Field

[0001] The present invention relates to strata control in civil engineering and mining operations, and in particular relates to a rock bolt for securing the roof or wall of a mine, tunnel or other ground excavation.

Background

[0002] One known method of stabilizing the roof or wall of mines, tunnels or other ground excavations is to secure a rock bolt into a bore hole drilled into the face of the rock to be stabilized. Rock bolts are typically formed with an elongate load bearing element, commonly formed of a rigid steel bar.

[0003] A known method of installing such a rock bolt involves first drilling a bore hole into the rock face. A sausage-like two-component resin filled cartridge is then inserted into the bore hole, followed by the rock bolt which pushes the resin filled cartridge towards the blind end of the bore hole. The rock bolt is then rotated by the installation rig which also thrusts the rock bolt upwardly whilst it is rotating to mix the resin components and shred the frangible cartridge casing, pushing it towards the blind end of the bore hole. Rotation of the rock bolt is then stopped for a few seconds to allow the resin to cure. The bolt is then tensioned by threading a nut along the threaded trailing end portion of the rock bolt, bearing the nut against a plate washer that engages the rock face adjacent to the bore hole opening.

[0004] Various means have previously been proposed to be formed with, or mounted on, the leading end portion of the rigid bar to assist in mixing of the resin components. Disadvantageously, such means do not adequately contribute to the geotechnical load carrying benefit of the rock bolt.

Object

[0005] It is an object of the present invention to substantially overcome, or at least ameliorate, the above disadvantage. Summary of Invention

[0006] The invention provides a rock bolt having a longitudinal axis and to be encapsulated within a settable material in a bore hole, the bolt including: an elongate bar having a length longitudinally extending between a bar leading end portion and a bar trailing end portion, the length including: an anchor portion trailing the leading end portion to at least aid in anchoring the bar in the settable material encapsulating the rock bolt; and a bar portion extending between the anchor portion and the trailing end portion, the bar portion having a first portion and a second portion, the first portion extending between the second portion and the anchor portion, with the second portion being configured to elongate at least upon application of a service load to the bar, wherein the anchor portion has an enlarged section relative to the first portion of the bar portion; and an element at least partially constrained to and extending along the first portion, to be bonded to the settable material to at least aid in resisting longitudinal displacement of the enlarged section of the anchor portion relative to the element at least upon application of the load to the bar.

[0007] In one or more embodiments, the element is a wire.

[0008] In one or more embodiments, the enlarged section is radially enlarged with respect to the axis.

[0009] In one or more embodiments, the enlarged section has a non-circular transverse cross- section.

[0010] In one or more embodiments, the anchor portion is a first anchor portion and the length includes a second anchor portion trailing the first anchor portion and leading the trailing end portion, with the second anchor portion having an enlarged section, and with the bar portion extending between the first and second anchor portions.

[0011] In one or more embodiments, the bar portion has a third portion extending between the second anchor portion and the second portion. [0012] In one or more embodiments, the wire is a first wire and the rock bolt further includes a second wire at least partially constrained to and extending along the third portion, wherein the second wire is configured to be bonded to the settable material to at least aid in resisting longitudinal displacement of the enlarged section of the second anchor portion relative to the second wire at least upon application of the load to the bar.

[0013] In one or more embodiments, the first wire helically extends along a longitudinal extent of the first portion between a first wire end and a second wire end.

[0014] In one or more embodiments, the longitudinal extent of the first portion is greater than a longitudinal extent of the first anchor portion.

[0015] In one or more embodiments, the second wire helically extends along a longitudinal extent of the third portion between a first wire end and a second wire end.

[0016] In one or more embodiments, the longitudinal extent of the third portion is greater than a longitudinal extent of the second anchor portion.

[0017] In one or more embodiments, the rock bolt further includes a ferrule to at least partially constrain the first wire end to the bar.

[0018] In one or more embodiments, the first wire end is welded to a portion of the ferrule.

[0019] In one or more embodiments, the ferrule is crimped onto the bar.

[0020] In one or more embodiments, the longitudinal extent of the third portion is different to the longitudinal extent of the first portion.

[0021] In one or more embodiments, the length further includes: a first deformation portion extending between the first and second portions to constrain the first wire to the first portion; and a second deformation portion extending between the second and third portions to constrain the second wire to the third portion.

