AU2016202822A1 - Friction bolt assembly - Google Patents

Abstract

FRICTION BOLT ASSEMBLY Abstract A friction bolt assembly (100) is provided. The friction bolt assembly (100) comprises a friction bolt body (110) longitudinally extending between a friction bolt body leading end (111) and a friction bolt body trailing end (112). The friction bolt body (110) defines a cavity (113) longitudinally extending through the friction bolt body (110). The friction bolt assembly (100) further comprises a rod (120) longitudinally extending through the cavity (113) between a rod leading end (121) and a rod trailing end (122); and a stopping means mounted on, or integrally formed with, the rod (120) and being longitudinally positioned between the friction bolt body leading end (111) and the friction bolt body trailing end (112). A first collar (117) is fixed to the friction bolt body (110) at or adjacent the friction bolt body trailing end (112). The stopping means and the first collar (117) are dimensioned to cooperate to at least substantially prevent the rod (120) from ejecting completely from the friction bolt body (110) through the friction bolt body trailing end (112). 1~o too c Figure 1

Description

ι 2016202822 03 May 2016

FRICTION BOLT ASSEMBLY

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

Background [0002] A current method of stabilizing the roof or wall of an underground mine involves the use of friction bolts, otherwise known as friction rock stabilizers. Friction bolts have a generally cylindrical body and a collar welded to the trailing end of the body. The leading end portion of the body is generally tapered to assist in inserting the friction bolt into a bore hole drilled into the rock strata. The body is split down one side such that, when it is driven into a slightly undersized hole in the rock strata, the friction bolt body deforms to reduce the size of the split in the body. This deformation exerts radial forces against the wall of the hole, providing a corresponding frictional force, retaining the friction bolt within the hole.

[0003] In a friction bolt previously proposed, additional anchoring of the friction bolt is achieved by way of an expansion element, which provides a point anchoring effect. During installation, the expansion element is retracted from a first position, located outside the friction bolt body, to a second position, located substantially within the friction bolt body, via actuation of a rod threadably connected to the expansion element. The expansion element radially deforms the friction bolt body in the second position, thereby point anchoring the friction bolt body within the bore hole.

[0004] It has been found that surrounding ground movement after installation can create additional loads in shear and/or tension on the friction bolt, which can lead to the rod fracturing. Once fractured, there may be a risk of the tail end of the rod ejecting with considerable force out of the trailing end of the friction bolt body.

Object of the Invention [0005] It is an object of the present invention to substantially overcome or ameliorate at least the above problem of known friction bolts, or to at least to provide a useful alternative.

AH25(9582247_1):MHT 2 2016202822 03 May 2016

Summary of the Invention [0006] The present invention provides a friction bolt assembly comprising: a friction bolt body longitudinally extending between a friction bolt body leading end and a friction bolt body trailing end, said friction bolt body defining a cavity longitudinally extending through said friction bolt body; a rod longitudinally extending through said cavity between a rod leading end and a rod trailing end; a stopping means mounted on, or integrally formed with, said rod and being longitudinally positioned between said friction bolt body leading end and said friction bolt body trailing end; a first collar fixed to said friction bolt body at or adjacent said friction bolt body trailing end; wherein said stopping means and said first collar are dimensioned to cooperate to at least substantially prevent said rod from ejecting completely from the friction bolt body through the friction bolt body trailing end.

[0007] In one or more embodiments, said first collar has an aperture for receiving said rod longitudinally therethrough, said stopping means being wider than the aperture, in one or more lateral directions, for at least substantially preventing said rod from ejecting completely therethrough. Preferably, said aperture is substantially cylindrical.

[0008] In one or more embodiments, said stopping means has a transverse cross-sectional area greater than a maximum cross-sectional area of said aperture.

[0009] In one or more embodiments, said stopping means is longitudinally positioned substantially within a half of said rod adjacent said rod trailing end.

[0010] In one or more embodiments, said stopping means comprises one or more swaged portions of the rod formed with the rod. Preferably, said stopping means comprises three swaged portions. Preferably, said swaged portions are spaced apart longitudinally along said rod.

[0011] In one or more embodiments, said stopping means comprises one or more sleeves. Preferably, said one or more sleeves are each in the form of a ferrule.

AH25(9582247 1):MHT 3 2016202822 03 May 2016 [0012] In one or more embodiments, said stopping means comprises one or more welds.

