WO2011151687A1 - Grout pack restraining envelope - Google Patents
Grout pack restraining envelope Download PDFInfo
- Publication number
- WO2011151687A1 WO2011151687A1 PCT/IB2011/000996 IB2011000996W WO2011151687A1 WO 2011151687 A1 WO2011151687 A1 WO 2011151687A1 IB 2011000996 W IB2011000996 W IB 2011000996W WO 2011151687 A1 WO2011151687 A1 WO 2011151687A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- rings
- restraining
- grout
- restraining rings
- pack
- Prior art date
Links
Classifications
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21D—SHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
- E21D15/00—Props; Chocks, e.g. made of flexible containers filled with backfilling material
- E21D15/48—Chocks or the like
- E21D15/483—Chocks or the like made of flexible containers, e.g. inflatable, with or without reinforcement, e.g. filled with water, backfilling material or the like
Definitions
- This invention relates to a support for underground mining operations and, in particular, to a restraining system for supporting an inflatable grout bag that, in use, is filled with a cementitious or other settable mix, typically, but not necessarily, including pulverised rock or backfill of processed or barren mined material.
- grout bag as used herein is intended to mean a generally permeable bag that is used to contain slurry pumped into it under pressure and to retain the solids while allowing excess moisture to permeate through the grout bag wall that is typically made of a suitable textile material such as a geotextile material.
- grout pack as used herein is intended to mean a grout bag that is used in combination with a restraining envelope encircling the generally upright walls of the grout bag, the restraining envelope including either or both of a reinforcing mesh and a series of elongate tension elements typically in the form of confinement rings or bands encircling the grout bag.
- stope support can utilise a vast range of materials, configurations and systems, including, gum poles, timber and composite packs, steel props, unmined ore pillars, rock anchors and granular (tailings) types of supports.
- cemented grout packs are increasingly being utilized as combination support products, consisting essentially of a support column formed by cured cemented backfill or a similar cured cementitious grout, contained within a geotextile bag and stiffened against lateral deformation under axial load with an external restraining envelope of either or both of a reinforcing mesh and a series of tension rings or bands encircling the grout bag, typically both.
- the mesh is typically a reinforcement of wire or polymer netting and the restraining rings are usually made of steel wire.
- restraining rings that encircle the mesh are made to fail at a minimum of a predetermined tension.
- the restraining rings or ring assemblies are able to yield under load thereby maintaining a measure of restraining force before their eventual failure.
- the grout pack Under vertical (axial) load the grout pack reduces in length and dilates laterally according to the Poisson's ratio of the grout material. Besides the cohesion of the cemented material, the geotextile bag, the surrounding mesh, as well as the restraining rings all contribute in some measure to the support resistance of the pack in that they restrain the lateral dilation of the grout column.
- the geotextile material is usually woven or knitted from low tenacity polymer fibres and offers little lateral confinement as it stretches easily under load. Its primary function is to provide suitable containment for the fluent grout slurry when it is introduced with optimal drainage and filtering properties.
- the mesh basically forms a support structure for the geotextile material, preventing excessive bulging (which would be accompanied by increased solids losses through the pores that become enlarged consequent on stretching of the fabric) under hydrostatic loading of the uncured fluent grout slurry.
- the netting wires or fibres are usually oriented at 45 degrees to the axis of the pack allowing the mesh to stretch in the horizontal direction whilst providing some additional lateral confinement to the pack.
- the circumferential restraining rings are the major structural confinement of the grout pack and their strengths contribute directly and significantly to the support resistance of the pack. It is these rings that largely control the compression behaviour of the grout pack.
- tensile strength refers to the totality of material tensile properties including yield stress, ultimate stress and associated strain values.
- ring is used in a broad sense and includes bands straps and other tension resisting members.
- a grout pack restraining envelope which includes a plurality of restraining rings shaped to extend circumferentially around a grout bag in a vertically spaced arrangement up at least a part of the height of the grout bag to provide support against lateral deformation of an installed grout pack as it occurs under axial load, the restraining envelope being characterised in that at least some of the rings are of differing tensile strengths or are configured to yield at differing tensions.
- the restraining envelope to include a collapsible polymer or wire mesh positioned on the inside of the restraining rings to which at least some of the restraining rings are fastened.
- rings of different tensile strengths are employed, the tensile strengths of the rings being selected so that rings of relatively higher tensile strength are provided at vertical positions at which relatively greater lateral deformation of the grout bag is expected, and rings of relatively lower tensile strength are provided at vertical positions at which relatively less lateral deformation of the grout bag is expected.
