WO2000011319A1 - Method of and apparatus for prestressing a support in underground mines - Google Patents

Method of and apparatus for prestressing a support in underground mines Download PDF

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Publication number
WO2000011319A1
WO2000011319A1 PCT/ZA1999/000071 ZA9900071W WO0011319A1 WO 2000011319 A1 WO2000011319 A1 WO 2000011319A1 ZA 9900071 W ZA9900071 W ZA 9900071W WO 0011319 A1 WO0011319 A1 WO 0011319A1
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WO
WIPO (PCT)
Prior art keywords
container
volume
expansible
voids
support
Prior art date
Application number
PCT/ZA1999/000071
Other languages
French (fr)
Inventor
Petrus Nicolaas Erasmus
Michael Reinhardt Grobbler
Original Assignee
Grinaker Construction Limited
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Grinaker Construction Limited filed Critical Grinaker Construction Limited
Priority to AU59297/99A priority Critical patent/AU5929799A/en
Publication of WO2000011319A1 publication Critical patent/WO2000011319A1/en

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Classifications

    • E—FIXED CONSTRUCTIONS
    • E21—EARTH OR ROCK DRILLING; MINING
    • E21D—SHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
    • E21D11/00—Lining tunnels, galleries or other underground cavities, e.g. large underground chambers; Linings therefor; Making such linings in situ, e.g. by assembling
    • E21D11/14—Lining predominantly with metal
    • E21D11/15—Plate linings; Laggings, i.e. linings designed for holding back formation material or for transmitting the load to main supporting members
    • E21D11/157—Laggings making use of fluid cushions, e.g. the fluid containing a hardenable material
    • E—FIXED CONSTRUCTIONS
    • E21—EARTH OR ROCK 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 the stressing of supports of the kind used, for example, in underground mining installations
  • a support such as an elongate support or support pack, when installed between a hanging and foot wall, should be stressed before closure of the hanging wall towards the foot wall takes place to enable the support to exhibit its load bearing capabilities at an early stage
  • the invention provides, in the first instance, a method of stressing a support which includes the steps of pressurising at least one expansible volume thereby to exert a force on the support, maintaining pressure inside the volume, and allowing a material to set around at least part of the volume
  • the expansible volume may be located inside a container which may be positioned between a surface of the support and an opposing surface against which the support reacts
  • the expansible volume may be pressurised so that a force is exerted between the support and the said opposing surface
  • the expansible volume may be located inside a substantially rigid housing which directs expansion of the volume in at least one direction
  • the container may be flexible or have relatively movable sections
  • the pressure may be exerted by an external pressure source, eg a pressurised fluid (liquid or gaseous), or by means which generates a pressure through chemical reaction
  • an external pressure source eg a pressurised fluid (liquid or gaseous)
  • the settable material may be positioned inside the flexible container, around the said expansible volume
  • the volume in which the settable material is located may also be pressurised
  • the expansible volume may be pressurised using any suitable medium, liquid or gaseous, but preferably use is made of water
  • the settable material may be a cementitious grout powder and water may be mixed with the grout powder to form a settable cementitious mixture Any other suitable settable material may be used, and the invention is not limited in this way
  • the settable material may include any appropriate additive, eg an accelerator to shorten its setting time
  • a plurality of expansible volumes may be pressurised substantially simultaneously It is to be understood that the net force which is exerted on the support is the product of the respective cross-sectional areas of the volumes and the pressure which prevails inside each volume
  • the invention also provides apparatus for stressing a support which includes a container, first means forming at least one expansible volume inside the container, and second means for confining a settable material inside the container around at least part of the volume
  • the first means may comprise any suitable flexible sheet material e g polyethylene
  • a plurality of the said expansible volumes may be defined by the said first means
  • the container may include relatively movable sections or may be flexible and may include a reinforced material e g woven polypropylene which surrounds the said flexible sheet material
  • the flexible container may be of any suitable shape and size
  • the container may include a medium inside the container which, upon actuation, results in the said settable material
  • the settable material may be a cementitious grout powder
  • the settable material may be located inside the container around the expansible volumes
  • the quantity of the settable material may be related to the maximum volume of the flexible container so that, when the flexible container is expanded by means of water which is introduced into the flexible container a suitable ratio of water to cementitious grout is present to ensure that, once these constituents are mixed with each other, a settable composition of adequate strength is achieved