[0013] In one or more embodiments, said first collar has a maximum external width substantially identical to the maximum external width of said friction bolt body.

[0014] In one or more embodiments, said friction bolt assembly further comprises a second collar longitudinally positioned between said first collar and said rod trailing end, said second collar being freely movable along said rod.

[0015] In one or more embodiments, said friction bolt body comprises failure means formed thereon and being longitudinally positioned at, or adjacent to, a mid-section of said friction bolt body, wherein said failure means is dimensioned to form a weakened region in said friction bolt body.

[0016] In one or more embodiments, said failure means comprises one or more slots formed on said friction bolt body so as to expose said cavity. Preferably, said failure means comprises two slots. Preferably, said slots are spaced apart and axially aligned.

Brief Description of the Drawings [0017] Preferred embodiments of the present invention will now be described, by way of examples only, with reference to the accompanying drawings, wherein: [0018] Figure 1 is a front elevation view of an embodiment of a friction bolt assembly; [0019] Figure 2 is a fragmentary isometric view of the rod of the friction bolt assembly of Figure i; [0020] Figure 3 is a cross-sectional view of a partially completed installation of the friction bolt assembly of Figure 1; [0021] Figure 4 is a cross-sectional view of a completed installation of Figure 3; [0022] Figure 5 is a cross-sectional view of the completed installation of Figure 4, with a fractured and partially ejected rod;

AH25(9582247_1):MHT 4 2016202822 03 May 2016 [0023] Figure 6 is a fragmentary isometric view of an alternative embodiment of the rod of Figure 2; [0024] Figure 7 is a front elevation view of a second embodiment of a friction bolt assembly, pre-installation; [0025] Figure 8 is a partially cross-sectioned view of a completed installation of the friction bolt assembly of Figure 7; [0026] Figure 9 is a partially cross-sectioned view of the completed installation of Figure 8, with a deformed and elongated rod; [0027] Figure 10 is a partially cross-sectioned view of the completed installation of Figure 8, with a fractured and partially ejected rod.

[0028] Figure 11 is a front elevation view of a third embodiment of a friction bolt assembly, preinstallation; [0029] Figure 12 is a side elevation view of the friction bolt assembly of Figure 11; [0030] Figure 13 is a rear elevation view of the friction bolt assembly of Figure 11; [0031] Figure 14 is a partially cross-sectioned front view of a completed installation of the friction bolt assembly of Figure 11, with a fractured friction bolt body; [0032] Figure 15 is a partially cross-sectioned rear view of the completed installation of Figure 14; and [0033] Figure 16 is a partially cross-sectioned view of a completed installation of Figure 14, with a fractured rod.

Description of Embodiments [0034] Figures 1 and 2 show a first embodiment of a friction bolt assembly 100. The friction bolt assembly 100 has a generally tubular friction bolt body 110 that longitudinally extends between a friction bolt body leading end 111 and a friction bolt body trailing end 112. The friction bolt

AH25(9582247_1):MHT 5 2016202822 03 May 2016 body 110 defines a cavity 113 longitudinally extending through the friction bolt body 110. The friction bolt body 110 has a split 114 extending along the friction bolt body 110 to the friction bolt body leading end 111 to allow for radial compression of the friction bolt body 110 in the usual manner. Here the split 114 extends along the full length of the friction bolt body 110 from the friction bolt body trailing end 112. The friction bolt body 110 has a tapered leading portion 115 that tapers toward the friction bolt body leading end 111 in the usual manner to enable the friction bolt body 110 to be driven into a bore hole having a smaller diameter than the constant diameter of the primary portion 116 of the friction bolt body 110. A collar 117 is welded to the friction bolt body 110 adjacent the friction bolt body trailing end 112. The collar 117 has a substantially cylindrical aperture (not shown) extending therethrough. In the particular embodiment depicted, the aperture of the collar 117 has a diameter between approximately 23.8 to 24.0 mm.

[0035] In one embodiment, the external diameter of the primary portion 116 of the friction bolt body 110, being the maximum diameter of the friction bolt body 110, is approximately 47 mm, whilst the cross-section of the leading portion 115 of the friction bolt body 110 at the friction bolt body leading end 111 is of a reduced cross-sectional area, being the minimum cross-sectional area of the friction bolt body 110. In one embodiment, the cross-section of the leading portion 115 at the friction bolt body leading end 111 is of an oval configuration having a maximum lateral axis diameter of 40 mm and minor lateral axis diameter of 26 mm, although it is also envisaged that the leading portion 115 at the friction bolt leading 111 may be generally circular. In one embodiment, the wall thickness of the friction bolt body 110 is approximately 3 mm. The friction bolt body 110 is typically formed of structural grade steel.

