GB2094712A

GB2094712A - Collapsible structure and method of building using such a structure

Info

Publication number: GB2094712A
Application number: GB8204496A
Authority: GB
Original assignee: Magnex Ltd
Current assignee: Magnex Ltd
Priority date: 1981-02-16
Filing date: 1982-02-16
Publication date: 1982-09-22
Also published as: GB2094712B; DE3205349A1; FR2500028A1; AU8051682A

Abstract

A collapsible structure which is rigid when dry and is collapsible under the action of a liquid comprises a separating structure (3) whose rigidity is attacked by the liquid, for example water, sandwiched between two sheets of material (1, 2) at least part of the collapsible structure being treated or formed of such a material as to enable the ingress of moisture to be retarded. <IMAGE>

Description

SPECIFICATION Collapsible structure and method of building using such a structure This invention relates to a collapsible structure which is suitable for use in building construction and to a method of building using such a structure.

With present day building methods and in particular with constructions such as the laying of concrete floors at substantially ground level and the provision of concrete structures below ground, problems related to moisture occur. This is particularly the case where the building takes place in areas having soil which is predominantly subject to expansion or other spacing between the structure and the surrounding soil.

Difficulties occur particularly where concrete is to be laid in or on soils which are predominantly of a clay nature. In this case, the problem which arises depends on the fact that clay will swell when moisture is introduced and will shrink when moisture is removed. With clay situated under a house or other building, the difference in level between dry clay and wet clay may be as much as 30 mm.

Variations in the conditions of the soil can have a very serious effect on any structure which is laid directly thereon or therein and when the structure is providing a support for walls or other structural elements, variations in the soil can cause severe damage to the building of which the structural element is a part. In fact, this damage can be so severe that the building has to be demolished as being uneconomical to repair.

Other considerations which require there to be a void beneath or around the concrete structure are present where it is necessary to enable the soil beneath the structure to breathe.

In order to overcome this problem, it has been proposed to provide, for example, precast floor elements which can be mounted in a position which leave a void between the underside of the floor elements and the ground. This process is of a very costly nature because, in most instances, it necessitates the transport of large concrete elements and the provision at the site of a relatively large crane in order to unload the concrete elements and to place them in their appropriate position. Furthermore, this only solves the problem with regard to horizontal elements and is of no assistance when dealing with vertical or inclined structures.

It has been proposed to use collapsible structures which can be used as a spacer when laying floors.

Nevertheless, this structure requires, in many cases, expensive materials and difficulties in use may appear.

Furthermore, significant difficulties arise in conditions where the ground is of a somewhat marshy consistency and where it is required to mount the concrete structure in a hole or trench in the ground which rapidly fills up with water. In these circumstances, any collapsible structure which is significantly affected by water may not last long enough to allow the concrete, which it is surrounding, to set.

The present invention seeks to provide a collapsible structure which is generally rigid initially but which can be caused to collapse under relatively controlled conditions and to provide a method of building using such a collapsible structure.

According to a first aspect of the invention, there is provided a collapsible structure which is rigid when dry and is collapsible under the action of a liquid, comprising a separating structure, whose rigidity is attacked by the liquid, sandwiched between two sheets of material, at least part of the collapsible structure being treated or formed of such a material as to enable the ingress of the liquid to be retarded.

Preferably the liquid is water but it may be another liquid such as a detergent.

In one embodiment of the invention, at least one of the said two sheets of material is such as to allow passage of moisture therethrough and a membrane is provided covering at least one side of this sheet of material, the membrane being of a material such that it will prevent water, at least partially, from attacking the separating structure.

In a second embodiment, the separating structure is treated so as to retard the action of water therein.

According to a second aspect of the invention, a method of building comprises laying a collapsible material as described above in or on the ground as a base or shuttering, pouring concrete thereonto or thereinto and allowing the concrete to set and allowing or providing for ingress of liquid into the collapsible structure to permit or encourage the structure to collapse after a suitable time lapse.

The invention will now be described in greater detail, by way of example, with reference to the drawings in which: Figure 1 is a perspective view, partly broken away of part of a collapsible structure in accordance with the invention; Figure 2 is a sectional view of a collapsible structure in accordance with the invention in which the separating structure is coated with a water soluble plastics material; Figure 3 is a sectional view, similar to Figure 2, in which a collapsible structure is shown in which the separating structure is wrapped in a water soluble plastics material; Figure 4 is a sectional view similar to Figure 2, in which the collapsible structure of Figure 2 is additionally provided with a coating of water soluble plastics material on the inside of the sandwiching sheets;; Figure 5 is a sectional view of a collapsible structure in accordance with the invention which has an exterior coating of a water soluble plastics material; Figure 6 is a view similarto Figure 5 but showing a wrapping of the collapsible structure in a suitable plastics sheet, and Figure 7 is a view similar to Figures 5 and 6 showing the collapsible structure provided with a minimum external coating of water soluble plastics material.

