WO2015189537A1

WO2015189537A1 - An inflatable tunnel plug

Info

Publication number: WO2015189537A1
Application number: PCT/GB2015/000164
Authority: WO
Inventors: Duncan Godfrey Mervyn THOMPSON
Original assignee: UK Secretary of State for Defence
Current assignee: UK Secretary of State for Defence
Priority date: 2014-06-10
Filing date: 2015-06-10
Publication date: 2015-12-17
Anticipated expiration: 2016-12-10
Also published as: GB201509896D0; GB2527205A; GB201410255D0

Abstract

There is provided an inflatable tunnel plug (20) comprising a first inflatable portion (24) and a second inflatable portion (26) that is inflatable to support the first inflatable portion (26) against an interior surface (11, 12, 14, 16) of the tunnel. The first inflatable portion (24) inflates to a lower pressure than the second inflatable portion (26). There is also provided a composite tunnel plug (50, 100). The composite tunnel plug comprises a first inflatable tunnel plug for blocking the tunnel and a second inflatable tunnel plug for blocking the tunnel. The top ends (TE) of the first and second inflatable tunnel plugs adjoin one another and the bottom ends (BE) of the first and second inflatable tunnel plugs are spaced apart from one another in a length direction (LD) of the composite tunnel plug when the composite tunnel plug is deployed.

Description

AN INFLATABLE TUNNEL PLUG

Technical Field of the Invention

This invention relates to an inflatable tunnel plug, for example for blocking a tunnel.

Background to the Invention

Inflatable tunnel plugs are known in the art, and may be installed into tunnels in a packed state. If a need arises to block the tunnel, then the tunnel plug can be deployed, for example by inflating the tunnel plug to unpack it. One of the main purposes of tunnel plugs is to disrupt movement of air through the tunnels, for example to prevent smoke or fumes travelling along the full length of the tunnel. Furthermore, the deployment of two tunnel plugs on either side of a fire in the tunnel can starve the fire of oxygen to help put the fire out.

The patent publication US 4,023,372 discloses a tunnel plug for mines, wherein the tunnel plug has an inflatable outer that can be filled with gas to deploy the tunnel plug and block the mine. However, the shape of the inflatable outer needs to match the shape of the mine in order to fully block the mine tunnel.

Even if an inflatable outer of the type described above is shaped to substantially match the tunnel, the inflatable outer still may not create a very good seal against interior surfaces of the tunnel, for example against rail tracks, or against corners. The gas pressure inside the inflatable outer tends to make the inflatable outer arc across corners, rather than filling them fully, leaving gaps where air can bypass the tunnel plug.

An improved seal between the tunnel plug and the internal surfaces of the tunnel is desirable to improve the sealing offered by the tunnel plug and the resulting restriction of airflow. An improved seal may be particularly important if the tunnel plug is intended to block toxic fumes or biological agents from passing along a tunnel to where people or animals are located.

It is therefore an aim of the invention to provide a tunnel plug that provides improved sealing against internal surfaces of a tunnel. Summary of the Invention

A high inflation pressure is desirable to provide structural strength to a tunnel plug and prevent the tunnel plug from bending or flapping about within the tunnel. However, the inventor has noted that high inflation pressures can result in the tunnel plug failing to conform to the internal surfaces of the tunnel, for example bridging across corners instead of fully filling them. A tunnel plug material that is designed to constrain higher inflation pressures is also typically thicker and less able to confirm to the internal surfaces of the tunnel.

Therefore, according to a first aspect of the invention, there is provided an inflatable tunnel plug for blocking a tunnel, the tunnel plug comprising at least a first inflatable portion and a second inflatable portion that is inflatable to support the first inflatable portion against an interior surface of the tunnel. The first inflatable portion is configured to inflate to a lower pressure than the second inflatable portion upon deployment of the tunnel plug.