  • the second means may also be flexible sheet material
  • the sheet material used for the first and second means may form at least part of the container
  • the apparatus preferably includes valve means for introducing and pressurising fluid into the expansible volume
  • a settable material such as a cementitious grout may be used to provide a sustainable load bearing capability for the apparatus, this is only by way of a non-limiting example, for any appropriate material can be used in place of the grout
  • the settable material may be mixed inside the container, or it may be mixed outside the container and the mixed material may then be introduced into the container Ingredients which react with each other to produce the settable material may also be introduced into the container
  • any appropriate means may be used to expand the volumes
  • a pressurised fluid, gaseous or liquid, or a mixture thereof may be introduced into the volumes
  • the volumes may alternatively be expanded by means of a chemical reaction between appropriate substances Clearly the volumes should be expanded, and held in a pressurised state, until such time as the settable material has, in fact, set and is capable of carrying a load
  • Figure 1 is a somewhat schematic plan view of apparatus according to the invention for stressing a support
  • Figure 2 is a cross-sectional view through the apparatus of Figure 1 taken on the line 2-2
  • Figure 3 is a side view of a support pack in an underground installation which includes apparatus of the kind shown in Figures 1 and 2 for stressing the pack,
  • Figure 4 is a cross-sectional view of an apparatus according to another form of the invention
  • Figure 5 illustrates a variation of the invention
  • Figure 6 shows the use of the principles of the invention with an elongate support
  • FIGS. 1 and 2 of the accompanying drawings illustrate apparatus 10 according to the invention for stressing a support pack
  • the apparatus includes a flexible container 12 which is formed from an outer layer of woven polypropylene sheet material 14 and an inner container 16 which is made from a relatively weak and inexpensive material such as polyethylene
  • the polyethylene container is conveniently referred to herein as a single container but it may comprise a plurality of interconnected separate containers
  • the container 16 is formed from opposing sheets of polyethylene which are heat welded or otherwise secured to one another in such a way that a plurality of voids 18 are formed by the polyethylene sheets
  • Each void 18 has an elongate shape extending in the direction of the width 20 of the container 12
  • Tubes 22 interconnect the voids 18
  • the tubes are formed by appropriately welding the sheets of polyethylene to each other
  • a filler tube 24 extends from the voids through the wall of the container
  • the container is conveniently referred to herein as having a plurality of interconnected voids in a two-dimensional plan, but it may comprise a plurality of interconnected voids in a three-dimensional relationship as is shown from the side in Figure 4
  • a one-way valve 26, of a kind which is known in the art and which is therefore not described herein, is connected to a mouth of the filler tube
  • each void has a number of relatively small perforations or apertures 28
  • a cementitious grout powder 30 of any appropriate kind known in the art is located inside the polyethylene container As far as is possible air is excluded from the interior of the container 16 and the quantity of grout 30, which is initially in the container 16 and which is indicated by means of a dotted line 32, effectively determines the volume of the container 12 at the time
  • FIG 3 illustrates the manner in which the apparatus 10 is used
  • the apparatus is positioned on top of a support pack 34 which is constructed in any appropriate way using techniques known in the art
  • An upper surface 34 of the pack opposes a hanging wall 38 in an underground excavation
  • the apparatus 10 is then positioned on top of the pack, resting on the surface 36, and underlying the hanging wall 38
  • Water under pressure is introduced from any appropriate source through the valve 26 and the filler tube 24 into the voids 18
  • the water fills the voids thereby extending the voids into the elongate shapes shown in Figure 2
  • the extent to which the voids are in fact expanded, in their longitudinal directions, depends at least on the spacing between the surface 36 and the hanging wall 38
  • the water which enters the voids is able to escape to a limited extent through the apertures or holes 28 in the walls of the voids
  • This water is sprayed into the grout powder 30 and mixes with the grout powder thereby forming a settable composition
  • the cementitious mixture while still in a fluent state, gradually fills the interior of, and expands, the container 16 while, at the same time, surrounding each of the voids 18 and supporting the sheet material which defines the voids
  • valve 26 When the source of water is disconnected from the valve 26 the pressure inside the container 12 is maintained for, as noted, the valve 26 is a one-way valve
  • the cementitious grout sets, trapping water inside each of the voids which in turn are encompassed by the set grout In this way the stressing force which is initially exerted by the voids and which may be considered to be of a temporary nature is replaced by a force exerted by the cementitious grout
  • the set grout has a load bearing capability which is maintained even if water leaks from the voids
