AU2016202745B2

AU2016202745B2 - A reinforcing mesh and method of installing a reinforcing mesh

Info

Publication number: AU2016202745B2
Application number: AU2016202745A
Authority: AU
Inventors: David William Evans
Original assignee: DSI Underground Australia Pty Ltd
Current assignee: DSI Underground Australia Pty Ltd
Priority date: 2015-05-18
Filing date: 2016-04-29
Publication date: 2021-05-06
Anticipated expiration: 2036-04-29
Also published as: AU2016202745A1

Abstract

A REINFORCING MESH AND METHOD OF INSTALLING A REINFORCING MESH ABSTRACT A chain wire reinforcing mesh (100) for securing a rock face (10) has an array of interwoven wire elements (101) each bent into a zig-zag pattern and extending in a first direction (A). Each pair of adjacent wire elements (101) is interwoven to define a plurality of joints (102) between adjacent wire elements (101). The joints (102) are arranged in a series of rows (108) extending in the first direction (A) and a series of columns (109) extending in a second direction (B) perpendicular to the first direction (A). A plurality of supports (110) each restrain one of the joints (102) against relative displacement between the respective wire elements (101) at the joint (102) in the first and second directions (A, B) to form a restrained joint (102'). 1015 (050 k3o (0-7 0 103

Description

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A REINFORCING MESH AND METHOD OF INSTALLING A REINFORCING MESH

Field

[0001] The present invention relates to strata control in civil engineering and mining operations and in particular relates to a reinforcing mesh for supporting the roof or wall surface of a mine, tunnel or other ground excavation, and a method of installing a reinforcing mesh.

Background

[0002] Rock faces forming the roof or wall of mines, tunnels or other ground excavations are typically secured with the use of rock bolts in conjunction with sheets of reinforcing mesh. Rock bolts, which may be in the form of a rigid steel bar or flexible steel strand, are secured into bore holes drilled through the rock face and consolidate and reinforce the rock strata. Sheets of mesh extend across the rock face to locally confine the rock surface and prevent small fragments of rock from falling down and endangering occupants of the mine or tunnel.

[0003] The mesh is typically secured against the rock face by being sandwiched between the rock face and the plate washer associated with each rock bolt that acts to transfer load between the rock bolt and the rock face.

[0004] The sheets of mesh are typically formed with a length of the order of 2 to 6 m and a width of 0.5 to 2.4 m that can be manually handled and installed. The mesh is typically in the form of rigid steel wire mesh, in which individual elements of the mesh are welded together. Attempts have also been made to utilise a mesh in the form of chain wire mesh, which is formed of interlinked or woven wire elements that are bent into a zig-zag pattern, with adjacent wire elements being woven to define a network of diamond shaped apertures, providing a highly flexible mesh given that the joints between the woven wire elements are not mechanically constrained.

[0005] To install a sheet of rigid steel wire mesh, the mesh is typically manually held against the rock face whilst a series of bore holes are drilled into the rock face through the apertures in the wire mesh and rock bolts are subsequently installed into the bore holes. The plate washers that secure the trailing head of each rock bolt against the rock face engage the wire elements of the mesh about the aperture through which the rock bolt is installed, sandwiching the wire mesh between the plate washer and the rock face, thereby securing the mesh sheet against the rock face. In one typical method, a first bore hole is drilled and a first rock bolt installed so as to provide an initial pinning of the mesh against the rock face, following which further bore holes are drilled and further rock bolts subsequently installed. One or more of the bore holes are at times also drilled prior to location of the mesh against the rock face.

Summary of Invention

[0006] In a first aspect the present invention provides a chain wire reinforcing mesh for securing a rock face, said mesh comprising: an array of interwoven wire elements each bent into a zig-zag pattern and extending in a first direction, each pair of adjacent said wire elements being interwoven to define a plurality of joints between said adjacent wire elements, saidjoints being arranged in a series of rows extending in said first direction and a series of columns extending in a second direction perpendicular to said first direction; and a plurality of supports each restraining individually one of said joints against relative displacement between the respective said wire elements at said joint in said first and second directions to form a restrained joint.

[0007] Preferably, in a band of said joints extending in said first direction and comprising a plurality of rows of said joints, a plurality of said joints in at least a majority of said rows in said band are restrained joints.

[0008] Preferably, a plurality of said joints in each of said rows in said band are restrained joints.

[0009] In a preferred form, said band is located adjacent a first edge of said mesh extending in said first direction.

