AU6509990A - A method of sealing an opening - Google Patents

Description

A METHOD OF SEALING AN OPENING

This invention relates to a method of sealing an opening, for example a shaft or a tunnel. A particular example of the invention has application in sealing or "stopping" tunnels in gastight manner in underground mines.

In underground mining it is often necessary to seal or stop a tunnel or a section thereof primarily to control gas movement throughout the mine. For example, a tunnel may be sealed to control ventilation in the mine or to control and contain gases in a particular tunnel of the underground mine.

In accordance with the invention there is provided a method of sealing an opening against the flow of gas therethrough, comprising: placing a bag in the opening, inflating the bag with gas to conform to the periphery of the opening, and introducing a filler material into the bag to displace gas from the bag until the material substantially fills the bag.

The filler material is preferably settable or setting. Inflating the bag initially to conform to the periphery of the opening, has the advantage that it is not necessary for the filler material tx> remain un-set until the bag conforms to the periphery. There are advantages to using a fast setting filler material in that, for example, if filler material introduced initially sets while further material is being added, the hydrostatic pressure which the bag has to contain is reduced. The bag may thus be less strong, or less strongly supported, than would be necessary if the whole contents remained unset during the entire filling operation.

The set filler material may be degradable by air and/or the gas against the flow of which the opening is sealed, and in order that the seal has a useful life, the bag wall is sufficiently impervious to eliminate or reduce the rate of degradation.

The filler material may be a foam or may be supplied as a composition which forms a foam, for example an air entrained ce entitious grout.

Preferably, the filler material does not shrink substantially on setting. In the case of a low density cementitious grout, the provision of an impervious bag assists in the prevention of shrinkage which could occur if the set material were able to dry out on hydration.

Even if the filler material is degradable, sufficient protection from the air or gas outside the bag and which causes the degradation may be obtained if the bag walls are stitched together. The bag may in some such circumstances be sufficiently 3 leaky for the inflation gas to escape through the stitched seams when replaced by the filler material. In other circumstances, it may be desirable to provide one or more discrete outlets. There should be sufficient restriction in the outlet, however, to enable the bag to be inflated.

In a preferred example, the bag includes one or more valved outlets, and the method includes allowing the gas to escape through the outlet(s) as it is replaced by the filler material.

One way of ensuring that there is sufficient restriction in the outlet(s) is that the or each outlet includes a pressure relief valve. Significant pressure can then be generated to conform the bag to the periphery of the opening in some detail.

In an alternative, the bag may be inflated to less pressure in which case the or each outlet may include a vent valve.

In either case the filler material may close the outlet valve(s) when the bag is substantially full. In an example in which the filler material is introduced into the bag by pumping, pumping may be continued after the outlet valve(s) close(s) to increase the pressure in the bag.

The filler material is preferably introduced to the bag via one or more inlets located at or near the top of the bag. 4

Examples of the invention, given by way of illustration only, will now be described with reference to the accompanying drawings in which:

Figure 1 is a schematic perspective view of a bag for use in a method of the sealing of a tunnel or a shaft and exemplifying the invention;

Figure 2a is a sectional elevation of the bag of Figure 1 ; Figure 2b is a sectional elevation of an alternative bag;

Figure 3a shows the bag of Figure 1 inflated in a tunnel; and

Figure 3b shows the bag of Figure 3a before inflation.

As illustrated in Figures 1 and 2a, there is provided a bag TO for use in the sealing of a tunnel or shaft. The bag wall 10 is formed from a polypropylene fabric material which is both flexible and substantially impervious to gas.

As illustrated, the bag is in the shape of a rectangular prism approximately 4 to 5 m wide, 2 to 3m high and 1 m thick. However, it must be realised that a bag could have any profile suitable for the shape of the perimeter of the tunnel or shaft opening to be sealed. The bag has a top surface 11, a bottom surface 12 and side surfaces 13. The prism is formed from sheets of the polypropylene fabric which are stitched at their seams 14 such that the bag is relatively airtight.

Inlets 15 in the form of filler tubes or spouts are located on one of the side surfaces 13 of the bag 10. These filler spouts are arranged for connection to a pump nozzle (not shown). Furthermore, the inlets 15 can be sealed off by being tied by tie straps 19.

Located on the top surface 11 of the bag 10 are outlets 1β.