- rings of three different tensile strengths are used; an upper set of rings of highest tensile strength, a middle set of rings of intermediate tensile strength and a lower set of rings of lowest tensile strength.
- the rings may be made from metal wire and may have differing tensile strength by virtue of having differing cross-sectional areas. Alternatively, the rings may have differing tensile strengths by virtue of having different material properties.
- At least some of the rings carry secondary outer rings of greater diameter, the outer rings being configured to provide restraint to the expansion of the grout pack prior to failure of the rings of lesser diameter, thereby providing a progressive yield of the grout pack.
- the outer rings may be of different tensile strength from the inner rings.
- components in the form of rings suitable for inclusion in a grout restraining envelope are provided that are configured to yield at differing tensions, the tension at which the rings are configured to yield being selected so that rings which yield at higher tension are provided at vertical positions at which relatively greater lateral deformation of the grout bag is expected and rings which yield at relatively lower tension are provided at vertical positions at which relatively less lateral deformation of the grout bag is expected.
- the yielding rings may be formed by elongate elements that have first and second opposing ends connected to each other in an overlapping configuration to form an expansion zone so that the rings yield by controlled extension of their length when the tension applied to the rings by lateral deformation of the bag exceeds a predetermined tension force.
- the opposing ends may be connected by means of at least one collar that provides a predetermined swaging force thereby creating a predetermined frictional or shear resistance to movement between the first and second opposing ends.
- the rings may be evenly spaced apart up the height of the grout pack or may be spaced in a non-uniform arrangement in which the rings are more closely spaced at vertical positions at which relatively greater lateral deformation of the grout bag is expected.
- the invention extends to a grout pack comprising a grout bag and a restraining envelope encircling the grout bag, where the restraining envelope is as described herein.
- FIG. 1 is a partly broken away elevation of a first embodiment of a grout pack having a restraining envelope according to the invention.
- Figures 2 to 7 are each a schematic isometric view of the restraining rings of first, second, third, fourth, fifth and sixth embodiments of grout pack restraining envelopes according to the invention.
- a grout pack is of generally known construction and has, in the operative position, a geotextile bag [2] confined by means of a generally cylindrical mesh [3] that is used to retain a cementitious grout mixture [4] within the bag.
- Encircling the mesh is a plurality of vertically spaced restraining rings that, in all of the embodiments of the invention described below, form a restraining envelope together with the mesh and geotextile bag.
- the grout pack assembly is suspended in a mining excavation from the hanging wall [5] to contact the foot wall [6] and, with the assembly properly installed, liquid cementitious grout is pumped into the grout bag to fill it to its maximum capacity.
- the lateral hydraulic dilation is confined by the restraining envelope composed of the mesh and restraining rings.
- the grout pack is able to take axial load from the descending rock hanging wall.
- the dilation of the cured cemented grout (due to the material's Poisson's ratio) is then impeded primarily by the pack's restraining rings, thereby stiffening the pack's load-deformation response.
- fixed diameter restraining rings [7, 8] are threaded into the periphery of the mesh of the envelope.
- the restraining rings are, in this embodiment of the invention, evenly distributed over the height of the grout pack, from the top to the bottom.
- the three upper restraining rings [7] are fixed high strength rings, whilst the three lower restraining rings [8] are three fixed medium strength rings.
- the spacing of the rings in this case may be considered to be the normal ring spacing.
- the restraining rings of which are illustrated in Figure 3 there are five fixed high strength restraining rings [9], positioned within the upper part of the grout pack, and six fixed medium strength restraining rings [10] positioned in the lower part of the grout pack. All the rings are spaced approximately equally up the height of the grout pack. With almost double the number of restraining rings, this grout pack is substantially stronger than the one described with reference to Figure 1.
- the restraining rings of which are illustrated in Figure 4 three fixed high strength restraining rings [11] are positioned at the upper part of the grout pack, and three fixed medium strength restraining rings [12] are positioned in the lower part of the grout pack.
- a set of floating restraining rings of larger diameter is provided with two floating high strength restraining rings [13] being suspended from the top two fixed restraining rings [11] and a single floating medium strength restraining ring [14] suspended from the third fixed restraining ring from the top.
- the floating restraining rings are positioned in between the fixed rings in the vertical direction.
- This ring set illustrates how the compressive strength and the yield performance of a grout pack can be modified, utilizing various combinations of restraining rings.
- a restraining envelope has unequal spacing of two different restraining ring types.
- the arrangement of the restraining rings in the lower part of the grout pack is depleted in that one of the rings that would have been positioned between the two rings present, has been omitted.
