Related Applications

[001] This application claims priority for Australian provisional patent application No. 2016902767 filed on 14 July 2016, the contents of which are incorporated by reference.

Technical Field

[002] The invention relates to a seal, a seal forming system, a method of forming a seal and an associated formwork support, in particular, in relation to seals formed of a cement based material used in underground mining to isolate one area from another area.

Background

[003] During the normal course of underground coal mining, it sometimes becomes necessary to install permanent seals to isolate abandoned or worked out areas of the mine. This practice eliminates the need to ventilate those areas. Seals may also be used to isolate fire zones or areas susceptible to spontaneous combustion.

[004] To effectively isolate areas within a mine, a seal should: control the gas air exchanges between the sealed and open areas to prevent toxic and/or flammable gases from entering active workings and oxygen from entering the sealed area; and be capable of preventing an explosion initiated on one side from propagating to the other side.

[005] Underground seals may be formed by erecting straight formwork across the mine passage or roadway, and spraying a concrete material such as shotcrete or the like over the formwork to form the seal. The concrete material is formed from a mixture that when set forms a ridged seal across the mine passage or roadway.

[006] A problem with these seals is that the rigid seal may crack or otherwise become compromised due to roof or wall convergence. Accordingly, these seals are formed relatively thick as a factor of safety. As such, another problem with these seals is the quality of concrete material that is required to be used in an attempt to avoid cracking of the seal.

[007] Another problem is the properties of concrete / shotcrete have low flexural and shear strength and when it fails is fails in a catastrophic manner

[008] The invention disclosed herein seeks to overcome one or more of the above identified problems or at least provide a useful alternative.

Summary

[009] In accordance with a first broad aspect there is provided, a system for forming a seal of a mine passage, the system including: a plurality support members adapted to extend between a roof and floor of the passage, each of the plurality of support members having a ground engaging end, a roof engaging end and a body being substantially arched in side profile between the ground and roof engaging ends, a backing arranged to be supported and shaped to a corresponding arch by the plurality of support members so as to substantially span the passage; and a material adapted to be applied to the backing so as to form the seal extending therefrom having an arch shape substantially corresponding to that of the backing.

[0010] In an aspect, each of the plurality of support members are height adjustable.

[0011] In another aspect, each of the plurality of support members are spaced apart from one another with the backing extending therebetween. [0012] In yet another aspect, each of the plurality of support members includes one or more thickness indicators arranged to extend in the direction of the thickness of the applied material.

[0013] In yet another aspect, the one or more thickness indicators extend from a convex side of the plurality support members.

[0014] In yet another aspect, each of the plurality support members includes a plurality of thickness indicators at spaced apart interval between the ground engaging end and the roof engaging end.

[0015] In yet another aspect, each of the plurality of the thickness indicators are the same length.

[0016] In yet another aspect, the material includes cement and fibres adapted to provide the seal with flexural strength.

[0017] In yet another aspect, the backing is a mesh material.

[0018] In yet another aspect, the bodies of the plurality support members are each adapted to be telescopically height adjustable and include a locking means to retain the height thereof.

[0019] In yet another aspect, the bodies of each of the plurality support members include an upper section and a lower section that are adjustability moveable relative to one another.

[0020] In accordance with a second broad aspect there is provided, a kit for forming a seal of a mine passage, the kit including: a plurality support members adapted to extend between a roof and floor of the passage, each of the plurality of support members having a ground engaging end, a roof engaging end and a body being substantially arched in side profile between the ground and roof engaging ends, a backing arranged to be supported and shaped to a corresponding arch by the plurality support members so as to substantially span the passage; and a mortar mix including cement and fibres adapted to be applied to the backing so as to from the seal extending therefrom.

[0021] In accordance with a third broad aspect there is provided, a formwork member for supporting a backing against which a curved seal of a mine passage is formable, the formwork member including a ground engaging end, a roof engaging end and a body extending therebetween, the body being arched in side profile between the ground and roof engaging ends such that the curved seal is formable therewith.

[0022] In an aspect, the formwork member is adapted to be height adjustable.