Referring firstly to Figure la a collapsible structure comprises two sheets 1 and 2 of a water permeable material such as chipboard, composition board, or the like separated by a separator 3 in the form of a honeycomb of paper or cardboard, particularly regenerated cardboard. This honeycomb separator is impregnated with a water soluble plastics material such as water soluble polymers and in particular polyvinyl alcohol of the cold water soluble type or the material sold under the trade name "CELLULIS TIC". The sheets of chipboard or composition board 1 and 2 may suitably be glued to the separator 3 and this glue may, if desired, be water soluble. Where the material of the sheets are not porous, i.e. when using hardboard, at least one sheet may be perforated to permit the passage of moisture.

Figure 2 shows an alternative form of collapsible structure in which the honeycomb 3 is not impregnated but is coated with the water soluble plastics material, e.g. by dipping the honeycomb 3 in the liquid material prior to assembly between the sheets 1 and 2 of, in this embodiment, hardboard. The coating is indicated here at 5. In the embodiment shown, the sheet 2 is provided with perforations 6 to permit ingress of moisture.

It will be appreciated that the sheet 2 does not require perforations 6 if it is otherwise porous and will allow the penetration of moisture.

Figure 3 shows a third form of collapsible structure in which the honeycomb is located inside a wrapping 8 of water soluble plastic sheet. In this case, the honeycomb may be glued to the wrapping 8 as it is formed and the wrapping 8 is then glued to the outer sheets 1 and 2.

Figure 4 shows a further form of collapsible structure in which, in addition to the coating of the honeycomb 3, the inside surfaces of the sheets 1 and 2 are also coated with the water soluble plastics material, indicated at 10.

Figure 5 shows a fifth form of collapsible structure.

Surrounding the structure on all sides is a thin film 11 of water soluble plastics material and, as can be particularly seen, the film covering the lower sheet 2 of the structure closes the apertures 6 therein.

Having assembled the actual structure itself, the plastics material 11 can be applied thereto by dipping or spraying or where the water soluble plastics is available in sheet form, this could in fact be wrapped around the structure.

In Figure 6 there is shown a different solution to the problem in which a non liquid-destructable plastics material 12 e.g. polythene sheeting is wrapped around the structure, the board being constructed in a similar way to that shown in Figure 5.

Such a sheeting may be that sold under the trade name "VISOUEEN". The covering sheet 12 is arranged to be severable, for example, at the edge of the board once the board has been laid so that the access of moisture can be achieved. Since it is intended that this severing operation should take place after the formation of the concrete structure it is intended to protect, the fact that the area in which the structure lies is absolutely saturated with water is of no account since the water will not enter the structure until the severance has taken place.

Figure 7 shows that where a collapsible structure of the same construction as in Figures 5 and 6, is to be used in a situation where there is no such saturation, a water soluble plastics layer 13 need only be applied to the underneath of the structure, i.e. to the sheet 2 through which it is intended that the water will penetrate. Possibly, the sides of the structure are also covered (indicated at 13') where these are accessible to the moisture. Thus a saving in the plastics material used is achieved.

When using the water soluble plastics, the thickness and the nature of the layer (Figures 2,3,4,5 and 7) or the amount and nature of the penetration (Figure 1) is determined by the length of time which is to pass before the layer disintegrates. In this way, by variation of the thickness of the layer or the amount of the penetration, structures can be provided with different lives.

In use in building construction, once the area in which the building structure is to be used is prepared, the collapsible structures are laid with their water permeable surface facing outwards i.e. towards the soil. The desired construction can then be produced by either laying the concrete on top of the board, when a horizontal structure is being produced or the boards may be used vertically in, for example, trenches, as shuttering. (Of course any other orientation of the structures is possible.) With suitable dimensioning of the materials used in producing the structures, the rigidity of the structures will remain during the period when it is necessary to set the concrete, i.e. a period normally in excess of 16 hours, the eventual admission of moisture to the board being caused either by the breakdown of the soluble plastics material or by the severing of the plastics wrapping where a non-soluble plastics is used.

Where the structure is used to provide a void, for example, in places where a void is necessary without there being significant moisture, once the use of the board has been completed, it may be saturated with water from a separate source and on collapse, a void will be left. This void, if desired, can be augmented by removal of the exterior sheets together with any remains of the disintegrated separator. On the other hand, with the suitable coatings or impregnations as previously described, the exterior sheets can also be of a material which will disintegrate, the only requirement being that the structure in its rigid condition is sufficiently strong forthe load which it is required to carry during the construction process.