  • the invention thus provides a two-phase process for stressing the support 34 Initially the stressing force is provided by the pressurised voids and thereafter the grout sets around the voids in such a way that the set grout is capable of maintaining the stressing force, and of carrying load which may be exerted by closure of the hanging wall.
  • the voids within the set grout can be designed so that, under loading which occurs as closure of the hanging wall takes place towards the foot wall, the voids fracture and crumble providing a controlled yielding characteristic.
  • Figures 1 to 4 relate to the use of the principles of the invention for stressing a pack-type support.
  • the voids which are formed in the flexible container may extend in a two-dimensional array or in a three-dimensional array.
  • the invention is not limited in this regard.
  • a single void may be formed in the container, but generally, as the size of the support increases it will be found to be desirable to increase the number of voids.
  • the voids are pressurised, in the example, by introducing water under pressure into the voids. This water expands the voids and at the same time provides a means for mixing the cementitious grout powder. Again it is to be understood that this is merely exemplary.
  • a settable material such as a pre-mixed grout composition may be injected into the volume which surrounds the voids through a suitable valve, not shown.
  • a pressurised medium may be injected into the voids through the filler valve 26.
  • the flexible material which forms the voids would, in this example, normally not be perforated.
  • the voids would therefore be expanded by means of a first operation and the settable material would be placed around the voids and would be confined to provide a supporting structure for the voids, in a second operation.
  • Another possibility is to pressurise the voids using a chemical reaction.
  • a chemical reaction For example bicarbonate mixed with water and citric acid releases gas in the form of carbon dioxide.
  • the gas can be used to expand and pressurise the voids. This aspect is further described in connection with the embodiment shown in Figure 6.
  • Figure 5 illustrates another form of the invention wherein grout powder 40 is pre-packaged into flexible pockets 42 inside a flexible container 44 which is suitably reinforced, for example in the manner which has been described in connection with Figure 1
  • Adjacent each pocket of grout are pre-packaged flexible containers 46 of water 48
  • the quantity of water 48 adjacent each pocket of grout 40 is such that when the constituents are mixed the resulting mixture has the right composition and sets with adequate strength
  • a filler tube 50, to which is connected a one-way filler valve 52, is in communication with voids 54 inside the container 44
  • Figure 6 illustrates the principles of the invention used in connection with an elongate support 70 of any appropriate kind
  • a cup-shaped housing 72 of a substantially rigid material is placed over an upper end of the support and an upper end of the housing 72 bears against a hanging wall 74
  • a flexible container 76 Positioned inside the housing is a flexible container 76 which is substantially similar to what has been described in connection with Figures 1 to 5, although it has smaller dimensions Voids 78 are defined inside the container and are connected to a filler tube 80 with a one-way filler valve 82 A second filler tube 84 extends to the volume of the container which surrounds the voids
  • the support 70 is initially pressurised by introducing water under pressure through the one-way valve 82 into the voids 78 In this way the voids are expanded At the same time a pre-mixed cementitious grout is directed from a source, not shown, through the tube 84 into the volume around the voids These processes take place substantially simultaneously so that the settable material is placed in position around the voids at the same time as the voids are being pressurised Once the settable material has, in fact, set the material is capable of continuous load-bearing action
  • the voids may be pressurised using a pressure medium such as water under pressure, but this is not essential for a suitable pressure may be generated by means of an appropriate chemical reaction
  • Figure 7 illustrates a void 80 which contains a pre-packaged paste 82 of bicarbonate and a small pocket 84 which is formed by a flexible container and which contains citric acid 86
  • a filler tube 88 extends to the void
  • the void 80 is one of a plurality of similar voids inside a container 90 which, in use, is filled with a settable material 92, such as a cementitious grout, substantially in a manner which has been described hereinbefore
  • the void 80 is pressurised by means of a chemical reaction which is initiated when water 88 is introduced into the void
  • the water under pressure fractures a wall 94 inside the void and releases the paste 82
  • Substantially simultaneously the wall of the pocket 84 is fractured and the citric acid 86 is released into the void
  • the mixture of the water, citric acid and bicarbonate paste 82 gives rise to a chemical reaction which causes the release of carbon dioxide
  • the gas pressurises the void and the pressure is maintained while the grout 92 sets
  • the housing 72 thus confines the expansion of the voids and ensures that the expansive movement takes place principally in a direction which coincides with the longitudinal direction of the elongate support

