AU2021101229A4

AU2021101229A4 - Roof support assembly

Info

Publication number: AU2021101229A4
Application number: AU2021101229A
Authority: AU
Inventors: Peter Harold Craig; Matthew Raffaele Holden; Zacharia PETERS
Original assignee: FCI Holdings Delaware Inc
Current assignee: FCI Holdings Delaware Inc
Priority date: 2021-03-09
Filing date: 2021-03-09
Publication date: 2021-05-06
Anticipated expiration: 2029-03-09

Abstract

Disclosed is a roof support assembly for support rock strata of a mine. The roof support assembly including first and second truss plates, at least one truss cable, and a truss cable tensioning arrangement. The at least one truss cable 5 extends along an axis between the first and second truss plates. The truss cable tensioning arrangement is for tensioning the at least one truss cable, and the tensioning arrangement is disposed at said first truss plate. Also disclosed is a truss plate for rock strata support. The truss plate including a body having an interior face arranged to be in facing arrangement with rock strata, and an 10 opposite exterior face. The truss plate also includes an aperture extending through the body between the interior and exterior faces and arranged to receive a rock bolt to secure the truss plate to the rock strata. The truss plate also includes at least one retaining structure disposed on the exterior face and configured to engage a truss cable. The retaining structure is configured to 15 prevent rotation of the truss cable relative to the plate to facilitate tensioning of the truss cable in use. [Fig. 1] 17486292_1 (GHMatters) P114846.AU 1/10 0 r.J0 00 Jemnur 00 LO mr.J0 rPIT ly. r.0 rJ 0m N'.

Description

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ROOF SUPPORT ASSEMBLY TECHNICAL FIELD

This disclosure relates a roof support assembly suitable for use in mining and tunnelling to provide rock and wall support. This disclosure also relates to a truss plate for the roof support assembly for supporting the roof of a mine. This disclosure also relates to a method of installation of the system, assembly and truss plate. The system, assembly is suitable for use in hard rock applications as well as 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 reduce the possibility of collapse. Rock bolts, such as rigid shaft rock bolts and flexible cable bolts, are widely used for consolidating the rock strata.

Truss systems may be used in conjunction with rock bolts to provide further support to the rock formation. Truss systems combine into-rock face support (e.g., the rock bolts) with lateral-rock face support, usually including truss cable bolts. The truss cables vary in the tensioning methods and assemblies. For example, truss systems can include truss blocks positioned between two truss plates in the centre of the roadway which allow tensioning of the truss cables. The truss cables are tensioned at the truss block, and the rock bolts may also be secured and tensioned using the truss blocks. This tensioning is performed using large hydraulic tensioning machines and the truss blocks can hang down into the roadway which may be hazardous.

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.

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17486292_1(GHMatters) P114846.AU

SUMMARY

In a first aspect, disclosed is a truss plate for rock strata support. The truss plate comprises a body having an interior face arranged to be in facing arrangement with rock strata, and an opposite exterior face. The truss plate furthers comprise an aperture extending through the body between the interior and exterior faces. The aperture is arranged to receive a rock bolt to secure the truss plate to the rock strata. The truss plate further comprises at least one retaining structure disposed on the exterior face and configured to engage a truss cable. The retaining structure is configured to prevent rotation of the truss cable relative to the plate to facilitate tensioning of the truss cable in use. Such a system would allow the use of simple and conventional techniques for fastening and securing the truss plate to the rock strata. Further, the truss plate may be positioned at the edge of a roadway of a mine including the rock strata, which is beneficial as it is then positioned in a low traffic area of the roadway.

The rock bolt may be in the form of a rigid bolt, a cable bolt or a cable bolt including an end termination disposed about the cable bolt. The rock bolt may also in the form of a vertical bolt or an angled bolt. In the case of a vertical bolt or an angled bolt, the aperture may extend through the body at different angles relative to the interior and exterior faces to accommodate either the vertical or angled bolt.

In some embodiments, the retaining structure incorporates a passage to receive the truss cable. The passage can be defined by an interior wall including one or more key surfaces that are arranged to engage with complementary key surface on the truss cable to prevent truss cable rotation during tensioning of the at least one truss cable. The key surfaces enable the passage of the retaining structure to act as a guide for the truss cable to be secured while preventing rotation of the truss cable during tensioning.