[0010] In a preferred form, said restrained joints in said band are arranged in a plurality of groups of adjacent restrained joints, said groups being mutually spaced in said first direction.

[0011] In one form, a plurality of said bands are provided, said bands being mutually spaced in said second direction.

[0012] In one particular form, each said band extends over at least three said rows of joints.

[0013] In a preferred embodiment, each of said supports comprises a first support element extending about the respective said joint in said first direction and a second support element extending about the respective said joint in said second direction.

[0014] In a preferred form, each of said support elements comprises a tie.

[0015] In one preferred form, each of said ties comprises a cable tie.

[0016] In another form, each of said ties comprises a wire tie.

[0017] In another form, each of said support elements is a swage.

[0018] In a second aspect the present invention provides a method of installing the mesh of the first aspect to secure a rock face, said method comprising: a) locating said reinforcing mesh with a plurality of said restrained joints located adjacent a rock face to be secured; b) drilling a plurality of bore holes into the rock face; c) installing a plurality of rock bolts, each into one of said bore holes; and d) securing said mesh against the rock face by a plate washer mounted on each of said rock bolts, with said rock bolts extending through apertures of said mesh, such that said mesh is secured between said plate washers and the rock face.

[0019] Typically, step a) is carried out prior to step b), each of said bore holes being drilled through an aperture of said mesh. Alternatively, step b) may be carried before step a), for at least some of said bore holes.

[0020] Typically, a first of said rock bolts is extended through an aperture of said mesh adjacent at least one of said restrained joints. Preferably, each of said rock bolts is extended through an aperture of said mesh adjacent at least one of said restrained joints.

[0021] Typically, step a) is carried out before step c). In an alternative method, step c) is carried out before step a).

[0022] In one form of such an alternative method, a first plate washer is mounted on each said rock bolt during step c), a second plate washer being mounted on each of said rock bolts during step d) such that said mesh is secured between said first plate washers and said second plate washers.

Brief Description of Drawings

[0023] A preferred embodiment of the present invention will now be described, by way of an example only, with reference to the accompanying drawings wherein:

Fig. 1 is a plan view of a chain wire reinforcing mesh;

Fig. 2 is an enlarged fragmentary plan view of the chain wire mesh of Fig. 1;

Fig. 3 is an isometric view of the chain wire mesh of Fig. 1;

Fig. 4 is an enlarged fragmentary isometric view of the chain wire mesh of Fig. 1;

Figs. 5 to 7 are isometric views depicting successive stages of installation of the chain wire reinforcing mesh of Fig. 1.

Description of Embodiments

[0024] Figures 1 to 4 of the accompanying drawings depict a sheet of chain wire reinforcing mesh 100 according to a first embodiment. The mesh 100 comprises an array of interwoven wire elements 101 that are each bent into a zig zag pattern and extend in a first direction A. The wire elements 101 are typically formed of steel. Each pair of adjacent wire elements 101 is interwoven to define a plurality of joints 102, interlinking the apexes and troughs of the zig zag pattern of each of the adjacent wire elements 101.

[0025] The series of joints 102 of each pair of adjacent wire elements 101 are aligned in a row 108 extending in the first direction A. The joints 102 of successive pairs of adjacent wire elements 101 (that is, in successive rows of joints) are offset in the first direction A, whilst corresponding joints 102 of every second pair of adjacent wire elements 101 (that is, in every second column of joints) are aligned in a series of columns 109 extending in a second direction B that is perpendicular to the first direction A. The joints 102 are thus arranged in a series of rows 108 and a series of columns 109. A diamond shaped aperture 103 is defined between adjacent wire elements 101 between successive joints 102 therebetween.

[0026] The interweaving of the mesh elements 101 does not restrain the joints 102, such that the joints 102 are able effectively to separate on handling, by displacing adjacent pairs of wire elements 101 towards each other, collapsing the apertures 103 and allowing the mesh 100 to sag.

[0027] The mesh 100 further comprises a plurality of supports 110 that each restrain one of the joints 102 against relative displacement between the wire elements 101 at the joint 102, thus forming a restrained joint 102'. Each support 110 restrains relative displacement between the interwoven wire elements 101 both in the first and second directions A, B.

[0028] In a preferred form, each support 110 comprises first and second support elements 111, 112. The first support element 111 extends about the joint 102 in the first direction A, encircling the joint 102. The first support element 111 restrains the joint 102 against relative displacement between the adjacent wire elements 101 at the joint 102 in the first direction A. The second support element 112 extends about the joint 102 in the second direction B, again encircling the joint 102. The second support element 112 restrains the joint 102 against relative displacement between the wire elements 101 at the joint 102 in the second direction B.

