FIELD OF THE INVENTION

This invention relates generally to the field of support structures primarily used in subterranean operations such as the mining industry. In particular, the invention relates to prevention of fall of rock and, more particularly, to a surface containment method and apparatus.

BACKGROUND OF THE INVENTION

Although, the health and safety of all personal working in underground operations are of utmost importance, fall of ground remain a common problem.

Recent developments led to utilization of ground support methods such as roof or rib support to protect against ground fall. Despite these developments, fall of ground, today still, represents a significant hazard to underground operators including mine workers. Appropriate support selection and adequate support system design is thus critical to the prevention of ground fall and ground fall accidents.

It is further well known that an objective of a support system for a hanging wall in a mining environment is to mobilize and conserve the inherent strength of the rock mass so that it becomes self-supporting. The concept of reinforcing mining mesh with wire rope (cables) is not new. This was traditionally done in conventional mining (non-mechanised) by installing a mining bolt into the hanging wall. The bolt has a loop protruding from the rock face, a 3-4mm woven wire mesh was then placed over this covering most of the exposed rock face. After this a wire rope (cable) is then threaded through the loops in the bolts on the outside of the mesh to secure the mesh as in Picture B on the following page. This was a manual system and is usually done in three steps.

(a) (b)

The mining industry is moving to mechanised mining and this makes the process, hereinbefore described, impractical. To replace this process, they are using a ridged 5,6mm welded mesh as shown as the outer layer of mesh in Picture A above.

The difference is that the system in Picture B behaves much more favourable during seismic events but tends to involve a manual three step installation process.

The difference between the two surface containment methods and associated apparatus revolves around the rigidity of the mesh. The mesh in picture B is flexible while in A it is not. To find a common ground, variations of A have been made by adding wire rope having more strands of the 5,6mm wire. The main failure mode however remained the same in that the mesh builds up load around the bolts and to the point where the mesh fails.

The applicant believes that a surface containment method and apparatus, in accordance with this invention, addresses at least in part the shortcomings associated with known surface containment methods and apparatus and may hold great benefit in industry. SUMMARY OF THE INVENTION

In accordance with a broad aspect of this invention there is provided a surface containment kit for covering a surface, whether smooth or unevenly shaped, in an underground environment where stability or load carrying capability of said surface is required to be maintained with rock anchors and a surface covering mesh, said kit comprising: a tether having an elongate body disposed between first and second ends, said elongate body being flexible to permit interlacing thereof with an arrangement of interlocking strands of said mesh while partially overlying itself between said first and second ends; at least one yielding device, disposed between first and second ends of the tether in the vicinity where said tether partially overlies itself, adapted to resist slip of overlying parts of the elongate body relative to each other and relative to said yielding device when the tether, yielding device and mesh combination, connected to rock anchors anchored to said surface, is exposed to zero to site anticipated dynamic and/or static loading (x) of said surface, but to allow slip of overlying parts of the elongate body relative to each other and relative to said yielding device when the tether, yielding device and mesh combination is exposed to dynamic and/or static loading greater than the site anticipated dynamic and/or static loading (x).

In an embodiment the yielding device comprises a catch, clasp, buckle, or ferrule with slots or openings allowing it to be connected to overlying parts of the tether.

In accordance with a further broad aspect of this invention there is provided a surface containment kit for covering a surface, whether smooth or unevenly shaped, in an underground mining environment, said kit comprising: a mesh having an arrangement of interlocking strands with openings defined between said strands; a tether having an elongate body disposed between first and second ends, said elongate body being interlaced with said arrangement of interlocking strands and partially overlies itself between said first and second ends; a plurality of spaced apart rock bolts extending through openings of the mesh, each rock bolt having a tether accepting end opposite an operative rock surface engaging end, wherein said tether is passed through or around tether accepting ends of said plurality of rock bolts; and at least one yielding device, disposed between first and second ends of the tether in the vicinity where said tether partially overlies itself, adapted to resist slip of overlying parts of the elongate body relative to each other and relative to said yielding device when the mesh, rock bolts and tether combination is exposed to zero to mine site anticipated dynamic and/or static loading (x), but to allow slip of overlying parts of the elongate body relative to each other and relative to said yielding device when the mesh, rock bolts and tether combination is exposed to dynamic and/or static loading greater than the mine site anticipated dynamic and/or static loading (x).