[0023] In another aspect, the support member includes a thickness indicator arranged to extend in the direction of a thickness of an applied material by which the curved seal is formable.

[0024] In yet another aspect, the formwork member is telescopically height adjustable and includes a locking means to retain the height thereof.

[0025] In yet another aspect, the thickness indicator extends from a convex side of the bodies each of the plurality support members.

[0026] In yet another aspect, the plurality support members each include a plurality of thickness indicators at spaced apart intervals between the ground engaging end and the roof engaging end.

[0027] In yet another aspect, the plurality of thickness indicators are the same length.

[0028] In accordance with a fourth broad aspect there is provided, a method for forming a seal for a mine passage, the method including: Arranging a plurality support members in a spaced apart relationship across the mine passage with bodies of the plurality support members being arched in side profile between a ground engaging and a roof engaging ends thereof; Fitting a backing to the plurality support members to be shaped thereby and substantially span the passage; Applying cement based material to the backing so as to form the seal having a thickness extending form the backing.

[0029] In an aspect, the method further includes the step of: applying the cement based material to the thickness in accordance with a visual indicator extending from the concave sides each of the plurality support members.

[0030] In another aspect, the method further including the step of: applying the cement based material to the backing such that the seal has a substantially similar thickness across its height and width.

[0031] In yet another aspect, the method further including the step of: adjusting the height of the plurality support members such that the ground engaging and the roof engaging ends thereof are engaged with the ground and roof of the passage, respectively.

[0032] In accordance with a fifth broad aspect there is provided, a seal formed using a system as defined above and herein.

[0033] In accordance with a sixth broad aspect there is provided, a seal formed by a method as defined above and herein.

[0034] In accordance with a seventh broad aspect there is provided, a seal of a mine passageway, the seal including a seal body shaped so as to be substantially arched in side profile between a ground and a roof of the mine passageway, the seal body being formed of a seal material including a cement material and a fibrous material such that the seal material is at least partially flexible.

[0035] In an aspect, the seal is also arched in plan-form between opposing sides of the mine passageway.

[0036] In another aspect, the seal includes a plurality of supporting members adapted to extend between a roof and floor of the passageway, each of the support members having a ground engaging end, a roof engaging end and a body being substantially arched in side profile between the ground and roof engaging ends.

[0037] In accordance with a eighth broad aspect there is provided, a system for forming a seal of a mine passage having opposing walls, the system including: a plurality support members adapted to extend between the opposing walls of the mine passage, each of the plurality of support members having a opposing wall surface engaging ends, and a body being substantially arched in plan form profile between the wall surface engaging ends, a backing arranged to be supported and shaped to a corresponding arch by the plurality of support members so as to substantially span the passage; and a material adapted to be applied to the backing so as to form the seal extending therefrom having an arch shape substantially corresponding to that of the backing.

Brief Description of the Figures

[0038] The invention is described, by way of non-limiting example only, by reference to the accompanying figures, in which;

[0039] Figure 1 is a side view illustrating a formwork member for forming a seal;

[0040] Figure 2 is a front view illustrating a formwork member for forming the seal;

[0041] Figure 3 is top view of a first arrangement of formwork members spanning a mine passage;

[0042] Figure 4 is top view of a second arrangement of formwork members spanning a mine passage;

[0043] Figure 5 is a side view of a seal formed with the formwork members, a mesh and concrete materials;

[0044] Figure 6 is a front view of the seal; [0045] Figure 7 is a top view of the seal; and

[0046] Figure 8 is a side view illustrating the seal in isolation and showing design parameters.

Detailed Description

[0047] Referring to Figures 1 to 4, there is shown a formwork support member 10 that forms part of a system or kit 5 for forming a seal 12 (shown in Figure 5). The support member 10 includes a ground engaging end 14, a roof engaging end 16 and a body 18 being substantially arched or continuously curved in side profile (as best shown in Figure 1) between the ground and roof engaging ends 14, 16. The body 18 includes a convex side 13 and a concave side 19. The formwork support member 10 may be formed from a structural material suitable for underground use. Some examples may employ a suitable metal.