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  • Engineering & Computer Science (AREA)
  • Mining & Mineral Resources (AREA)
  • Structural Engineering (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • Geochemistry & Mineralogy (AREA)
  • Geology (AREA)
  • Architecture (AREA)
  • Civil Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Filling Or Discharging Of Gas Storage Vessels (AREA)

Abstract

Method and apparatus for stressing a support (34, 70) which includes pressuring at least one extensible volume (18) thereby to exert a force on the support, maintaining pressure inside the volume (18), and allowing a material (30) to set around at least part of the volume.

Description

METHOD OF AND APPARATUS FOR PRESTRESSING A SUPPORT IN
UNDERGROUND MINES
BACKGROUND OF THE INVENTION
This invention relates to the stressing of supports of the kind used, for example, in underground mining installations
A support such as an elongate support or support pack, when installed between a hanging and foot wall, should be stressed before closure of the hanging wall towards the foot wall takes place to enable the support to exhibit its load bearing capabilities at an early stage
SUMMARY OF THE INVENTION
The invention provides, in the first instance, a method of stressing a support which includes the steps of pressurising at least one expansible volume thereby to exert a force on the support, maintaining pressure inside the volume, and allowing a material to set around at least part of the volume
The expansible volume may be located inside a container which may be positioned between a surface of the support and an opposing surface against which the support reacts
The expansible volume may be pressurised so that a force is exerted between the support and the said opposing surface
Alternatively the expansible volume may be located inside a substantially rigid housing which directs expansion of the volume in at least one direction The container may be flexible or have relatively movable sections
The pressure may be exerted by an external pressure source, eg a pressurised fluid (liquid or gaseous), or by means which generates a pressure through chemical reaction The settable material may be positioned inside the flexible container, around the said expansible volume The volume in which the settable material is located may also be pressurised
The expansible volume may be pressurised using any suitable medium, liquid or gaseous, but preferably use is made of water
The settable material may be a cementitious grout powder and water may be mixed with the grout powder to form a settable cementitious mixture Any other suitable settable material may be used, and the invention is not limited in this way
The settable material may include any appropriate additive, eg an accelerator to shorten its setting time
A plurality of expansible volumes may be pressurised substantially simultaneously It is to be understood that the net force which is exerted on the support is the product of the respective cross-sectional areas of the volumes and the pressure which prevails inside each volume
The invention also provides apparatus for stressing a support which includes a container, first means forming at least one expansible volume inside the container, and second means for confining a settable material inside the container around at least part of the volume
The first means may comprise any suitable flexible sheet material e g polyethylene
A plurality of the said expansible volumes may be defined by the said first means
The container may include relatively movable sections or may be flexible and may include a reinforced material e g woven polypropylene which surrounds the said flexible sheet material The flexible container may be of any suitable shape and size
The container may include a medium inside the container which, upon actuation, results in the said settable material
The settable material may be a cementitious grout powder The settable material may be located inside the container around the expansible volumes
The quantity of the settable material may be related to the maximum volume of the flexible container so that, when the flexible container is expanded by means of water which is introduced into the flexible container a suitable ratio of water to cementitious grout is present to ensure that, once these constituents are mixed with each other, a settable composition of adequate strength is achieved
The second means may also be flexible sheet material
The sheet material used for the first and second means may form at least part of the container
The apparatus preferably includes valve means for introducing and pressurising fluid into the expansible volume
Although a settable material such as a cementitious grout may be used to provide a sustainable load bearing capability for the apparatus, this is only by way of a non-limiting example, for any appropriate material can be used in place of the grout
The settable material may be mixed inside the container, or it may be mixed outside the container and the mixed material may then be introduced into the container Ingredients which react with each other to produce the settable material may also be introduced into the container
Similarly, with regard to the expansible volumes, any appropriate means may be used to expand the volumes Thus a pressurised fluid, gaseous or liquid, or a mixture thereof, may be introduced into the volumes
The volumes may alternatively be expanded by means of a chemical reaction between appropriate substances Clearly the volumes should be expanded, and held in a pressurised state, until such time as the settable material has, in fact, set and is capable of carrying a load
