Pumpable Crib Bag Assembly

The present invention relates to a pumpable crib bag for mine support in mining applications. However, the invention is not limited to this particular use and is also suitable for use in numerous other applications which require columnar ‘standing support’, such as support in civil applications.

A Pumpable Crib Bag (PCB) is a flexible-walled bag that is inflated with a settable material, such as cementitious grout, to form a support. Grout filled PCB's are typically utilised as roof supports within ‘tailgates’ and ‘bleeder headings’ (as they are known) of an underground longwall mine for geotechnical and ventilation purposes. The PCB is positioned at a designated installation site within the mine opening and filled with the settable grout material. Once the grout material has cured, the PCB forms a load-bearing support column between the roof and floor of the mine opening. In geotechnical applications, the PCB is configured to eventually collapse into and become part of the goaf or void.

PCB's may be reinforced with hoops or helically wound wire or cord to restrain excessive lateral expansion or bulging of the bag when the column is under compressive load. Disadvantageously, such reinforced PCB's still have insufficient load carrying capacity, may rupture or fail prematurely, and/or exhibit variable, inconsistent or erratic loading behaviour.

It is an object of the present invention to substantially overcome, or at least ameliorate, one or more of the above drawbacks.

An aspect of the present invention provides a pumpable crib bag assembly for forming a load-bearing support, the assembly including:

In one or more embodiments, the reinforcing member is in the form of a strap.

In one or more embodiments, the sidewall has an inner wall surface and an outer wall surface each defining a total surface area, and wherein the strap is at least partially secured to and extends along at least one of the inner and outer wall surfaces.

In one or more embodiments, the strap has an upper edge and a lower edge, and wherein the flattened major surface extends between the upper edge and the lower edge.

In one or more embodiments, the flattened major surface has a width extending between the upper edge and the lower edge such that the flattened major surface contacts about one quarter to two thirds of the total surface area of the at least one of the inner and outer wall surfaces.

In one or more embodiments, the flattened major surface contacts about one quarter of the total surface area of the at least one of the inner and outer wall surfaces.

In one or more embodiments, the sidewall is generally cylindrical in configuration.

In one or more embodiments, the reinforcing member or the strap helically encompasses the sidewall.

In one or more embodiments, the reinforcing member or the strap helically encompasses the sidewall in a manner of a double or opposed helix.

In one or more embodiments, the reinforcing member or the strap helically encompasses the sidewall with a pitch of between about 50 mm to 150 mm.

In one or more embodiments, the reinforcing member or the strap helically encompasses the sidewall with a variable pitch.

In one or more embodiments, the assembly further includes a pocket attached to the sidewall for positioning the reinforcing member or the strap therein.

In one or more embodiments, the pocket is dimensioned for supporting conformity with the reinforcing member or the strap to minimise movement of the reinforcing member or the strap with respect to the containment bag.

In one or more embodiments, the reinforcing member or the strap is bonded to the upper and lower end portions of the sidewall of the containment bag.

In one or more embodiments, the reinforcing member or the strap is at least partially bonded to the sidewall of the containment bag along a majority of a length of the reinforcing member or the strap.

In one or more embodiments, the reinforcement member or the strap is comprised of plastics, metal, natural fiber, composites, or a combination thereof.

In one or more embodiments, the containment bag is comprised of polyvinyl chloride (PVC) laminated polyester.

In one or more embodiments, the assembly further includes a mesh reinforcement positioned within the containment bag.

In one or more embodiments, the mesh reinforcement includes permeable outer and inner wall surfaces, and wherein the assembly further includes an additional reinforcement member which encompasses at least one of the outer and inner wall surfaces of the mesh reinforcement.

In one or more embodiments, the flattened major surface includes a surface profile to vary the coefficient of friction between the reinforcing member or the strap and the sidewall.

In another aspect, the invention provides a load-bearing support including:

In yet another aspect, the invention provides a method for forming a load-bearing support, the method including steps of:

Referring firstly toof the accompanying drawings there is depicted a pumpable crib bag assemblyaccording to a first embodiment. The assemblyhas a primary application in forming a load-bearing roof support column() in an underground mine. In one preferred application, the assemblyis utilised within the ‘tailgate’ roadway of a longwall mining operation to assist with keeping the tailgate open for geotechnical and ventilation purposes as the longwall face advances. The assemblymay also be utilised in other applications which require columnar ‘standing support’, such as support in civil applications.

