Self drilling point anchored bolt

Abstract

A self-drilling rock bolt (100, 300) including: a drill head (102) to be rotated in a first direction to form a borehole (202); a shaft (152) extending between a leading end portion (156a) and a trailing end portion (156b), the leading end portion of the shaft being coupled to the drill head such that rotation of the shaft in the first direction enables the shaft to rotate the drill head whereas rotation of the shaft in a second direction opposite the first direction enables the leading end portion of the shaft to move relative to the drill head; and an expansion mechanism (170) arranged to move relative to the drill head from a retracted configuration to an expanded configuration to anchor the rock bolt in the borehole, the expansion mechanism being operatively associated with the shaft such that rotation of the shaft in the second direction enables the leading end portion of the shaft to engage the expansion mechanism thereby moving the expansion mechanism from the retracted configuration to the expanded configuration.

Description

SELF DRILLING POINT ANCHORED BOLTField

[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] Rock bolts are typically used in stabilising the roof or wall of mines, tunnels or other ground excavations by securing or anchoring the rock bolt within a borehole drilled into the face of the rock to be stabilised.

[0003] Self-drilling rock bolts may provide a single drilling and anchoring function, negating the need for a separate drill rod to drill a borehole for subsequent insertion and anchoring of a standard rock bolt therein.

[0004] Disadvantageously, such self-drilling rock bolts may be expensive, heavy, cumbersome, difficult and time consuming to install correctly, and / or unreliable.Summary of Invention

[0005] It is an object of the present invention to substantially overcome or ameliorate at least one drawback of present arrangements or to provide a useful alternative.

[0006] In one aspect, the invention provides a self-drilling rock bolt including: a drill head to be rotated in a first direction to form a borehole; a shaft extending between a leading end portion and a trailing end portion, the leading end portion of the shaft being coupled to the drill head such that rotation of the shaft in the first direction enables the shaft to rotate the drill head whereas rotation of the shaft in a second direction opposite the first direction enables the leading end portion of the shaft to move relative to the drill head; and an expansion mechanism arranged to move relative to the drill head from a retracted configuration to an expanded configuration to anchor the rock bolt in the borehole, theexpansion mechanism being operatively associated with the shaft such that rotation of the shaft in the second direction enables the leading end portion of the shaft to engage the expansion mechanism thereby moving the expansion mechanism from the retracted configuration to the expanded configuration.

[0007] In one or more embodiments, the drill head includes a hollow body defining a cavity, with the expansion mechanism being located with respect to the cavity for movement relative to the body of the drill head.

[0008] In one or more embodiments, the leading end portion of the shaft is coupled to the drill head so that rotation of the shaft in the second direction is able to advance the leading end portion of the shaft into the cavity.

[0009] In one or more embodiments, in the retracted configuration, the expansion mechanism has a first width which does not exceed a maximum width of the drill head corresponding to a diameter of the borehole to be formed, and, in the expanded configuration, the expansion mechanism has a second width which exceeds the maximum width of the drill head.

[0010] In one or more embodiments, the expansion mechanism includes a plurality of expansion elements providing for the movement of the expansion mechanism from the retracted configuration to the expanded configuration, wherein, in the retracted configuration, a majority of each of the elements is located within the cavity to define the first width of the expansion mechanism, and wherein, in the expanded configuration, a majority of each of the elements is located outside the cavity to define the second width of the expansion mechanism.

[0011] In one or more embodiments, the expansion mechanism further includes a deformable retainer arranged with respect to each of the expansion elements, the retainer being configured to deform from a first state, in which the retainer maintains the expansion elements in the retracted configuration, to a second state, in which the retainer yields or fails to enable the expansion elements to move to the expanded configuration.

[0012] In one or more embodiments, the retainer is in the form of an annular ring arranged to partially encompass a periphery of each of the expansion elements.

[0013] In one or more embodiments, the ring is comprised of a polymeric material.

[0014] In one or more embodiments, the leading end portion of the shaft is configured to engage each of the expansion elements as the shaft is rotated in the second direction.

[0015] In one or more embodiments, the drill head has a leading end to engage a blind end of the borehole as the drill head is rotated in the first direction, and wherein the leading end portion of the shaft is configured to push each of the expansion elements relative to the body of the drill head towards the leading end of the drill head as the shaft is rotated in the second direction.

[0016] In one or more embodiments, the drill head includes a plurality of bearing surfaces, and wherein each of the expansion elements includes an engagement surface for complementary sliding engagement with a respective one of the bearing surfaces to cause movement of the expansion elements from the retracted configuration to the expanded configuration as the leading end portion of the shaft pushes each of the expansion elements.

[0017] In one or more embodiments, the self-drilling rock bolt further includes a stopping mechanism formed at the leading end portion of the shaft and operatively associated with the drill head to inhibit relative rotation between the shaft and the drill head as the shaft is rotated in the first direction whilst permitting relative rotation between the shaft and the drill head as the shaft is rotated in the second direction.

[0018] In one or more embodiments, the stopping mechanism is in the form of a mechanical stop which projects from the leading end portion of the shaft to engage a portion of the drill head as the shaft is rotated in the first direction.