BRIEF DESCRIPTION OF THE DRAWINGS
The invention is further described by way of examples with reference to the accompanying drawings in which
Figure 1 is a somewhat schematic plan view of apparatus according to the invention for stressing a support, Figure 2 is a cross-sectional view through the apparatus of Figure 1 taken on the line 2-2,
Figure 3 is a side view of a support pack in an underground installation which includes apparatus of the kind shown in Figures 1 and 2 for stressing the pack,
Figure 4 is a cross-sectional view of an apparatus according to another form of the invention, Figure 5 illustrates a variation of the invention, and
Figure 6 shows the use of the principles of the invention with an elongate support
DESCRIPTION OF PREFERRED EMBODIMENTS
Figures 1 and 2 of the accompanying drawings illustrate apparatus 10 according to the invention for stressing a support pack The apparatus includes a flexible container 12 which is formed from an outer layer of woven polypropylene sheet material 14 and an inner container 16 which is made from a relatively weak and inexpensive material such as polyethylene
The polyethylene container is conveniently referred to herein as a single container but it may comprise a plurality of interconnected separate containers The container 16 is formed from opposing sheets of polyethylene which are heat welded or otherwise secured to one another in such a way that a plurality of voids 18 are formed by the polyethylene sheets Each void 18 has an elongate shape extending in the direction of the width 20 of the container 12
Tubes 22 interconnect the voids 18 The tubes are formed by appropriately welding the sheets of polyethylene to each other A filler tube 24 extends from the voids through the wall of the container
The container is conveniently referred to herein as having a plurality of interconnected voids in a two-dimensional plan, but it may comprise a plurality of interconnected voids in a three-dimensional relationship as is shown from the side in Figure 4
A one-way valve 26, of a kind which is known in the art and which is therefore not described herein, is connected to a mouth of the filler tube
The material which forms the wall of each void has a number of relatively small perforations or apertures 28
Prior to installation and use of the apparatus 10 a cementitious grout powder 30 of any appropriate kind known in the art is located inside the polyethylene container As far as is possible air is excluded from the interior of the container 16 and the quantity of grout 30, which is initially in the container 16 and which is indicated by means of a dotted line 32, effectively determines the volume of the container 12 at the time
Figure 3 illustrates the manner in which the apparatus 10 is used The apparatus is positioned on top of a support pack 34 which is constructed in any appropriate way using techniques known in the art An upper surface 34 of the pack opposes a hanging wall 38 in an underground excavation The apparatus 10 is then positioned on top of the pack, resting on the surface 36, and underlying the hanging wall 38 Water under pressure is introduced from any appropriate source through the valve 26 and the filler tube 24 into the voids 18 The water fills the voids thereby extending the voids into the elongate shapes shown in Figure 2 The extent to which the voids are in fact expanded, in their longitudinal directions, depends at least on the spacing between the surface 36 and the hanging wall 38
The water which enters the voids is able to escape to a limited extent through the apertures or holes 28 in the walls of the voids This water is sprayed into the grout powder 30 and mixes with the grout powder thereby forming a settable composition The cementitious mixture, while still in a fluent state, gradually fills the interior of, and expands, the container 16 while, at the same time, surrounding each of the voids 18 and supporting the sheet material which defines the voids
As the voids are expanded in the manner described a force is generated which is substantially equal to the product of the cross-sectional areas of the voids and the internal pressure which is exerted inside the voids by the water This force is exerted between the hanging wall 38 and the upper surface 36 of the pack and, in this way, the apparatus 10 is fully expanded to fill the gap between the hanging wall 38 and the surface 36 and, as a consequence, the pack 34 is placed under stress
When the source of water is disconnected from the valve 26 the pressure inside the container 12 is maintained for, as noted, the valve 26 is a one-way valve The cementitious grout sets, trapping water inside each of the voids which in turn are encompassed by the set grout In this way the stressing force which is initially exerted by the voids and which may be considered to be of a temporary nature is replaced by a force exerted by the cementitious grout Also, the set grout has a load bearing capability which is maintained even if water leaks from the voids
Once the grout has set there is in fact no adverse consequence of any significance if water leaks from the voids
The invention thus provides a two-phase process for stressing the support 34 Initially the stressing force is provided by the pressurised voids and thereafter the grout sets around the voids in such a way that the set grout is capable of maintaining the stressing force, and of carrying load which may be exerted by closure of the hanging wall.
The voids within the set grout can be designed so that, under loading which occurs as closure of the hanging wall takes place towards the foot wall, the voids fracture and crumble providing a controlled yielding characteristic.