[0036] The friction bolt assembly 100 further includes an elongate rod 120 longitudinally extending through the aperture of the collar 117 and the cavity 113 in the friction bolt body 110 between a rod leading end 121 and a rod trailing end 122. In one embodiment, the maximum diameter of the rod 120 is approximately 23.5 mm, which is less than the aperture diameter of the collar 117. The rod 120 is typically formed of rigid steel bar.

[0037] The friction bolt assembly 100 further comprises a stopping means longitudinally positioned substantially within a half of the rod 120 adjacent the rod trailing end 122. The stopping means is dimensioned to cooperate with the collar 117 such that in the event that the rod 120 fails, the stopping means will engage with the collar 117 to at least substantially prevent the rod 120 from ejecting completely from the friction bolt body 110 through the friction bolt

AH25(9582247_1):MHT 6 2016202822 03 May 2016 body trailing end 112. In the embodiment depicted in Figure 2, the stopping means is in the form of three swaged portions 118a, 118b, 118c integrally formed with the rod 120 and are longitudinally positioned adjacent each other between the friction bolt body leading end 111 and the friction bolt body trailing end 112. Each of the swaged portions 118a, 118b, 118c has a transverse cross-sectional area greater than a maximum cross-sectional area of the aperture of the collar 117. In one embodiment, each of the swaged portions 118a, 118b, 118c is wider than the aperture diameter of the collar 117 in one or more lateral directions. In this particular embodiment, the effective lateral width is between approximately 25 to 27 mm, which is greater than the aperture diameter of the collar 117, so as to prevent the rod 120 from ejecting completely from the friction bolt body 110.

[0038] An expansion element 130 is also mounted on the rod 120. The expansion element 130 is typically located toward the rod leading end 121 and in the embodiment depicted the expansion element 130 is located at or adjacent the rod leading end 121. The expansion element 130 is threadingly mounted onto a threaded leading portion 123 of the rod 120. The threaded leading portion 123 of the rod 120 is received within an aperture 133 extending through the expansion element 130. The expansion element 130 is in the general form of a body of revolution having a frusto-conical tapered leading surface 134 extending and tapering to a closed expansion element leading end 131, a generally cylindrical mid-surface 135 trailing the leading surface 134 and defining the maximum diameter of the expansion element 130 and a trailing generally frusto-conical engagement surface 136 that tapers, here in a non-linear manner, from the mid-surface 135 to the expansion element trailing end 132. Here the engagement surface 136 has a slightly concave form. In the embodiment depicted, the maximum diameter of the expansion element 130, defined by the mid-surface 135, is approximately 43 mm. This is greater than the internal diameter of the friction bolt body 110 at the friction bolt body leading end 111 and less than the maximum diameter of the friction bolt body 110.

[0039] The expansion element 130 may further comprise means, for at least substantially preventing rotation of the expansion element 130 relative to the friction bolt body 110. In this embodiment, the means is in the form of a surface feature of the expansion element 130, particularly in the form of a key 137. The key 137 projects from, and is integrally formed with, the engagement surface 136 and extends from the expansion element trailing end 132 to the midsurface 135. The key 137 projects into the split 114 formed in the friction bolt body 110. As a result, rotation of the rod 120, which would tend to rotate the expansion element 130, results in the key 137 engaging an edge of the friction bolt body 110 bounding the split 114, preventing

AH25(9582247_1):MHT 7 2016202822 03 May 2016 relative rotation, at least beyond minor movement associated with the free play of the key 137 within the slightly broader width of the split 114 at the friction bolt leading end 111.

[0040] The friction bolt assembly 100 further comprises a drive head 140 threadingly mounted on the rod 120 at or adjacent the rod trailing 122. In the particular embodiment depicted, the drive head 140 is in the form of an open hexagonal nut that is threadingly mounted on a threaded trailing portion 124 of the rod 120. A sacrificial plastic sheathing (not shown) may cover the exposed region of the threaded trailing portion 124 so as to avoid the thread of the threaded trailing portion 124 being fouled by debris during transport and handling in the mine. In the embodiment depicted, the drive head 140 is provided with a coarse thread 141 on its hexagonal drive faces to allow for securing of a roof mesh to the friction bolt assembly 100 after installation.

