AU2021218166A1

AU2021218166A1 - Rock bolt

Info

Publication number: AU2021218166A1
Application number: AU2021218166A
Authority: AU
Inventors: Anthony Bennett; Matthew Raffaele Holden
Original assignee: FCI Holdings Delaware Inc
Current assignee: FCI Holdings Delaware Inc
Priority date: 2021-08-19
Filing date: 2021-08-19
Publication date: 2023-03-09

Abstract

Disclosed is a rock bolt including a shaft extending along an axis between a leading end and a trailing end. The shaft including a hollow passage defined by an internal wall. The rock bolt also including at least one reinforcing member disposed in the hollow passage of the shaft. The at least one reinforcing member increases loading capacity of the rock bolt. Also disclosed is a rock bolt assembly including the rock bolt and a method of installing the rock bolt. [FIG. 1] 17988011_1 (GHMatters) P109836.AU.2 0 to N '-II

Description

to N '-II

ROCK BOLT TECHNICAL FIELD

The present disclosure is directed to a rock bolt assembly that is suitable for use in mining and tunnelling to provide rock and wall support. The rock bolt assembly is suitable for use in hard rock applications as well as in softer strata, such as that often found in coal mines. Thus, the term "rock" as used in the specification is to be given a broad meaning to cover all such applications.

BACKGROUND ART

Roof and wall support is vital in mining and tunnelling operations. Mine and tunnel walls and roofs consist of rock strata, which must be reinforced to prevent the possibility of collapse. Rock bolts, such as rigid shaft rock bolts and flexible cable bolts are widely used for consolidating the rock strata.

Known methods for reinforcing rock faces include the use of tensionable rock bolts with self-drilling capability that are configured to allow pre- or post tensioning and grouting of the rock bolt into a rock bore hole. Both rigid rock bolts and flexible cable bolts may include a hollow passage to allow drilling fluids to be delivered to the drilling location as well as performing pre- or post tensioning grouting. Cable bolts which are usually made from a plurality of steel filaments wound together to form a tendon are strong in shear. The cable bolt may be fully encapsulated with grout, which allows load transference of any ground movements to the cable, creating a stiffer support system.

Cable bolts are also good for longer anchorage lengths due to their flexibility. Rigid bolts have shorter anchorage lengths. However, both cable bolts and rigid bolts can be susceptible to slow installation times. This can be due to multiple passes being required to drill and install the bolts as hole closure problems in poor ground can prevent rigid bolts and cable bolt from being installed efficiently.

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17988011_1(GHMatters) P109836.AU.2

Hollow self-drilling bolts are able to be create the hole and be installed in the hole at the same time which does not present the same issues regarding hole closure.

It is to be understood that, if any prior art is referred to herein, such reference does not constitute an admission that the prior art forms a part of the common general knowledge in the art, in Australia or any other country.

SUMMARY

According to a first aspect, disclosed is a rock bolt. The rock bolt comprises a shaft extending along an axis between a leading end and a trailing end. The shaft may also include a hollow passage defined by an internal wall. The rock bolt also comprises at least one reinforcing member disposed in the hollow passage of the shaft. The at least one reinforcing member increases the loading capacity of the rock bolt. This prevents the rock bolt from failure due to external forces on the rock bolt causing load deformation such as movement of rock strata.

In some embodiments, the at least one reinforcing member is in the form of a longitudinal element.

In some embodiments, the rock bolt is a semi-rigid bolt. In some embodiments, the rock bolt is a rigid bolt. In some embodiments, the rock bolt includes a drilling arrangement extending from the leading end. The shaft of the rock bolt is arranged to withstand a load transfer from surrounding rock when the drilling arrangement is in operation to drill into the surrounding rock. The drilling arrangement allows simultaneous installation of the rock bolt and this has the effect of reducing installation time as well as eliminating problems associated with hole closures. It is understood that a semi rigid bolt includes outer material which may be impact resistant and suitable for drilling but also flexible if a material other that steel is used.

In some embodiments, the drilling arrangement includes a drill bit secured to the leading end of the shaft enabling the rock bolt to be self-drilling.

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17988011_1 (GHMatters) P109836.AU.2

In some embodiments, the rock bolt includes at least one outlet extending from a grout passage and/or the hollow passage to an external surface of the shaft, the at least one outlet being in fluid communication with the grout passage and/or the hollow passage. This allows passage of fluids including drilling fluids, settable materials (e.g., grouting materials) into the rock bolt and annular spaces between the rock bolt and the drilled hole. The grout passage may extend through the hollow passage and/or be separate to the hollow passage. For example, the grout passage may extend through the shaft of the rock bolt and/or extend through the reinforcing member.

In some embodiments, the at least one outlet includes an annular recess extending between the drilling arrangement and the rock bolt.

In some embodiments, the rock bolt includes a retaining arrangement arranged to retain the at least one reinforcing member disposed in the hollow passage of the shaft. Such an arrangement can allow for improved load transfer between the reinforcing member and the shaft.

In some embodiments, the retaining arrangement includes one or more of the following: an end cap, a plug, a swaged anchor, and a barrel and wedge.

In some embodiments, the retaining arrangement may be fitted to proximal the leading end and/or trailing end of the shaft.

In some embodiments, the shaft of the rock bolt includes external profiling extending along an external surface. Such external profiling improves the adhesion between the settable material and the shaft.

In some embodiments, the external profiling includes any of corrugations, threading (coarse or fine), protrusions, flat surfaces extending in the longitudinal direction to define a non-circular cross-section.

In some embodiments, the shaft of the rock bolt may not include external profiling which facilitates debonding and allows elongation of the shaft.

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17988011_1 (GHMatters) P109836.AU.2

In some embodiments, the reinforcing member may also include profiling. This profiling improves adhesion between the reinforcing member and the shaft.

In some embodiments, the reinforcing member profiling includes spaced apart deformations or protrusions.

In some embodiments, the reinforcing member can include multiple wound co extending strands. The use of multiple wound co-extending strands improves the shear loading capacity of the rock bolt. In this way, the reinforcing member is a longitudinal section of cable bolt. The cable bolt is flexible relative to the rock bolt in the form of a rigid bolt, and thus, in circumstances where the rigid bolt fails due to shear loading, the cable bolt reinforcing member does not fail due its flexibility. The reinforcing member may also include a single strand.