[0019] In one or more embodiments, the leading end portion of the shaft is coupled to the drill head via a threaded coupling.

[0020] In one or more embodiments, the drill head has an axis of rotation around which the drill head is rotatable in the first direction to form the borehole, with the leading end portion of the shaft being coupled to the drill head such that rotation of the shaft in the second direction enables the leading end portion of the shaft to move axially relative to the drill head.

[0021] An aspect of the present disclosure provides a rock bolt including: a head to be inserted into a borehole;a shaft extending between a leading end portion and a trailing end portion, the leading end portion of the shaft being coupled to the head such that rotation of the shaft in a first direction enables the leading end portion of the shaft to move relative to the head; and an expansion mechanism arranged to move relative to the head from a retracted configuration to an expanded configuration to anchor the rock bolt in the borehole, the expansion mechanism being operatively associated with the shaft such that rotation of the shaft in the first direction enables the leading end portion of the shaft to engage the expansion mechanism thereby moving the expansion mechanism from the retracted configuration to the expanded configuration.

[0022] Another aspect of the present disclosure provides a self-drilling rock bolt including: a drill head to be rotated in a drilling direction to form a borehole; a hollow shaft extending between a leading end portion and a trailing end portion, the leading end portion of the shaft being coupled to the drill head such that rotation of the shaft in the drilling direction enables the shaft to rotate the drill head; and a conduit extending between the shaft and the drill head to promote fluid flow from the shaft through the drill head.Brief Description of Drawings

[0023] 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:

[0024] FIG. l is a fragmentary, perspective view of a rock bolt according to an embodiment;

[0025] FIG. 1A is an enlarged detail view of part of FIG. 1, showing drill tip inserts of the rock bolt of FIG. 1;

[0026] FIG. 2 is an enlarged detail, three-quarter sectioned, isometric view of a drill head of the rock bolt of FIG. 1;

[0027] FIG. 3 is a fragmentary, front view of the rock bolt of FIG. 1;

[0028] FIG. 4 is a cross-sectioned, right-side view of the rock bolt taken along line A-A of FIG.

[0029] FIG. 5 is a fragmentary, perspective view of the rock bolt of FIG. 1, shown with an expansion mechanism of the rock bolt removed;

[0030] FIG. 6 is a fragmentary, front view of the rock bolt of FIG. 5;

[0031] FIG. 7 is a cross-sectioned, right-side view of the rock bolt taken along line B-B of FIG. 6;

[0032] FIG. 8 is a fragmentary, cross-sectioned, front view of a partially completed drilling operation of a rock bolt installation utilising the rock bolt of FIG. 1;

[0033] FIG. 9 is a fragmentary, cross-sectioned, front view of a completed drilling operation of the rock bolt installation utilising the rock bolt of FIG. 1;

[0034] FIG. 10 is a fragmentary, cross-sectioned, front view of a partially completed anchoring operation of the rock bolt installation utilising the rock bolt of FIG. 1;

[0035] FIG. 11 is a fragmentary, cross-sectioned, front view of a completed anchoring operation of the rock bolt installation utilising the rock bolt of FIG. 1;

[0036] FIG. 12 is an enlarged detail, fragmentary, cross-sectioned, front view of a completed rock bolt installation utilising the rock bolt of FIG. 1;

[0037] FIG. 13 is a fragmentary, perspective view of a rock bolt according to another embodiment, shown with a portion of an expansion mechanism of the rock bolt removed;

[0038] FIG. 14 is a fragmentary, front view of the rock bolt of FIG. 13; and

[0039] FIG. 15 is a cross-sectioned, right-side view of the rock bolt taken along line W-W of FIG. 14.Description of Embodiments

[0040] Referring firstly to FIG. 1 of the accompanying drawings, a self-drilling rock bolt 100 according to an embodiment is depicted. The rock bolt 100 is configured to be anchored in aself-drilled borehole 202 (see FIG. 8) to secure the roof or wall of a mine, tunnel or other ground excavation, as will be described in detail below.

[0041] In the embodiment depicted, the rock bolt 100 is rotatable in a clockwise direction during a drilling operation from a point of view of an operator. The clockwise direction is also referred to as a right-handed direction. Throughout this specification, various features of the rock bolt 100 will be referred to as “leading” or “trailing”, with this terminology indicating features that lead or trail respectively as the rock bolt 100 rotates in the intended manner during the drilling operation. Alternate embodiments are envisaged where the rock bolt is configured to be rotated in a counterclockwise or left-handed direction during a drilling operation. In either form, the direction of intended rotation during a drilling operation may be referred to as a firsthanded direction or a drilling direction.

[0042] As shown in FIG. 1, the rock bolt 100 includes a generally elongated drill head 102 having a bifurcated leading (drilling) end 102a and a trailing (coupling) end 102b. The drill head 102 has an axis of rotation X extending between the leading and trailing ends 102a, 102b of the drill head 102. The drill head 102 is configured to be rotated around the axis of rotation X in the drilling direction to form the borehole 202. The drill head 102 is particularly configured for forming a borehole in rock strata, although the drill head 102 may be configured to form a borehole in other rock bodies or solid mediums.