- the lower part is substantially weakened, not only by using medium strength rings, but also by the omission of one of those rings. It is envisaged that in many applications the lower half of a grout pack is never dilated by vertical stress and an arrangement such as that illustrated could be adequate as well as more cost- effective.
- the restraining rings of which are illustrated in Figure 6 the restraining ring arrangement includes two fixed high strength restraining rings [17] positioned in the top part of the envelope; two fixed medium strength intermediate restraining rings [18] positioned in the central part of the envelope; and two fixed low strength restraining rings [19] positioned in the lower part of the envelope.
- This grout pack is therefore partitioned into three restraint zones; a high strength zone; a medium strength zone; and a low strength zone.
- the restraining rings of which are illustrated in Figure 7 a similar arrangement of restraining rings to that described with reference to Figure 6 is provided.
- the uppermost two high strength restraining rings [20]; the two intermediate medium strength intermediate restraining rings [21] and the two lower low strength rings [22] are each made as yielding rings formed by elongate elements that have first and second opposing ends connected to each other in an overlapping configuration to form an expansion zone so that the rings yield by controlled extension of their length.
- the opposing ends are connected by means of a pair of spaced collars [23] that provide a predetermined swaging force thereby creating a predetermined frictional resistance to movement between the first and second opposing ends.
- the restraining rings may be of any desired configuration with different diameters and different vertical arrangements and different arrangements of any floating rings that may be present. The arrangement may be configured to provide different positions of strong restraint zones within a grout pack.
Abstract
Description
Claims
Priority Applications (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
AP2012006646A AP2012006646A0 (en) | 2010-06-02 | 2011-05-10 | Grout pack restraining envelope |
AU2011259999A AU2011259999A1 (en) | 2010-06-02 | 2011-05-10 | Grout pack restraining envelope |
US13/700,948 US20130129426A1 (en) | 2010-06-02 | 2011-06-10 | Grout pack restraining envelope |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
ZA201003920 | 2010-06-02 | ||
ZA2010/03920 | 2010-06-02 |
Publications (1)
Publication Number | Publication Date |
---|---|
WO2011151687A1 true WO2011151687A1 (en) | 2011-12-08 |
Family
ID=45066245
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/IB2011/000996 WO2011151687A1 (en) | 2010-06-02 | 2011-05-10 | Grout pack restraining envelope |
Country Status (5)
Country | Link |
---|---|
US (1) | US20130129426A1 (en) |
AP (1) | AP2012006646A0 (en) |
AU (1) | AU2011259999A1 (en) |
WO (1) | WO2011151687A1 (en) |
ZA (1) | ZA201103869B (en) |
Families Citing this family (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US9334735B2 (en) * | 2011-02-24 | 2016-05-10 | Natalie Killassy | Preloadable support |
US11053683B2 (en) * | 2018-01-24 | 2021-07-06 | Strata Products Worldwide, Llc | Apparatus for controlling yield performance of props for roofs, and methods |
US10883366B2 (en) * | 2018-10-24 | 2021-01-05 | Crosscut Enterprises LLC | Mine roof support |
Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
AU766110B2 (en) * | 1999-04-23 | 2003-10-09 | Industrial Netting And Mining Products (Proprietary) Limited | Reinforcing structure for a support pillar |
US20070231085A1 (en) * | 2006-03-28 | 2007-10-04 | Nils Mittet Skarbovig | Grout pack restraining system |
-
2011
- 2011-05-10 AU AU2011259999A patent/AU2011259999A1/en not_active Abandoned
- 2011-05-10 AP AP2012006646A patent/AP2012006646A0/en unknown
- 2011-05-10 WO PCT/IB2011/000996 patent/WO2011151687A1/en active Application Filing
- 2011-05-26 ZA ZA2011/03869A patent/ZA201103869B/en unknown
- 2011-06-10 US US13/700,948 patent/US20130129426A1/en not_active Abandoned
Patent Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
AU766110B2 (en) * | 1999-04-23 | 2003-10-09 | Industrial Netting And Mining Products (Proprietary) Limited | Reinforcing structure for a support pillar |
US20070231085A1 (en) * | 2006-03-28 | 2007-10-04 | Nils Mittet Skarbovig | Grout pack restraining system |
Also Published As
Publication number | Publication date |
---|---|
AP2012006646A0 (en) | 2012-12-31 |
US20130129426A1 (en) | 2013-05-23 |
ZA201103869B (en) | 2012-04-25 |
AU2011259999A1 (en) | 2012-12-20 |
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