In some embodiments, the reinforcing member profiling is in the form of spaced apart bulbous portions. These portions offer a locking effect and prevent movement in the longitudinal direction of the shaft. The bulbous portions may include birdcage formations, and may include a spacer inside the bulbous portion.

In some embodiments, the rock bolt includes a settable material, wherein the at least one reinforcing member is embedded in the settable material. In some embodiments, the at least one reinforcing member is disposed and embedded in the settable material in the hollow passage. In some embodiments, the settable material bonds to both the internal wall of the passage of the shaft and the at least one reinforcing member to allow load transference between the internal wall and the reinforcing member. This allows for a transfer of load between the different components of the rock bolt thereby dispersing the stress concentration. The settable material forms an intimate mechanical bond with both the surface of the rock bolt and the rock strata to allow load transference. The settable material may be in the form of a cementitious or resinous-based thixotropic grout which may be pumped through the hollow passage to fully encapsulate the rock bolt. The settable material may flow into the outer annulus. This may be followed by inserting at least one reinforcing member in the hollow passage before and/or after

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17988011_1 (GHMatters) P109836.AU.2 the settable material. In some embodiments, a grout passage may be provided in the hollow passage and/or in the reinforcing member and/or the shaft of the rock bolt as a passage for the settable material.

In some embodiments, the length of the at least one reinforcing member is less than the length of the shaft. In some embodiments, the length of the at least one reinforcing member is more than the length of the shaft. In some embodiments, the at least one reinforcing member is arranged to be disposed in the shaft in a region vulnerable to shearing through discontinuity in the rock strata. In this manner, the reinforcing member provides an additional support to the shaft at locations of stress concentration.

In some embodiments, the at least one reinforcing member is relatively inflexible compared to the shaft. Such a rigid reinforcing member provides additional support to counter the forces generated by movement of rock strata.

In some embodiments, the at least one reinforcing member is more flexible compared to the shaft of the rock bolt. This allows the rock bolt to take up a higher shearing load.

In some embodiments, the at least one reinforcing member may be steel and/or polymeric and may be formed as a single element or from multiple strands. Thus, a variety of materials can be employed depending on the requirements which can result in cost savings.

In some embodiments, the leading end of the shaft is configured for anchoring to rock strata, and the trailing end is configured for receiving the settable material.

In some embodiments, the at least one reinforcing member improves the shear capacity of the rock bolt. In some embodiments, the at least one reinforcing member improves the tensile capacity of the rock bolt.

In a second aspect disclosed herein is a rock bolt assembly comprising the rock bolt as discussed above. The rock bolt assembly includes a tensioning assembly

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17988011_1 (GHMatters) P109836.AU.2 mounted on an end of the shaft, the tensioning assembly may be arranged in use to tension the rock bolt. The rock bolt assembly allows for reinforcing rock strata at desired locations in a mine.

In some embodiments, the tensioning assembly comprises an end fitting being mounted adjacent the trailing end of the shaft. In some forms, the end fitting may comprise a barrel and wedge assembly. The end fitting provides a mechanism to apply the required force to secure and tension the rock bolt.

In some embodiments, the tension assembly further comprises a bearer plate which is mounted to the shaft between the end fitting and the distal end of the shaft. The end fitting together with the bearer plate allows the rock bolt to be securely fastened to the rock strata and tensioned appropriately.

In a third aspect, disclosed herein is a method of installing a rock bolt. The method includes installing a rock bolt in a bore in a rock substrate. The rock bolt includes an internal passage defined by an internal wall. This is followed by disposing a settable material into the hollow passage of the cable and inserting at least one reinforcing member in the hollow passage. In some embodiments, disposing the settable material into the hollow passage occurs prior to inserting the at least one reinforcing member in the hollow passage. In some embodiments, the rock bolt may further comprise a grout passage which allows grout to pass through the rock bolt. The grout passage may form part of the hollow passage or be separate to the hollow passage. The grout passage may extend through the reinforcing member and/or the shaft.

In some embodiments, inserting the at least one reinforcing member disposes the at least one reinforcing member in the settable material and allows the settable material to harden so that the at least one reinforcing member is retained in the hardened settable material allowing load transference between the internal wall of the rock bolt and the at least one reinforcing member. The advantage of disposing the reinforcing member in the settable material is that the reinforcing member will create a pressure on the settable material that would enable it to move and fill out

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17988011_1 (GHMatters) P109836.AU.2 minor voids which may not have been filled during the process of disposing the settable material.

In some embodiments, the method comprises inserting the at least one reinforcing member into the hollow passage of the rock bolt prior to installing the rock bolt in the bore of the rock substrate. The advantage here is that this step can be performed in a factory and the pre-assembled unit can be transported to the location to be installed. This would be especially useful in locations where there are constraints on the working space available and where such assembly may be difficult to do.

In some embodiments, the method comprises disposing the settable material into the hollow passage of the rock bolt after the at least one reinforcing member and the rock bolt are installed in the bore of the rock substrate and allowing the settable material to harden so that the at least one reinforcing member is retained in the hardened settable material allowing load transference between the internal wall of the rock bolt and the at least one reinforcing member.