[0043] The drill head 102 includes a tapered region 104 adjacent to and spaced from the leading end 102a of the drill head 102, a pair of cutter arms 106 projecting longitudinally from the tapered region 104 towards the leading end 102a of the drill head 102, a shank 108 adjacent the trailing end 102b of the drill head 102, and a shell body 110 (see FIG. 5) connecting the tapered region 104 and the shank 108. In the embodiment depicted, the shell body 110 is integrally formed with the tapered region 104 and the shank 108.

[0044] The tapered region 104 includes a plurality of external facets 112 each of which tapers in a direction toward the leading end 102a of the drill head 102 from the shell body 110 and terminates at a free end 114 of the tapered region 104. Each of the facets 112 is generally planar or slightly rounded and inclined relative to the axis of rotation X to facilitate conveying or clearing of cuttings or chips away from the leading end 102a of the drill head 102 as the borehole 202 is drilled. A passageway 116 (see FIG. 2) extends axially through the taperedregion 104 and communicates with an exterior of the tapered region 104 via a mouth or port 118 formed through the free end 114 of the tapered region 104.

[0045] In the embodiment depicted, each of the cutter arms 106 is integrally formed at a base thereof with respective adjoining facets 112 of the tapered region 104 and contoured therewith. In other embodiments, each of the cutter arms 106 may be brazed, welded, soldered, threaded, bonded, slotted within or otherwise secured to the tapered region 104. The cutter arms 106 project from the tapered region 104 in an opposing relationship with respect to the axis of rotation X to form a generally “wing-like” configuration. Whilst two cutter arms are shown, other embodiments are envisaged where the drill head includes one cutter arm axially projecting from the free end of the tapered region, or more than two cutter arms circumferentially arranged around the tapered region.

[0046] Each of the cutter arms 106 has a longitudinal extent which extends from the base and terminates at a free end 120 beyond the port 118 of the tapered region 104 adjacent to the leading end 102a of the drill head 102. The longitudinal extent of each of the cutter arms 106 is optimised to adequately space the free end 114 of the tapered region 104 from the leading end 102a of the drill head 102 whilst ensuring sufficient rigidity or stiffness of the cutter arm 106.

[0047] Each of the cutter arms 106 has a seat 122 which is rectangularly recessed at the free end 120 of the cutter arm 106. To further facilitate the clearing of the chips, an adjoining pair of flutes 124a, 124b are formed along each of the cutter arms 106 and which spirally extend in a right-handed direction from the respective seat 122 towards the tapered region 104.

[0048] To facilitate drilling of the borehole 202, the drill head 102 further includes first and second drill tip inserts 126a, 126b each of which is engaged to a respective seat 122 of each of the cutter arms 106. Each of the drill tip inserts 126a, 126b may be brazed, welded, soldered, bonded, integrally formed with or otherwise secured to the respective cutter arm 106. Other embodiments are contemplated in which the drill head 102 does not include drill tip inserts and instead utilises a hardened cutter arm to facilitate drilling of the borehole 202.

[0049] With particular reference to FIG. 1 A, each of the drill tip inserts 126a, 126b is formed, such as by grinding, to provide first and second cutting edges 128a, 128b which are each inclined relative to each other and intersect at a cutting point 130 to define the leading end 102a of the drill head 102. Preferably, each of the cutting edges 128a, 128b is formed of carbidematerial, such as tungsten carbide, although the cutting edges 128a, 128b (and more generally, the drill tip inserts 126a, 126b) may be formed of hardened steel or other suitable material depending upon the material to be drilled. A relief surface 132a, 132b recedes from each of the first and second cutting edges 128a, 128b, respectively, to provide clearance from the rock material being drilled to reduce drag and friction as the drill head 102 rotates in the intended manner during the drilling operation.

[0050] Each of the drill tip inserts 126a, 126b has parallel first and second margin edges 134a, 134b which each extend longitudinally in a direction parallel with the axis of rotation X. Each of the first cutting edges 128a extends from the cutting point 130 to the corresponding first margin edge 134a. Likewise, each of the second cutting edges 128b extends from the cutting point 130 to the corresponding second margin edge 134b. Each of the drill tip inserts 126a, 126b has a cutting face 136 having a transverse extent or width which is defined between the first and second margin edges 134a, 134b of each of the drill tip inserts 126a, 126b.

[0051] In the embodiment depicted, the drill tip inserts 126a, 126b are offset with respect to each other to define a gap between the second margin edge 134b of the first drill tip insert 126a and the first margin edge 134a of the second drill tip insert 126b when these edges are projected on a plane which extends along and is coincident with the axis of rotation X. Other embodiments are contemplated in which the drill tip inserts 126a, 126b are positioned with respect to each other so that there is a minimal or no gap between the second margin edge 134b of the first drill tip insert 126a and the first margin edge 134a of the second drill tip insert 126b when these edges are projected on the plane which extends along and is coincident with the axis of rotation X. Each of the cutting faces 136 is orientated such that a normal vector of each of the cutting faces 136 points generally in the direction of tangential velocity of the respective cutting face 136 as the drill head 102 rotates in the drilling direction. Each of the cutting faces 136 is also slightly inclined relative to the axis of rotation X to further enhance cutting efficiency. In this arrangement, a distance between a point of intersection A of the first margin edge 134a and first cutting edge 128a of the first drill tip insert 126a and a point of intersection B of the second margin edge 134b and second cutting edge 128b of the second drill tip insert 126b defines a maximum width of the drill head 102, which in turn determines a diameter of the borehole 202 to be drilled.