[0029] In the configuration depicted, each of the support elements 111, 112 is in the form of a tie, and specifically a cable tie. It is also envisaged that each of the ties may be in the form of a wire tie. It is still further envisaged that each of the support elements 111, 112 may be a swage, with first and second swages encircling the joint 102 in the first and second directions A, B respectively. Rather than being in the form of first and second support elements, it is also envisaged that each support 110 may be an integral form of connector that restrains the joint 102 in the first and second direction A, B.

[0030] Referring to Figure 1, in the embodiment depicted, a first band 120 of the joints 102 extend in the first direction A. In the embodiment depicted, the first band 120 is located adjacent a first edge 104 of the mesh 100 that extends in the first direction A. The first band 120 comprises a plurality of rows 108 of the joints 102, and in the embodiment depicted comprises four rows 108 of joints 102. The first band 120 will typically comprise at least three rows 108 of joints 102 and will typically have a width in the second direction B of about 300 mm to 600 mm. In at least a majority of the rows 108 of the first band 120, a plurality of the joints 102 are restrained joints 102'. Specifically, in the embodiment depicted, a plurality of restrained joints 102' are provided in each of the rows 108 of the first band 120. In the particular configuration depicted, the restrained joints 102' of the first band 120 are grouped into three groups of adjacent restrained joints 102'. The groups are spaced in the first direction A across the mesh 100. In total, five restrained joints 102' are provided along each row 108 of the first band 120, with two adjacent restrained joints 102' being located in edge groups located adjacent opposing second and third edges 105, 106 of the mesh 100, that each extend in the second direction B, and an additional restrained joint 102' located in a central group located approximately midway between the second and third edges 105, 106. In each group, the restrained joints 102' are typically grouped so as to be located in adjacent columns 109. The restrained joints 102' are thus typically arranged in a continuous sequence of joints 102 within each group, although it is envisaged that they may be arranged in a discontinuous sequence. Provision of the restrained joints 102' locally stiffens the first band 120, whilst leaving a majority of the joints 102 within the first band 120 unrestrained.

[0031] In the configuration depicted, second and third bands 130, 140 of joints 102 are provided with groups of restrained joints 102' in the same general manner as discussed above in relation to the first band 120. The second and third bands 130, 140 again extend in the first direction A and each of the bands 120, 130, 140 are mutually spaced in the second direction B. In the configuration depicted, the second band B is located generally centrally relative to the first edge 104 and an opposing fourth edge 107 of the mesh 110 that extends in the first direction A. The restrained joints 102' serve to locally stiffen the second and third bands 130, 140, to further ease handling of the mesh 100.

[0032] Installation of the mesh 100 to reinforce a rock face 10, in the form of a mine roof, will now be described with reference to Figures 5 to 7.

[0033] Referring firstly to Figure 5, the mesh 100 is located with the first band 120, including restrained joints 102', located adjacent the rock face 10. The restrained joints 102' in the first band 120 act to locally stiffen the first band 120, reducing the tendency for apertures 103 within the first band 120 to collapse or for the mesh 100 to sag in the area within the first band 120. The remaining portions of the mesh 100, outside of the first band 120, may be allowed to sag vertically away from the rock face 10. Bore holes are drilled into the rock face 10, through apertures 103 of the mesh 100 within the first band 120 (or prior to locating the first band 120 adjacent the rock face 10), preferably adjacent at least one of the restrained joints 102'. A rock bolt 20 is then installed into each bore hole, through the corresponding aperture 103 in the mesh

100. A plate washer 30 is mounted on each of the rock bolts 20 beneath the mesh 100, such that the mesh 100 is secured between each plate washer 30 and the rock face 10. Figure 5 depicts installation of a first rock bolt 20, in a position corresponding to the central group of restrained joints 102' of the first band 120. In this example installation, the first bore hole is drilled, and the first rock bolt 20, installed prior to drilling of subsequent bore holes and installation of subsequent rock bolts 20 in the first band 120. This provides initial pinning of the mesh 100 to the rock face 10 prior to installation of subsequent rock bolts 20. Figure 6 shows the arrangement following installation of two further rock bolts 20, in locations corresponding to the edge groups of restrained joints 102' located adjacent the second and third edges 105, 106 of the mesh 100.