Brief Description of the Drawings

Embodiments will now be described by way of example only, with reference to the accompanying drawings in which

Fig. 1 is a cross-sectional view of an embodiment of a rock bolt including a hollow passage and an embodiment of at least one reinforcing member disposed in the hollow passage;

Fig. 2a is a side view of an embodiment of a rock bolt according to the present disclosure;

Fig. 2b is an end view of the rock bolt of Fig. 2a;

Fig. 3a is a side view of an embodiment of a rock bolt according to the present disclosure;

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17988011_1 (GHMatters) P109836.AU.2

Fig. 3b is an end view of the rock bolt of Fig. 3a;

Fig. 4a is a side view of an embodiment of a rock bolt according to the present disclosure;

Fig. 4b is an end view of the rock bolt of Fig. 4a;

Fig. 5a is a side view of an embodiment of a rock bolt according to the present disclosure;

Fig. 5b is an end view of the rock bolt of Fig. 5a;

Fig. 6a is a side view of a rock bolt according to the present disclosure;

Fig. 6b is an end view of the rock bolt of Fig. 6a;

Fig. 7a is a side view an embodiment of a reinforcing member according to the present disclosure;

Fig. 7b is an end view of the reinforcing member of Fig. 7a;

Fig. 8a is a side view of an embodiment of a reinforcing member according to the present disclosure;

Fig. 8b is an end view of the reinforcing member of Fig. 8a;

Fig. 9a is a side view of an embodiment of a reinforcing member according to the present disclosure;

Fig. 9b is an end view of the reinforcing member of Fig. 9a;

Fig. 10a is a side view of an embodiment of a reinforcing member according to the present disclosure.

Fig. 1Ob is an end view of the reinforcing member of Fig. 1Oa;

Fig. 11a is a side view of an embodiment of a reinforcing member according to the present disclosure;

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17988011_1 (GHMatters) P109836.AU.2

Fig. I1b is an end view of the reinforcing member of Fig. 11a;

Fig. 12a is a sectional view of an embodiment of the rock bolt with a hollow passage with an embodiment of a reinforcing member disposed inside;

Fig. 12b is a sectional view of a first embodiment of the retaining arrangement according to the present disclosure;

Fig. 12c is a sectional view of a second embodiment of the retaining arrangement according to the present disclosure;

Fig. 12d is a sectional view of a third embodiment of the retaining arrangement according to the present disclosure;

Fig. 12e is a sectional view of a fourth embodiment of the retaining arrangement according to the present disclosure;

Fig. 12f is a sectional view of a fifth embodiment of the retaining arrangement according to the present disclosure;

Fig. 12g is a sectional view of a sixth embodiment of the retaining arrangement according to the present disclosure;

Fig. 13a - 13b are side views of an embodiment of the rock bolt assembly comprising an embodiment of a rock bolt with a drilling arrangement according to the present disclosure;

Figs. 14a - 14c are sectional views of an embodiment of the rock bolt assembly comprising an embodiment of a rock bolt with a drilling arrangement according to the present disclosure;

Fig. 15a is a sectional view of an embodiment of the rock bolt assembly showing the shear plane;

Fig. 16a - 16d are sectional views showing the various steps in a first embodiment of a method of installing the rock bolt; and

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17988011_1 (GHMatters) P109836.AU.2

Figs. 17a - 17c are sectional views showing the various steps in a second embodiment of a method of installing the rock bolt.

DETAILED DESCRIPTION

In the following detailed description, reference is made to accompanying drawings which form a part of the detailed description. The illustrative embodiments described in the detailed description, depicted in the drawings and defined in the claims, are not intended to be limiting. Other embodiments may be utilised and other changes may be made without departing from the spirit or scope of the subject matter presented. It will be readily understood that the aspects of the present disclosure, as generally described herein and illustrated in the drawings can be arranged, substituted, combined, separated and designed in a wide variety of different configurations, all of which are contemplated in this disclosure.

Referring to Figures 1 to 17, illustrated are embodiments of a rock bolt assembly 100 and methods of installing a rock bolt assembly 100. The rock bolt assembly 100 is used to reinforce surrounding rock of mining shafts at desired locations. It can be installed into holes drilled into the rock strata. Standard settable material, i.e., grouting materials such as a cementitious or resinous-based grout can be used to secure a rock bolt 101 to the walls of the holes drilled in the rock strata. Furthermore, the illustrated embodiment of the rock bolt assembly 100 includes a drilling arrangement and anchoring systems which greatly reduces the time of drilling and installation. Thus, the rock bolt assembly 100 offers improved performance while reducing installation time. It is understood that other anchoring systems such as resin cartridges or mechanical anchors may be used in accordance with the embodiments of the rock bolt disclosed herein.

The rock bolt assembly 100 disclosed herein is able to withstand shear stresses generated by movement of the rock strata. In the embodiment shown in Fig.1, the rock bolt 101 comprises a shaft 102 that extends along an axis between a proximal end 112 (i.e., a trailing end) and a distal end 114 (i.e., a leading end). In use, the

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17988011_1 (GHMatters) P109836.AU.2 distal end 114 or the leading end is located at a blind end of the hole that is formed at an end of the drilled hole of the rock strata during or prior to installation of the rock bolt 101. The distal end 114 of the shaft 102 may also be configured to receive a drilling arrangement 122 to enable the rock bolt to be self-drilling. The proximal end 112 or the trailing end is configured to extend proximal to, or outwards from, the roof of the rock strata and may comprise an end fitting configured for tensioning of the rock bolt assembly 100 including the rock bolt 101. The proximal end 112 also comprises an inlet for introducing settable material 140 into the rock bolt 101 which when cured enables it to be secured to the rock strata. In the illustrated embodiment, the rock bolt is a rigid bolt which is suitable for self-drilling. In alternative embodiment, the rock bolt may be a semi rigid bolt. It is understood a semi-rigid bolt includes an outer material that may be impact resistant and suitable for drilling but also flexible if a material other than steel is used.

The rock bolt 101 further comprises a hollow passage 120 that extends in the direction of the axis from the proximal end 112 to the distal end 114. In the illustrated embodiment, the passage 120 extends axially through its centre. The hollow passage 120 is defined by an internal wall 118 and is configured to receive at least one reinforcing member 132. In use, the at least one reinforcing member 132 provides internal support to the rock bolt 101. The at least one reinforcing member 132 improves the load bearing characteristics of the rock bolt 101 and allows for transfer of any tensile/shear loads that act on the rock bolt 101 and would, without the presence of the reinforcing member, result in an early failure of the rock bolt 101. The rock bolt assembly 100 may also include a bearing plate 155 and an anchoring mechanism 156 in the form of a nut or a barrel and wedge to form an assembly that enables tensioning and securing the rock bolt 101 to the rock strata.

