to a skilled addressee are deemed to be within the scope of the present invention.

Claims (18)

1. An apparatus (10) for supporting a rock body, comprising: a first portion (12) comprising an elongated body (20) having a first end (24), second end (22) and a contoured outer portion (17) defining, at least in part, a lumen (19); an elongated support member (50) received by, and extending substantially through, the lumen (19) of the elongated body (20) having a thrust plate (62) secured to a peripheral end (52) of the elongated support member (50); and a second portion (14) comprising a resilient collar (42), wherein the collar (42) abuts the first end (24) of the elongated body (20) and comprises an interior wall (43) defining a lumen (44) that receives the elongated support member (50) and secures at least part of the elongated support member (50) therein by a frictional communication, and wherein: the apparatus (10) is adapted to be installed in a borehole formed within the rock body; the outer portion (17) frictionally engages an inner surface of the borehole to anchor the apparatus (10) in the borehole; during installation, a movement of the elongated support member (50) causes the collar (42) to move, at least in part, inside the lumen (44) of the elongated body (20) and displace outwardly the outer portion (17) to further anchoring the apparatus (10) in the borehole; and in use, a movement of the rock body against the thrust plate (62) causes the elongated support member (50) to overcome the frictional communication between the elongated support member (50) and the collar’s (42) lumen (44) and travel through the lumen (44) thereby permitting the apparatus (10) to yield and govern the rock body movement.

2. An apparatus (10) for supporting a rock body according to claim 1 , wherein the collar’s (42) lumen (44) has a section where a diameter of the collar’s (42) lumen (44) is less than a diameter of at least one other section of the collar’s (42) lumen (44) to increase the frictional communication between the collar’s (42) lumen (44) and the elongated support member (50)

3. An apparatus (10) for supporting a rock body according to claim 1 or 2, wherein: the outer portion (17) of the elongated body (20) comprises, at least in part, a substantially arcuate wall (26) formed about the lumen (19) of the elongated body (20); and the outer portion (17) has a gap (28): formed between opposed edges (30, 32) of the arcuate wall (26), and disposed substantially along a longitudinal axis of the elongated body (20).

4. An apparatus (10) for supporting a rock body according to claim 1 or 2, wherein: the outer portion (17) of the elongated body (20) comprises a wall (26) having a plurality of longitudinal lobes (27) spaced apart and connected together by inwardly disposed junctions (29); each lobe (27) runs substantially along an elongated length of the outer portion (17); and in use, a peripheral surface of each lobe (27) abuts the inner surface of the borehole.

5. An apparatus (10) for supporting a rock body according to claim 3 or 4, wherein when the apparatus (10) is inserted into the borehole during installation: the elongated body (20) is received forcibly by the borehole causing the elongated body (20) to undergo radial compression; and the outer portion (17) of the elongated body (20) frictionally engages with the inner surface of the borehole.

6. An apparatus (10) for supporting a rock body according to any preceding claim, wherein the collar (42) comprises a nose portion (45) and a tail portion (48) and the nose portion (45) comprises a wedge member (46).

7. An apparatus (10) for supporting a rock body according to claim 6, wherein the wedge member (46) is a split wedge apparatus comprising: a plurality of complementary wedge segments (220) each disposed about a common longitudinal axis; a substantially tapered lumen (265) arranged to receive at least a portion of the tail portion (48) of the collar (42); an outer portion (17) arranged to engage with the lumen (19) of the elongated body (20) at the first end (24) of the elongated body (20); and a raised portion (210) defining a face (215) that is arranged to abut the first end (24) of the elongated body (20) for limiting a travel of the wedge member (46) into the lumen (19) of the elongated body (20).

8. An apparatus (10) for supporting a rock body according to claim 7, wherein: each wedge segment has a recess (270) running radially about an outer surface (280) of the segment; and biasing means are disposed within the recesses (270) of the wedge segments for biasing the wedge segments collectively in a closed position.

9. An apparatus (10) for supporting a rock body according to any of claims 6 to 8, wherein the nose portion (45) is substantially tapered.

10. An apparatus (10) for supporting a rock body according to claim 9, wherein the nose portion (45) comprises a section that is substantially knurled to provide a gripping section (15).

11. An apparatus (10) for supporting a rock body according to any preceding claim, wherein: a peripheral end (52) of the elongated support member (50) comprises a substantially threaded portion (53); a press plate (60) attaches to the peripheral end (52) of the elongated support member (50) and abuts the elongated body (20) of the first portion (12) of the apparatus (10); a nut (55) complementary to the threaded portion (53) threadedly engages with the threaded portion (53); and the thrust plate (62) is disposed between the nut (55) and the press plate (60).

12. An apparatus (10) for supporting a rock body according to claim 11, wherein the press plate (60) comprises a seating recess (60a) complementary to the second end (22) of the first portion (12) of the apparatus (10).

13. An apparatus (10) for supporting a rock body according to any preceding claim, wherein a stop means (56) is affixed to the elongated support member (50) for limiting travel of the elongated support member (50) through the lumen (44) of the collar (42).

14. An apparatus (10) for supporting a rock body according to claim 13, wherein the stop means (56) comprises a raised resilient portion (210) having a diameter greater than a diameter of the lumen (44) of the resilient collar (42).

15. A ground support apparatus (10) according to any of claims 11 to 14, wherein the nut (55) is a locking nut.

16. An apparatus (10) for supporting a rock body according to claim 15, wherein the locking nut comprises vibration damping means.

17. An apparatus (10) for supporting a rock body according to claim 16, wherein the vibration damping means comprises a polymer portion.

18. An apparatus (10) for supporting a rock body according to any of claims 11 to 17, wherein a substantially cylindrical seat (61) having a substantially tapered top end (61a): attaches to the peripheral end (52) of the elongated support member (50); and is disposed between the nut (55) and the thrust plate (62).