In some embodiments, the one or more key surfaces include at least one flat surface extending in the direction of the passage. Such an arrangement will allow

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17486292_1 (GHMatters) P114846.AU a portion of the truss cable to be secured properly to the truss plate. The one of more key surfaces may include any suitable profile or shape to prevent rotation of the truss cable during tensioning. For example, the key surfaces may include a corresponding ridge and groove.

In some embodiments, the passage can extend in a direction transverse to the direction of the aperture. In this manner, any force applied during tensioning would be transmitted along the axis of the passage. For example, if the truss cable is oriented along the same direction, then the full force applied during tensioning is able to act along the cable.

In some embodiments, the passage can extend between a first end and a second end. The retaining structure can further comprise an abutment surface at the first end that extends at least partially about the passage. The abutment surface provides a stopping mechanism as well as a surface where the applied torque can be converted to a tensioning force.

In some embodiments, the abutment surface is substantially normal to the interior face. Such a positioning ensures that the force to be transmitted during tensioning is able to act along the axis of the passage.

In some embodiments, the second end of the passage is raked to strengthen the retaining structure. The raked configuration has a gradually reducing cross sectional area as opposed to a stepped cross-sectional area. A stepped cross sectional area would produce a distinct edge that can act as a stress concentrator thereby causing early failure.

In some embodiments, the interior wall of the passage diverges or tapers away from the abutment surface. This will allow for a degree of movement of the truss cables during installation as well as use.

In some embodiments, the truss plate comprises two retaining structures that are spaced apart on the exterior face of the body. This will allow the load acting on

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17486292_1 (GHMatters) P114846.AU the truss plate to be distributed uniformly. The retaining structures are positioned relative to one another such that, when installed, the truss cables extend substantially parallel to one another. This may include the degree of movement permitted by passage as discussed above.

In some embodiments, the truss plate comprises a boss extending about the aperture for receiving the rock bolt. The boss enables forces to be distributed uniformly in all directions surrounding the aperture. The boss may extend at an angle relative to the interior and exterior faces of the truss plate if the aperture is configured to receive an angled bolt when assembled and installed.

In some embodiments, the boss is positioned between the two retaining structures. In this manner, the boss acts to oppose a downward force that would act at the retaining structures during tensioning.

In some embodiments, the boss and the retaining structures can be formed as an integral structure. This will eliminate the need for joints that can act as stress raisers and cause failure of the truss plate.

In some embodiments, the boss is recessed between the two retaining structures. In this manner, the truss plate can maintain a low overall profile even after the rock bolt is installed in the boss.

In a second aspect, disclosed is a roof support assembly for supporting rock strata of a mine. The roof support assembly comprises first and second truss plates. The roof support assembly can also comprise at least one truss cable extending along an axis between the first and second plates. The roof support assembly can also comprise a truss cable tensioning arrangement for tensioning the at least one truss cable. The tensioning arrangement can be disposed at the said first truss plate. By using more than one such an assembly, any desired portion of the rock strata can be easily reinforced or supported. For example, multiple pairs of truss plates, each connected by two truss cables could be employed to cover a large portion of a rock face.

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In some embodiments, the truss cable tensioning arrangement comprises a thread formation disposed on the truss cable, a tensioning nut threadingly engaged with the thread formation. The arrangement may also comprise a retaining structure formed on the first truss plate. The retaining structure may be engageable with the truss cable and configured to prevent rotation of the truss cable relative to the plate. The presence of threaded portions allows for easy engagement with conventional tools such as spanner for example. Thus, there is no need for use of complex equipment such as a hydraulic tensioning device.

In some embodiments, the retaining structure further comprises an abutment surface which is arranged to resist movement of the nut in the direction of the truss cable axis on tensioning of the truss cable. When torque is applied to the tensioning member that is stopped from moving, the torque is transformed into a tensioning force, acting along the axis of the passage.

In a third aspect, disclosed is a method of installing a roof support assembly at a rock substrate. The method comprises mounting first and second truss plates to the rock strata in a spaced relationship from one another. The method also comprises securing at least one truss cable to the first and second truss plates. The method also comprises tensioning of the at least one truss cable through a tensioning arrangement disposed at one of the first and second truss plates. Such a method of installing is easy to implement and requires the use of smaller and less complicated equipment (e.g., spanners) than the hydraulic tensioning devices used to tension the rock bolts and truss cables in the prior art. This is significant especially in an underground mine where the volume of space available to work with can be quite limited and may even preclude the use of complicated/large equipment to perform installation.