Since the first inflatable portion is configured to inflate to a lower pressure than the second inflatable portion, the first inflatable portion is able to closely conform to the shape of the interior surface of the tunnel. The higher inflation pressure of the second inflatable portion provides the tunnel plug with sufficient structural strength once it has been deployed to prevent the tunnel plug from bending or deforming.

The first inflatable portion may comprise a first chamber into which fluid can be passed to inflate the first inflatable portion, and the second inflatable portion may comprise a second chamber into which fluid can be passed to inflate the second inflatable portion. The second inflatable portion may be inside of the first chamber of the first inflatable portion, or the second inflatable portion may be immediately adjacent the first inflatable portion.

Each inflatable portion may each be formed from one or more flexible layers of material defining a closed interior that constitutes the chamber of the inflatable portion. The chamber may be filled with fluid to inflate the inflatable portion from a packed configuration to an unpacked configuration. The flexible layer(s) of material forming the first inflatable portion may be thinner and/or more malleable than the flexible layer(s) of material forming the second inflatable portion, to help the first inflatable portion conform to the interior surfaces of the tunnel, and since the flexible layers of material forming the first inflatable portion do not have to constrain as much fluid pressure as the flexible layers of material forming the second inflatable portion.

Advantageously, the tunnel plug may further comprise an inflation device for filling the first and second inflatable portions with fluid to inflate the first and second inflatable portions upon deployment of the tunnel plug. The fluid is normally gaseous, although the use of liquids would also be possible. The inflation device may comprise a gas/smoke sensor for automatically triggering the inflation device, and/or the inflation device may be remotely triggered by an operator via radio communications or wiring, in order to deploy (unpack) the tunnel plug. The inflation device may comprise an explosive for producing fluid, a store of compressed fluid, or a pump for pumping fluid, such as a fan.

The inflation device may comprise a first fluid output connected to the first inflatable portion for filling the first inflatable portion to a first pressure, and a second fluid output connected to the second inflatable portion for filling the second inflatable portion to a second pressure higher than the first pressure. Alternatively, the inflation device may be configured to fill the first inflatable portion with fluid via the second inflatable portion.

To help set the pressure difference between the first and second inflatable portions, the tunnel plug may comprise a pressure relief valve that is configured to pass fluid from the second inflatable portion into the first inflatable portion when a fluid pressure within the second inflatable portion is a threshold pressure higher than a fluid pressure within the first inflatable portion. Accordingly, the difference in pressure between the first and second inflatable portions may be set by the threshold pressure of the pressure relief valve.

Advantageously, the first inflatable portion may be fitted with an exhaust pressure relief valve, the exhaust pressure relief valve configured to exhaust fluid to atmosphere when a fluid pressure in the first inflatable portion is an exhaust threshold pressure above atmospheric pressure. Then, an excess quantity of fluid supplied by the inflation device will not raise the pressures of the first and second inflatable segments above the desired levels, since the excess fluid can escape to atmosphere via the exhaust pressure relief valve, and so the quantity of fluid supplied by the inflation device does not need to be accurately specified provided the quantity is greater than a minimum amount for full inflation to occur. The further pressure relief maintains a relatively low pressure inside the first inflatable portion, so that the shape of the first inflatable portion readily adapts to seal against the tunnel wall.

Preferably, the tunnel plug is larger than the tunnel which it is intended to fill, for example 5% larger, so that there is ample material of the first inflatable portion to enter into corners and depressions within the interior surface of the tunnel. The tunnel plug may comprise a centre and an outer periphery extending around the centre, and the outer periphery may be formed by the first inflatable portion so that it is presented to the interior surface of the tunnel. The outer periphery extends at least half the way around the centre, and may extend all of the way around the centre. The second inflatable portion may extend around the centre between the centre and the outer periphery, so that the second inflatable portion helps force the first inflatable portion forming the outer periphery against the interior surface of the tunnel.