In an embodiment, the surface in the underground mining environment may be selected from a hanging wall, side wall, high wall, working face, blast face or an area where dynamic deformation of the rock is expected.

The elongate body of the tether may be interlaced with said arrangement of interlocking strands approximate a perimeter of the mesh. Moreover, the elongate body may be woven to be in abuttance with criss-cross portions of the mesh.

In an embodiment, the strands may be metal links.

In an embodiment, each tether accepting end may be a looped end.

In an embodiment, the yielding device comprises a 19,05mm 0 x 1 ,6mm wall x 50mm long steel SAE 1008 or equivalent Stainless-Steel tube or other deformable metal alloy. The tube may be crimped at a pre-defined pressure and with a die set to provide a certain resistance between overlying sections of the tether and the tube. This pre-defined resistance will result in a certain “yield load” that is requested by the mine site where surface protection is required. Changing the pressure and the die set will result in a change in “yield load”.

In an embodiment, the elongate body of the tether may be of uniform width along its length.

The invention is believed to extend to a method of forming a surface containment kit that can be supplied to a mining operation where protection of a surface or inhibiting of deformation in an underground mining environment is required, the method comprising: providing a mesh having an arrangement of interlocking strands with openings defined between said strands; providing a tether which has an elongate body disposed between first and second ends, and, approximate a perimeter of the mesh, interlacing said elongate body with said arrangement of interlocking strands with at least two sections of said elongate body is overlying each other; providing a plurality of rock bolts and positioning same to extend through openings approximate a perimeter of the mesh, each rock bolt having a tether accepting end opposite an operative rock surface engaging end, and passing said interlaced tether through or around tether accepting ends of said plurality of rock bolts to form a surface containment kit wherein the rock bolts, tether and mesh are joined.

The invention is further believed to extend to a method of protecting, or reducing the unravelling and deterioration of, a surface in an underground mining environment, the method comprising: providing a mesh having an arrangement of interlocking metal links with openings defined between said links; providing a tether which has an elongate body disposed between first and second ends, and, interlacing said elongate body with said arrangement of interlocking metal links; providing a plurality of selectively spaced apart rock bolts and positioning same to extend through openings approximate of the mesh, each rock bolt having a tether accepting end opposite an operative rock surface engaging end, and passing said tether through or around tether accepting ends of said plurality of rock bolts to form a perimeter around the rock bolts and in doing so creating a surface containment kit; and securing said kit to a surface area at a mine site where ground conditions are rock-burst prone or where inhibiting of deformation in an underground mining environment is required.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention are now described, by way of example, with reference to the accompanying non-limiting diagrammatic drawings. In the drawings:

Figure 1 shows an in-use perspective view of a surface containment kit in accordance with an embodiment of the invention functioning to reduce the unravelling and deterioration of a hanging wall in a mining or underground environment;

Figure 2 shows an in-use perspective view of the surface containment kit of Figure 1 functioning to reduce the unravelling and deterioration of a side wall in a mining or underground environment;

Figure 3 shows a plan view of the surface containment kit of Figure 1 ;

Figure 4 shows an exploded view of part of the surface containment kit of Figure 1 ; Figure 5 shows a perspective view of a mesh, tether, and a first type of yielding device for the surface containment kit of Figure 1 ;

Figure 6 shows an exploded view of an overlying portion of the tether of Figure 5, interlaced with the mesh of Figure 5;

Figure 7 shows an exploded view of a first type of yielding device used in the surface containment kit of Figure 1 , integrated with the tether of Figure 5 and interlaced with the mesh of Figure 5;

Figure 8 shows a perspective view of a second type of yielding device that can be used in a surface containment kit similar to that of Figure 1 ;

Figure 9 shows a plan view of the yielding device of Figure 8;