[0041] The threaded leading portion 123 and threaded trailing portion 124 of the rod 120 are like handed, each having a left handed thread for installation with a standard installation rig configured to rotate in an anti-clockwise direction, although it is also envisaged that both the threaded leading portion 123 and threaded trailing portion 124 may be right handed, for installation by clockwise rotation of an installation rig.

[0042] To initially secure the expansion element 130 and drive head 140 on the rod 120 during transportation and handling, the expansion element 130 may be tack welded to the rod 120 adjacent the rod leading end 121 and the drive head 140 tack welded to the rod 120 adjacent the rod trailing end 122. The tack welds would then fail during rotation of the expansion element 130 and drive head 140 relative to the rod 120 during installation. Alternatively, after mounting the expansion element 130 and drive head 140 on the rod 120, the thread of the threaded leading portion 123 and threaded trailing portion 124 of the rod 120 may be crimped or otherwise deformed adjacent to the rod leading and trailing ends 121, 122 respectively. The expansion element 130 and drive head 140 may then be reverse threaded to abut against the crimp to temporarily lock the expansion element 130/drive head 140 to the rod 120 and specifically prevent the expansion element 130 and drive head 140 from unscrewing off the rod 120 during transport and handling. As another alternative, heat shrink material may be applied over the expansion element 130 and adjacent portion of the threaded leading portion 123 of the rod 120, both to protect the expansion element 130 during transport and any rough handling and also to secure the expansion element 130 on the rod 120. During installation, the heat shrink would be

AH25(9582247 1):MHT 8 2016202822 03 May 2016 tom away by rotation of the rod 120, allowing relative movement between the expansion head 130 and rod 120.

[0043] Installation of the friction bolt assembly 100 will now be described with reference to Figures 3 and 4. Firstly, a bore hole 10 is drilled into the rock face 12 of a rock strata 11 to be stabilized. In the embodiment depicted, the bore hole 10 is drilled with a standard installation rig (not shown) with a drill bit having a diameter of 43 mm, which will typically result in a bore hole diameter of 44 to 45 mm. Accordingly, the maximum diameter of the friction bolt body 110 (being approximately 47 mm in a preferred embodiment) is slightly greater than the diameter of the bore hole 10, so as to provide for an interference fit in the usual manner, whilst the maximum diameter of the expansion element 130, here being approximately 43 mm, is less than the maximum diameter of the friction bolt body 110 and slightly less than the diameter of the bore hole 10 such that the expansion element 130 may be readily inserted into the bore hole 10.

[0044] Before inserting the friction bolt assembly 100 into the bore hole 10, a plate washer 170 (and optionally a ball washer) is mounted on the friction bolt body 110 adjacent the collar 117 and the friction bolt assembly 100 is mounted on the installation rig, particularly with the drive head 140 being received within a mating socket of the installation rig. The installation rig then drives the friction bolt assembly 100 into the bore hole 10, applying percussive force via the drive head 140 (and rod trailing end 122) until the plate washer 170 is firmly engaged with the rock face 12. The frictional forces due to the interference fit between the friction bolt body 110 and bore hole wall 13 retain the friction bolt assembly 100 in the bore hole 10, and allow for the transfer of loads between the rock strata 11 and the friction bolt body 110.

[0045] Additional anchoring of the friction bolt body 110 in the bore hole 10 is achieved by way of the expansion element 130, which provides a point anchoring effect. This is achieved by actuating the rod 120 by rotating the drive head 140. Specifically, the drive head 140 is driven in a direction tending to advance the drive head 140 along the threaded trailing portion 124 of the rod 120 (here in an anti-clockwise direction). During rotation of the drive head 140, as tension in the rod 120 increases, friction due to inter-engagement of the threaded trailing portion 124 of the rod 120 with the internal thread of the drive head 140 will tend to rotate the rod 120. This in turn will tend to advance the threaded leading portion 123 of the rod 120 through the expansion element 130, rotation of which is substantially prevented by virtue of the key 137 in the manner described above. Accordingly, during rotation of the drive head 140, the expansion element 130 will be drawn toward the friction bolt body trailing end 112 into the cavity 113, tending to

AH25(9582247_1):MHT 9 2016202822 03 May 2016 outwardly deform the friction bolt body 110 at the friction bolt body leading end 111 as shown in Figure 4. In particular, the expansion element 130 is drawn fully into the tapered leading portion 115 of the friction bolt body 110, which is radially outwardly deformed by both the engagement surface 136 and mid-surface 135 of the expansion element 130, bearing the leading portion 115 of the friction bolt body 110 against the bore hole 10, thereby point anchoring the friction bolt body 110 within the bore hole 10.