As illustrated in Fig. 2a to 6b, some embodiments of the rock bolt 101 are shown. The shaft 102 of the embodiments of the rock bolt 101 are shown, in the form of a rigid hollow bar, having an outer surface 116. The primary difference between the

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17988011_1(GHMatters) P109836.AU.2 embodiments of the rock bolt 101 are the profile of the outer surface 116. In an embodiment, as shown in Fig. 2a-2b, the profile of the outer surface 116 may comprise a coarse thread formation or helical corrugations 124. The coarse thread 124 increases the surface area of the shaft 102 which in turn results in a greater contact area with the settable material 140 thus improving adhesion of the settable material with the shaft 102. Other surface profiles (including profiles with different surface textures) that lead to improved adhesion while avoiding the creation of 'stress concentrators' (points where the profile results in a concentration of stress thus acting as points for failure) are also contemplated. For e.g., it would be possible to use a surface profile with a matte finish, knurled patterns etc. A matte textured finish in general increases the roughness of a surface and thereby increases the surface area that is available for contacting the settable material thus improving adhesion. Similarly, a 'knurled' pattern is typically used to improve the gripping ability of objects and is obtained by embossing an object using knurling rollers (typically consists of diamond shaped patterns).

In the embodiments shown in Fig. 3a-5b, the outer wall 116 of the shaft 202 can have a smooth segment 128 disposed at various locations along the longitudinal direction of the shaft 102. This segment 128 provides the shaft 202 with the ability to elongate/stretch in the longitudinal direction when the rock bolt assembly 100 is tensioned. Generally, the segment 128 has a smooth surface profile (as opposed to corrugations or a coarse thread formation). The smooth surface enables the segment to easily detach from the settable material (thus enabling elongation during tensioning). In the embodiments shown in Figs. 3a and 4a, the segment 128 comprises a smooth cylindrical section. In the embodiment shown in Fig.5a, the segment 228 may comprise a non-circular cross section, such as the hexagonal portion. The shaft 302 can also have a non-circular cross section, such as the hexagonal portion illustrated in Figs. 5a and 5b, and may also have other cross sections such as, but not limited to, rectangular or square. In the embodiments shown in Figs. 3a to 5a, the segment 128 can take the form of a

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17988011_1 (GHMatters) P109836.AU.2 single large section. In other embodiments as best shown in Fig.6a, the segment 328 can comprise a plurality of smooth sections of shaft 402. Between the smooth sections are spaced apart helical formations 129. The formations may be in the form of ribs or recesses and may extend in any direction relative to the shaft, such as axially, circumferentially.

The segments 328 containing a plurality of smooth sections may be formed by any suitable method such as machining from a single piece or welding multiple sections together. In alternative embodiments the smooth sections may be disposed anywhere along the shaft 402, and may be spaced apart sections, and are not limited to being in the central region of the bar. The length of the segment 328 can also be varied to obtain different properties (e.g., a longer section would facilitate debonding of the reinforcing member from the settable material). In alternative non-illustrated embodiments, the entire profile of the shaft may be formed of smooth sections or be entirely smooth.

Further, in the embodiments shown in Figs. 3a to 6b, the distal end 114 and proximal 112 end regions include the external profiling in the form of threading 130. The threading provides a coupling arrangement for coupling other components of the rock bolt assembly, such as a tensioning arrangement, or an anchor arrangement or a mesh net extending across the rock face to catch loose rock. The length of such threading can be varied according to the requirements for anchoring and dimensions of the reinforcing member. In alternative embodiments the coupling arrangement can be achieved through welding, swaging or adhesive connections.

Turning to Figures 7a to 1Ib, embodiments of the at least one reinforcing member 132 are shown. Like reference numerals are used for like features in the various embodiments. To illustrate a further embodiment, a higher value number is used in the hundreds position. For example, to indicate a first embodiment of the reinforcing member, the reference numeral '132' is used, and to indicate a second embodiment of the reinforcing member, the reference numeral '232' is used.

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17988011_1 (GHMatters) P109836.AU.2

The at least one reinforcing member 132, in use, is disposed in the hollow passage 120 to increase the loading capacity of the rock bolt assembly 100. In the illustrated embodiment, the at least one reinforcing member 132 is in the form of one reinforcing member 132, but in alternative arrangements, there may be more than one reinforcing member disposed in the hollow passage 120 and abutting end to end or in side by side relation. The reinforcing member 132 increases the rock bolt's 101 tensile loading capacity and the rock bolt's 101 shear loading capacity. The dimensions of the reinforcing members can be chosen based on the performance requirements (such as tensile/shear loads expected etc) of the rock bolt assembly 100. The dimensions are chosen such that the reinforcing member may be disposed in the hollow passage 120 of the rock bolt 101. The load transfer from the rock face goes through both the rock bolt and the reinforcing member to varying degrees. The primary load path may go through either the rock bolt and/or the reinforcing member depending on the embodiment of the rock bolt and reinforcing member and the load forces coming form the rock face.

In some embodiments, the reinforcing member 132 can have a rigid shaft as illustrated in Fig. 7-9, and in some embodiments, the reinforcing member 132 can have a flexible shaft.

As shown in Figs. 7a-7b, the reinforcing member 132 includes profiling in the form of upsets 134 spaced along the length of the shaft. In the embodiments shown in these figures, the upsets 134 are provided as pairs of projections located on the reinforcing member 132 in a diametrically opposing manner to one another. The upsets 134 are spaced apart equidistant from one another, but in other embodiments the number and spacing of the upsets 134 may be varied and non-uniform. For example, it is possible to have three upsets located at an angle of 120 or four upsets located at an angle of 90° to each other etc. Each upset 134 has a dimension that is larger than the diameter of the sections of the reinforcing member 132 without the upsets. When the reinforcing member 132 is disposed in the hollow passage 120 and settable material 140 has been introduced into the shaft 102 and cured, each upset acts as an anchor point that retains the reinforcing

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17988011_1 (GHMatters) P109836.AU.2 member opposes any attempt to move the reinforcing member in a longitudinal manner. The sections of the reinforcing member 132 between the upsets 134 allows elongation of the reinforcing member 132 when it is subjected to load from the rock strata, which may include shear forces. The upsets may be integrally formed while manufacturing the reinforcing member, may be formed by deforming the shaft, or alternatively be attached separately by welding, joining etc to the reinforcing member 132.