The tunnel plug may comprise a centre portion at its centre, wherein the centre portion is non-inflatable. For example, the centre portion may be a single layer of material, such as a wall or web. The centre portion could comprise more than one layer of material, for example to improve the strength of the centre portion. Preferably, the centre portion fully extends over an area enclosed by the first or the second inflatable portions, so that the centre portion together with the first and second inflatable portions fully blocks the tunnel when the tunnel plug is deployed.

Advantageously, the centre portion may comprise a door which is openable to allow a person to pass through the centre portion. Then, the deployment of the tunnel plug will not risk trapping people since they can use the door to move through the tunnel plug.

The tunnel plug may further comprise a third inflatable portion and a fourth inflatable portion that is inflatable to support the third inflatable portion against an interior surface of the tunnel, wherein the third inflatable portion is configured to inflate to a lower pressure than the fourth inflatable portion upon deployment of the tunnel plug, and wherein the first and third inflatable portions are spaced apart from one another at a base of the tunnel plug and next to one another at a top of the tunnel plug when the tunnel plug is deployed. The tunnel plug may therefore take an A shape when deployed, to provide greater stability to the tunnel plug. The third and fourth inflatable portions provide an additional impediment to fluid flow along the tunnel, increasing the effectiveness of the tunnel plug.

The first chamber of the first inflatable portion may extend into the third inflatable portion to enable inflation of the third inflatable portion. For example, the first and third inflatable portions may be integrally formed as a single inflatable portion having the first chamber. Alternatively, the first and third inflatable portions may be separate from one another such that the third inflatable portion has its own third chamber.

According to a second aspect of the invention, there is provided a composite tunnel plug for blocking a tunnel. The composite tunnel plug comprises a first inflatable tunnel plug for blocking the tunnel and a second inflatable tunnel plug for blocking the tunnel, wherein the first and second inflatable tunnel plugs each have a top end and a bottom end opposite the top end, wherein the top ends of the first and second inflatable tunnel plugs adjoin one another and the bottom ends of the first and second inflatable tunnel plugs are spaced apart from one another in a length direction of the composite tunnel plug when the composite tunnel plug is deployed, the composite tunnel plug configured to deploy with the length direction of the composite tunnel plug aligned with a length of the tunnel.

Since the composite tunnel plug. comprises two inflatable tunnel plugs, for example two of the inflatable tunnel plugs as hereinbefore described, there is a double barrier to any fluids or gases flowing along the tunnel. For example, if each one of the first and second inflatable tunnel plugs reduce airflow through the tunnel to 10%, then the combined effect of the first and second inflatable tunnel plugs is to reduce airflow through the tunnel to 1 %. The composite tunnel plug may take an A shape when deployed, to provide greater stability to the composite tunnel plug, each inflatable tunnel plug forming one side of the "A".

Brief Description of the Drawings

Embodiments of the invention will now be described by way of example only and with reference to the accompanying drawings, in which:

Fig. 1 shows a schematic diagram of a tunnel incorporating a tunnel plug in a packed configuration, the tunnel plug according to a first embodiment of the invention; Fig. 2a shows a schematic diagram of the tunnel of Fig. 1 with the tunnel plug in an unpacked configuration following its deployment within the tunnel;

Fig. 2b shows a cross-sectional diagram of the tunnel plug of Fig. 2a, the cross- section taken along line AA marked on Fig. 2a;

Fig. 3a shows a schematic diagram of the tunnel of Fig. 1, with a tunnel plug according to a second embodiment of the invention in an unpacked configuration following its deployment within the tunnel;

Fig. 3b shows a cross-sectional diagram of the tunnel plug of Fig. 3a, the cross- section taken along line BB marked on Fig. 3a;

Fig. 4 shows a schematic perspective diagram of a tunnel plug according to a third embodiment of the invention in an unpacked configuration, the tunnel plug being suitable for use in the tunnel of Fig. 1 ; and

Fig. 5 shows a schematic perspective diagram of a tunnel plug according to a fourth embodiment of the invention in an unpacked configuration, the tunnel plug being suitable for use in the tunnel of Fig. 1.