[0046] The rod leading and trailing ends 121, 122 will tend to protrude through the open ends of the expansion element 130 and the drive head 140, respectively. Protrusion of the rod trailing end 122 through the drive head 140 will provide a visual confirmation that the point anchoring of the friction bolt body 110 within the bore hole 10 has been achieved.

[0047] After installation, surrounding ground movement may create additional loads of shear and/or tension on the friction bolt assembly 100. When the additional loads exceed the tensile strength of the rod 120, the rod 120 will typically fail by fracture as shown in Figure 5. In this embodiment, the fracture occurs in location F of the rod 120. It is, however, envisioned that fracturing of the rod 120 can occur in any other position between the first swaged portion 118a and the rod leading end 121. Once fractured, the tail portion 125 of the rod 120 may eject in a direction towards the friction bolt body trailing end 112 due to the diameter of the rod 120 being less than the aperture diameter of the collar 117. The leading portion 126 of the rod 120 is retained by the threaded connection between the threaded leading portion 123 of the rod 120 and the expansion element 130. The first swaged portion 118a is dimensioned to cooperate with the collar 117 to at least substantially prevent the tail portion 125 of the rod 120 from ejecting completely from the friction bolt body 110. In this embodiment, the first swaged portion 118a cooperates with the collar 117 by engaging with the collar 117 as the tail portion 125 of the rod 120 is displaced through the friction bolt body trailing end 112, but is unable to pass through the aperture of the collar 117 due to the first swaged portion 118a being wider than the aperture diameter of the collar 117. The tail portion 125 of the rod 120 is thereby prevented from ejecting completely from the friction bolt body 110. Protrusion of the tail portion 125 through the collar 117 will provide a visual indication that the rod 120 has failed due to mechanical overload.

[0048] It is envisaged that there may a circumstance in which high loads on the tail portion 125 may deform or fracture the first swaged portion 118a, resulting in the effective width of the first swaged portion 118a being less than the aperture diameter of the collar 117. In this instance, the tail portion 125 of the rod 120 will eject further through the collar 117. However, it is envisaged

AH25(9582247_1):MHT ίο 2016202822 03 May 2016 that the second swaged portion 118b will subsequently provide a second tier of engagement with the collar 117, in a similar manner described above, thereby preventing the tail portion 125 of the rod 120 from ejecting completely from the friction bolt body 110. Similarly, if the second swaged portion 118b deforms or fractures, the third swaged portion 118c will provide a third tier of engagement, in the manner described above.

[0049] A friction bolt assembly 200 according to a second embodiment is depicted in Figure 7. Features of the friction bolt assembly 200 that are identical to those of the friction bolt assembly 100 of the first embodiment are provided with identical reference numerals, whilst equivalent or alternate features of the friction bolt assembly 200 are provided with reference numerals equivalent to those of the friction bolt assembly 100 of the first embodiment, incremented by 100.

[0050] The friction bolt assembly 200 is identical to the friction bolt assembly 100, except that the collar 217 has a reduced profile. In this particular embodiment, the collar 217 has a maximum external diameter of approximately 47 mm, identical to the maximum external diameter of the friction bolt body 110. As with the first embodiment, the collar 217 is welded to the friction bolt body 110 adjacent the friction bolt body trailing end 112. A second collar 290 is mounted on the rod 120 between the collar 217 and the drive head 140 and is freely moveable along the rod 120. The second collar 290 may be in the form of an enlarged ball washer, or similar.

[0051] The friction bolt assembly 200 is installed in a similar manner as the friction bolt assembly 100 of the first embodiment as described above. As with the friction bolt assembly 100 of the first embodiment, prior to inserting the friction bolt assembly into the bore hole 10, a plate washer 170 (and optionally an additional ball washer) is mounted on the friction bolt body 110 adjacent the second collar 290. The friction bolt assembly 200 is then installed into the bore hole 10 utilising an installation rig in the same general manner as described above, firstly applying percussive force by the drive head 140 to drive the friction bolt assembly 200 into the bore hole 10 until the plate washer 170 is firmly engaged with the rock face 12.