Brief Description of Drawings [0022] Exemplary embodiments of the present disclosure will now be described, by way of examples only, with reference to the accompanying description and drawings in which:

[0023] FIG. l is a fragmentary, isometric view of a rock bolt according to a first embodiment;

[0024] FIG. 2 is a fragmentary, front elevation view of the rock bolt of FIG. 1;

[0025] FIG. 3 is an enlarged detail view of portion A of the rock bolt of FIG. 2;

[0026] FIG. 4 is an enlarged detail view of portion B of the rock bolt of FIG. 2;

[0027] FIG. 5 is an enlarged detail view of portion C of the rock bolt of FIG. 2;

[0028] FIG. 6 is a partially cross-sectioned, front elevation view of a partially completed rock bolt installation utilising the rock bolt of FIG. 1;

[0029] FIG. 7 is a partially cross-sectioned, front elevation view of a completed rock bolt installation utilising the rock bolt of FIG. 1;

[0030] FIG. 8 is a fragmentary, isometric view of a rock bolt according to a second embodiment;

[0031] FIG. 9 is a fragmentary, front elevation view of the rock bolt of FIG. 8;

[0032] FIG. 10 is an enlarged detail view of portion A of the rock bolt of FIG. 9;

[0033] FIG. 11 is an enlarged detail view of portion B of the rock bolt of FIG. 9;

[0034] FIG. 12 is an enlarged detail view of portion C of the rock bolt of FIG. 9;

[0035] FIG. 13 is a fragmentary, isometric view of a rock bolt according to a third embodiment;

[0036] FIG. 14 is a fragmentary, front elevation view of the rock bolt of FIG. 13;

[0037] FIG. 15 is an enlarged detail view of portion A of the rock bolt of FIG. 14; [0038] FIG. 16 is an enlarged detail view of portion B of the rock bolt of FIG. 14;

[0039] FIG. 17 is an enlarged detail view of portion C of the rock bolt of FIG. 14;

[0040] FIG. 18 is a fragmentary, isometric view of a rock bolt according to a fourth embodiment;

[0041] FIG. 19 is a fragmentary, front elevation view of the rock bolt of FIG. 18;

[0042] FIG. 20 is a fragmentary, isometric view of a rock bolt according to a fifth embodiment;

[0043] FIG. 21 is a fragmentary, front elevation view of the rock bolt of FIG. 20;

[0044] FIG. 22 is an enlarged detail view of portion A of the rock bolt of FIG. 21;

[0045] FIG. 23 is an enlarged detail view of portion B of the rock bolt of FIG. 21;

[0046] FIG. 24 is a fragmentary, isometric view of a rock bolt according to a sixth embodiment;

[0047] FIG. 25 is a fragmentary, front elevation view of the rock bolt of FIG. 24;

[0048] FIG. 26 is an enlarged detail view of portion A of the rock bolt of FIG. 25;

[0049] FIG. 27 is an enlarged detail view of portion B of the rock bolt of FIG. 25;

[0050] FIG. 28 is an enlarged detail view of portion C of the rock bolt of FIG. 25;

[0051] FIG. 29 is a partially cross-sectioned, front elevation view of a partially completed rock bolt installation utilising the rock bolt of FIG. 24;

[0052] FIG. 30 is a partially cross-sectioned, front elevation view of a completed rock bolt installation utilising the rock bolt of FIG. 24;

[0053] FIG. 31 is a fragmentary, isometric view of a rock bolt according to a seventh embodiment; [0054] FIG. 32 is a fragmentary, front elevation view of the rock bolt of FIG. 31;

[0055] FIG. 33 is a fragmentary, isometric view of a rock bolt according to an eighth embodiment;

[0056] FIG. 34 is a fragmentary, front elevation view of the rock bolt of FIG. 33;

[0057] FIG. 35 is an enlarged detail view of portion A of the rock bolt of FIG. 34;

[0058] FIG. 36 is an enlarged detail view of portion B of the rock bolt of FIG. 34;

[0059] FIG. 37 is a fragmentary, isometric view of a rock bolt according to a ninth embodiment;

[0060] FIG. 38 is a fragmentary, front elevation view of the rock bolt of FIG. 37;

[0061] FIG. 39 is an enlarged detail view of portion A of the rock bolt of FIG. 38; and [0062] FIG. 40 is an enlarged detail view of portion B of the rock bolt of FIG. 38.

Description of Embodiments

[0063] Referring to FIGs. 1 to 5 of the accompanying drawings, a rock bolt 100 according to a first embodiment is depicted. The rock bolt 100 is configured for resin encapsulated installation in a bore hole 144 (FIGs. 6 and 7). It will, however, be appreciated that other settable materials may be utilised for encapsulating the rock bolt 100 during installation.

[0064] The rock bolt 100 has an elongate load bearing element in the form of a rigid bar 102. The bar 102 has a length 103 longitudinally extending between a bar leading end portion 104 and a bar trailing end portion 106. The bar 102 will typically be formed of steel. In other embodiments, the material of the bar 102 may be replaced by cable of suitable form.