[0052] With particular reference to FIG. 5, the shell body 110 is generally cylindrical in geometric form and has a lengthwise extent between the shank 108 and the tapered region 104. An outer diameter of the shell body 110 is slightly less than the maximum width of the drill head 102 to minimise engagement with the wall 202a (see FIG. 8) of the borehole 202 as the borehole 202 is drilled. The shell body 110 is hollow to define an internal cavity 138 of the drill head 102 which longitudinally extends between the tapered region 104 and the shank 108, and has a width determined by an inner diameter of the shell body 110. The cavity 138 is fluidly communicable with the passageway 116 of the tapered region 104.

[0053] A majority of the lengthwise extent of the shell body 110 is cutaway through to the cavity 138 to form a pair of generally rectangular apertures 140 (see FIG. 6) on either side of the cavity 138, opening the cavity 138 to an exterior of the shell body 110. The remainder of the shell body 110 forms a pair of laterally opposing arcuate sidewalls 142a, 142b bordering either side of the apertures 140, and which longitudinally extend between the tapered region 104 and the shank 108 to partially surround the cavity 138 of the drill head 102.

[0054] With particular reference to FIGs. 4 and 5, the shank 108 has a bottom surface 108a, which defines the trailing end 102b of the drill head 102, and a cylindrical sidewall 144 extending from the bottom surface 108a to the shell body 110. An external surface of the sidewall 144 of the shank 108 is continuous with an external surface of each of the arcuate sidewalls 142a, 142b of the shell body 110 (see FIG. 5). The shank 108 has an outer arcuate edge 146 which circumferentially extends between respective points of intersection of the external surfaces of the arcuate sidewalls 142a, 142b of the shell body 110 with the external surface of the sidewall 144 of the shank 108. An annular ledge or shoulder surface 148 (see FIG. 5) extends from the outer arcuate edges 146 of the shank 108 and projects radially inwardly towards the axis of rotation X. The shank 108 further includes a central bore or hole 150 extending between the shoulder surface 148 and the bottom surface 108a of the shank 108 (that is, the trailing end 102b of the drill head 102). In the embodiment depicted, the hole 150 is internally threaded in a left-handed direction along its length.

[0055] The rock bolt 100 further includes an elongate load bearing element in the form of a rigid shaft, rod or bar 152. The bar 152 has a length longitudinally extending between leading and trailing ends 152a, 152b of the bar 152 (see FIG. 4). The bar 152 will typically be formed of steel but other suitable materials may be utilised such as fibre reinforced polymers. The bar 152may have any of various lengths and diameters selected to suit the reinforcement or performance requirements for the particular borehole in which the rock bolt 100 is to be installed.

[0056] With particular reference to FIG. 5, the bar 152 has a central bore 154 and an external left-handed thread along its length to define threaded leading and trailing end portions 156a, 156b adjacent the leading and trailing ends 152a, 152b, respectively, of the bar 152.

[0057] The external thread of the leading end portion 156a of the bar 152 is threadingly engaged with the internal thread of the shank 108 (see FIG. 4) to couple the bar 152 with the drill head 102. Preferably, the internal thread of the shank 108 is configured to threadingly engage an R25 thread of the bar 152. As shown in FIG. 7, the bar 152 is threadingly engaged with the shank 108 until the leading end 152a of the bar 152 is located within the cavity 138 of the drill head 102 and clears the shoulder surface 148 of the shank 108 by a height or spacing S defined as the axial distance between the leading end 152a of the bar 152 and the shoulder surface 148 of the shank 108.

[0058] With particular reference to FIGs. 5 and 7, a stopping mechanism 158 is formed at the leading end portion 156a of the bar 152 and projects within the spacing S between the leading end 152a of the bar 152 and the shoulder surface 148 of the shank 108. The stopping mechanism 158 projects laterally towards the inner diameter of the shell body 110 but terminates short thereof to permit free rotation of the stopping mechanism 158 within the cavity 138 of the drill head 102. In the embodiment depicted, the stopping mechanism 158 is in the form of a mechanical stop or pin 158 which projects from a hole drilled through the leading end portion 156a of the bar 152. In other embodiments, the stopping mechanism may be in the form of a coiled pin, dowel, weld, swage, deformation or other enlargement at the leading end portion of the bar 152 which is sized to locate within the spacing S between the leading end 152a of the bar 152 and the shoulder surface 148 of the shank 108, and which terminates short of the inner diameter of the shell body 110 for rotating freely within the cavity 138.