The drawings are purely illustrative and are not to scale. Same or similar reference signs denote same or similar features.

Detailed Description

A first embodiment of the invention will now be described with reference to the schematic diagrams of Fig. 1 to Fig. 2b, which show schematic diagrams of a tunnel 10 incorporating a tunnel plug 20. The schematic diagram of Fig.l shows a view of the tunnel 10 taken in a direction along the length of the tunnel 10.

As shown in Fig. 1, the tunnel 10 comprises railway lines 12 at a base of the tunnel for guiding railway cars, a lighting strip 14 mounted at the left side of the tunnel for lighting the tunnel, a cable trunking 16 mounted at the left side of the tunnel beneath the lighting strip 14, and the tunnel plug 20 mounted at the right side of the tunnel. The cable trunking 16 supports cables carrying power and/or signals relevant to the railway, for example power and/or signals for railway signalling equipment. The railway lines 12, lighting strip 14, and cable trunking 16 extend substantially along the full length of the tunnel, and the tunnel plug 20 extends only a short distance along the length of the tunnel, for example 2 metres. In this embodiment, further tunnel plugs the same as the tunnel plug 20 are mounted at 100 metre intervals along the length of the tunnel.

The tunnel plug 20 is shown in a packed configuration in Fig. 1, and only takes up a small portion of the tunnel 10, so as not to impede railways cars travelling through the tunnel along the railway lines 12. The tunnel plug 20 comprises an inflation device 21, which in this embodiment is a container 21 of compressed air. A valve of the container 21 may be opened to release the compressed air from the container 21 when the tunnel plug 20 is to be deployed. Electrical wiring (not shown in Figs) is connected between the container 21 and a control centre (also not shown in Figs) external to the tunnel to control the opening of the valve of the container 21. Optionally, the inflation device 21 may also comprise a gas or smoke sensor configured to automatically open the valve of the container 21 when gas or smoke is detected.

The schematic diagram of Fig. 2a shows the tunnel plug 20 once it has been deployed within the tunnel 10. In order to deploy the tunnel plug 20 into the unpacked configuration shown in Fig. 2a, the control centre signals the valve of the container 21 to open via the electrical wiring, and the compressed air within the container 21 exits the container 21 to inflate the tunnel plug 20 and unpack it.

The tunnel plug 20 comprises a centre portion 22, a first inflatable portion 24, and a second inflatable portion 26. The first inflatable portion 24 is a first continuous tube running fully around the perimeter of the centre portion 22. Also referring to the cross-sectional diagram of Fig. 2b, which is taken along line AA marked in Fig. 2a, the second inflatable portion 26 is a second continuous tube that runs inside of the first continuous tube 24, substantially concentric with the first continuous tube 24. The tubes are referred to as continuous since they each form a closed circuit.

The first continuous tube 24 forms a first chamber 25 inside of the first continuous tube 24, and the second continuous tube 26 forms a second chamber 27 inside of the second continuous tube 26. A pressure relief valve 28 is positioned in the wall forming the second continuous tube 26, and so the pressure relief valve 28 leads from the second chamber 27 of the second continuous tube 26 into the first chamber 25 of the first continuous tube 24. The pressure relief valve is configured to pass fluid (air) from the second chamber 27 to the first chamber 25 when there is greater than a threshold pressure differential from the second chamber to the first chamber. In this embodiment the threshold pressure differential of the pressure relief valve is set at 50KPa, although other values are also possible.

An exhaust pressure relief valve 28a is positioned in the wall forming the first continuous tube 24, and exhausts air from the first chamber 25 to atmosphere if the pressure in the chamber 25 rises to an exhaust threshold pressure above atmospheric pressure. In this embodiment, the exhaust threshold pressure is set at 50KPa, although other values are also possible.