[0065] The bar 102 may have any of various diameters selected to suit the particular bore hole 144 in which it is to be installed, and may typically have a diameter of between 12 and 30 mm, with a typical diameter being 24 mm to suit a 35 mm or 36 mm diameter borehole. It will be appreciated that the diameter of the borehole will vary generally proportionally to the particular diameter of the bar 102. The bar 102 will typically have an overall longitudinal length of the order of 1.8 to 2.4 m, but it will be appreciated that the bar 102 may have any length to suit the particular application. For example, the length of the bar 102 could be greater than 2.4 m, and particularly could be 3 m.

[0066] With particular reference to FIG. 2, the bar 102 is threaded at the trailing end portion 106 to define a threaded trailing end 107 of the bar 102. In the arrangement depicted, an end fitting in the form of a hexagonal threaded drive nut 108, anti-friction washer 109 and dome washer 110 is mounted on the thread of the trailing end portion 106, with the drive nut 108 threadingly engaging the thread of the trailing end portion 106 for tensioning of the rock bolt 100, as will be discussed below. The drive nut 108 is typically provided with a mechanism which fixes the drive nut 108 onto the thread of the trailing end portion 106 up to a predetermined torque at which the mechanism fails, enabling the drive nut 108 to be threadingly advanced along the thread of the trailing end portion 106. Such mechanism may take the form of a disc shaped insert (not shown) located in the trailing end of the aperture (not shown) extending through the drive nut 108. The insert engages the trailing end 107 as the drive nut 108 attempts to advance, locking the drive nut 108 onto the bar 102 until a predetermined torque is exceeded, at which the insert is ejected from the drive nut 108, allowing the drive nut 108 to advance along the thread of the trailing end portion 106. Other known mechanisms for selectively fixing the drive nut 108 to the bar 102 may be utilised as desired. For example, a shear pin (not shown) could be drilled and inserted between the sidewall of the drive nut 108 and into the bar 102. A standard plate washer 112 is mounted on the bar 102, engaging the dome washer 110 in a known manner.

[0067] In the embodiment depicted, the length 103 includes first and second anchor portions 114, 116. The anchor portions 114, 116 are preferably of a non-circular transverse cross- section. The first anchor portion 114 trails the leading end portion 104. The first anchor portion 114 is arranged adjacent to a leading end 120 of the rock bolt 100. The second anchor portion 116 trails the first anchor portion 114 and is longitudinally spaced therefrom.

[0068] Each of the anchor portions 114, 116 comprises at least one deformation integrally formed in the bar 102. In the embodiment depicted, each of the anchor portions 114, 116 includes a pair of first and second flattened paddle-like deformations 122, 124. Each of the paddle-like deformations 122, 124 is formed by locally forging the bar 102 to form a flattened ‘paddle’. Preferably, each of the paddle-like deformations 122, 124 is cold forged to facilitate work hardening. Each of the flattened paddle-like deformations 122, 124 has a reduced thickness as compared to the undeformed diameter of the bar 102 and an increased width as compared to the undeformed diameter of the bar 102. The first and second paddle-like deformations 122, 124 constituting each pair of paddle-like deformations are arranged mutually adjacent and oriented at least substantially mutually perpendicular. That is, the second paddle like deformation 124 is flattened in a direction substantially perpendicular to the direction of flattening of the first paddle-like deformation 122. The widened or broadened edges of the first paddle-like deformation 122 project laterally in a substantially perpendicular plane. For a 22 mm diameter bar, each of the paddle-like deformations 122, 124 typically has a length of the order of 60 mm, a width of the order of 30 mm and a thickness (at the location of minimum thickness) of the order of 12 mm. In this way, each of the paddle-like deformations 122, 124 has a widened or enlarged section relative to the diameter of the bar 102, that is, each of the paddle-like deformations 122, 124 has a width in transverse cross-section which is greater than a diameter of the bar 102. Each of the paddle-like deformations 122, 124, in use, at least aid in anchoring the bar 102 in resin encapsulating the rock bolt 100, as will be discussed below. In other embodiments, each of the anchor portions 114, 116 may be formed by a piece of metal welded to the bar 102 or a piece of metal swaged onto the bar 102, and shaped to provide the form of the paddle-like deformations 122, 124.