[0059] The stopping mechanism or pin 158 is configured to engage the shoulder surface 148 of the shank 108 as the bar 152 attempts to eject or unscrew from the drill head 102 as the bar 152 is rotated in the drilling direction relative to the drill head 102 (by virtue of the opposite-handed thread of the bar 152). When such engagement occurs, the pin 158 locks the bar 152 with respect to the drill head 102 due to friction between the pin 158 and the shoulder surface 148 ofthe shank 108, allowing the bar 152 to rotate the drill head 102 in the drilling direction. In other words, the pin 158 enables conjoined or simultaneous rotation of the bar 152 and the drill head 102 in the drilling direction. Optionally, a fillet 160 (see FIG. 5) may be provided between the shoulder surface 148 of the shank 108 and the respective arcuate sidewall 142a, 142b of the shell body 110 to facilitate the frictional engagement as the bar 152 is rotated in the drilling direction. Rotation of the bar 152 in a direction opposite the drilling direction (that is, in a counterclockwise or left-handed direction) relative to the drill head 102 separates or disengages the pin 158 from the shoulder surface 148, enabling the leading end portion 156a of the bar 152 to threadedly advance into the cavity 138 of the drill head 102 along the axis of rotation X.

[0060] In other embodiments, the stopping mechanism may engage a spiral groove, keyway or slot having a blind end formed through the shoulder surface 148 of the shank 108 to inhibit relative rotation between the bar 152 and drill head 102 as the bar 152 is rotated in the drilling direction, whilst permitting relative rotation between the bar 152 and drill head 102 as the bar 152 is rotated in the direction opposite the drilling direction. Other locking means may be employed to selectively inhibit and permit relative rotation between the bar 152 and drill head 102. For example, a locking mechanism could be provided which fixes the shank 108 onto the leading end portion of the bar 152 as the bar 152 is rotated in the drilling direction and releases the shank 108 when the bar 152 is rotated in the direction opposite the drilling direction.

[0061] Referring back to FIG. 1, the rock bolt 100 further includes an end fitting in the form of a hexagonal threaded drive nut 162, anti-friction washer 164 (see FIG. 8) and dome washer 166 which are each mounted on the thread of the trailing end portion 156b of the bar 152, with the drive nut 162 threadingly engaging the thread of the trailing end portion 156b for tensioning of the rock bolt 100, as will be discussed below. The drive nut 162 is typically provided with a mechanism 168 which fixes the drive nut 162 onto the thread of the trailing end portion 156b up to a threshold torque at which the mechanism 168 fails, enabling the drive nut 162 to be threadingly advanced along the thread of the trailing end portion 156b. In the embodiment depicted, the mechanism is in the form of a shear pin 168 which is inserted through a hole drilled between the sidewall of the drive nut 162 and into the bar 152. Other known mechanisms for selectively fixing the drive nut 162 to the bar 152 may be utilised as desired.

[0062] With particular reference to FIGs. 2 and 4, the rock bolt 100 further includes an expansion mechanism 170 which is operable to anchor the rock bolt 100 in the borehole 202. Inthe embodiment depicted, the expansion mechanism 170 includes a plurality of expansion members or elements in the form of leaves 172. Whilst two leaves are shown, other embodiments are envisaged where the expansion mechanism includes more than two leaves or only one leaf.

[0063] Each of the apertures 140 of the shell body 110 is sized to accommodate for placement and movement of the leaves 172 with respect to the cavity 138 of the drill head 102. Each of the leaves 172 are configured to move with respect to the shell body 110 from a first (retracted) configuration to a second (deployed or expanded) configuration to effectively increase the overall width of the expansion mechanism 170.

[0064] In the retracted configuration (see FIG. 8), a majority of each of the leaves 172 is located within the cavity 138 of the drill head 102 such that each of the leaves 172 are in a tight-fitting or cramped relationship with respect to each other to define a first width of the expansion mechanism 170 which does not exceed the maximum width of the drill head 102. In the retracted configuration, the tight-fitting arrangement of the leaves 172 also functions to generally seal the cavity 138 of the drill head 102 from the exterior of the rock bolt.

[0065] In the expanded configuration (see FIG. 11), a majority of each of the leaves 172 is located outside the cavity 138 of the drill head 102 such that each of the leaves 172 are in a separated or spread relationship with respect to each other to define a second width of the expansion mechanism 170 which exceeds the maximum width of the drill head 102.

[0066] With particular reference to FIG. 4, each of the leaves 172 includes an outer side 174 to face the exterior of the rock bolt 100, and an inner side 178 to face one another. The outer side 174 of each of the leaves 172 is serrated defining a series of ridges in the form of curved wedges 176 for engagement with the wall 202a of the borehole 202. The inner side 178 of each of the leaves 172 includes a laterally projecting abutment in the form of an overhang 180 which is configured to overlie the hole 150 of the shank 108 and thus the leading end 152a of the bar 152. Part of the inner side 178 of each of the leaves 172 is cut or removed so that a tunnel 182 (see FIG. 2) is formed between each of the leaves 172 to permit fluid communication between the central bore 154 of the bar 152 and the passageway 116 of the tapered region 104 when the leaves 172 are in the retracted configuration. Each of the leaves 172 further includes a base orfoot 184 projecting away from the inner and outer sides 178, 174 of each of the leaves 172 for resting or standing on the respective shoulder surface 148 of the shank 108.