[0048] The body 18 is adapted to be telescopically height adjustable and includes a lower telescopic section 20 received by and slidable relative to an upper telescopic section 22. The arc or curvature of the body 18 is symmetrical about and peaks at an intermediate point 31 on the body 18 which defines the furthest lateral point from the ground and roof engaging ends 14, 16. The arc or curvature of the body 18 traces that of a part of a radial circumference of a circle, as is illustrated in Figure 8.

[0049] Each of the lower and upper telescopic sections 20, 22 are continuously curved to form the arc when coupled together. The lower and upper telescopic sections 20, 22 may include a locking arrangement 32 including a pin 33 and corresponding apertures 35 that allow for the adjustment of the support member 10 and locking to the desired length. The lower and upper telescopic sections 20, 22 may be square or rectangular or circular in cross-section.

[0050] The ground and roof engaging ends 14, 16 are provided in the form of respective tabs 24, 26 extending from ends of respective ones of the lower and upper telescopic sections 20, 22. The tabs 24, 26 extend from and in a direction away from the concave side 19 of the body 18. However, in other examples, the tabs 24, 26 could extend in any direction. Each of the respective tabs 24, 26 include holes 29 to allow the respective tabs 24, 26 to be secured with a fastener to the mine floor and roof respectively.

[0051] The body 18 also include depth indicators 28 provided in the form of further indicators tabs 30 that extend from the concave side 19. The indicators tabs 30 extend perpendicularly from the arc of the body 18. The indicators tabs 30 are about the same length.

[0052] Referring now additionally to Figures 3 to 7, in use, a plurality of the support members 10 are arranged at spaced apart intervals so as to span between sides or side ribs 21 a mine passage or roadway to be sealed. It is noted that the sides 13 are arranged to face the area to be sealed and from which a possible pressure event such as a gas explosion could be expected. The direction of the possible pressure event is shown with arrows "P" in the drawings.

[0053] It is noted in some examples, the formwork support members 10 may be rotated 90 degrees and span widthwise between the opposing walls 21. In this case, the seal 12 may be curved in plan form view.

[0054] Each of the support members 10 is telescopically extended and retracted so that the respective ends 14, 16 abut with a floor 15 and a roof 17, respectively. The plurality of the support members 10 may be arranged to extend straight across the passage, in plan form view, as shown in Figure 3. Or, the plurality of the support members 10 may be arranged to form a further arc in plan form view, as shown in Figure 4. The further arc may be the same or a similar curvature to the arc provide by the shape of the support members 10 in the side view as shown in Figure 1. The supports 10 are typically oriented with the vertical using a plumb-bob or the like.

[0055] Referring more specifically to Figure 5, the system 5 further includes a backing 40 arranged to be supported and shaped by the plurality of support members 10 so as to substantially span the passage and a seal material 45 adapted to be applied to the backing 40 so as to from a seal 12 extending therefrom. [0056] In more detail, once the supports 10 have been installed and anchored, the backing 40 is secured to the concave 18 of the supports 10 by forming or moulding the backing 40 to the shape of the concave curvature of the supports 10. The backing 10 is then secured to the supports 10 with screws, wire ties, cable ties or other suitable means. The backing 40 may be a board, mesh, metal rib-lath or other suitable material that is securable to the plurality of support members 10. In this example, the backing 40 is preferably metal rib-lath.

[0057] Once the support members 10 and backing 40 are secured in place, the seal material 45 is applied to the backing 40 to a thickness as defined by the thickness indicators 28 to form the seal 12. The seal material 45 is formed from a mortar mix. The mix preferably includes Portland cement about 20 - 60%, fly ash about 20 - 60%, and fillers 5 -30% and fibres exhibiting flexural strength >7mpa and tensile strain capacity > 2%. The fibres may be polymer fibres and give the seal material 45 the flexural strength as is further detailed below. This type of material is also referred to as Engineered Cementitious Composites "ECC" materials. ECCs are a group of fibre- reinforced cement-based composites which possess the unique ability to flex and self- strengthen before fracturing. The mortar mix may be mixed with water, and then sprayed via a typical shotcrete style pump. A suitable pump is commercially available from ANTEC Pty Ltd. An example the design seal material properties of the mortar mix when cured is provided below in Table 1.