Figs. 8a-8b illustrate an embodiment of the reinforcing member 232 having a rigid shaft, a smooth surface and a circular cross section. For example, any commonly available steel rebar (such as used in the construction industry) of suitable dimensions could be employed as a reinforcing member.

In the embodiment shown in Figs. 9a-9b, the reinforcing member 332 is in the form of a rigid shaft comprising protrusions spaced apart along the length of the shaft. In the illustrated embodiment, the protrusions are in the form of ribs 136. The ribs 136 extend about an external surface of the reinforcing member in the lateral, e.g., circumferential direction. The ribs 136 may extend continuously about the reinforcing member, or may be interrupted. The ribs 136 may extend from the external surface of the reinforcing member at any angle, or pitch, and may taper towards the external surface at the interrupted regions 145. Fig. 9b illustrates that in the illustrated embodiment, the ribs 136 include two opposing ribs which include two opposing interrupted regions. Each rib 136 includes ends which taper to the external surface at each interrupted region. The interrupted regions extend along a longitudinal direction of the reinforcing member from one end to the other. In the illustrated embodiment, there are two interrupted regions spaced 180° apart. In other embodiments, one or more of the interrupted regions may be included which may be in opposing arrangement. For example, there could be three interrupted regions spaced apart at 120° or 4 interrupted regions spaced 900apart from each other. The ribs 136 improve adhesion with the settable material (an effect similar to this is seen in the use of ribbed rebars in constructing

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17988011_1 (GHMatters) P109836.AU.2 concrete structures). The spacing and dimensions of the ribs can be varied to predetermine the extent of desired support characteristics.

In some embodiments, the reinforcing member 132 may comprise any combination of the features outlined in Figs. 7a-9b. For example, the reinforcing member may comprise an array of upsets and ribs, which may be spaced by smooth sections. A combination of features from embodiments may also be used, for example, threaded and smooth sections, and/or upsets and ribs together.

It is also possible to have non-rigid, relatively flexible reinforcing members. As shown in Figures 10a-1Ib, the reinforcing member 432, 532 may be in the form of a cable bolt 138, 238. The cable bolt includes a plurality of co-extending wound strands and may include a centre strand. In the illustrated embodiment, the cable bolt 138 is formed from a seven-strand prestressed concrete steel strand ('PC strand'). Depending on the performance requirements to be met, any number of wound strands may be employed to fabricate such a PC strand reinforcing member. In alternative embodiments, more or fewer outer steel filaments may be used for the reinforcing member, in which case their relative diameter with respect to the internal diameter of the shaft 102 may be adjusted accordingly such that the diameter of the reinforcing member 132 is only slightly smaller than the internal diameter of the shaft 102 so as to create a close fit between the reinforcing member 132 and the internal walls 118 of the hollow passage 120. For example, in the embodiment shown in Fig. 10a, the PC strand is surrounded by a further 6 strands. Furthermore, these outer strands are provided with spaced apart bulbs 144. The bulbs provide for a much greater strength compared to the embodiment shown in Fig. 11a allowing the settable material to be disposed within each bulb 144 while also preserving the advantages of the upsets described above for the embodiment of Fig. 7a.

The reinforcing member 132 in the form of a flexible shaft 138, 238 is configured to increase the shear loading capacity of the rock bolt 101. For example, as the rock bolt 101 is subjected to shearing load about a shear plane 130 (see Fig.15a),

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17988011_1 (GHMatters) P109836.AU.2 the reinforcing element 432, 532 is pinned to interior walls 118 of the shaft 102 on either side of the shear plane 130. The shear plane is generally the plane along which maximum stress and thus deformation or failure tends to occur. In the illustrated embodiment, for example, when rock strata near the distal end 114 starts moving in a direction 131 and the rock strata near the proximal end 112 opposes this motion in direction 133 (e.g., under shear load), there will be maximum stress along the shear plane (indicated by dotted line). This stress along the shear plane acts on the shaft 102 of the rock bolt 101. As the stress builds up in the shaft 102 beyond the failure stress, the shaft 102 will fail. This failure allows the reinforcing member 132 to take up the shearing load and thereby continue resisting the shearing load. The strands of the cable bolt 138 are able to deform and/or move to defuse a stress build up that can cause failure. In this manner, the cable bolt 138 provides the capability to support higher shearing loads thus increasing the loading capability of the rock bolt assembly. In other words, without the cable bolt 138, the shearing load would simply be concentrated at the shaft 102 causing the stress to be raised beyond the failure stress of the shaft thus causing early failure. The reinforcing member 132 may also increase the tensile capacity of the rock bolt 101. This is because, any applied load will now be distributed across the combined cross-sectional area of the shaft 102 as well as the reinforcing member 132.

The reinforcing member 132 can also be inserted into unhardened settable material that has been filled into the shaft 102. Once hardened, the settable material 140 may retain the reinforcing member 132 in position in the hollow passage with the bond formed by the settable material 140 between the inner wall 118 of rock bolt 101 and reinforcing member 132 allowing load transference to improve the rock bolt's 101 ability to accommodate tensile loading. This will be discussed in more detail below in relation to the methods of installing the rock bolt 101.

In the illustrated embodiments, the reinforcing member 132 is in the form of a longitudinal element. The reinforcing member 132 has a diameter smaller than

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17988011_1 (GHMatters) P109836.AU.2 the inner diameter of the rock bolt 101. Also, the reinforcing member 132 may have a length less than, equal to or greater than the length of the shaft 102 extending between the proximal and distal ends 112, 114. The length of the reinforcing member 132 may extend to cover at least the length of the zone in the rock strata susceptible to shearing. The zone susceptible to shearing can be determined on a site by site basis and will vary between sites. As a result, the reinforcing member 132 may be positioned at different distances between the proximal and distal ends of the rock bolt 112, 114 depending on the site, and on the position of the rock bolt 101 at the site to be aligned with the area or zone susceptible of shearing in relation to the specific cable bolt.