[0067] As shown in FIGs. 2 and 4, each of the leaves 172 is tapered in a direction away from the foot 184 to define a sloped engagement face 186 formed along a portion of the inner side 178 such that the pair of engagement faces 186 form a generally “V”-shaped cross-section parallel with the axis of rotation X when the leaves 172 are in the retracted configuration. The tapered region 104 includes a pair of bearing faces 188 to respectively oppose the engagement faces 186, with each bearing face 188 being formed on a periphery of the tapered region 104 between the facets 112 of the tapered region 104 and the corresponding aperture 140 of the shell body 110. Each of the bearing faces 188 is sloped or inclined relative to the axis of rotation X to complement the slope of the corresponding engagement face 186 such that sliding engagement between each of the bearing faces 188 of the tapered region 104 and the corresponding engagement face 186 of each of the leaves 172 as the leaves 172 move relative to the drill head 102 towards the leading end 102a of the drill head 102 causes the leaves 172 to move from the retracted configuration to the expanded configuration, that is, causes the leaves 172 to displace outwardly or radially expand with respect to the axis of rotation X. Other embodiments are envisaged in which each of the bearing faces and the corresponding engagement face may be keyed to each other via, for example, a cooperating slot and protrusion arrangement. In the retracted configuration, each of the bearing faces 188 is initially engaged with the corresponding engagement face 186 to promote the sliding engagement.

[0068] As shown in FIG. 2, the expansion mechanism 170 further includes a deformable retainer in the form of an annular band or ring 190 extending around or encompassing a flattened portion 192 formed on a periphery of the outer side 174 of each of the leaves 172 which interrupts the wedges 176. In one form, the ring 190 is formed of a heat shrink polymeric material that is in tight-fitting or compressive engagement around the leaves 172 to conform to the external geometric form of the expansion mechanism 170. The ring 190 is configured to deform from a first state, in which the ring 190 biases or maintains the leaves 172 in the retracted configuration (such as via compression or application of hoop stress), to a second state, in which the ring 190 yields or fails, enabling the leaves 172 to move to the expanded configuration. The first and second states of the ring 190 may be provided by virtue of the mechanical behavior of the polymeric material of the ring 190, that is by exhibiting initial elastic deformation followed by yielding into a region of plastic deformation upon application ofincreased stress. In other embodiments, the ring may be in the form of tape, a split ring, a rubber band, spring steel ring or other flexible element which is configured to exhibit the first and second states.

[0069] In other embodiments, the ring may be replaced by a frangible connection between each of the leaves 172 which maintains the leaves 172 in the retracted configuration up to a threshold tensile force at which the frangible connection fails, enabling the leaves 172 to move to the expanded configuration.

[0070] Installation of the rock bolt 100 will now be described with reference to FIGs. 8 to 12.

[0071] The rock bolt 100 is firstly loaded on to an installation rig 194, with a standard plate washer 196 fitted to the rock bolt 100 and positioned against a rock face 198 of the rock strata 200 to be stabilised. In this initial step, the ring 190 is in the first state to maintain the leaves 172 in the retracted configuration.

[0072] The rig 194 is then operated to commence the drilling operation by advancing or thrusting the drill head 102 against the rock face 198, whilst simultaneously rotating the bar 152 via the drive nut 162 in the drilling direction (that is, the right-handed direction). Initially, the bar 152 rotates relative to the drill head 102 as the drill head 102 is held steady against the rock face 198 until the pin 158 at the leading end portion 156a of the bar 152 engages the shoulder surface 148 of the shank 108. Once sufficient frictional engagement between the pin 158 at the leading end portion 156a of the bar 152 and the shoulder surface 148 of the shank 108 has occurred, rotation from the bar 152 is imparted to the drill head 102 so that both the bar 152 and the drill head 102 rotate in unison in the drilling direction. As the bar 152 rotates the drill head 102 in the drilling direction, the cutting edges 128a, 128b of each of the drill tip inserts 126a, 126b engage the rock strata 200 and begin forming the borehole 202.

[0073] During the drilling operation, an optional water delivery subassembly (not shown) may be fitted to the rig 194 to supply water under pressure to the rock bolt 100 from an external source for wet drilling. In this way, the fluid communication between the central bore 154 of the bar 152, the internal cavity 138, the tunnel 182 between the leaves 172 and the passageway 116 and port 118 of the tapered region 104 forms a flushing channel or path through the rock bolt 100 to supply water under pressure to the leading end 102a of the drill head 102 to flush the borehole 202 during the drilling operation. In other embodiments, the flushing channel may beconfigured to deliver air, grout or resin through the rock bolt 100 to the exterior of the drill head 102 via the port 118. In other embodiments, vacuum drilling or other drilling methods may be employed to negate the need for the central bore 154 of the bar 152, the tunnel 182 between the leaves 172 and the passageway 116 and port 118 of the tapered region 104. As shown in FIG. 8, a sealing member 195 is optionally provided to form a fluid seal between the rig 194 and the trailing end 152b of the bar 152 during the drilling operation, substantively minimising drilling water from leaking from the interface between the rig 194 and the bar 152.

[0074] The rig 194 continues to thrust the rock bolt 100 toward the blind end 204 of the borehole 202 whilst simultaneously rotating the bar 152 in the drilling direction until a borehole having a desired (or slightly less than desired) longitudinal extent or depth is formed. At this stage, the drilling operation concludes to permit commencement of an anchoring operation to anchor the rock bolt 100 in the borehole 202.