[0034] Once rock bolts 20 have been installed in the first band 120, subsequent portions of the mesh 100 may be subsequently lifted to a position adjacent the rock face 10. With the second band 130 located adjacent the rock face 10, further bore holes are drilled and rock bolts 20 installed. The same process is carried out for the third band 140, leaving a fully installed sheet of mesh 100 as depicted in Figure 7. The various bore holes may either be predrilled, prior to location of the relevant band 130, 140 adjacent the rock face 10, or may otherwise drilled through the apertures 103 of the mesh following lifting of the relevant band 130, 140 to adjacent the rock face 10.

[0035] A person skilled in the art will appreciate various other modifications and alterations may be made to the mesh and installation method described above to suit different application. In relation to the installation method, it is envisaged, for example, that the bore holes may be drilled before locating the mesh 100 adjacent the rock face 101. The rock bolts 20 could also be secured to the rock face 20 by way of a series of first plate washers prior to installation of the mesh 100. The mesh 100 would then be installed by being positioned with elongate tails of the rock bolts projecting beyond the heads of the rock bolts, passing through the apertures 103 of the mesh 100. A series of second plate washers would be mounted on the exposed tails of the rock bolts to secure the mesh between the first and second plate washers.

Claims

1. A chain wire reinforcing mesh for securing a rock face, said mesh comprising: an array of interwoven wire elements each bent into a zig-zag pattern and extending in a first direction, each pair of adjacent said wire elements being interwoven to define a plurality of joints between said adjacent wire elements, said joints being arranged in a series of rows extending in said first direction and a series of columns extending in a second direction perpendicular to said first direction; and a plurality of supports each restraining individually one of said joints against relative displacement between the respective said wire elements at said joint in said first and second directions to form a restrained joint.

2. The mesh of claim 1, wherein in a band of said joints extending in said first direction and comprising a plurality of rows of saidjoints, a plurality of saidjoints in at least a majority of said rows in said band are restrained joints.

3. The mesh of claim 2, wherein a plurality of said joints in each of said rows in said band are restrained joints.

4. The mesh of either one of claims 2 and 3, wherein said band is located adjacent afirst edge of said mesh extending in said first direction.

5. The mesh of any one of claims 2 to 4 wherein said restrained joints in said band are arranged in a plurality of groups of adjacent restrained joints, said groups being mutually spaced in said first direction.

6. The mesh of any one of claims 2 to 5, wherein a plurality of said bands are provided, said bands being mutually spaced in said second direction.

7. The mesh of any one of claims 2 to 6, wherein each said band extends over at least three said rows of joints.

8. The mesh of any one of claims I to 7, wherein each of said supports comprises a first support element extending about the respective said joint in said first direction and a second support element extending about the respective said joint in said second direction.

9. The mesh of claim 8, wherein each of said support elements comprises a tie.

10. The mesh of claim 9, wherein each of said ties comprises a cable tie.

11. The mesh of claim 9, wherein each of said ties comprises a wire tie.

12. The mesh of claim 8, wherein each of said support elements is a swage.

13. A method of installing the mesh of any one of claims I to 12 to secure a rock face, said method comprising: a) locating said mesh with a plurality of said restrained joints located adjacent said rock face; b) drilling a plurality of bore holes into the rock face; c) installing a plurality of rock bolts, each into one of said bore holes; d) securing said mesh against the rock face by a plate washer mounted on each of said rock bolts, with said rock bolts extending through apertures of said mesh, such that said mesh is secured between said plate washers and the rock face.

14. The method of claim 13, wherein step a) is carried out prior to step b), each of said bore holes being drilled through an aperture of said mesh.

15. The method of claim 13, wherein step b) is carried out before step a), for at least some of said bore holes.

16. The method of any one of claims 13 to 15, wherein a first of said rock bolts is extended through an aperture of said mesh adjacent at least one of said restrained joints.

17. The method of claim 16, wherein each of said rock bolts is extended through an aperture of said mesh adjacent at least one of said restrained joints.

18. The method of any one of claims 13 to 17, wherein step a) is carried out before step c).

19. The method of claim 15, wherein step c) is carried out before step a).

20. The method of any one of claims 13 to 19, wherein a first plate washer is mounted on each said rock bolt during step c), a second plate washer being mounted on each of said rock bolts during step d) such that said mesh is secured between said first plate washers and said second plate washers.

DYWIDAG-Systems International Pty Limited Patent Attorneys for the Applicant/Nominated Person SPRUSON & FERGUSON