[0069] The length 103 further includes a bar portion 126 extending between the first and second anchor portions 114, 116. In the embodiment depicted, the bar portion 126 is relatively smooth. In other embodiments, the bar portion 126 may have a ribbed or threaded exterior profile. The bar portion 126 extends between the second paddle-like deformation 124 of the first anchor portion 114 and the first paddle-like deformation 122 of the second anchor portion 116. The bar portion 126 includes first and third portions 128, 130 and a second portion 132. The second portion 132 is preferably of a generally circular transverse cross-section. In the embodiment depicted, the first portion 128 is adjacent to and trails the first anchor portion 114 and constitutes about a third of the overall longitudinal extent of the bar portion 126. The third portion 130 is adjacent to and leads the second anchor portion 116 and constitutes about a third of the overall longitudinal extent of the bar portion 126. The second portion 132 extends between the first and third portions 128, 130 and constitutes the remaining third of the overall longitudinal extent of the bar portion 126. It will be appreciated, however, that the ratio of the longitudinal extent of each of the first and third portions 128, 130 and the second portion 132 relative to the bar portion 126 may be varied to suit the particular application. For example, the longitudinal extent of the second portion 132 may be significantly greater than the longitudinal extents of each of the first and third portions 128, 130. Preferably, the longitudinal extent of each of the first and third portions 128,130 is greater than a longitudinal extent of the respective anchor portion 114, 116. In other embodiments, the longitudinal extent of each of the first and third portions 128, 130 may be less than the longitudinal extent of the respective anchor portion 114, 116.

[0070] The second portion 132 is configured to be debonded from the resin, in use, as will be further discussed below. The second portion 132 has a smooth outer surface that results in debonding of the second portion 132 from the resin encapsulating the rock bolt 100 in use, upon application of a service load to the bar 102 which exceeds the shear bond strength between the resin and the smooth outer surface of the second portion 132. Accordingly, whilst when initially installed the second portion 132 may be relatively lightly bonded to the encapsulating resin, the resin readily debonds from the second portion 132 upon application of the service load. Such a load may result from movement or fracture of the rock that is resisted by yielding deformation of the second portion 132. It is also envisaged that a surface coating, such as a low-friction paint surface coating, may be applied to the second portion 132 to further promote debonding. Suitable surface coatings include low-friction, lubricating paints such as polyolefin based paints.

[0071] The rock bolt 100 further includes first and second resistance elements in the form of wires 134, 136 at least partially constrained to and extending over the full longitudinal extent of the respective first and third portions 128, 130. As shown in the detail views of FIGs. 3 to 5, each of the wires 134, 136 helically extends between a first wire end 138 and a second wire end 140 (only the end 138 of the wire 134 is shown in FIG. 3). Each wire end 138 terminates adjacent a respective anchor portion 114, 116. Each wire end 140 terminates adjacent the bar portion 126 and lies on a boundary defined between the respective first and third portions 128, 130 and the second portion 132. That is, the wire end 138 of the first wire 134 terminates adjacent the second paddle-like deformation 124 of the first anchor portion 114, and the wire end 140 of the first wire 134 terminates adjacent the bar portion 126 at the boundary between the first portion 128 and the second portion 132. Similarly, the wire end 138 of the second wire 136 terminates adjacent the first paddle-like deformation 122 of the second anchor portion 116, and the wire end 140 of the second wire 136 terminates adjacent the bar portion 126 at the boundary between the third portion 130 and the second portion 132. In this way, the wire end 138 of the first wire 134 leads the wire end 140 of the first wire 134. The wire end 138 of the second wire 136 trails the wire end 140 of the second wire 136. By this arrangement, the wires 134, 136 extend longitudinally inwardly relative to each of the anchor portions 114, 116. That is, the anchor portion 114 leads the wire 134, and the anchor portion 116 trails the wire 136. In other words, the anchor portions 114, 116 are arranged on the ‘outside’ of the wires 134, 136.

In one or more embodiments, the first wire 134 (and the corresponding first portion 128) may have a longitudinal extent which is greater than a longitudinal extent of the second wire 136 (and the corresponding third portion 130). Although, it will be appreciated that the wires 134, 136 may have varying lengths depending on the application.

[0072] The length 103 also preferably includes a tail portion 133 extending between the thread of the trailing end portion 106 and the second paddle-like deformation 124 of the second anchor portion 116. In the embodiment depicted, the tail portion 133 extends over a longitudinal extent generally equal to or greater than a longitudinal extent of the thread of the trailing end portion 106. The tail portion 133 is configured to ensure adequate positioning and resin encapsulation of the second wire 136 and second anchor portion 116 combination, that is, if resin is lost from the bottom of the drilled borehole.

[0073] As shown in FIGs. 4 and 5, the rock bolt 100 includes first and second ferrules 142a, 142b crimped onto the bar 102 adjacent the boundary between the respective first and third portions 128, 130 and the second portion 132. The ferrules 142a, 142b each have an outwardly- directed face configured to abut the respective wire ends 140 to hold each of the wires 134, 136 in their relative positions with respect to the bar 102. The ferrule 142b further includes an outwardly directed lug 143 configured for engagement and rotational driving of the wire end 140 of the second wire 136 during left handed rotation of the rock bolt 100. In other embodiments, the lug 143 may not be present. In yet other embodiments, the wire end 140 of the second wire 136 may be welded to the lug 143 to provide additional engagement of the wire end 140 thereby further preventing rotational slippage of the wire 136.