The first continuous tube 24 and the second continuous tube 26 are formed of a plasticised fabric material, the plasticised fabric material forming the second continuous tube 26 being a heavier duty material than the plasticised fabric material forming the first continuous tube 24 in view of the higher pressure that the second continuous tube 26 must constrain, and in view of the need for the first continuous tube 24 to easily conform to the inside surfaces of the tunnel 10. Clearly, the plasticised fabric materials could be replaced by other types of flexible air-tight materials in alternate embodiments of the invention, for example glass fibre fabric coated with silicone rubber.

The centre portion 22 is formed of a web of plasticised fabric material that is connected to the first continuous tube 24 and fully extends over the region enclosed by the first continuous tube 24. The centre portion 22 comprises a door 30 that is defined by a zip 32, the zip 32 allowing part of the centre portion to be unzipped from the remainder of the centre portion so that a person can move through the door 30 if required.

The container 21 is inside of the second continuous tube 26. Accordingly, when compressed air is emitted from the container 21 upon deployment of the tunnel plug 20, the second continuous tube 26 is inflated to help block the tunnel 10 with the tunnel plug. Once the second continuous tube 26 is fully inflated and/or begins to be constrained by the interior surfaces of the tunnel 10, such as between the lighting strip 14 and the right side 11 of the tunnel, the pressure within the second continuous tube 26 continues to rise until the pressure relief valve 28 begins to allow air to flow from the second continuous tube 26 into the first chamber 25 of the first continuous tube 24. This air inflates the first continuous tube 24 to press the first continuous tube 24 into the regions of the tunnel where the second continuous tube 26 was unable to reach, such as in the corners of the tunnel, between the railway lines 12, and between the lighting strip 14 and the cable trunking 16, as shown in Fig. 2a.

The first continuous tube 24 is formed larger than the size of the tunnel 10 so that there is ample material of the continuous tube 24 to conform to the shapes of the railway lines 12 and the lighting strip 14 and cable trunking 16. The container 21 holds sufficient compressed air to inflate the second continuous tube 26 to a pressure of lOOKPa above atmospheric pressure, meaning that the first continuous tube 24 is inflated to a pressure of 50KPa above atmospheric pressure given the 50KPa threshold pressure differential of the pressure relief valve 28, and the 50KPa exhaust threshold pressure of the exhaust pressure relief valve 28a. Clearly, other values of pressures may alternatively be used by setting the amount of compressed air in the container 21 and the threshold pressure differential of the pressure relief valve 28. One or more pressure relief valves 28 may be provided between the second continuous tube 26 and the first chamber 25 of the first continuous tube 24.

A second embodiment of the invention will now be described with reference to Figs. 3a and 3b. The second embodiment is the same as the first embodiment, except for that the second inflatable portion is arranged adjacent to the first inflatable portion, instead of inside the first inflatable portion, and for that a different inflation device is used. The schematic diagram of Fig. 3a shows a tunnel plug 40 in an unpacked configuration after deployment within the tunnel 10 of Fig. 1.

As best seen in the cross-sectional diagram of Fig. 3b, which is taken along line BB marked on Fig. 3a, the tunnel plug 40 comprises a central portion 42 similar to the central portion 22, a first inflatable portion 44 formed as a first continuous tube, and a second inflatable portion 46 formed as a second continuous tube. The first continuous tube 44 is spaced apart from the central portion 42 by the second continuous tube 46. A pressure relief valve 48 similar to the valve 28 is connected at an interface between the first and second continuous tubes 44 and 46, and allows air to flow from a second chamber 47 of the second continuous tube 46 into a first chamber 45 of the first continuous tube 44. An exhaust pressure relief valve 48a similar to the valve 28a is positioned through a wall forming the first continuous tube 44, and so allows excess pressure within first chamber 45 to exhaust to atmosphere. The tunnel plug 40 comprises an inflation device, which in this embodiment includes a propellant 41 of sodium azide. The propellant 41 is within the second continuous tube 46, and is ignited via electrical wiring (not shown in Figs) to deploy the tunnel plug 41 within the tunnel 10. The ignition of the sodium azide rapidly produce gas which inflates the second continuous tube 46, and subsequently the first continuous tube 44 via the pressure relief valve 48, in a similar manner as described in relation to the first embodiment. In alternative embodiments the propellant 41 may be formed of gas-producing materials other than sodium azide, for example nitroguanidine. The inflation device also comprises a gas and smoke sensor 49, which is mounted on an outside surface of the second continuous tube 46. The gas and smoke sensor 49 is configured to automatically ignite the propellant 41 to inflate the tunnel plug 40 in the event that gas or smoke is detected.