With particular reference to, the assemblyincludes a containment bagfor receiving and containing a settable material pumpable therein under pressure. The settable material is curable to form a hardened material with a suitable compressive strength depending upon the desired load-bearing application of the assembly. In a preferred embodiment, the settable material is comprised of cementitious grout, typically low-strength (e.g. 6 MPa to 8 MPa) grout, although other settable grouts, cementitious materials, or fillers may be utilised, such as such as high-strength (e.g. up to 120 MPa) grout, fly ash cement, or pumpable polymers that cure as a solid or foam (e.g. urea silicate or polyurethane). The bagis preferably constructed of a suitable textile or fabric with sufficient strength and durability to maintain form whilst the settable material is pumped under pressure and allowed to cure within the bag. In the illustrated embodiment, the fabric is comprised of polyvinyl chloride (PVC) laminated polyester which may be formed by, for example, laminating a polyester scrim or fabric between two or more layers of PVC film. In another embodiment, the fabric may be a breathable fabric, such as a geotextile fabric. In other embodiments, the fabric may be comprised of rubber, polyurethane, silicone or neoprene-dipped polyester fabric. In some other embodiments, the bagmay be constructed of a metalised film such as metalised polyethylene terephthalate (PET).

The bagincludes an upper end portion, a lower end portionspaced from the upper end portion, and a sidewallextending between the upper and lower end portions,. The sidewallhas an outer wall surfaceand an inner wall surfaceeach defining a total surface area (see). In one embodiment, the upper and lower end portions,may be integrally formed with the sidewall. In another embodiment, the upper and lower end portions,may be separate from the sidewalland welded, stitched or otherwise joined to the sidewall. In the illustrated embodiment, the upper and lower end portions,are generally circular and the sidewallis generally cylindrical in configuration, although other suitable configurations may be utilised, such as rectangular or other polygonal.

The sidewallhas a longitudinal extent L (see) which is predetermined so that the assemblyis configured, in use, to span a support dimension (i.e. height) between a mine roof surfaceand a mine floor surface(or other support surface) within the mine opening (see). That is, for geotechnical applications, the longitudinal extent L of the sidewallis selected based on the seam height that is being mined. In the illustrated embodiment, the longitudinal extent L is between about 2.0 m to 4.0 m, however it will be appreciated that some applications will require a longitudinal extent L that is less than or greater than this range. In some embodiments, the longitudinal extent L may be slightly oversized to accommodate variance in seam roof height.

The sidewall, together with the upper and lower end portions,, surrounds an interior chamber(see) of the bagfor receiving the settable material. The sidewallhas an internal diameter D(see) which may be varied to change the volume of the chamber, and hence the volume of settable material to be received, to suit the desired load-bearing application. In the illustrated embodiment, the sidewallhas an internal diameter Dof between about 0.8 m to 1.2 m. In other embodiments, the internal diameter Dmay be less than 0.8 m or greater than 1.2 m.

The settable material is pumpable into the chambervia a fill portfitted to the upper end portionof the bagand fluidly communicable with the chamber. In one embodiment, the fill portmay include a one-way valve (not shown) to prevent the settable material from exiting the bagvia the fill portwhen the bagis being pumped with the settable material. The assembly further includes an air escape ventfitted to the bagadjacent or on the upper end portionto exhaust air within the chamberas the bagis being filled with the settable material.

With particular reference to, the assemblyfurther includes a reinforcing memberretained on the sidewallor at least partially secured to the bagto constrain the hardened material within the bagas a service load is applied to the assemblyfollowing installation. In this way, the reinforcing memberis primarily configured to provide tensile strength to oppose or resist hoop and radial stresses as compressive loads are applied to the assemblyfollowing installation.