[0074] Each of the wires 134, 136 preferably helically extends in a direction opposing the intended direction of rotation of the rock bolt 100 during installation. Accordingly, for installation of the rock bolt 100 with a standard left-handed installation rig, each of the wires 134, 136 will typically helically extend in a right-handed direction as depicted. Each of the wires 134, 136 will be typically formed of steel. In some embodiments, a weld may be placed part way along the length of each of the wires 134, 136. For ease of manufacture, it may be permissible to place a tack weld on the wire ends 138 at the broadened edges of the respective paddle-like deformation 122, 124.

[0075] As will be discussed below, in use, each of the wires 134, 136 is configured to be substantially bonded to the resin to at least aid in resisting longitudinal displacement of the enlarged section of the respective anchor portion 114, 116 relative to the wire 134, 136 at least upon application of the service load to the bar 102. In this way, under the onset of dynamic ground loads, the second portion 132 will partially debond from the resin and start to slip. In turn, the paddle-like deformations 122, 124 arranged on the outer extremities of the wires 134, 136 will partially displace longitudinally and effectively ‘puli’ into the respective wire 134, 136 which is at least partially constrained to the first or third portion 128, 130. As the wires 134, 136 are well embedded and anchored within the set resin due to their open or helical geometry, and given the enlarged transverse width of the respective adjacent paddle-like deformation 122, 124 relative to the diameter of the bar 102, the wires 134, 136 increase resistance to the longitudinal displacement of the respective paddle-like deformation 122, 124, thereby adding to the anchoring force of the rock bolt 100. As resistance increases to the displacement of the paddle-like deformations 122, 124, the rock bolt 100 elongates to provide a load bearing response to the dynamic ground load. In the embodiment depicted, during installation, the first wire 134 is further configured for mixing of the resin, and the second wire 136 is further configured for retention of wet resin.

[0076] Installation of the rock bolt 100 of the first embodiment will now be described with reference to FIGs. 6 and 7 of the accompanying drawings. The anti -friction washer 109, dome washer 110, drive nut 108 and plate washer 112 are mounted on the thread of the trailing end portion 106. Typically, the anti -friction washer 109, dome washer 110, and drive nut 108 will be pre-assembled onto the bar 102 off-site and the plate washer 112 positioned on-site. The bore hole 144 is drilled into a rock face 146 to be stabilised, optionally with one or more sheets of reinforcing mesh (not shown) held against the rock face 146. A two-component resin filled cartridge 148 is then inserted into the bore hole 144. The rock bolt 100, with the assembled anti-friction washer 109, dome washer 110, drive nut 108 and plate washer 112 is mounted on an installation rig (not shown) and maneuvered toward the bore hole 144. As the rock bolt 100 is guided toward the bore hole 144, the leading end portion 104 assists in guiding the bar 102 into the bore hole 144. [0077] Once the leading end portion 104 is guided into the bore hole 144, the rock bolt 100 is thrust deeper into the bore hole 144 using the installation rig, pushing the resin filled cartridge 148 toward the blind end of the bore hole 144. As the rock bolt 100 is thrust toward the blind end of the bore hole 144, the installation rig also rotates the drive nut 108 of the rock bolt 100, in an anti-clockwise direction in the embodiment depicted. The insert (or other mechanism for selectively fixing the drive nut 108 to the bar 102) retains the drive nut 108 in a fixed relationship to the bar 102, such that rotation of the drive nut 108 results in rotation of the bar 102 in unison with the drive nut 108. When the cartridge 148 advances to the blind end of the bore hole 144, the leading end 120 ruptures the frangible casing of the cartridge 148, resulting in the resin flowing over the bar 102 in the narrow annulus defined between the bar 102 and the wall of the bore hole 144, where the two components of the resin are thoroughly mixed by the wires 134, 136. The wires 134, 136 may also assist in shredding the casing of the cartridge 148. With the wires 134, 136 helically extending in an opposing direction to the direction of rotation of the rock bolt 100, the resin is actively encouraged via an Archimedean pumping action towards the blind end of the bore hole 144, although sufficient resin will typically be utilised to substantially fill the annulus, thereby fully resin encapsulating the rock bolt 100. As the resin flows past the anchor portions 114, 116, the paddle-like deformations 122, 124 assist in further mixing of the resin, although they are typically less effective than the wires 134, 136 in mixing the resin. The resin is then allowed to cure for a few seconds.