In further alternative embodiments, different grades of steel may be used for the strands which will impact the strength, ductility etc of the reinforcing member 132 and therefore improve the response of the rock bolt under dynamic loading. In further alternative embodiments, the reinforcing member may be in the form of a fibre reinforced polymer, a polymer, or other materials such as composites or fibrous materials.

In the illustrated embodiments, the reinforcing member 132 may be in a 'floating' configuration within the shaft 102 (as shown in Fig 12a). Alternatively, the reinforcing member may be anchored/secured to the shaft 102 through the use of a retaining arrangement 135 arranged to retain the at least one reinforcing member disposed in the hollow passage of the shaft 102. Embodiments of retaining arrangements are illustrated in Figs. 12a to 12g. Such a configuration would allow the tensioning of the reinforcing member 132 as well in addition to the rock bolt 101. In all of the embodiments, the retaining arrangement 135 may be positioned relative to the distal end and/or the proximal end. When the retaining arrangement is positioned at the distal end, the retaining arrangement may also include a point anchor to secure the rock bolt assembly to the rock face at the blind end, such as a mechanical or resin anchor. When the retaining arrangement is positioned at the proximal end, the retaining arrangement may be positioned on the tail of the rock

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17988011_1 (GHMatters) P109836.AU.2 bolt extending from the tensioning arrangement (such as the nut) to secure the reinforcing member relative to the rock bolt.

Further, in all the arrangements, the retaining arrangement 135 may include a hollow passage in order to allow settable material to flow through it. In alternative non-illustrated embodiments, a grout passage may also be included to allow the passage of grout through the rock bolt. The grout passage may form part of the hollow passage, may extend through the reinforcing member, and/or through the shaft of the rock bolt.

In the embodiment shown in Fig. 12b, the reinforcing member 132 is coupled to the shaft 102 using a retaining arrangement 135 in the form of an end cap 137. The end cap be a screw-on type cap to mate with the coarse thread provided on the external surface of the rigid bolt 101 as well as an internal wall of the cap 137 which defines a collar 139. The end cap 137 may have a hollow passage and outlet to allow settable material to flow through it while retaining the reinforcing member 132. As discussed for the embodiments shown in Figs. 3a-6b, it is possible to have threaded sections 130 on the external surface of the rigid bolt that can engage with complementary threaded sections on the internal wall of cap 137. Alternatively, the cap could be a push-on type cap which offers a friction or snap fit. In either case, the collar 139 of the cap 137 locates around and covers the distal end 114 of the shaft 102. While a screw-on type cap may not be suitable for use with a cable bolt reinforcing member 138, further types of retaining arrangements may be used as will be described below.

In the embodiment shown in Fig. 12c, the retaining arrangement 135 is in the form of a screw-on or push-on type cap 137'. This is different from the embodiment of Fig. 12b in that the collar 139' of the cap 137' is now located within the hollow passage 120 of the shaft 102. Threads provided on the external surface of the collar 139' engage with threads provided on the inner wall 118 of the distal end 114 of the shaft. The cap 137' also may include a recess for receiving an end portion of the reinforcing member 132. The diameter of the

19

17988011_1 (GHMatters) P109836.AU.2 recess may be slightly larger than the diameter of the reinforcing member 132 thus allowing for a close fit to be established when the reinforcing member is inserted into the recess. An end portion of the reinforcing member abuts and/or engages the cap 137' which in turn abuts and/or engages the shaft 102 thus retaining the reinforcing member 132 in relation to the rock bolt 101. The more distance the screw-in type cap 137' is able to move, the greater the retaining engagement established (e.g., frictional engagement, mechanical interference). Alternatively, a push-in type cap may be employed. This would function similarly to the embodiment of Fig. 12b except that instead of establishing a compression fit from the outer surface of the distal end 114 of the shaft 102, there is frictional contact established between the collar 139' of the cap 137' and the inner wall 118.

In the embodiment shown in Fig. 12d, the retaining arrangement 135 is in the form of a swaged ferrule 141. In this embodiment, the ferrule is deformed, e.g., swaged or tightly crimped, around a section of the reinforcing member 132 that extends beyond the distal end 114 of the shaft 102. Through the swaging process, the swaged ferrule bonds the reinforcing member 132 to the shaft 102. In the illustrated embodiment, the swaged ferrule bonds to the distal end 114 of the shaft 102. Consequently, the reinforcing member 132 once installed in this manner is restrained from moving in the axial direction of the shaft 102. Such a retaining arrangement would be especially suitable for use with reinforcing members in the form of cable bolts 138 described above due to the textured surface of the co extending wound cable strands.

In the embodiment shown in Fig. 12e, the retaining arrangement 135 is in the form of a swaged ferrule 142. The swaged ferrule 142 includes an external thread that engages with a corresponding internal thread formed on the inner wall 118 of the passage 120 extending from the proximal end 112. The ferrule 142 is swaged onto the reinforcing member 132, and then the external thread is formed. The reinforcing member 132 is subsequently disposed in the passage 120 and torque is applied to the reinforcing member to allow engagement of the corresponding

20

17988011_1 (GHMatters) P109836.AU.2 threads. The mechanical interference of the corresponding threads acts to retain the reinforcing member to the rock bolt 101.

In the embodiment shown in Fig. 12f, a retaining arrangement in the form of a barrel and wedge anchor 143 is used to secure the reinforcing member 132 to the distal end 114 of the shaft 102.

In the embodiment shown in Fig. 12g, the inner wall 118 of the passage is shaped to act as a barrel while a wedge with a complementary profile could complete a barrel and wedge anchor 143' that locates in a flush manner with the shaft 102. In the illustrated embodiment, the inner wall 118 of the passage is tapered towards the distal end extending from the proximal end.

It should be noted that the embodiments of the hollow anchors discussed above could be employed at the proximal end 112 of the shaft 102 as well to secure the reinforcing member to the shaft 102.

Turning to Figs 13a to 13c, a rock bolt 101 is illustrated with an attachable drill bit 122. The attachable drill bit provides the ability to drill the hole and install the rock bolt 101 at the same time. This may avoid problems related to hole closures as well as improve the efficiency of the installation process. Furthermore, the attachable drill bit also allows for the ability to couple multiple lengths of anchors together thereby allowing for creating a longer anchorage in the rock. For example, there may be large sections of rock strata that need to be supported. Alternatively, the attachable drill bit can also be used as a conventional drill bit if desired (i.e. it can be taken out after the hole is drilled and then the rock bolt can be installed).