[0075] To begin the anchoring operation, the rig 194 rotates the bar 152 in the left-handed direction (that is, the direction opposite the drilling direction) whilst simultaneously thrusting the drill head 102 against the blind end 204 of the borehole 202 to hold the drill head 102 steady, thereby causing the bar 152 to rotate relative to the drill head 102 which disengages the pin 158 from the shoulder surface 148 and threadedly advances the leading end portion 156a of the bar 152 into the cavity 138 of the drill head 102. During this step, the dome washer 166 has also engaged the plate washer 196 in a typical manner.

[0076] Further thrust and simultaneous left-handed rotation of the bar 152 causes the leading end 152a of the bar 152 to directly engage the overhang 180 of each of the leaves 172 which pushes each of the leaves 172 relative to the shell body 110 and the tapered region 104 toward the leading end 102a of the drill head 102 (that is, towards the blind end 204 of the borehole 202), forcing the engagement face 186 of each of the leaves 172 to slidingly engage the corresponding bearing face 188 of the tapered region 104. At this stage, the ring 190 experiences a tensile force produced by virtue of the sliding engagement which is sufficient to configure the ring 190 into the second state (that is, causes the ring to yield or fail) enabling the leaves 172 to move to the expanded configuration whereby the wedges 176 on the outer side 174 of each of the leaves 172 engage the wall 202a of the borehole 202, compressing the surrounding rock strata 200.

[0077] The rig 194 then, without thrust, rotatably drives the drive nut 162 in the left-handed direction at an increased torque that results in failure of the shear pin 168 fixing the drive nut 162 onto the bar 152. Further torque applied to the drive nut 162 thus threads the drive nut 162 along the trailing end portion 156b of the bar 152. Continued driving of the drive nut 162 bears the drive nut 162 against the anti -friction washer 164 which in turn bears the dome washer 166 and plate washer 196 firmly against the rock face 198. Application of further torque to the drive nut 162 tensions the bar 152 by drawing the drill head 102 with respect to the leaves 172 away from the blind end 204 of the borehole 202 (via the threaded coupling between the leading end portion 156a of the bar 152 and the hole 150 of the shank 108) until the engagement faces 186 of each of the leaves 172 binds the tapered region 104, effectively point-anchoring the rock bolt 100 to complete the installation.

[0078] A self-drilling rock bolt 300 according to another embodiment is depicted in FIGs. 13 to 15 of the accompanying drawings. The rock bolt 300 is of an identical configuration to the rock bolt 100 of the first embodiment, except that the rock bolt 300 is provided with a pipe, conduit or tube 316 to convey or promote fluid flow through the drill head 102. As shown in FIG. 15, the tube 316 is arranged along the flushing channel or path defined between the central bore 154 of the bar 152, the internal cavity 138, the tunnel 182 between the leaves 172, the passageway 116 and the port 118 of the tapered region 104. The tube 316 effectively bridges the longitudinal gap or spacing between the central bore 154 of the bar 152 and the port 118 of the tapered region 104 to minimise fluid leakage therebetween, thereby providing a sealed passageway through the drill head 102 to promote fluid flow directly between the central bore 154 of the bar 152 and the exterior of the tapered region 104. The tube 316 is configured to be collapsible or is otherwise displaceable as the bar 152 threadedly advances into the cavity 138 of the drill head 102.

[0079] The rock bolt 300 also differs to the rock bolt 100 in that the stopping mechanism of the rock bolt 300 is formed from a separate component 358 in lieu of the pin 158. In the embodiment depicted, the separate component is in the form of a collar 358 which is welded or otherwise fixed to the leading end 152a of the bar 152, terminating short of the inner diameter of the shell body 110 for rotating freely within the cavity 138.

[0080] The rock bolt 300 also includes a sealing connector 395 fitted to the trailing end portion 156b of the bar 152 for sealing engagement with the rig 194 in a similar manner to the sealing member 195 of the rock bolt 100.

[0081] 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 15. For features that are identical between the rock bolt 100 and the rock bolt 300, it will be appreciated that the above description of those features in relation to the rock bolt 100 is also applicable to the corresponding identical features found in the rock bolt 300. 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.

[0082] The rock bolt 100, 300 according to the present disclosure may provide improved anchoring reliability via the direct engagement of the bar 152 with the expansion leaves 172 as the bar 152 advances through the cavity 138 of the drill head 102. By virtue of this arrangement, greater clearances may be permitted between the wedges 176 of the leaves 172 and the borehole 202 during the drilling operation, thereby enabling a greater annulus between the rock bolt 100 and wall 202a of the borehole 202 to facilitate, for example, flushing of the borehole 202.Reference Numeral List100 Rock bolt according to a first embodiment102 Drill head102a Leading end of drill head102b Trailing end of drill headX Axis of rotation104 Tapered region106 Cutter arm108 Shank108a Bottom surface of shank110 Shell body112 Facet of the tapered region114 Free end of tapered region116 Passageway118 Port120 Free end of cutter arm122 Seat of cutter arm124a, 124b Flutes126a, 126b Drill tip inserts128a, 128b Cutting edges 130 Cutting point132a, 132b Relief surfaces 134a, 134b Margin edges 136 Cutting face138 Cavity of drill head140 Aperture142a, 142b Arcuate sidewalls144 Sidewall of shank146 Outer arcuate edge of shank148 Shoulder surface of shank150 Hole through shank152 Bara Leading end of bar b Trailing end of barCentral bore of bar a Leading end portion of barb Trailing end portion of bar SpacingStopping mechanism / PinFilletDrive nutAnti -friction washerDome washerShear pinExpansion mechanismLeavesOuter side of leafWedgesInner side of leafOverhangTunnelFootEngagement faceBearing faceRingFlattened portion of leafInstallation rigSealing memberPlate washerRock faceRock strataBorehole a Wall of boreholeBlind end of boreholeRock bolt according to another embodiment Tube Collar Sealing connector