[0078] After the resin has cured, the drive nut 108 is driven by the installation rig at an increased torque that results in failure of the insert fixing the drive nut 108 onto the bar 102. Further torque applied to the drive nut 108 thus threads the drive nut 108 along the thread of the bar trailing end portion 106. Continued driving of the drive nut 108 bears the drive nut 108 against the anti -friction washer 109 which in turn bears the dome washer 110 and plate washer 112 against the rock face 146, thereby resulting in tensioning of the bar 102. In a particularly preferred installation method, the two-component resin filled cartridge 148 contains two separate resins, with a relatively fast setting resin at the top or leading portion of the cartridge 148 used to encapsulate the leading end portion 104, the first anchor portion 114, the first portion 128 and the first wire 134, and a slower setting resin at the bottom or trailing portion of the cartridge 148 used to encapsulate the second portion 132, the third portion 130, the second wire 136 and the second anchor portion 116. In this configuration, the rock bolt 100 will be pretensioned once the first, faster setting resin has cured, anchoring the leading end portion 104, the first anchor portion 114, the first portion 128 and the first wire 134, but prior to the second, slower setting resin curing. This enables elongation of the second portion 132, the third portion 130 and the second anchor portion 116 within the second, slower setting resin during the pretensioning process. The separate fast and slow setting resins could alternatively be housed in separate cartridges.

[0079] In the completed installation, depicted in FIG. 7 (with the resin rendered clear for clarity), the first and second anchor portions 114, 116, and the first and second wires 134, 136 are firmly anchored within the resin, whilst the second portion 132 is debonded from, or only lightly bonded to, the resin by virtue of the smooth outer surface of the second portion 132. As a result, in the event of any movement or fracture of unstable rock the second portion 132 is able to yield over its full longitudinal extent, effectively “slipping” within the encapsulating resin, allowing the bar 102 to absorb movement of the rock over the second portion 132. As the second portion 132 begins to yield, the paddle-like deformations 122, 124 at the outer extremities of the wires 134, 136 will partially displace longitudinally and effectively ‘puli’ into the respective wire 134, 136. As the wires 134, 136 are well embedded and anchored within the set resin due to their open or helical geometry, and given the enlarged transverse width of the respective adjacent paddle-like deformation 122, 124 relative to the diameter of the bar 102, the wires 134, 136 increase resistance to the longitudinal displacement of the respective paddle-like deformation 122, 124, thereby adding to the anchoring force of the rock bolt 100. As resistance increases to the displacement of the paddle-like deformation 122, 124, the rock bolt 100 elongates to provide a load bearing response to the dynamic ground load.

[0080] In this way, not only do each of the first and second wires 134, 136 serve a primary purpose to mix and pump the two-component resin during the installation process, the wires 134, 136 also serve a secondary purpose of increasing load-transfer of the anchor portions 114, 116 by virtue of the arrangement of the wires inwardly relative to the anchor portions 114, 116. This surprising and counter intuitive result results in benefits in load-transfer performance and geotechnical ground support efficiencies.

[0081] It will be appreciated that the terms "primary" and "secondary" are used merely as labels, and are not intended to impose numerical requirements on or to establish a certain ranking of importance of their objects. A person skilled in the art will appreciate various other modifications and alterations of the rock bolt 100 may be made to suit specific applications. [0082] For example, each or any of the anchor portions 114, 116 may have more than a pair of flattened paddle-like deformations 122, 124. For example, embodiments with four or five paddle-like deformations comprising a first anchoring portion may serve to increase resin mixing and subsequent anchoring proximal to the leading end portion 104 of the bolt 100.

These additional paddle-like deformations may also help to guide the rock bolt 100 into the bore hole, reducing the tendency for the ends of the wires 134, 136 to catch at the entry of the bore hole. Alternatively, each or any of the anchor portions 114, 116 may have a single flattened paddle-like deformation.

[0083] Furthermore, although it is preferred for a pair of paddle-like deformations to be orientated mutually perpendicular, they are not limited to this arrangement. When an anchoring portion comprises more than a pair of paddle-like deformations, they may be orientated at various angles to one another.

[0084] Furthermore, although it is preferred for the rock bolt 100 to include wires as the resistance elements, the elements may alternatively be in the form of a wire cage device, steel sleeve or other suitable device to restrict or impede movement of the respective paddle-like deformation under load.

[0085] Furthermore, although it is preferred for the rock bolt 100 to be installed using cartridge resin, it is not limited to this application. The rock bolt 100 may alternatively be installed into pre- or post-injected resin, grout, or other embedment media.

[0086] A rock bolt 200 according to a second embodiment is depicted in FIGs. 8 to 12 of the accompanying drawings. The rock bolt 200 is of an identical configuration to the rock bolt 100 of the first embodiment, except that each of the wires 134, 136 are secured to an exterior face of the ferrule 142 by welding proximal to the wire end 140, as shown in FIGs. 11 and 12. Whilst welding each of the wires 134, 136 to the exterior face of the ferrule 142 will still result in heating of the underlying bar 102, given that the wires 134, 136 are not welded directly to the bar 102 will result in a significantly lower heat load being applied to the bar 102 such that there might not be any significant weakening of the bar.