In the illustrated embodiments (see Fig. 1, 13a-14c), the attachable drill bit is attached to the proximal end 112 of the shaft 102 of the rock bolt 101. The drill bit 122 is characterised by drilling 'teeth' which are typically made up of hardened materials that are resistant to abrasion and wear. The number, orientation and location of these teeth can be varied as desired to achieve optimum cutting performance. The attachment of the drill bit 122 to the shaft 102 may be 21

17988011_1 (GHMatters) P109836.AU.2 accomplished by screw type connections (or other connections such as square or hex socket on drill bit). The shaft 102 is designed support the load transfer that occurs from the rock strata through the drill bit 122 during the drilling operation. For example, the shaft 102 may have a male end fitting that allows a female socket drill bit to be attached or vice versa. The drill bit 122 also has provisions to allow fluid, such as coolant, to be fed through the shaft 102 to the drilling edge. The hollow passage 120 of the shaft 102 facilitates such a transfer of fluids such as coolants or other liquids. In order to ensure that the coolant is able to exit the passage 120 and contact the drill bit where the heat is generated, an outlet 148 is provided that couples the hollow passage 120 to an external surface of the drill bit and the annular space between the drill bit/shaft 102 and the internal wall of the hole (see Figs.1, 14a-14c). The outlet 148 may also be in the form of an annular recess formed between the shaft 102 of the rock bolt and an internal wall of the drill-bit. Multiple outlets 148 can be employed to provide a more uniform distribution of the coolant/grout as well as increase the volume of coolant/grout that can be flown through. It should be noted that the same passage 120 and outlet 148 can be subsequently used to deliver the settable material 140 discussed above. Further, in alternative embodiments, a grout passage may be provided for the passage of fluids. The grout passage may form part of the hollow passage or may be separate, such as extending through the reinforcing member of another part of the shaft.

On completion of drilling, the drill bit 122 can be taken out if desired or allowed to remain and be anchored in place as a part of the rock bolt 101 to reinforce the rock strata. In embodiments where the drill bit remains, for example as per self drilling bolts, the drill bit may function as an anchor for the rock bolt assembly.

Now turning to Figs. 16a to 17d, various embodiments of the methods of installation of the rock bolt 101 and the at least one reinforcing member 132 will now be described in detail. The primary difference between the embodiments of the methods is that the reinforcing member(s) may be installed prior to drilling at the time of drilling or following anchoring of the shaft 102 in the rock strata. This

22

17988011_1 (GHMatters) P109836.AU.2 offers flexibility with respect to installation depending on the mine site to be reinforced.

In the embodiment shown in Figs. 16a to 16d, the rock bolt 101 is first located into a drilled hole and the reinforcing member is inserted subsequently after settable material 140 has been disposed into the rock bolt 101. The drill bit 122 attached to the distal end 114 of the shaft drills a hole into the rock face as shown in Fig. 16a. A tensioning assembly in the form of a bearing plate 155 coupled to a nut/barrel and wedge anchor 156 is secured to the proximal end 112 of the shaft 102. The settable material 140 is delivered through an aperture at the proximal end 112 of the shaft 102. The settable material 140 enters the hollow passage 120 disposed within the shaft 102 and exits via the outlet 148 located at or near the distal end 114 of the shaft 102. The settable material 140 continues to flow into the annular space between the outer wall 116 of the shaft 102 and the inner wall of the drilled hole until the annular space is filled with the settable material. The end of this step is indicated by the settable material 140 flowing out through an aperture 157 in the bearing plate 155 (e.g., see Fig. 16b). The third step (see Fig. 16c) involves the insertion of the reinforcing member 132 into the hollow passage 120 which is now filled with the settable material 140. The annulus between the reinforcing member 132 and the shaft 102 is filled with grout. This step is performed immediately without delays that may cause the settable material to harden. After the reinforcing member 132 is fully inserted into the hollow passage 120, the assembly 100 may be tensioned while the settable material cures. The tensioning assembly can be used to tension the rock bolt 101 relative to the rock strata 152 through known methods (e.g., by applying torsion to the nut, forcing the bearing plate 155 against the rock strata 152 which axially forces the rock bolt into tension). Once the settable material 140 is fully cured (see Fig. 16d), a bond is established between the inner wall of the drilled hole and the outer wall 116 of the shaft 102. Similarly, the annular space remaining in the hollow passage 120 between the reinforcing member 132 and the inner wall 118 of the shaft 102 will

23

17988011_1 (GHMatters) P109836.AU.2 also be filled with cured settable material thus providing a strong bond that secures the reinforcement member 132 within the rock bolt 101.

In embodiments where the reinforcing member 132 may be secured to the shaft 102 using a retaining arrangement 135, this can either be pre-installed at the factory or installed on-site after drilling; but must be done before the settable material 140 has cured in hollow passage 120. Reinforcing member may be secured at the distal or proximal end or anywhere in between by means such as screwing in or plugging as discussed herein.

In the embodiment shown in Figs. 17a to 17c, the rock bolt 101 is first assembled with the reinforcing member 132 and tensioning assembly comprising the bearing plate 155 and nut 156. This assembly could be performed for example at a factory or a mine site as desired. The reinforcing member 132 is secured to the shaft 102 using suitable retaining arrangements 135 described above. Once the rock bolt assembly 100 is assembled, it is inserted into a pre-drilled bore hole and secured to the rock strata using the installation assembly (as shown in Fig. 17b). Alternatively, in case of a self-drilled hole, the assembled rock bolt 101 comprising a drill bit is connected to a drilling machine to power the drill bit to drill the hole. Once the hole is ready, the settable material 140 is introduced into the annular region of the hollow passage 120 between the reinforcing member 132 and the inner wall 118 of the shaft 102 (see Fig. 17c). Under pressure, the settable material 140 flows along the annular region and exits the passage 120 via the outlet 148 and enters the annular region defined by the inner wall of the drilled hole and the outer wall 116 of the rock bolt 101. The process continues until all the void space within the rock bolt 101 and between the rock bolt and the hole are filled with the settable material 140. Once the delivery of the settable material 140 is completed, it cures and hardens to secure the assembly together.