Once the tunnel plug 40 has been deployed, the second continuous tube 46 supports the first continuous tube 44 to conform to the interior surfaces of the tunnel 10, in a similar manner as described in relation to the first embodiment.

A third embodiment of the invention will now be described with reference to Fig. 4, which shows a schematic perspective diagram of a tunnel plug 50 in an unpacked

configuration. The tunnel plug 50 is the same as the tunnel plug 20 of the first embodiment, except for that the two of the tunnel plugs 20 are connected in an A shape to provide better stability to the tunnel plug, and for that a different inflation device is used. An additional benefit of the A frame design is in doubling the contact area of plug in contact with the tunnel wall, thus providing a more efficient seal against the transport of particles and vapour.

The tunnel plug 50 comprises a first centre portion 62, a first inflatable portion 64, and a second inflatable portion 66. The first inflatable portion 64 is a first continuous tube running fully around the perimeter of the first centre portion 62. The second inflatable portion 66 is a second continuous tube that runs around the inside of the first continuous tube 64, substantially concentric with the first continuous tube 64.

The tunnel plug 50 further comprises a second centre portion 72, a third inflatable portion 74, and a fourth inflatable portion 76. The third inflatable portion 64 is a third continuous tube running fully around the perimeter of the second centre portion 72. The fourth inflatable portion 76 is a fourth continuous tube that runs around the inside of the third continuous tube 74, substantially concentric with the third continuous tube 74.

The first continuous tube 64 and the third continuous tube 74 are joined together at a top of the tunnel plug 50, and are spaced apart from one another by a strut 80 at a base of the tunnel plug 50, effectively forming an A shape. The base of the tunnel plug 50 is intended to sit upon the base of the tunnel 10, and the top of the tunnel plug is intended to press against the top of the tunnel 10. The tunnel plug 50 typically provides a better seal than the tunnel plug 20, since there are effectively two of the tunnel plugs 20 in series with one another.

The tunnel plug 50 comprises an inflation device 83, which in this embodiment is an air pump. The air pump 83 comprises an aerial 85 for receiving radio signals to control the air pump. The air pump 83 has a first fluid outlet pipe 81 that is connected to the first continuous tube 64, and a second fluid outlet pipe 811 that is connected to the second continuous tube 66. A first pipe 88 connects the first continuous tube 64 to the third continuous tube 74, and a second pipe 881 connects the second continuous tube 66 to the fourth continuous tube 76.

The tunnel plug 50 is normally in a packed configuration, similar to the packed tunnel plug 20 shown in Fig. 1. When the aerial 85 receives a radio signal commanding the deployment of the tunnel plug 50, the air pump 83 pumps air at a first pressure along the first fluid outlet pipe 81, into the first continuous tube 64. The air travels from the first continuous tube 64 into the third continuous tube 74 via the first pipe 88, and so the first and third continuous tubes are both inflated up to the first pressure. The air pump 83 also pumps air at a second pressure along the second fluid outlet pipe 811, into the second continuous tube 66. The air travels from the second continuous tube 66 into the fourth continuous tube 76 via the second pipe 881, and so the second and fourth continuous tubes are both inflated up to the second pressure.

The first pressure is lower than the second pressure, and so the first and third continuous tubes are inflated to a lower pressure than the second and fourth continuous tubes, so that the first and third continuous tubes can easily conform to the interior surfaces of the tunnel 10, and so that the second and fourth continuous tubes can provide a good level of support to the first and third continuous tubes. For example, the first pressure may be 30KPa above atmospheric pressure and the second pressure may be 50KPa above atmospheric pressure.