In the illustrated embodiment, the reinforcing member is in the form of a band or strapwhich helically encompasses the longitudinal extent L of the sidewall. The strappreferably helically encompasses the outer wall surfaceof the sidewallwith a pitch of between about 50 mm to 150 mm, more preferably about 100 mm. The pitch may be varied to increase or decrease the ‘stiffness’ of radial restraint applied to the bagvia the arrangement of the strap. For example, the pitch may be varied along the longitudinal extent L of the sidewallto influence the mode of failure or collapse of the load-bearing support column. In some embodiments, the pitch may be tighter around portions of the outer wall surfacewhich are adjacent the upper and lower end portions,of the bagrelative to a middle or central portion of the outer wall surface. Optionally, the strapmay encompass the outer wall surfacein a manner of a double or opposed helix. In other embodiments, the strapmay encompass the outer wall surfacein a manner other than helical such as in a zig-zag, mesh-like or other spiral manner. In other embodiments, the assemblymay include a plurality of straps which are arranged in concentric rings or hoops spaced along the longitudinal extent L of the sidewall. Optionally, the strapmay be bonded to and encompass either or both of the outer and inner wall surfaces,of the sidewallin a manner described above.

The strapis preferably formed of plastics but may alternatively be formed of metal (such as steel), natural fiber, composites, and combinations thereof.

As shown in, the straphas a flattened major surfacefor contact with the outer wall surfaceof the sidewall(and/or the inner wall surface). In the context of this specification, it will be understood that the ‘flattened major surface’ is not necessarily completely planar but may have some curvature, particularly when helically wound about the containment bagand under load. However, the flattened major surfaceis flat enough that the radially inward compressive pressure is relatively uniform across a width W of the flattened major surface. The flattened major surfaceextends between an upper edgeand a lower edgeof the strapto define the width W (see) of the flattened major surface. Preferably, the width W is constant along the length of the strapand is in the range of about 20 mm to 30 mm, more preferably 25 mm. In other embodiments, the width W may be varied along the length of the strap. For example, the width W of the strapmay be greater adjacent the upper and lower end portions,of the bagrelative to the middle or central portion of the outer wall surface. In the illustrated embodiment, the width W is selected such that the flattened major surfacecontacts about one quarter to two thirds, preferably one quarter, of the total surface area of the outer wall surface. In other embodiments, a majority of the total surface area of the outer wall surfacemay be encapsulated by the width W of the strap. The width W may be varied so the flattened major surfacecontacts a lesser or greater surface area, respectively, of the outer wall surface. Optionally, the flattened major surfacemay be coated or surface treated to vary the coefficient of friction between the flattened major surfaceand the outer wall surface(and/or the inner wall surface). In some embodiments, the flattened major surfacemay have a surface profile/texture or surface feature which varies the coefficient of friction between the flattened major surfaceand the outer wall surface(and/or the inner wall surface). For example, in some embodiments, the flattened major surfacemay have a ribbed or roughened surface profile. In other embodiments, the flattened major surfacemay include a hook or loop feature for mating or binding with a corresponding loop or hook feature on the outer wall surface(and/or the inner wall surface) in the manner of a hook-and-loop fastening or touch fastening system.

Compared to a non-flattened surface (such as provided by a wire, cord or cable having a circular cross-section), the flattened major surfacedistributes frictional forces produced between the sidewalland the strapover a greater surface area of the sidewallthus reducing pressure and localised deformation in the region of the strap. By distributing the frictional forces over a greater surface area, there is reduced tendency for undue bulging of the hardened material between the pitch of the strapthereby minimising premature rupture or failure of the fabric of the bagwhen compressive loads are applied to the assemblyfollowing installation.

The bagpreferably includes a pockethelically coextending with the strapto position or hold the straptherein for frictional contact with the sidewalland the pocketwhilst permitting elongation or partial slippage of the strapwith respect to the bagas compressive loads are applied to the assembly. The pocketis dimensioned for geometric and supporting conformity with the strapto minimise lateral movement and/or separation of the strapwith respect to the bag, at least beyond minor movement associated with the free play of the strapwithin the slightly broader dimensions of the pocket. In this way, the pocketaids in increasing frictional forces by virtue of increasing the contact force between the flattened major surfaceand the outer wall surfaceof the sidewallas the pocketpresses the strapagainst the outer wall surface. In the illustrated embodiment, the pocketis formed by bonding lateral edges of a separate strip of fabric to the outer wall surface. In an alternative embodiment, the pocketmay be formed integrally with the sidewall. In some forms, the pocketmay be continuous or discontinuous. In an alternative embodiment, the bagmay not include a pocket and the strapis instead directly bonded (via gluing, plastic welding or otherwise secured) to the bagat discrete locations along a length of the strap, such as at either end and/or a mid-point of the strap. In other embodiments, the strapis continuously bonded to the bagalong the entire length of the strap. Optionally, the strapis secured to a majority of the circumference of each of the upper and lower end portions,of the bagto minimise slippage of the strapwith respect to the bag.