In the claims which follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word "comprise" or variations such as "comprises" or

24

17988011_1 (GHMatters) P109836.AU.2

"comprising" is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention.

25

17988011_1 (GHMatters) P109836.AU.2

Claims

1. A rock bolt comprising:

a shaft extending along an axis between a leading end and a trailing end, the shaft including a hollow passage defined by an internal wall; and

at least one reinforcing member disposed in the hollow passage of the shaft,

wherein the at least one reinforcing member increases loading capacity of the rock bolt.

2. A rock bolt according to claim 1, wherein the rock bolt is a semi-rigid or a rigid bolt.

3. A rock bolt according to claims 1 or 2, wherein the at least one reinforcing member is in the form of a longitudinal element.

4. A rock bolt according to any one of claims 1 to 3, comprising a drilling arrangement extending from the leading end enabling the rock bolt to be self drilling.

5. A rock bolt according to claim 4, wherein the drilling arrangement includes a drill bit secured to the leading end of the shaft.

6. A rock bolt according to either claim 4 or claim 5, further comprising at least one outlet extending from the hollow passage to an external surface of the shaft, the at least one outlet being in fluid communication with the hollow passage.

7. A rock bolt according to claim 6, wherein the at least one outlet includes an annular recess extending between the drilling arrangement and the rock bolt.

8. A rock bolt according to any one of the preceding claims, further comprising a retaining arrangement arranged to retain the at least one reinforcing member disposed in the hollow passage of the shaft.

9. A rock bolt according to claim 8, wherein the retaining arrangement includes any of the following: an end cap, a plug, a swaged anchor, and a barrel and wedge.

10. A rock bolt according to either claim 8 or claim 9, wherein the retaining arrangement is fitted to the leading end and/or the trailing end of the shaft.

11. A rock bolt according to any one of the preceding claims, wherein the shaft of the rock bolt includes external profiling extending along an external surface.

12. A rock bolt according to claim 11, wherein the external profiling includes any of corrugations, threading, protrusions, flat surfaces extending in the longitudinal direction.

13. A rock bolt according to any one of the preceding claims, wherein the at least one reinforcing member includes profiling.

14. A rock bolt according to claim 13, wherein the reinforcing member profiling includes spaced apart deformations or protrusions.

15. A rock bolt according to either claim 13 or claim 14, wherein the at least one reinforcing member includes multiple wound co-extending strands.

16. A rock bolt according to claim 15 when dependent on claim 13, wherein the reinforcing member profiling is in the form of spaced apart bulbous portions.

17. A rock bolt according to any one of the preceding claims, further comprising a settable material, wherein the at least one reinforcing member is embedded in the settable material and disposed within the hollow passage.

18. A rock bolt according to claim 17, wherein the settable material bonds to both the hollow shaft and the at least one reinforcing member to allow load transference between the hollow shaft and the reinforcing member.

19. A rock bolt according to either claim 17 or claim 18, wherein the settable material is a cementitious material or resin.

20. A rock bolt according to any one of the preceding claims, wherein the length of the at least one reinforcing member is less than the length of the shaft.

21. A rock bolt according to claim 20, wherein the at least one reinforcing member is arranged to be disposed in the shaft in a region vulnerable to shearing through discontinuity in the rock strata.

22. A rock bolt according to any one of the preceding claims, wherein the at least one reinforcing member is relatively inflexible compared to the shaft.

23. A rock bolt according to any one of claims 1 to 22, wherein the at least one reinforcing member is more flexible compared to the shaft of the rock bolt.

24. A rock bolt according to any one of the preceding claims, wherein the at least one reinforcing member may be steel and/or polymeric, and may be formed as a single element or from multiple strands.

25. A rock bolt according to any one of the preceding claims, wherein the leading end of the shaft is configured for anchoring to rock strata, and the trailing end is configured for receiving settable material.

26. A rock bolt according to any preceding claim, wherein the at least one reinforcing member improves the shear capacity of the rock bolt.

27. A rock bolt according to any preceding claim, wherein the at least one reinforcing member improves the tensile capacity of the rock bolt.

28. A rock bolt assembly including the rock bolt according to any one of the preceding claims further comprising a tensioning assembly mounted on an end of the shaft, the tensioning assembly arranged in use to tension the rock bolt.

29. A rock bolt assembly according to claim 28, wherein the tensioning assembly comprises an end fitting being mounted adjacent the trailing end of the shaft.

30. A rock bolt assembly according to claim 29, wherein the end fitting comprises a barrel and wedge assembly.

31. A rock bolt assembly according to any one of claims 28 to 30, wherein the tension assembly further comprises a bearer plate which is mounted to the shaft between the end fitting and the distal end of the shaft.

32. A method of installing the rock bolt comprising:

installing a rock bolt in a bore in rock substrate, the rock bolt including an internal passage defined by an internal wall;

disposing a settable material into the hollow passage of the rock bolt, and

inserting at least one reinforcing member in the hollow passage.

33. A method according to claim 32, wherein disposing the settable material into the hollow passage occurs prior to inserting the at least one reinforcing member in the hollow passage.

34. A method according to claim 33, wherein inserting the at least one reinforcing member disposes the at least one reinforcing member in the settable material; and

allowing the settable material to harden so that the at least one reinforcing member is retained in the hardened settable material allowing load transference between the internal wall of the rock bolt and the at least one reinforcing member.

35. A method according to claim 32, wherein inserting the at least one reinforcing member into the hollow passage of the rock bolt prior to installing the rock bolt in the bore of the rock substrate.

36. A method according to claim 35, wherein disposing the settable material into the hollow passage of the rock bolt after the at least one reinforcing member and the rock bolt are installed in the bore of the rock substrate, and allowing the settable material to harden so that the at least one reinforcing member is retained in the hardened settable material and allowing load transference between the internal wall of the rock bolt and the at least one reinforcing member.