[0052] Additional anchoring of the friction bolt body 110 in the bore hole is then again achieved by way of the expansion element 130 by actuating the rod 120 by rotating the drive head 140. Rotation of the drive head 140 rotates the rod 120. Rotation of the expansion element 130 is again at least substantially prevented by way of the key 137. Accordingly, rotation of the rod 120

AH25(9582247_1):MHT 11 2016202822 03 May 2016 draws the expansion element 130 along the threaded leading portion 123 of the rod 120 toward the friction bolt body trailing end 112 into the cavity 113, as shown in Figure 8. Accordingly, the engagement surface 136 again engages the friction bolt body 110 and radially outwardly deforms the tapered leading portion 115 of the friction bolt body 110, bearing against the wall of the bore hole 10.

[0053] After installation, surrounding ground movement may create additional loads of shear and/or tension on the friction bolt assembly 200. It is envisioned that movement in the rock strata 11 may place additional loads on the plate washer 170, which in turn bears against the second collar 290, which in turn displaces the drive head 140 longitudinally in a direction away from the friction bolt body trailing end 112, thus causing the rod 120 to deform and elongate in at least a half of the rod 120 adjacent the rod trailing end 122, as depicted in Figure 9. The reduced profile of the collar 217 allows the collar 217 to move through the bore hole 10 with the friction bolt body 110. In this way, loads acting on the collar 217 are reduced. When the additional loads exceed the tensile strength of the rod 120, the rod 120 will typically fail by fracture, as shown in Figure 10. In this embodiment, the fracture occurs in location G of the rod 120. It is, however, envisioned that fracturing of the rod 120 can occur in any other position between the first swaged portion 118a and the rod leading end 121. Once fractured, the tail portion 125 of the rod 120 may eject in a direction towards the friction bolt body trailing end 112, but is prevented from ejecting completely from the friction bolt body 110 by way of cooperation between the collar 217 and the swaged portions 118a, 118b, 118c in the same manner as described above in relation to the first embodiment.

[0054] A friction bolt assembly 300 according to a third embodiment is depicted in Figures 11 to 13. Again, the features of the friction bolt assembly 300 that are identical to those of the friction bolt assembly 100 of the first embodiment are provided with identical reference numerals, whilst equivalent or alternate features of the friction bolt assembly 300 are provided with reference numerals equivalent to those of the friction bolt assembly 100 of the first embodiment, incremented by 200.

[0055] The friction bolt assembly 300 is identical to the friction bolt assembly 100 of the first embodiment, except that the friction bolt body 310 includes a failure means longitudinally positioned at or adjacent to a mid-section of the friction bolt body 310. The failure means is dimensioned to form a weakened region in the friction bolt body 310 such that the tensile strength of the friction bolt body 310 at the weakened region is less than the tensile strength of

AH25(9582247_1):MHT 12 2016202822 03 May 2016 the rod 120. In this particular embodiment depicted in Figures 12 and 13, the failure means is in the form of two slots 350a, 350b cut longitudinally into the friction bolt body 310 so as to expose the cavity 113 of the friction bolt body 310. The slots 350a, 350b are located on either side of the split 114 of the friction bolt body 310 and are of substantially the same dimensions. The top and bottom ends of the first slot 350a are axially aligned with the top and bottom ends of the second slot 350b, respectively.

[0056] Installation of the friction bolt assembly 300 is identical to that described above in relation to the friction bolt assembly 100 of the first embodiment. After installation, surrounding ground movement may create additional loads of shear and/or tension on the friction bolt assembly 300. When the additional loads exceed the tensile strength of the friction bolt body 310 at the weakened region, the friction bolt body 310 will typically fail by fracture at the weakened region as shown in Figures 14 and 15. In this embodiment, the fracture occurs in location H of the friction bolt body 310. It is, however, envisioned that fracturing of the friction bolt body 310 can occur in any other position along the elongate slots 350a, 350b.