Also located at the top of the bag 10 are support straps 17 which are stitched to the upper end of the sides 13 of the bag 10.

Internal bracing 18a (see Figure 2a) is located with the bag 10. The bracing 18 is in the form of straps of the same material as the bag and interconnects opposite sides 13 of the bag 10, to resist bulging of the sides 13 of the bag 10, when the bag is pressurised. In an alternative shown in Figure 2b, the internal bracing is in the form of bolts 18b (or screw threaded rods) extending right through the bag, and having nuts 18c by which the width of the bag may be adjusted.

The filler spouts 15, valves 16 and straps 17 could be located anywhere on the bag 10 depending on the opening in which it is to be used. Examples of openings which may require to be sealed are tunnels, shafts, holes, doorways and so on.

In use, the bag 10 is positioned in the opening, e.g. tunnel or shaft, at the point at which it is to be sealed and typically the bag would be provided in a collapsed form as shown in Figure 3b.

In the example illustrated the bag is used to seal a tunnel. The bag 10 is hung in the tunnel by straps 17. Air or other gas is then pumped into the bag 10 through inlets 15, to inflate the bag to an expanded form or a partially expanded form. The bag is calculated to be oversized for the dimensions of the tunnel opening tunnel such that when the bag is inflated to an expanded form a part of the surface of the bag contacts the tunnel around its periphery as shown in Figure 3b.

Air is initially introduced into the bag as it facilitates the introduction of the filler material. Once the bag has been inflated, the filler material is then pumped into the bag via the inlets 15.

The filler material in the preferred form comprises an air entrained cementitious grout. The grout may be formed by mixing a dry cementitious composition known as TEKFOAM (trademark of Technik International Ltd) with water to form a high yield grout., and pumping that into the bag in such a way as to entrain air. The grout sets to form a body of a low density non-shrink hydrated foam material which can be compressed under load, eg on rock movement, without significant loss of integrity.

In another embodiment the filler is resin based. Two or more interactive components are pumped to a mixing device and the setting mixture so formed is then pumped into the bag, eg to form a polyurethane foam. The interactive components of the resin composition may be supplied separately into the bag.

The bag has a number of outlets 16 on its top surface. In one example illustrated, the outlets contain vent valves in the form of flaps 16a. As air can escape through the valves little pressure is developed inside the bag which is inflated until it conforms generally with the periphery of the tunnel. The filler material is then pumped into the bag displacing air through the vent valves. Although the bag may conform only generally to the periphery of the tunnel, introduction of the filler material urges the bag to conform in more detail to the periphery of the tunnel even when a rapid setting filler material is used, for example the aforementioned TEKFOAM which sets in 6 to 18 minutes.

In another example, there is no discrete outlet provided in the bag. The bag is, however, made by stitching sheets of material together and the stitching provides sufficient of an outlet for the air displaced from the bag to escape. A significant pressure may be generated by inflating the bag in this example. In a bag not otherwise provided with outlets, if in use a discrete outlet is desirable, one or more punctures may be made in the bag, preferably at or towards the top.

In yet another example, the outlets 16 contain pressure relief valves set to relieve at a predetermined pressure. In this case the bag may be inflated to conform more intimately with the periphery of the tunnel.

The filler material is introduced into the bag 15 under pressure and may cause the pressure within the bag 10 to increase. This causes additional pressure on the surface of the bag to conform to the perimeter of the tunnel opening and the pressure increases until it reaches a predetermined level wherein the pressure release valves 16 open. Opening of the pressure release valves 16 causes the air within the bag to be released while the filler material replaces the air within the bag 10. Sufficient filler material is introduced into the bag 10 until substantially all the air located within the bag 10 has escaped through the pressure release valves 16. Furthermore, once all the air has escaped from the release valves 16, the filler material then contacts the release valves 16 and effectively closes them. As a result, the pressure within the bag 10 can increase beyond the predetermined pressure.

Because the bag is flexible and because the filler material is 9 introduced in a liquid state, the filler material causes the surface of the bag 10 to remain in contact with the perimeter of the tunnel. Furthermore, with the increase in pressure the seal between the surface of the bag 10 and the perimeter of the tunnel improves.

Once the bag is completely filled with the filler material, the inlets 15 are tied off by ties 1 , and the pump is removed.