[0087] The remaining features of the rock bolt 200 that are identical to the rock bolt 100 will thus not be further described and are provided with identical reference numerals in FIGs. 8 to 12. The rock bolt 200 is installed in the same manner as the rock bolt 100 of the first embodiment as described above, and behaves under load in substantially the same manner as the rock bolt 100 of the first embodiment.

[0088] A rock bolt 300 according to a third embodiment is depicted in FIGs. 13 to 17 of the accompanying drawings. The rock bolt 300 is of an identical configuration to the rock bolt 100 of the first embodiment, apart from the configuration of the ferrules 342a, 342b. Rather than a 360 degree ‘radial’ swage around the ferrules 342a, 342b, the swage is simply made by two opposed dies with the intent that the swage deforms the ferrules 342a, 342b and also partially deforms the bar 102 thereby providing a relatively simpler means of manufacture. The ferrule 342b has an outwardly directed lug 343 configured for engagement and rotational driving of the wire end 140 of the second wire 136 during left handed rotation of the rock bolt 300. In other embodiments, the lug 343 may not be present. In yet other embodiments, the wire end 140 of the second wire 136 may be welded to the lug 343 to provide additional engagement of the wire end 140 thereby further preventing rotational slippage of the wire 136.

[0089] The remaining features of the rock bolt 300 that are identical to the rock bolt 100 will thus not be further described and are provided with identical reference numerals in FIGs. 13 to 17. The rock bolt 300 is installed in the same manner as the rock bolt 100 of the first embodiment as described above, and behaves under load in substantially the same manner as the rock bolt 100 of the first embodiment.

[0090] A rock bolt 400 according to a fourth embodiment is depicted in FIGs. 18 and 19 of the accompanying drawings. The rock bolt 400 is of an identical configuration to the rock bolt 100 of the first embodiment, except that the rock bolt 400 omits ferrules. Rather, each of the wires 134, 136 are welded directly to the bar 102. For example, a weld may be placed part way along the length of each of the wires 134, 136, and/or each of the wire ends 138 are tack welded at the broadened edges of the respective paddle-like deformation 122, 124. In the embodiment depicted, the bar 102 is of a steel grade which permits welding so as to minimise structural weakening caused by heat generated through the welding process. For example, the bar 102 may be formed of medium tensile steel having a tensile strength of about 600 MPa.

[0091] The remaining features of the rock bolt 400 that are identical to the rock bolt 100 will thus not be further described and are provided with identical reference numerals in FIGs. 18 and 19. The rock bolt 400 is installed in the same manner as the rock bolt 100 of the first embodiment as described above, and behaves under load in substantially the same manner as the rock bolt 100 of the first embodiment.

[0092] A rock bolt 500 according to a fifth embodiment is depicted in FIGs. 20 to 23 of the accompanying drawings. The rock bolt 500 is of an identical configuration to the rock bolt 100 of the first embodiment, except that the rock bolt 500 omits ferrules. Rather the ends 138, 140 of each of the wires 134, 136 are directly swaged, as shown in FIGs. 22 and 23. Optionally, a weld may also be placed part way along the length of each of the wires 134, 136, and/or each of the wire ends 138 are tack welded at the broadened edges of the respective paddle-like deformation 122, 124. In other embodiments, the end 138 of the wire 134 and/or the end 140 of the wire 136 may be tapered to minimise the risk of the wire 134, 136 catching upon entry into the bore hole 144.

[0093] The remaining features of the rock bolt 500 that are identical to the rock bolt 100 will thus not be further described and are provided with identical reference numerals in FIGs. 20 to 23. The rock bolt 500 is installed in the same manner as the rock bolt 100 of the first embodiment as described above, and behaves under load in substantially the same manner as the rock bolt 100 of the first embodiment.

[0094] A rock bolt 600 according to a sixth embodiment is depicted in FIGs. 24 to 28 of the accompanying drawings. The rock bolt 600 is of an identical configuration to the rock bolt 100 of the first embodiment, apart from the provision of additional third and fourth deformations 614, 616. The third and fourth deformations 614, 616 are located proximal to the boundary between the respective first and third portions 128, 130 and the second portion 132. In this configuration, the second portion 132 extends between the third and fourth deformations 614, 616. In this manner, each ferrule 142 is held in position by the deformations 614, 616 so that the wires 134, 136 are retained in position.