Figures 1 to 4 relate to the use of the principles of the invention for stressing a pack-type support. As noted the voids which are formed in the flexible container may extend in a two-dimensional array or in a three-dimensional array. The invention is not limited in this regard. Depending on the size of the support which is to be stressed a single void may be formed in the container, but generally, as the size of the support increases it will be found to be desirable to increase the number of voids.
The voids are pressurised, in the example, by introducing water under pressure into the voids. This water expands the voids and at the same time provides a means for mixing the cementitious grout powder. Again it is to be understood that this is merely exemplary. Thus, as an alternative, a settable material such as a pre-mixed grout composition may be injected into the volume which surrounds the voids through a suitable valve, not shown. At the same time a pressurised medium may be injected into the voids through the filler valve 26. The flexible material which forms the voids would, in this example, normally not be perforated. The voids would therefore be expanded by means of a first operation and the settable material would be placed around the voids and would be confined to provide a supporting structure for the voids, in a second operation.
Another possibility is to pressurise the voids using a chemical reaction. For example bicarbonate mixed with water and citric acid releases gas in the form of carbon dioxide. The gas can be used to expand and pressurise the voids. This aspect is further described in connection with the embodiment shown in Figure 6.
Figure 5 illustrates another form of the invention wherein grout powder 40 is pre-packaged into flexible pockets 42 inside a flexible container 44 which is suitably reinforced, for example in the manner which has been described in connection with Figure 1
Adjacent each pocket of grout are pre-packaged flexible containers 46 of water 48 The quantity of water 48 adjacent each pocket of grout 40 is such that when the constituents are mixed the resulting mixture has the right composition and sets with adequate strength A filler tube 50, to which is connected a one-way filler valve 52, is in communication with voids 54 inside the container 44
The apparatus shown in Figure 5 is used in the same way as what has been described in connection with Figures 1 to 4 When water is injected into the voids 54 through the filler tube 50, the voids are pressurised and expand The containers 46 are pressurised and the walls of the containers fracture thereby releasing the water 48 into the grout powder 40 As has been noted the water 48 mixes with the grout powder to form a composition of the correct constituency and the composition, once set, has load-bearing capability Until such time as the composition has set the pre-stressing force is generated and maintained by the water which is under pressure in the various voids 54
Figure 6 illustrates the principles of the invention used in connection with an elongate support 70 of any appropriate kind A cup-shaped housing 72 of a substantially rigid material is placed over an upper end of the support and an upper end of the housing 72 bears against a hanging wall 74
Positioned inside the housing is a flexible container 76 which is substantially similar to what has been described in connection with Figures 1 to 5, although it has smaller dimensions Voids 78 are defined inside the container and are connected to a filler tube 80 with a one-way filler valve 82 A second filler tube 84 extends to the volume of the container which surrounds the voids
The support 70 is initially pressurised by introducing water under pressure through the one-way valve 82 into the voids 78 In this way the voids are expanded At the same time a pre-mixed cementitious grout is directed from a source, not shown, through the tube 84 into the volume around the voids These processes take place substantially simultaneously so that the settable material is placed in position around the voids at the same time as the voids are being pressurised Once the settable material has, in fact, set the material is capable of continuous load-bearing action
As has been pointed out the voids may be pressurised using a pressure medium such as water under pressure, but this is not essential for a suitable pressure may be generated by means of an appropriate chemical reaction
Figure 7 illustrates a void 80 which contains a pre-packaged paste 82 of bicarbonate and a small pocket 84 which is formed by a flexible container and which contains citric acid 86 A filler tube 88 extends to the void
The void 80 is one of a plurality of similar voids inside a container 90 which, in use, is filled with a settable material 92, such as a cementitious grout, substantially in a manner which has been described hereinbefore
In this instance the void 80 is pressurised by means of a chemical reaction which is initiated when water 88 is introduced into the void The water under pressure fractures a wall 94 inside the void and releases the paste 82 Substantially simultaneously the wall of the pocket 84 is fractured and the citric acid 86 is released into the void The mixture of the water, citric acid and bicarbonate paste 82 gives rise to a chemical reaction which causes the release of carbon dioxide The gas pressurises the void and the pressure is maintained while the grout 92 sets
The housing 72 thus confines the expansion of the voids and ensures that the expansive movement takes place principally in a direction which coincides with the longitudinal direction of the elongate support