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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 bottom perspective view of an embodiment of a roof support assembly;

Fig. 2 is a bottom view of the roof support assembly of Fig. 1;

Fig. 3 is a side view of the roof support assembly of Fig. 1;

Fig. 4 is a bottom perspective close-up view of the roof support assembly of Fig. 1;

Fig. 5 is an end perspective view of an embodiment of a truss plate of the roof support assembly of Fig. 1;

Fig. 6 is an opposite end perspective view of the embodiment of the truss plate of Fig. 5;

Fig. 7 is a close-up cross-sectional view of a portion of the truss plate of Fig. 5;

Fig. 8 is a close-up perspective view of an embodiment of a retaining structure of the roof support assembly of Fig. 1;

Fig. 9 is a perspective view of a further embodiment of a roof support assembly; and

Fig. 10 is a side view of the roof support assembly of Fig. 9.

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

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17486292_1 (GHMatters) P114846.AU 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 Figs. I to 7, disclosed herein is an embodiment of a truss plate 14, 16 for supporting rock strata in mines. The truss plate 14, 16 forms a component of a roof support assembly 10 (best shown in Figs. I to 3) used for reinforcing and supporting rock strata that form part of the roofs of the mining shafts that are created during the process of mining. The roof support assembly 10 generally includes three primary components: the truss plates 14, 16, at least one truss cable 8, and a rock bolt 12 (e.g., a vertical bolt as shown in Figs. 1 to 8 or angled rock bolt as shown in Figs. 9 and 10). A typical mine includes the roof support assembly where each truss plate is positioned at or close to either side of a roadway to maintain (as much as possible) a clear passage through the centre of the roadway of the mine, and any truss cables 8 extending between the truss plates 14, 16 may extend across the roof of the roadway. Any components, such as long tails of rock bolts 12, or components of truss assemblies become a hazard in the roadway if they hang down into the roadway. Thus, a low-profile assembly is advantageous when installed in rock strata while simultaneously satisfying the structural performance requirements.

The truss plate 14, 16 has a body that can define and/or locate multiple sub structures or components therein or attached thereto. Together with these sub structures/components, the truss plate 14, 16 functions to secure the various components of the roof support assembly 10 to one another (e.g., the rock bolt 12 and the truss cables 8).

As illustrated in Figs. 4 - 6, the truss plate 14, 16 includes a body 70 including an interior face 19 is arranged to be in facing arrangement with rock strata when installed. The body 70 also comprises an opposite exterior face 20 that is in facing

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17486292_1 (GHMatters) P114846.AU arrangement with the roadway of the mine shaft when installed. The interior face 19 is typically planar while the opposite exterior face 20 comprises the multiple sub-structures or components therein or attached thereto. The truss plate 14, 16 is generally rectangular (including square) in shape. Other shapes such as circular are also contemplated by this disclosure.

The truss plate 14, 16 further comprises an aperture 60 that extends through the body 70 between the interior face 19 and exterior face 20. The aperture 60 receives the rock bolt 12 that secures the truss plate 14, 16 to the rock strata. For e.g., the rock bolt 12, when installed, supports the rock strata. Generally, this will be in a direction perpendicular to the rock face although the cable bolts may be installed at an angle to the rock face as well. The rock bolt 12 includes a tensioning assembly fitted to an end portion of the rock bolt 12 which tensions to the rock bolt 12 to reinforce the rock strata. The tensioning assembly may include a barrel and wedge anchor 18 surrounding the rock bolt 12. The barrel and wedge anchor 18 may locate into the aperture 60. By applying tension (through hydraulic or mechanical means) to the rock bolt 12 while holding the barrel and wedge anchor in the aperture 60, the truss plate 14, 16 is secured against the rock strata. The diameter of the aperture 60 may vary depending on the diameter of the rock bolt 12 to be utilized and the dimensions of the barrel and wedge anchor 18 required to clamp and tighten the rock bolt 12.