Figure 10 shows a section view along a longitudinal axis of the yielding device of Figure 8;

Figure 11 shows a perspective view of a mesh, tether, and a second type of yielding device for a surface containment kit similar to that of Figure 1 ;

Figure 12 shows an exploded view of the second type of yielding device used in the surface containment kit of Figure 11 , integrated with the tether of Figure 11 and interlaced with the mesh of Figure 11 ;

Figure 13 shows an exploded view of an overlying portion of the tether of Figure 11 , interlaced with the mesh of Figure 11 ;

Figure 14 shows a side view of part of interlaced mesh and tether of Figure 11 with tether extending through the second yielding device;

Figure 15 shows a plan view of part of interlaced mesh and tether of Figure 11 with tether extending through the second yielding device; and Figure 16 shows a plan view of part of interlaced mesh and tether that can be utilised in a surface containment kit similar to that of Figure 11 , where the tether extends in an alternative way through the second yielding device.

DETAILED DESCRIPTION OF THE DRAWINGS

In the drawings, reference numeral 10 generally refers to a surface containment kit consisting of a combination of rock bolts 12, mesh 14, and a tether 16 in combination with one or more yielding devices 30, in accordance with an embodiment of the invention.

Should rock bolts or other rock anchors as well as suitable mesh material be readily available at a site where surface stabilization is required, the surface containment kit supplied to such site may simply consist of the combination of tether 16 with one or more yielding devices 30. However, for the sake of illustration and explanation of the invention, the surface containment kit 10 is described in the detailed description of the drawings as a combination of rock bolts 12, mesh 14, tether 16 and one or more yielding devices 30 with the understanding that mesh and rock anchors are optional additions to the kit 10 and a kit falling within the scope of this invention can also be limited to only include one or more tethers 16 with one or more yielding devices 30.

The surface containment kit 10 has been developed to secure a surface area at a site where ground conditions are rock-burst prone or where inhibiting of deformation in an underground environment is required. The surface area in the underground environment where the surface containment kit 10 may find application is typically selected from a hanging wall, side wall, high wall, working face, blast face or other planar or irregularly shaped area where dynamic or static deformation of rock is expected. The kit 10 is suited to react to both dynamic (high velocity) rock movement or deformation as well as static (low velocity) rock movement or deformation.

As shown in Figures 1 to 3 and in Figure 5, the mesh 14 consists of an arrangement of interlocking strands 18, made preferably from metal alloy links with openings 20 defined between said links. The interlocking strands 18, in the first shown embodiment depicted in Figures 1 to 7, define generally square-shaped openings 20, but it will be appreciated that borders of the openings 20 defined by the interlocking strands 18 may take any polygonal shape.

Referring to Figures 3 and 4, the tether 16 is shown to include an elongate metallic body disposed between first and second ends (22, 24). The elongate body is interlaced with the arrangement of interlocking strands 18 and partially overlies itself between the first and second ends as best shown in Figures 6 and 7. The elongate body of the tether 16 is interlaced with the arrangement of interlocking strands 18, preferably but not necessarily proximate an outer perimeter of the mesh 14. The elongate body may be woven to be in abuttance with criss-cross portions of the mesh 14.

In Figures 1 to 3, four spaced apart rock bolts 12 extending through openings 20 of the mesh 14, is shown. Each rock bolt 12 has a tether accepting end 26 opposite an operative rock surface engaging end 28. In use, the tether 16 is passed through or around tether accepting ends 26 of the four spaced apart rock bolts 12. Positioning of the rock bolts 12 relative to each other is such that a square is defined with each rock bolt located at a corner of the square. The formed square is further within the perimeter of the mesh 14. It will, however, be appreciated that the plurality of rock bolts 12 may be positioned such that any polygonal shape is formed when a tether 16 is located through or around same. The elongate body of the tether 16 is preferably woven to be into the strand 18 forming an opening 20 with block-like perimeter nearest to the bolts 12 in order to contain the bolts 12 within the loop of the tether 16.