[0057] Once the friction bolt body 310 is fractured, surrounding ground movement can continue to create additional loads on the friction bolt assembly 300. It is envisioned that there will be sufficient frictional forces between the friction bolt body 310 and the rock strata 11 to retain the trailing portion 360 of the friction bolt body 310 in the bore hole 10 even after fracture. When the additional loads exceed the tensile strength of the rod 120, the rod 120 will typically fail by fracture, as shown in Figure 16. In this embodiment, the fracture occurs in location I. It is, however, envisioned that fracturing of the rod 120 can occur in any other position between the first swaged portion 118a and the rod leading end 121. Once the rod 120 has fractured, the tail portion 125 of the rod 120 may eject in a direction towards the friction bolt body trailing end 112. The tail portion 125, however, is prevented from ejecting completely from the friction bolt body 310 by way of cooperation between the collar 117 and the swaged portions 118a, 118b, 118c in the same manner as described above in relation to the first embodiment.

[0058] The person skilled in the art will appreciate other possible modifications and configurations of the friction bolt assembly described above. In particular, it is envisaged that the stopping means for preventing the rod 120 from ejecting completely from the friction bolt body 110 may take any of various alternate forms. In place of the swaged portions 118a, 118b, 118c described above, the stopping means may include alternate surface features mounted on, or integrally formed with, the rod 120 to increase the diameter of the rod 120 at predetermined

AH25(9582247_1):MHT 13 2016202822 03 May 2016 locations. Such alternate surface features might include, for example, a steel ferrule 180 welded on the rod 120 as shown in Figure 6, or a bead of weld (not shown) on the rod 120. A further alternative could include increasing the height of the transverse ribs of the rod 120.

AH25(9582247_1):MHT

Claims (17)

1. A friction bolt assembly comprising: a friction bolt body longitudinally extending between a friction bolt body leading end and a friction bolt body trailing end, said friction bolt body defining a cavity longitudinally extending through said friction bolt body; a rod longitudinally extending through said cavity between a rod leading end and a rod trailing end; a stopping means mounted on, or integrally formed with, said rod and being longitudinally positioned between said friction bolt body leading end and said friction bolt body trailing end; a first collar fixed to said friction bolt body at or adjacent said friction bolt body trailing end; wherein said stopping means and said first collar are dimensioned to cooperate to at least substantially prevent said rod from ejecting completely from the friction bolt body through the friction bolt body trailing end.

2. The friction bolt assembly according to claim 1, wherein said first collar has an aperture for receiving said rod longitudinally therethrough, said stopping means being wider than the aperture, in one or more lateral directions, for at least substantially preventing said rod from ejecting completely therethrough.

3. The friction bolt assembly according to claim 2, wherein said aperture is substantially cylindrical.

4. The friction bolt assembly according to claim 2 or 3, wherein said stopping means has a transverse cross-sectional area greater than a maximum cross-sectional area of said aperture.

5. The friction bolt assembly according to any one of the preceding claims, wherein said stopping means is longitudinally positioned substantially within a half of said rod adjacent said rod trailing end.

6. The friction bolt assembly according to any one of the preceding claims, wherein said stopping means comprises one or more swaged portions of the rod formed with the rod.

7. The friction bolt assembly according to claim 6, wherein said stopping means comprises three swaged portions.

8. The friction bolt assembly according to claim 7, wherein said swaged portions are spaced apart longitudinally along said rod.

9. The friction bolt assembly according to any one of claims 1 to 5, wherein said stopping means comprises one or more sleeves.

10. The friction bolt assembly according to claim 9, wherein said one or more sleeves are each in the form of a ferrule.

11. The friction bolt assembly according to any one of claims 1 to 5, wherein said stopping means comprises one or more welds.

12. The friction bolt assembly according to any one of the preceding claims, wherein said first collar has a maximum external width substantially identical to the maximum external width of said friction bolt body.

13. The friction bolt assembly according to any one of the preceding claims, further comprising a second collar longitudinally positioned between said first collar and said rod trailing end, said second collar being freely movable along said rod.

14. The friction bolt assembly according to any one of the preceding claims, wherein said friction bolt body comprises failure means formed thereon and being longitudinally positioned at, or adjacent to, a mid-section of said friction bolt body, wherein said failure means is dimensioned to form a weakened region in said friction bolt body.

15. The friction bolt assembly according to claim 14, wherein said failure means comprises one or more slots formed on said friction bolt body so as to expose said cavity.

16. The friction bolt assembly according to claim 15, wherein said failure means comprises two slots.

17. The friction bolt assembly according to claim 16, wherein said slots are spaced apart and axially aligned.