A fourth embodiment of the invention will now be described with reference to Fig. 5, which shows a schematic perspective diagram of a tunnel plug 100 in an unpacked configuration. The tunnel plug 100 is the same as the tunnel plug 50 of the third embodiment, except for that the first and third inflatable portions 84 and 94 are formed by a first common inflatable portion, the second and fourth inflatable portions 86 and 96 are formed by a second common inflatable portion, and a different inflation device is used.

The second common inflatable portion 86, 96 is inside of the first common inflatable portion 84, 94. A chamber of the first inflatable portion 84 extends into the third inflatable portion 94 to form the first common inflatable portion, and a chamber of the second inflatable portion 94 extends into the fourth inflatable portion 96 to form the second common inflatable portion. Accordingly, the first and third inflatable portions do not need to be inflated individually, but can be inflated as a whole, and the second and fourth inflatable portions do not need to be inflated individually, but can be inflated as a whole.

The area enclosed by the first inflatable portion 84 is spanned by a first centre portion 82, and the area enclosed by the third inflatable portion 86 is spanned by a second centre portion 92. The first inflatable portion 84 and the third inflatable portion 94 are joined together at a top of the tunnel plug 100, and are spaced apart from one another by a strut 90 at a base of the tunnel plug 100, effectively forming an A shape. The base of the tunnel plug 100 is intended to sit upon the base of the tunnel 10, and the top of the tunnel plug is intended to press against the top of the tunnel 10.

The inflation device for inflating the tunnel plug from a packed configuration into the unpacked configuration shown in Fig. 5 comprises two propellants 91 and 93 of sodium azide. The propellant 91 is within the first common inflatable portion 84, 94, and the propellant 93 is within the second common inflatable portion 86, 96. The propellants 91, 93 are ignited via electrical wiring (not shown in Figs) to produce gas that inflates and thereby unpacks the tunnel plug 100 within the tunnel 10. The propellants 91 and 93 are sized to inflate the second common inflatable portion 86, 96 to a higher pressure than the first common inflatable portion 84, 94, so that the second common inflatable portion supports the first common inflatable portion to conform to the interior surfaces of the tunnel 10, in a similar manner as described in relation to the third embodiment.

The tunnel plugs 50 and 100 of the third and fourth embodiments are composite tunnel plugs because they each effectively comprise two inflatable tunnel plugs, one inflatable tunnel plug formed by the first and second inflatable portions and another tunnel plug formed by the third and fourth inflatable portions. The first arid second inflatable tunnel plugs each have a top end TE and a bottom end BE opposite the top end, wherein the top ends TE of the first and second inflatable tunnel plugs adjoin one another and the bottom ends BE of the first and second inflatable tunnel plugs are spaced apart from one another in a length direction LD of the composite tunnel plug when the composite tunnel plug is deployed, the composite tunnel plug configured to deploy with the length direction LD of the composite tunnel plug aligned with a length of the tunnel.

The use of the word tube in the context of the continuous tubes described herein does not imply that the continuous tubes must have a circular cross section. Various other embodiments falling within the scope of the appended claims will also be apparent to the skilled person. For example, the continuous tubes described in the embodiments may be replaced by discrete sections of tubing, and/or one or more of the tubes may not fully extend all of the way around the centre portions.

Claims

1. Ail inflatable tunnel plug for blocking a tunnel, the tunnel plug comprising at least a first inflatable portion and a second inflatable portion that is inflatable to support the first inflatable portion against an interior surface of the tunnel, wherein the first inflatable portion is configured to inflate to a lower pressure than the second inflatable portion upon

deployment of the tunnel plug.

2 The inflatable tunnel plug of claim 1, wherein the tunnel plug further comprises an inflation device for filling the first and second inflatable portions with fluid to inflate the first and second inflatable portions upon the deployment of the tunnel plug.