The truss plate 14, 16 also includes at least one retaining structure 21 disposed on the exterior face 20 configured to engage a truss cable 8. The retaining structure 21 is configured to prevent rotation of the truss cables 8 relative to the truss plate 14, 16 to facilitate tensioning of the truss cable 8 in use. In the illustrated embodiment as best shown in Figs. 5 - 7, there are two retaining structures 21 that are defined and spaced apart on the exterior face 20 of the body 70 of truss plate 14. Each of the retaining structures 21 is configured to engage and secure one of the two ends of the two truss cables 8. The other end of the truss cables 8 is engaged by retaining structures 21 defined on the exterior face 20 of the other truss plate 16. The truss cable(s) 8 are used to connect two truss plates 14, 16, and

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17486292_1 (GHMatters) P114846.AU in some embodiments (not shown) support mesh which are able to catch any finer material falling from the roof of the rock strata. In the illustrated embodiment, the truss cables extend substantially parallel to one another.

To engage and secure the truss cables 8 to the truss plate 14, 16, each of the retaining structures 21 includes a passage 36. The passage extends between a first end 42 and a second end 44 in an axial direction. The passage is defined by an interior wall 40 that includes one or more key surfaces 28. In accordance with the disclosure, the one or more key surfaces 28 includes at least one flat surface that extends in the direction of the passage 36 (i.e., in the axial direction). In the illustrated embodiment, the passage 36 includes two opposing flat key surfaces 28, the key surfaces 28 do not extend along the entire length of the passage 36. The key surfaces 28 are configured to engage with respective complementary key surfaces 24 on the truss cable 8 to prevent rotation of the truss cable 8 during tensioning of the truss cable 8. In this embodiment, the complementary key surfaces 24 are machined on to an end termination including a partially threaded section 22 of the truss cable 8. It is understood that the one or more key surfaces and the complementary one or more key surfaces may be many different profiles provided the key surfaces prevent rotation truss cable rotation during tensioning of the at least one truss cable.

The end termination including the partially threaded section 22 (including a free end) of the truss cable is inserted into the passage 36 of the retaining structure 21 and extends out of the first end of the passage. The tensioning member is in the form of a nut 30 including internal threading complementary to the threading of the partially threaded section 22. It is understood that any suitable tensioning member or device may be used providing it tensions the truss cable, for example, is capable of transforming torque into axial movement, and thus tension.

Each retaining structure 21 comprises an abutment surface 46 that extends at least partially about the passage 36 at the first end 42. As best shown in Fig. 8, during installation, the nut 30 is threadingly engaged at the free end of the truss cable (on

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17486292_1 (GHMatters) P114846.AU the partially threaded section 22) and axially moves along the partially threaded section 22 of the truss cable 8 by applying torque to the nut 30. With continued application of torque, a complementary surface 48 on the nut 30 contacts the abutment surface 46 and engages the nut to limit further axial movement of the nut 30. In this position, any further torque applied to the nut 30 will result in the torque being transferred to the partially threaded section 22 of the truss cable 8. This force acts to tension the truss cable 8.

In some embodiments, the abutment surface 46 is substantially normal (e.g., extends in the radial direction of the passage) to the interior face 19 of the body 70. This allows the torque applied to the nut to be transferred fully to the truss cable 8. The abutment surface 46 could also be in other orientations in which case the force transferred may be altered to the truss cable 8 may be altered.

In some embodiments, the second end 44 of the passage 36 may be raked in order to strengthen the retaining structure. As best shown in Fig. 6, the raked second end 44 has a gradual tapered profile from the top of the retaining structure towards the exterior face 20 of the body 70 of the truss plate. This arrangement is able to distribute the loads experienced by the retaining structure 21 to other portions of the truss plates 14, 16 thereby enabling the retaining structure to have improved strength. The raked profile also results in a corresponding raked aperture. Such an aperture allows for a limited movement of the truss cable 8 during installation without the risk of the truss cable 8 causing damaging contact with the truss plate 14, 16.

As best shown in Fig. 7, the passage 36 is made up of three sections - a first section 52, a second section 54 and a third section 56. The first section 52 extends from the second end 44 of the passage in a direction towards the first end 42. The cross section of the passage in this section gradually reduces from a maximum at the second end 44. The second section 54 is a short, frusto-conical section that begins at the end of the first section 52 and results in an abrupt change in the cross section of the passage from the end of the first section 52. The third section 56

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17486292_1 (GHMatters) P114846.AU begins from the end of the second section 54 and again has a gradually decreasing cross section until the first end 42 of the passage. More importantly, the flat surfaces 28 located in the passage extends longitudinally throughout the entire length of the third section 56 and end at the second section 54.