As best shown in Figures 3, 5 and 7, the yielding device 30 is in the shape of a crimped ferrule and is disposed between first and second ends (22, 24) of the tether 16 in the vicinity where the tether 16 overlies itself. The yielding device 30 is designed to resist slip of overlying sections or parts of the elongate body of the tether 16 relative to each other and slip of the tether sections relative to an inner body of the yielding device 30 when the mesh 14, rock bolts 12 and tether 16 combination is exposed to zero to x amount of dynamic and/or static loading as anticipated at a particular mine site where the kit 10 is used. On the other hand, the yielding device 30 allows slip of overlying parts of the elongate body relative to each other and relative to an inner body of the yielding device when the mesh 14, rock bolts 12 and tether 16 combination is exposed to dynamic and/or static loading greater than the mine site anticipated dynamic and/or static loading (x). The yielding device 30 shown in Figures 3, 5 and 7 typically comprises a 19,05mm 0 x 1 ,6mm wall x 50mm long steel SAE 1008 cold rolled steel or equivalent stainless-steel tube or other deformable metal alloy. The tube may be crimped at a pre-defined pressure and with a die set to provide a certain resistance between overlying sections of the tether 16 and the tube. This pre-defined resistance will result in a certain “yield load” x that is requested by the mine site where surface protection is required. Changing the pressure and the die set will result in a change in “yield load” capable of carrying anticipated dynamic and/or static loading (x) at the underground site where stability or load carrying capability of the surface is required to be maintained. It is also anticipated that such site may be either be above or underground.

From test work conducted, the specific shape, pressure and dimensions of the crimp on the yielding device 30 was established.

Round oblong punch with Flat half Hex die.

Test 1 Crimp 1 (1Ton)

Slip on crimp ± 175mm no rope/cable/tether failure Crimp side A = 12,5mm Crimp side B = 12,03mm

Test 2 Crimp 2 (1 ,5ton)

Slip on crimp ± 300mm rope/cable/tether failure

Crimp side A = 11 ,35mm Crimp side B = 11 ,06mm

Test 3 Crimp 3 (2ton)

Slip on crimp ± 0mm slip no rope/cable/tether failure Crimp side A = 10,2mm Crimp side B = 10,05mm

Test 4 Crimp 3 (2ton)

Slip on crimp ± 90mm slip no rope/cable/tether failure

Crimp side A = 10,65mm Crimp side B = 11 ,04mm

Test 5 Crimp l (1ton)

Slip on crimp complete pull out, no rope/cable/tether failure

Crimp side A = 11 ,85mm Crimp side B = 12.10mm Test 6 Crimp 2 (1 ,5ton)

Slip on crimp ± 170mm slip no rope/cable/tether failure second drop complete pull out

Crimp side A = 11 ,15mm Crimp side B = 10,95mm

From test work and measurements, the summation can be made that a crimp of between 11.04 to 11 ,35mm will be sufficient to render resistance. This will allow for the rope/cable/tether 16 to slip from the yielding device secure position to a load carrying position where an additional section, or last bit of tether 16, is utilised for securing the load when exposed to dynamic and/or static loading (x). The last bit of tether 16, as shown in Figures 4 and 6, terminates in a stopper 32. The stopper 32 can be regarded as a movement arrestor. The stopper or arrestor 32 is anticipated to be formed at a first end, second end, or both first and second ends of the rope/cable/tether 16.

Figures 8 to 10, Figure 12, Figure 14 and Figure 15 shows various views of a second type of yielding device 300 that can be used in a surface containment kit similar to that of Figure 1 . A mesh 314, and a tether 316 and such yielding device or devices 300 as shown in Figure 11 then forms part of the surface containment kit similar to that of Figure 1 , in accordance with another embodiment of the invention. The difference is found in the shape and configuration of the yielding device 300 compared to device 30. IT will be understood that tether material, shape, and configuration may also differ but still fall within the ambit of the invention.

Yielding device 300 takes a buckle shape as best show in Figures 8 to 10, and preferably includes, as shown in the abovementioned Figures, two rows of spaced apart holes 334 through which the rope/cable/tether 316 can be positioned.