The filler material is then allowed to solidify. With the use of TEKFOAM the set time ranges from 6 to 18 minutes and the material introduced initially may have set well before the bag is full. Complete filling of the bag may take approximately an hour. The ultimate strengths are achieved within 24 hours.

Because of the nσn-shrink properties of the filler material, the surface of the bag remains in contact with the perimeter of the tunnel or shaft, thereby an effective seal has been obtained.

Figure 3a shows the bag 10 in position in a tunnel opening 20. As can be seen, the bag 10 has conformed to the perimeter of the tunnel 20 even though the tunnel has an irregular surface contour. This has occurred as the bag is larger than cross- section of the tunnel to thereby allow part of the surface of the bag 10 to contact all of the perimeter of the tunnel 20. 10 In another example no internal bracing is used and at the point at which the seal is to be located, two sets of support props, each comprising a timber truss, for example, are secured across the tunnel opening, with each truss having shuttering connected thereto. Typically the shuttering would be of any type commonly used in mining such as wire mesh, plasterboard or brattice cloth or any combination thereof. Once the filler material has solidified the seal incorporating the bag and the solidified filler material is completely self-supporting and the support props can then be removed and reused. In cases where the seal is used to control ventilation in a mine, it would often be possible to remove the props and shutters from both sides. However, in cases where the a part of the workings are sealed off by an explosion proof seal, for example, it will only be possible to recover the support props and shuttering from one side of the seal.

The tunnel has thus been sealed against the flow of gas. In some cases, small amounts of gas may leak past the filled bag, however. If it is important to prevent leakage between the surface of the bag 10 and the perimeter of the tunnel, a liguid sealant can then be applied to the interface between the surface of the bag and the perimeter of the tunnel.

The method of the present invention provides an efficient and simple method of providing a long term seal for a tunnel. Because the filler material is completely encased by the bag 10, it is not directly exposed to the atmosphere. Even in the case where the filler material is degraded by air or the gas against which the opening has been sealed, the bag protects the filler material so it is better able to retain its structural integrity and is less likely to degrade. The seal is able to remain intact on convergence of the tunnel as the filler material will compress and conform to the change of shape of the tunnel.

Claims (17)

1. A method of sealing an opening against the flow of gas therethrough, comprising: placing a bag in the opening, inflating the bag with gas to conform to the periphery of the opening, and introducing a filler material into the bag to displace gas from the bag until the material substantially fills the bag.

2. A method as claimed in claim 1 , wherein the filler material is a settable or setting material.

3. A method as claimed in Claim 1 or 2, wherein the filler material is degradable by air and/or the gas against the flow of which the opening is sealed, and wherein the bag is sufficiently impervious to reduce the rate of degradation.

4. A method as claimed in claim 3, including introducing into the bag a filler material which degrades by drying on exposure to air.

5. A method as claimed in any one of claims 2, 3 or 4, including introducing into the bag a filler material which is a low density cementitious grout.

6. A method as claimed in Claim 2 ,3, 4 or 5 wherein the introduced filler material is a foam or comprises a composition which forms a foam.

7. A method as claimed in Claim 5 or 6 wherein the filler material is an air entrained cementitious grout.

8. A method as claimed in any one of claims 2 to 7, wherein the filler material does not shrink substantially on setting.

9. A method as claimed in any preceding Claim, including introducing a filler material which can be compressed when set.

10. A method as claimed in any preceding Claim, wherein the bag includes one or more valved outlets, and the method includes allowing the gas to escape through the outlet(s) as it is replaced by the filler material.

11. A method as claimed in Claim 10, wherein the or each outlet includes a pressure relief valve.

12. A method as claimed in Claim 10, in which the or each outlet includes a vent valve.

13. A method as claimed in any one of Claims 10, 11 or 12, including introducing the filler material until it closes the outlet valve(s) when the bag is substantially full.

14. A method as claimed in Claim 13, wherein the filler material is introduced into the bag by pumping and wherein pumping is continued after the outlet valve(s) close(s) to increase the pressure in the bag.

15. A method as claimed in any preceding Claim, in which filler material introduced initially to the bag set(s) before the bag is full.

16. A method as claimed in any preceding Claim, wherein the filler material is introduced to the bag via one or more inlets located at or near the top of the bag.

17. A method substantially as herein before described in any one example.