The installation of the truss cable 8 is further facilitated by the interior wall of the passage that diverges or tapers away from the abutment surface 46 at the first end of the passage through the sections as discussed above. For example, such a diverging interior wall has the benefit of allowing lateral movement of up to 5° for the partially threaded section 22 of the truss cable 8. This tolerance for movement is very beneficial to compensate for surface non-uniformities that may naturally occur in the rock face. Such non-uniformities can, for example, result in an unfavourable orientation of one truss plate with respect to another truss plates. Thus, a degree of angular flexible movement of the truss cable is advantageous to compensate for such an unfavourable orientation.

As shown in Figs. 4 and 5, the passage 36 extends in a direction transverse to the direction of the aperture 60. Such an arrangement facilitates the rock bolt 12 to be installed in a direction transverse to that of the truss cables 8. For example, the rock bolt 12 could be located in a direction that is generally perpendicular to the rock strata. The truss cables 8 would then be installed to run parallel to the surface of the rock strata.

As discussed above, two retaining structures 21 may be included on each truss plate 14, 16. The retaining structures 21 can be spaced apart on the exterior face 20 of the body 70. In the illustrated embodiment, the retaining structures 21 are located along a pair of opposite edges of the truss plate 14, 16. Such an arrangement allows two truss cables 8 to be connected to the truss plate 14, 16. The load resulting from such a positioning of the two truss cables 8 will be evenly distributed around the truss plate 14, 16.

In the illustrated embodiment, the truss plate 14, 16 also includes a boss 58 extending about the aperture 60 for receiving the rock bolt 12. The edges of the

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17486292_1(GHMatters) P114846.AU boss 58 take the form of a volcano as best shown in Fig. 6. The main function of the boss 58 is to receive the rock bolt 12 and fasten it using the clamping device in the form of a barrel and wedge anchor 18 (as discussed above). Another function is to distribute the loads that arise from securing the rock bolt 12 uniformly to the truss plates 14,16. In the illustrated embodiment, the boss 58 is located such that it is positioned between the two retaining structures 21. This results in a distribution of forces by the volcano shaped edges around aperture 60. Such a distribution of forces acts to pin the truss plate 14,16 into the rock face thus achieving an improved clamping effect. Depending on the position of this boss 58 and the associated aperture 60, the load distribution of the entire truss plate 8 can be varied.

In accordance with the disclosure, the boss 58 is recessed with respect to the retaining structures 21. Such a configuration allows the plate to have a low-profile (even after the installation of the barrel and wedge anchor 18 in the aperture 60) which is highly desirable in applications such as underground mining.

To have improved strength and toughness, the boss 58 may be formed together with the retaining structures as an integral structure. For example, the boss 58 and the retaining structures 21 could be cast together as a single piece on the exterior face 20 of the truss plate 14, 16.

In the illustrated embodiment, a tail portion 64 is formed on the exterior face of the truss plate extending away from the boss 58 tapering towards an edge of the truss plate 14, 16 between the retaining structures 28. The tail portion 64 increases the rigidity of the truss plate. The tapering surface of the tail portion 64 may have a variable radius such that the surface is substantially normal to the interior face adjacent the boss and tapers to substantially parallel to the interior face towards the edge of the truss plate.

During the tensioning of the truss cables 8, forces act to drag the truss plates 14, 16 towards one another in the longitudinal direction of the truss cables. However, the rock bolt (e.g., vertical rock bolt) has the truss plate in compression against the

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17486292_1 (GHMatters) P114846.AU rock surface. In other words, the rock bolt clamps the truss plate against the rock strata so the truss plates 14 remain in position.

The truss plates may be made of steel or any other suitable metallic material. Generally, the truss plate is cast as one integral piece in order to enhance the structural integrity. Alternatively, the disclosed embodiments may also be obtained via (a combination of techniques such as casting/machining etc).

At the second truss plate 14, an end of the truss cable 8 is connected to the truss plate passage via a clamping device 36 in the form of a barrel and wedge anchor 18.