3. The inflatable tunnel plug of claim 2, wherein the inflation device comprises an explosive for producing fluid, a store of compressed fluid, or a pump for pumping fluid.

4. The inflatable tunnel plug of claim 1, 2,. or 3, wherein the tunnel plug further comprises a pressure relief valve that is configured to pass fluid from the second inflatable portion into the first inflatable portion when a fluid pressure within the second inflatable portion is a threshold pressure higher than a fluid pressure within the first inflatable portion.

5. The inflatable tunnel plug of any preceding claim, wherein the tunnel plug further comprises an exhaust pressure relief valve that is configured to exhaust fluid from the first inflatable portion to atmosphere when a fluid pressure in the first inflatable portion is an exhaust threshold pressure above atmospheric pressure.

6. The inflatable tunnel plug of any preceding claim, wherein the first inflatable portion comprises a first chamber into which fluid can be passed to inflate the first inflatable portion, and wherein the second inflatable portion comprises a second chamber into which fluid can be passed to inflate the second inflatable portion.

7. The inflatable tunnel plug of claim 6, wherein the second inflatable portion is inside of the first chamber of the first inflatable portion.

8. The inflatable tunnel plug of claim 6, wherein the second inflatable portion is immediately adjacent the first inflatable portion.

9. The inflatable tunnel plug of any preceding claim, wherein the tunnel plug comprises a centre and an outer periphery extending around the centre, and wherein the outer periphery is formed by the first inflatable portion.

10. The inflatable tunnel plug of claim 9, wherein the second inflatable portion extends around the centre between the centre and the outer periphery.

11. The inflatable tunnel plug of claim 9 or 10, further comprising a centre portion at the centre, wherein the centre portion is non-inflatable.

12. The inflatable tunnel plug of claim 11, wherein the centre portion fully extends over an area enclosed by the first or the second inflatable portions.

13. The inflatable tunnel plug of claim 11 or 12, wherein the centre portion comprises a door which is openable to allow a person to pass through the centre portion.

14. The inflatable tunnel plug of any preceding claim, wherein the second inflatable portion is configured to provide structural strength to the tunnel plug when the tunnel plug is deployed and wherein the first inflatable portion is configured to deform against interior surfaces of the tunnel to seal the tunnel when the tunnel plug is deployed.

15. The inflatable tunnel plug of any preceding claim, wherein the tunnel plug further comprises a third inflatable portion and a fourth inflatable portion that is inflatable to support the third inflatable portion against an interior surface of the tunnel, wherein the third inflatable portion is configured to inflate to a lower pressure than the fourth inflatable portion upon the deployment of the tunnel plug, and wherein the first and third inflatable portions are spaced apart from one another in a length direction of the tunnel plug at a base of the tunnel plug and next to one another at a top of the tunnel plug when the tunnel plug is deployed.

16. The inflatable tunnel plug of claim 15 when appended to claim 6, wherein the first chamber of the first inflatable portion extends into the third inflatable portion to enable inflation of the third inflatable portion.

17. A composite tunnel plug for blocking a tunnel, wherein the composite tunnel plug comprises a first inflatable tunnel plug for blocking the tunnel and a second inflatable tunnel plug for blocking the tunnel, wherein the first and second inflatable tunnel plugs each have a top end and a bottom end opposite the,top end, wherein the top ends of the first and second inflatable tunnel plugs adjoin one another and the bottom ends of the first and second inflatable tunnel plugs are spaced apart from one another in a length direction of the composite tunnel plug when the composite tunnel plug is deployed, the composite tunnel plug configured to deploy with the length direction of the composite tunnel plug aligned with a length of the tunnel.

18. The composite tunnel plug of claim 17, wherein each one of the first and second inflatable tunnel plugs are according to the inflatable tunnel plug of any one of claims 1 to 13.

19. A tunnel plug substantially as described herein with reference to the accompanying drawings.