Table 1: Seal Material Design Properties

[0058] The supports 10 and backing 40 are adapted to support the seal material 45 until it is cured. The cured seal 12 has an arc shape between the floor 15 and the roof 17 that substantially matches that of the arc of supports 10 and backing 40. The seal 12 when cured has a degree of flexing motion. By having an arched shaped seal 12, as forces are exerted on the perimeter of the seal 12 the flexing motion is will be in a pre-determined direction, due to the existing arc or curvature (i.e. the seal 12 is preformed in a first-mode of compressive bending) and therefore the direction of deformation is able to be predicted to simplify design.

[0059] The flexing motion along with the arc shape allows the seal 12 to withstand a limited amount of bending movement (such as that caused by convergence) in the underground roadway strata without damaging the seal 12. The convex face or "belly" of the seal 12 that faces the expected pressure event also assists in the ability to withstand the pressure event, as an increase of pressure on the "belly" of the seal 12 will increase the force of the seal 12 to lock into the surrounding strata.

[0060] Referring to Figure 8, in this example the radius "R" of the arc of the seal 12 may be calculated by: R = L ² /8d + d/2 (where: "L" is equal to the passage/tunnel height and "d" is the belly bulge).

[0061] The thickness "t" of the seal may be calculated by three methods including for compression, "t _b " for buckling and "t _s " for slenderness. The greater of the thicknesses may then be used as the design thickness.

[0062] The compressive thickness "t _c " may be calculated by =Rw x (F of S)/f'c (where: R is the radius, w is the "overpressure", f c is the characteristic concrete material strength and "F of S" is the Factor of Safety).

[0063] The buckling thickness "tb" may be calculated by huckie = 0.0254(F of S x .0024 wb (39.37R) ^1'5 ) ^0'4 , and the seal thickness "t _s " may simply be calculated as per a ratio that in this example is 1/25, so that t _s =L/25. [0064] An example set of calculations for a typical passageway or tunnel is provided below with reference to Table 2.

( niiix of t,. t _h . niid U

Table 2: Example Seal Dimensions

[0065] In view of Table 2, in this specific example, the design thickness "t" (being the greatest of "t _c , ¾ and ts" above) of the seal 12 is 0.128 meters (being the greatest of and as such the length of the indictors 28 may be about 0.128 meters in length. Of course, the specific thickness of the seal 12 may change depending the design parameters above such as the tunnel height and the above calculations are provided for example purposes only. [0066] Advantageously, there has been provided a system and method for forming a curved or arched seal spanning a passageway or the like. The system provides formwork including extendable arched supports and a backing that is likewise arched or curved on which the seal material is applied to form the seal. The arched shape of the formed seal and the use of at least partially flexible material including fibres allows the seal to flex or bend due to convergence without compromising cracking that may affect the service life of the seal.

[0067] The arched shape ensures the seal flexes or bends in a pre-determined manner. The convex or belly side of the seal also assist to distribute forces associated with a potential pressure event into the surrounding strata such as into the roof and floor. The seal may be arched shaped in side profile and also arched shape in plan form profile so as to form a convex dish for facing toward the potential pressure event. Other examples may only arch in plan form profile, depending on the application. Accordingly, the arched seal shape formed from at least partially flexible material allows less material to be used thereby being quicker and more cost effective to install whist improving the service life of the seal.

[0068] Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

[0069] The reference in this specification to any known matter or any prior publication is not, and should not be taken to be, an acknowledgment or admission or suggestion that the known matter or prior art publication forms part of the common general knowledge in the field to which this specification relates.

[0070] While specific examples of the invention have been described, it will be understood that the invention extends to alternative combinations of the features disclosed or evident from the disclosure provided herein. [0071] Many and various modifications will be apparent to those skilled in the art without departing from the scope of the invention disclosed or evident from the disclosure provided herein.