The construction of the second truss plate 14 is the same as that of the first truss plate 16. The primary difference between the second truss plate 14 and the first truss plate 16 is the position of the truss plate relative to the rock strata and the roadway and the securement device of the truss cable 8. As shown in Figs. 1 to 3, the truss plate 14 is positioned as a mirror image of the truss plate 16. The diameter of the truss cable inserted into the passage 36 is smaller and thus there is a clearance about the truss cable relative to the internal wall of the passage (unlike the other end of the truss cable 8 which has the end termination including the partially threaded section 22 coupled to the attachment section 25 - both of which are designed to engage the internal wall to prevent rotation of the truss cable relative to the retaining structure). In this way, the truss cable 18 does not contact the internal wall of the passage 36 of the truss plate 14 during installation or in use.

The truss cable 8 is tensioned at the first truss plate 14, and a clamping device is used to secure the truss cable relative to the second truss plate 16. In the illustrated embodiment, the clamping device is in the form of a barrel and wedge. The clamping device allows the truss cable to be tensioned at the first truss plate. As the truss cable is pulled in the direction of the first truss plate (through the application of torque on the tensioning member) the wedges clamp down on the truss cable within the barrel and anchor the truss cable in position within the

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17486292_1 (GHMatters) P114846.AU second truss plate and allows the initial slack to be taken out of the truss cable. Each barrel and wedge contacts the respective retaining structure to provide the anchorage to the truss cable. In alternative embodiments, the end termination may also be in the form of a tensioning member, such as a nut and thread as used in relation to the first truss plate.

In this manner, each truss plate 14, 16 acts as a coupling and anchoring point for the rock bolt 12 and the truss cables 8 that are oriented in different directions (i.e. the rock bolt that is installed into the rock face vertically and the truss cables that extend between different truss plates parallel to the rock face). Such an assembly can support mesh to catch finer rock material falling from the rock strata. The truss cables also act as reinforcement. to be transferred from the rock bolt 12 installed into the rock face to the truss cables 8 through the truss plates (14, 16).

Multiple roof support assemblies 10 may be employed to secure large portions of the rock face to be supported using the roof support assembly 10.

Referring to Figs. 1 to 3, the truss cables 8 will be described in more detail. The truss cables are formed of strands of steel or other metallic strands that are wound together to form a thick cable. In some forms, they also include a centre strand or may have a hollow tubular portion extending along a longitudinal axis of the cable. Such an arrangement allows the truss cables to have a higher tensile strength than the individual strands that they are composed off while also having a degree of flexibility. The diameter of the individual strands, the number of strands wound together, the material of the strands can all be controlled and varied to change the load carrying capabilities depending upon user requirements. As described above, the truss cables 8 comprise end sections that include threaded sections 22 that have flat surfaces 24 machined into them. The end termination may also include an attachment section 25. In this way, the threaded section 22 may extend into the attachment section 25 that enables the truss cable 8 to be attached to the threaded bolt 22. The end termination is disposed about the truss cable 8. In some forms, the attachment section 25 may be swaged, formed, or

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17486292_1 (GHMatters) P114846.AU crimped about the truss cable. The length of the end termination (including both the threaded section and the attachment section) may vary as required depending on the size of the truss plate and the length of the threaded section required to tension the truss cable.

The embodiments described above may be used to implement the following method for installing a roof support at a rock substrate. In a first step, first and second truss plates 14 and 16 are mounted to the rock strata in a spaced relationship from one another. The distance between them can vary providing the length of the truss cables 8 that can be secured to them. The orientation of the truss plates is important while mounting them. It must be in such a manner that the retaining structures 21 together with the respective passages 36 of both the truss plates are located along a common line. Once the truss plates 14, 16 have been positioned and mounted using rock bolts 12, the truss cable 8 are secured to the first and second truss plates 14 and 16. This can be performed using a barrel and wedge anchor 18 at one end and applying torque to the tensioning member in the form of nut 30 at the other end of the truss cable 8. Once the truss cable 8 is secured to the first and second truss plates 14 and 16, the cable is tensioned through a tensioning arrangement disposed at one of the first and second truss plates. For example, if the barrel and wedge anchor is provided at the first truss plate 14, then the tensioning arrangement comprising the nut 30 and the retaining structure 21 would be provided at the second truss plate 16.