Claims

1 A method of stressing a support which includes the steps of pressurising at least one expansible volume thereby to exert a force on the support, maintaining pressure inside the volume, and allowing a material to set around at least part of the volume
2 A method according to claim 1 wherein the expansible volume is pressurised by introducing a fluid under pressure into the volume
3 A method according to claim 2 wherein some of the fluid is allowed to mix with a suitable material thereby to form the settable material
4 A method according to claim 1 wherein the expansible volume is pressurised by causing a chemical reaction, which results in pressure being generated, to take place inside the expansible volume
5 A method according to any one of claims 1 to 4 wherein a plurality of expansible volumes are pressurised substantially simultaneously
6 A method according to any one of claims 1 to 5 wherein the expansible volume and the settable material are located inside a flexible container
7 A method according to claim 6 wherein the flexible container is located inside a substantially rigid housing which directs expansion of the volume in at least one direction
8 Apparatus for stressing a support which includes a container, first means forming at least one expansible volume inside the container, and second means for confining a settable material inside the container around at least part of the volume
9 Apparatus according to claim 8 wherein the first means is flexible sheet material Apparatus according to claim 8 or 9 wherein the second means is flexible sheet material
Apparatus according to any one of claims 8 to 10 which includes valve means for introducing a pressurised fluid into the expansible volume
Apparatus according to any one of claims 8 to 11 which includes a medium inside the container which, upon actuation, results in the said settable material
Apparatus according to any one of claims 8 to 12 which includes a housing in which the container is located and which allows movement of the container in at least one direction relatively to the housing
Apparatus for stressing a support which includes a flexible container, flexible sheet material which is inside the container and which forms a plurality of expansible volumes inside the container, settable material inside the container around the flexible sheet material, and valve means for introducing a pressurised fluid into the volumes in order to expand the volumes
PCT/ZA1999/000071 1998-08-24 1999-08-24 Method of and apparatus for prestressing a support in underground mines WO2000011319A1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU59297/99A AU5929799A (en) 1998-08-24 1999-08-24 Method of and apparatus for prestressing a support in underground mines

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
ZA98/4504 1998-08-24
ZA984504 1998-08-24

Publications (1)

Publication Number Publication Date
WO2000011319A1 true WO2000011319A1 (en) 2000-03-02

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PCT/ZA1999/000071 WO2000011319A1 (en) 1998-08-24 1999-08-24 Method of and apparatus for prestressing a support in underground mines

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AU (1) AU5929799A (en)
WO (1) WO2000011319A1 (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2002042573A2 (en) * 2000-11-21 2002-05-30 Chimica Edile Production (Pty) Limited Method and apparatus for pre-stressing a roof support
EP1762698A1 (en) * 2005-09-08 2007-03-14 Amberg Engineering AG Yielding element for an underground cavity

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1752101A (en) * 1926-12-22 1930-03-25 Meutsch Heinrich Mining prop
EP0186905A1 (en) * 1985-01-03 1986-07-09 F. Willich GmbH & Co. Container for filling mine cavities
DE4343313A1 (en) * 1992-12-23 1994-07-14 Langerbein Scharf Gmbh & Co Kg Active support threshold for pit expansion in longwall and track
DE4430552A1 (en) * 1994-08-27 1996-02-29 Gebhardt & Koenig Gesteins Und Walling equipment for underground mining
US5683182A (en) * 1994-03-17 1997-11-04 Nampak Products Limited High pressure bag

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1752101A (en) * 1926-12-22 1930-03-25 Meutsch Heinrich Mining prop
EP0186905A1 (en) * 1985-01-03 1986-07-09 F. Willich GmbH & Co. Container for filling mine cavities
DE4343313A1 (en) * 1992-12-23 1994-07-14 Langerbein Scharf Gmbh & Co Kg Active support threshold for pit expansion in longwall and track
US5683182A (en) * 1994-03-17 1997-11-04 Nampak Products Limited High pressure bag
DE4430552A1 (en) * 1994-08-27 1996-02-29 Gebhardt & Koenig Gesteins Und Walling equipment for underground mining

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2002042573A2 (en) * 2000-11-21 2002-05-30 Chimica Edile Production (Pty) Limited Method and apparatus for pre-stressing a roof support
WO2002042573A3 (en) * 2000-11-21 2003-02-20 Chimica Edile Production Pty L Method and apparatus for pre-stressing a roof support
EP1762698A1 (en) * 2005-09-08 2007-03-14 Amberg Engineering AG Yielding element for an underground cavity

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