The Yielding device or buckle 300 will perform the same duty as the original yielding device (Crimped Ferrule 30) but is more precise in its functioning as yielding device. The one end of the rope/cable/tether 316 typically a steel wire rope is laced through the first of holes 334 and the third and the other end through the second and fourth holes 334 from the one side as shown in Figure 15. An alternative lacing is also envisaged as shown in Figure 16 where the one end of the rope/cable/tether 316 is laced through holes one and two of holes 334 and the other end through holes three and four of holes 334. Once the steel wire rope 316 is under tension whether dynamically of statically the buckle 300 renders a much more even resistance than the crimped ferrule 30.

By altering the hole size and the distance between the holes the applicant has found that it can manipulate the loads. The buckles 300 are manufactured from Stainless Steel to ensure the loads for as long as possible.

In a further embodiment, the applicant adds an extra 100mm of steel wire rope to each end of the steel wire rope 316, this is then looped, and a Stainless-Steel Ferrule 332 is then crimped onto the loop as shown in Figure 11 . This acts as a secondary yielding point at a higher load (y) and ultimately a stopper or movement arrestor on the steel wire rope 316. In the description of the selection of crimp on the yielding device or ferrule 30, different “Crimps” indicated by a crimp 1 , 2 and 3, perform the same function as the distance variance between the holes in the “buckle”.

It is anticipated that a final user such as an underground mining facility may select a “Crimp” amount much higher than they actually require in order to ensure safe working environment. It is envisaged that adjustments may be made to suit its specific application, all, however, falling within the spirit and scope of the invention.

In use, the invention extends to a method of protecting a surface or to a method of reducing the unravelling and deterioration of a surface, in an underground environment, the method comprising: providing a mesh 14 having an arrangement of interlocking metal links 18 with openings 20 defined between the links 18; providing a tether 16 which has an elongate body disposed between first 22 and second 24 ends, and, interlacing the body with the arrangement of interlocking metal links 18; providing a plurality of selectively spaced apart rock bolts 12 and positioning same to extend through openings 20 approximate a perimeter of the mesh, each rock bolt having a tether accepting end 26 opposite an operative rock surface engaging end 28, and passing the tether 16 through or around tether accepting ends 26 of the plurality of rock bolts 12 to form a perimeter around the rock bolts 12 and in doing so creating a surface containment kit 10; passing the tether through a yielding device 30 in the form of a tube that has been suitably crimped to permit a desired dynamic and/or static loading (x) before slipping of overlapping tether portions 16 relative to the tube 30 is allowed; and securing said kit 10 to a surface area, such as a hanging wall, at a mine site where ground conditions are rock-burst prone or where inhibiting of deformation in an underground mining environment is required.

While a preferred embodiment of the invention is shown and described, it will be understood that it is not intended to limit the extent of the invention, but rather it is intended to cover all modifications and alternate methods, including: methods, for manufacturing the kit 10 and components thereof, falling within the spirit and the scope of the invention.

The applicant believes that it has a unique solution to dangerous underground conditions, in that by altering the configuration of the integration of the wire rope or tether 16 with the mesh 14 and then incorporating a system and methodology that allows for controlled deformation (yield). For example, if the mining environment has rock bolts designed to yield at 10 ton and the mesh fails at 5 ton the integration of the wire rope or tether 16 and the kit 10 attached to it will give the mesh 14 the ability to stay active to the same load as the bolts 12. In a seismic event the combination of bolt 12, mesh 14 and wire rope I tether 16 will then react together and the yield of the bolt 12 and that of the mesh 14 will then become a system formed by the kit 10. In other words, the alteration or addition of the wire rope or tether 16 and the kit 10 will actively respond in correlation to the bolt 12.

The applicant believes that the kit 10 of the present invention, at least in part, addresses shortcomings in conventional ground support in that the surface containment kit or apparatus 10 provides a neat, easy to use and safe alternative to the known art. The invention for which protection is sought is defined in the set of claims that follows herein.