Now referring to Figs. 9 and 10, a second embodiment of a rock support assembly is shown. The primary difference between the second embodiment and the first embodiment is that an angled rock bolt is used with the truss plate rather than a vertical rock bolt. Both the vertical rock bolt and the angled rock bolt may be in the form of a rigid bolt, a cable bolt or a cable bolt including an end termination disposed about the cable bolt. The end termination may be similar to the end termination discussed in relation to the first truss plate including a threaded section and an attachment section disposed around the cable bolt. The roof support assembly according to this embodiment is configured to support rock

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17486292_1 (GHMatters) P114846.AU strata that is not regular or relatively planar. For example, the roof can have an irregular/contoured profile in a radial or parallel direction of the roadway. In this case, it may not be possible to use the roof support assembly of the first embodiment to secure the rock strata.

In the illustrated embodiment, the associated aperture 160 and the boss 158 are oriented in a direction that is transverse to the interior face 19 of the truss plate 14, 16 (as in the first embodiment). Rather, they are angled transversely with respect to the interior face 19 of the truss plate to accommodate the angled rock bolt 12. The aperture 160, as in the case of thefirst embodiment, extends between the interior face 19 and exterior face 20 and receives the angled rock bolt 12. The diameter of the aperture 160 is dependent on the diameter of the rock bolt 12 and is generally selected such that the rock bolt 12 has a clearance that allows a degree of freedom such that the orientation of the rock bolt may be changed within the aperture 160. The diameter of the aperture 160 also depends on the size of the barrel and wedge anchor 18.

The barrel and wedge anchor 18 is configured to locate into the boss 158. In this embodiment, the barrel and wedge anchor comprises a dome shaped portion. The profile of the dome shaped portion is complementary to the profile of the inner portion of the boss. This allows the orientation of the barrel and wedge anchor 18 to be changed within the boss 158. This would in turn allow the rock bolt 12 to be oriented at different angles with respect to the axis of the aperture160/boss 158.

It should be noted that the angle of the boss 158/aperture 160 can be varied to prepare truss plates that can be secured to a variety of different rock strata profiles.

In some embodiments the aperture which extends the interior and exterior faces has a constant diameter, and in some embodiments the diameter increases towards the interior face from the exterior face. In some embodiments, the diameter increases consistently towards the interior face.

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The system described above has multiple benefits. A major benefit is that this system eliminates the need for using hydraulic tensioning systems to tension the truss cables that connect two truss plates. Generally, in an underground mine environment, it will be quite cumbersome to hold and connect the hydraulic tensioning device in a direction along the truss cables connecting the two truss plates. This system utilizes simple and widely available devices such as spanners and hexagonal nuts to achieve the same effect as with hydraulic tensioning.

Secondly, the construction and configuration of the truss plate allows for a lightweight and low-profile plate without compromising on the performance aspects. Low profile is a significant concern especially in enclosed and limited spaces such as underground mines. Similarly, the effort required to hold the plates while performing a standard rock bolting procedure is reduced owing to the lightweight nature of the truss plate.

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 "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.

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Claims

1. A truss plate for rock strata support, the truss plate comprising:

a body having an interior face arranged to be in facing arrangement with rock strata, and an opposite exterior face,

an aperture extending through the body between the interior and exterior faces and arranged to receive a rock bolt to secure the truss plate to the rock strata; and

at least one retaining structure disposed on the exterior face and configured to engage a truss cable, wherein the retaining structure is configured to prevent rotation of the truss cable relative to the plate to facilitate tensioning of the truss cable in use.

2. A truss plate according to claim 1, wherein the retaining structure incorporates a passage to receive the truss cable, the passage being defined by an interior wall including one or more key surfaces that are arranged to engage with complementary key surface on the truss cable to prevent truss cable rotation during tensioning of the at least one truss cable.

3. A truss plate according to claim 2 or 3, wherein the passage extends in a direction transverse to the direction of the aperture.

4. A roof support assembly for support rock strata of a mine, the assembly comprising:

first and second truss plates;

at least one truss cable extending along an axis between the first and second plates; and

a truss cable tensioning arrangement for tensioning the at least one truss cable, the tensioning arrangement being disposed at said first truss plate.

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5. A roof support assembly according to claim 14, wherein the truss cable tensioning arrangement comprises a thread formation disposed on the truss cable, a tensioning nut threadingly engaged with the thread formation, and a retaining structure formed on the first truss plate, the retaining structure being engageable with the truss cable and configured to prevent rotation of the truss cable relative to the plate.

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12 12 14 16

42 44 8 44 22 25 20

1/10

42 21 24 25 8 18 42 18 18 21 Fig. 1