Claims

CLAIMS1. A self-drilling rock bolt including: a drill head to be rotated in a first direction to form a borehole; a shaft extending between a leading end portion and a trailing end portion, the leading end portion of the shaft being coupled to the drill head such that rotation of the shaft in the first direction enables the shaft to rotate the drill head whereas rotation of the shaft in a second direction opposite the first direction enables the leading end portion of the shaft to move relative to the drill head; and an expansion mechanism arranged to move relative to the drill head from a retracted configuration to an expanded configuration to anchor the rock bolt in the borehole, the expansion mechanism being operatively associated with the shaft such that rotation of the shaft in the second direction enables the leading end portion of the shaft to engage the expansion mechanism thereby moving the expansion mechanism from the retracted configuration to the expanded configuration.

2. The self-drilling rock bolt of claim 1, wherein the drill head includes a hollow body defining a cavity, with the expansion mechanism being located with respect to the cavity for movement relative to the body of the drill head.

3. The self-drilling rock bolt of claim 2, wherein the leading end portion of the shaft is coupled to the drill head so that rotation of the shaft in the second direction is able to advance the leading end portion of the shaft into the cavity.

4. The self-drilling rock bolt of claim 3, wherein, in the retracted configuration, the expansion mechanism has a first width which does not exceed a maximum width of the drill head corresponding to a diameter of the borehole to be formed, and wherein, in the expanded configuration, the expansion mechanism has a second width which exceeds the maximum width of the drill head.

5. The self-drilling rock bolt of claim 4, wherein the expansion mechanism includes a plurality of expansion elements providing for the movement of the expansion mechanism from the retracted configuration to the expanded configuration, wherein, in the retracted configuration, a majority of each of the elements is located within the cavity to define the first width of theexpansion mechanism, and wherein, in the expanded configuration, a majority of each of the elements is located outside the cavity to define the second width of the expansion mechanism.

6. The self-drilling rock bolt of claim 5, wherein the expansion mechanism further includes a deformable retainer arranged with respect to each of the expansion elements, the retainer being configured to deform from a first state, in which the retainer maintains the expansion elements in the retracted configuration, to a second state, in which the retainer yields or fails to enable the expansion elements to move to the expanded configuration.

7. The self-drilling rock bolt of claim 6, wherein the retainer is in the form of an annular ring arranged to partially encompass a periphery of each of the expansion elements.

8. The self-drilling rock bolt of claim 7, wherein the ring is comprised of a polymeric material.

9. The self-drilling rock bolt of any one of claims 5 to 8, wherein the leading end portion of the shaft is configured to engage each of the expansion elements as the shaft is rotated in the second direction.

10. The self-drilling rock bolt of claim 9, wherein the drill head has a leading end to engage a blind end of the borehole as the drill head is rotated in the first direction, and wherein the leading end portion of the shaft is configured to push each of the expansion elements relative to the body of the drill head towards the leading end of the drill head as the shaft is rotated in the second direction.

11. The self-drilling rock bolt of claim 10, wherein the drill head includes a plurality of bearing surfaces, and wherein each of the expansion elements includes an engagement surface for complementary sliding engagement with a respective one of the bearing surfaces to cause movement of the expansion elements from the retracted configuration to the expanded configuration as the leading end portion of the shaft pushes each of the expansion elements.

12. The self-drilling rock bolt of any one of the preceding claims further including a stopping mechanism formed at the leading end portion of the shaft and operatively associated with the drill head to inhibit relative rotation between the shaft and the drill head as the shaft is rotated inthe first direction whilst permitting relative rotation between the shaft and the drill head as the shaft is rotated in the second direction.

13. The self-drilling rock bolt of claim 12, wherein the stopping mechanism is in the form of a mechanical stop which projects from the leading end portion of the shaft to engage a portion of the drill head as the shaft is rotated in the first direction.

14. The self-drilling rock bolt of any one of the preceding claims, wherein the leading end portion of the shaft is coupled to the drill head via a threaded coupling.

15. The self-drilling rock bolt of any one of the preceding claims, wherein the drill head has an axis of rotation around which the drill head is rotatable in the first direction to form the borehole, with the leading end portion of the shaft being coupled to the drill head such that rotation of the shaft in the second direction enables the leading end portion of the shaft to move axially relative to the drill head.

Images