depict a pumpable crib bag assemblyaccording to a second embodiment. The embodimentis of an identical construction to the pumpable crib bag assemblyof the first embodiment, except that the assemblyfurther includes a cylindrical mesh reinforcement(see) located internally within the bag and which generally coextends with the sidewall. The mesh reinforcementis spaced from the inner wall surfaceof the sidewalland joined with the upper and lower end portions,. The mesh reinforcementis preferably constructed of a permeable plastic mesh material to permit the settable material to pass therethrough. During installation of the assembly, the settable material is pumped via the fill portinto the chamberof the bagto thereby fill the bagand also entirely encapsulate the mesh reinforcement. The mesh reinforcementhas permeable outer and inner wall surfaces,(see) which may each be encompassed by an additional strapwithin an additional pocketof an identical or similar construction to the strapand pocketencompassing the sidewall.

A method of installation of the assembly,will now be described with particular reference to. Initially, the assembly,may be in a collapsed state to facilitate portability to an installation site within an underground mine. When the assembly,is ready to be installed at the installation site, the upper end portionof the bagis secured against the mine roofvia a plurality of securement tabs(see) attached to the upper end portionof the bag. In the embodiment depicted, there are four of the securement tabs, although the number of the securement tabsmay vary. Retaining spikesor other suitable securing means are driven through the securement tabsinto the mine roofvia manual or assisted driving means. In the event that the retaining spikescannot be readily driven into the mine roofor the material of the mine roofwill not adequately hold the retaining spikes, the upper end portionmay be temporarily propped against the mine roofuntil the installation is completed. Alternatively, the upper end portionmay be secured to or hung against a roof mesh (not shown) with ties. In some embodiments, the bagis suspended from the mine rooffor relaxation under gravity prior to filling.

The settable material is then pumped into the chambervia the fill portthereby causing the bagto inflate and extend towards the mine floor. As the bagis being filled, air within the chamberis able to exhaust via the air escape vent. The bagis filled under pressure to a predetermined limit for positioning or setting the bagbetween the mine roofand mine floorprior to application of the service load, thereby causing the upper and lower end portions,to bear against and conform to the respective local surface contours of the mine roofand mine floor. The lower end portionis then secured against the mine floorvia additional securement tabs(see) attached to the lower end portionof the bag. In the embodiment depicted, there are four of the securement tabs, although the number of the securement tabsmay vary. Alternatively, the lower end portionmay be secured against the mine floorprior to filling of the bag. In other embodiments, the lower end portionmay sit or rest against the mine floorunder its own weight as the bagis filled progressively with the settable material.

Once the settable material cures, the assembly,of the present disclosure forms a load-bearing support columnbetween the mine roofand mine floor. The support columnof the present disclosure has effective initial strength and also improved sustainability under compressive loading, minimising occurrence of significant sudden load-releasing or load-shedding events. This is facilitated by the flattened major surfaceof the strapproviding improved radial constraint or confinement of the bagwhich at least aids in achieving initial compressive loads, and more particularly assists with maintaining sustained compressive loads by resisting the tendency for outward bulging of the columnand enabling the settable material to fail progressively in a compressive fashion. In turn, the load-bearing support columnis able to achieve more consistent loading behaviour. The flattened major surfacealso contributes to a reduced footprint of the columnby utilising the strapwith greater performance for radial confinement, as well as improved safety by minimising risk of ‘snagging’ of the strapvia mine equipment, personnel or the like. Although, the assembly,may also be utilised in other applications which require columnar ‘standing support’, such as support in civil applications.