[0095] The remaining features of the rock bolt 600 that are identical to the rock bolt 100 will thus not be further described and are provided with identical reference numerals in FIGs. 24 to 28. As shown in the installation views of FIGs. 29 and 30, the rock bolt 600 is installed in the same manner as the rock bolt 100 of the first embodiment as described above, and behaves under load in substantially the same manner as the rock bolt 100 of the first embodiment. [0096] A rock bolt 700 according to a seventh embodiment is depicted in FIGs. 31 and 32 of the accompanying drawings. The rock bolt 700 is of an identical configuration to the rock bolt 600 of the sixth embodiment, except that the rock bolt 700 omits ferrules and that the rock bolt 700 includes third and fourth deformation portions 714, 716 each having a pair of first and second flattened paddle-like deformations 722, 724. The paddle-like deformations 722, 724, 122, 124 are configured and oriented in a similar manner as the first and second paddle-like deformations 122, 124 of the first embodiment, albeit the paddle-like deformations 122, 722 of the seventh embodiment are oriented in the same manner as the paddle-like deformation 124 of the first embodiment, and, similarly, the paddle-like deformations 124, 724 of the seventh embodiment are oriented in the same manner as the paddle-like deformation 122 of the first embodiment. In this manner, the second portion 132 extends between the paddle-like deformation 724 of the third deformation portion 714 and the paddle-like deformation 722 of the fourth deformation portion 716. Additionally, the wire end 140 of the first wire 134 terminates adjacent the paddle like deformation 722 of the third deformation portion 714, and the wire end 140 of the second wire 136 terminates adjacent the paddle-like deformation 724 of the fourth deformation portion 716. In this manner, the wire 134 is held in position between the anchor portion 114 and deformation portion 714, and similarly, the wire 136 is held in position between the anchor portion 116 and deformation portion 716.

[0097] The remaining features of the rock bolt 700 that are identical to the rock bolt 600 will thus not be further described and are provided with identical reference numerals in FIGs. 31 and 32. The rock bolt 700 is installed in the same manner as the rock bolt 600 of the sixth embodiment as described above, and behaves under load in substantially the same manner as the rock bolt 600 of the sixth embodiment.

[0098] A rock bolt 800 according to an eighth embodiment is depicted in FIGs. 33 to 36 of the accompanying drawings. The rock bolt 800 is of an identical configuration to the rock bolt 100 of the first embodiment, except that the rock bolt 800 omits a second anchor portion, a third portion and a second wire. In the embodiment depicted, the second portion 132 extends between the first portion 128 and the thread of the trailing end portion 106. Also, the paddle like deformation 122 of the eighth embodiment is oriented in the same manner as the paddle-like deformation 124 of the first embodiment, and, similarly, the paddle-like deformation 124 of the eighth embodiment is oriented in the same manner as the paddle-like deformation 122 of the first embodiment. [0099] The remaining features of the rock bolt 800 that are identical to the rock bolt 100 will thus not be further described and are provided with identical reference numerals in FIGs. 33 to 36. The rock bolt 800 is installed in the same manner as the rock bolt 100 of the first embodiment as described above, and behaves under load in substantially the same manner as the rock bolt 100 of the first embodiment, except with reduced anchoring force within the encapsulating resin as compared to the rock bolt 100.

[0100] A rock bolt 900 according to a ninth embodiment is depicted in FIGs. 37 to 40 of the accompanying drawings. The rock bolt 900 is of an identical configuration to the rock bolt 800 of the eighth embodiment, except that the rock bolt 900 includes the second anchor portion 116. In the embodiment depicted, the second portion 132 extends between the first portion 128 and the paddle-like deformation 122 of the second anchor portion 116.

[0101] The remaining features of the rock bolt 900 that are identical to the rock bolt 800 will thus not be further described and are provided with identical reference numerals in FIGs. 37 to 40. The rock bolt 900 is installed in the same manner as the rock bolt 800 of the eighth embodiment as described above, and behaves under load in substantially the same manner as the rock bolt 800 of the eighth embodiment, except with increased anchoring force within the encapsulating resin as compared to the rock bolt 800.

Reference list 200 rock bolt according to a second embodiment

100 rock bolt according to a first embodiment 300 rock bolt according to a third

102 bar embodiment

103 length 342a first ferrule

104 bar leading end portion 342b second ferrule

106 bar trailing end portion 343 lug

107 trailing end

108 drive nut 400 rock bolt according to a fourth

109 anti -friction washer embodiment

110 dome washer

112 plate washer 500 rock bolt according to a fifth

114 first anchor portion embodiment

116 second anchor portion

120 leading end 600 rock bolt according to a sixth

122 first paddle-like deformation embodiment

124 second paddle-like deformation 614 third deformation

126 bar portion 616 fourth deformation

128 first portion

130 third portion 700 rock bolt according to a seventh

132 second portion embodiment

133 tail portion 714 third deformation portion

134 first wire 716 fourth deformation portion

136 second wire 722 first paddle-like deformation

138 first wire end 724 second paddle-like deformation

140 second wire end

142a first ferrule 800 rock bolt according to an eighth

142b second ferrule embodiment

143 lug

144 bore hole 900 rock bolt according to a ninth

146 rock face embodiment

148 resin filled cartridge