It will be appreciated that various modifications may be made to the above described embodiments without departing from the scope of the invention.

For example, the outer sheets in any of the embodiments may be either permeable as shown in Figures 1,3 and 4, or impermeable with perforations as shown in Figures 2 and 5 to 7. Mixed structures are possible with one sheet being impermeable and the other permeable. The honeycomb structure shown may be replaced by other separating means providing that this is suitably degradable, for example, longitudinal webs could be used instead of a honeycomb structure. As stated, the water permeable exterior sheet may be a porous material such as chipboard, but with the use of a chipboard or other permeable sheet on the side adjacent to the concrete, it is necessary to coat this sheet so that the water in the concrete which is being set cannot penetrate the board prior to setting.

If desired, the water soluble material may be replaced by materials soluble in other liquids so that absolute control of the collapsibility of the structure may be achieved. Such liquids may include liquid detergents.

There are some circumstances in which the collapsible structure may be required to remain in or on the ground for very long periods, e.g. for a number of weeks, to allow the construction of specialised steel work or piping prior to the pouring of concrete.

In these circumstances adequate control may be achieved by using materials soluble in different liquids, the structure being collapsed by these liquids at the appropriate time. Alternatively wrapping technique of Figure 6 may be used.

Combinations of the features of the various embodiments may be used.

In an alternative method of construction one or both of the exterior sheets may be coated prior to assembly of the structure as well as the separator if desired.

The collapsible structure of the invention may be used anywhere it is desired to create a void and to which water may be applied to achieve collapse.

Claims

1. A collapsible structure which is rigid when dry and is collapsible under the action of a liquid, comprising a separating structure, whose rigidity is attacked by the liquid sandwiched, between two sheets of material, at least part of the collapsible structure being treated or formed of such a material as to enable the ingress of liquid to be retarded.

2. A structure as claimed in claim 1, wherein the structure is collapsible under the action of water.

3. A structure as claimed in claim 1, wherein the structure is collapsible under the action of a detergent liquid.

4. A structure as claimed in claim 2 wherein at least one of the said two sheets of material is such as to allow passage of moisture therethrough and wherein a membrane is provided covering at least one side of this sheet material, the membrane being of a material such that it will prevent water at least partially, from attacking the separating structure.

5. A structure as claimed in claim 4, wherein the material of the membrane is water soluble.

6. A structure as claimed in claim 4 or 5, wherein the membrane is arranged to surround the whole of the structure.

7. A structure as claimed in claim 6, wherein the membrane is applied by dipping the structure in a suitable liquid.

8. A structure as claimed in claim 6, wherein the membrane is in sheet form and is wrapped around the structure.

9. A structure as claimed in any one of claims 4 to 8, wherein the membrane is applied as a coating only to the outer surface of the said at least one sheet.

10. A structure as claimed in any one of claims 4 to 8, wherein the membrane is applied, as a coating only to the outer surface of said at least one sheet and to the edges of the separating structure.

11. A structure as claimed in any one of claims 4 to 8, wherein the membrane is applied to one or both sides of the said at least one sheet prior to assembly of the structure.

12. A structure as claimed in claim 4 or 6 when appendant directly thereto, wherein the membrane is insoluble in water but is severable to admit moisture when collapse is desired.

13. A structure as claimed in claim 2, wherein the separating structure is treated so as to retard the action of the water therein.

14. A structure as claimed in claim 13, wherein the separating structure is coated with a water soluble plastics material.

15. A structure as claimed in claim 13, wherein the separating structure is impregnated with a water soluble plastics material.

16. A structure as claimed in claim 13 wherein the separating structure is wrapped in a wrapping of water soluble plastics material.

17. A structure as claimed in claim 2, wherein the separating structure is formed of a water soluble plastics material.

18. A structure as claimed in any one of claims 2 or 13 to 17, wherein one or both sheets of sandwiching material are coated on the inner surface with a water soluble plastics material.

19. A structure as claimed in any one of claims 2 or 13 to 18 wherein one or both sheets of sandwiching material are impregnated with water soluble plastics material.

20. A structure as claimed in any one of claims 5, 14, 15, 16, 17, 18, 19 and any claim directly or indirectly appendant to any of these claims, wherein the water soluble material is polyvinyl alcohol.

21. A method of building comprising laying a collapsible structure in accordance with any one of claims 1 to 20 in or on the ground as a base or shuttering, pouring concretethereonto orthereinto and allowing the concrete to set and allowing or providing for ingress of liquid into the collapsible structure to permit or encourage the structure to collapse after a suitable time lapse.

22.A method as claimed in claim 21, wherein an insoluble wrapping for the structure is broken open to permit the ingress-of liquid after setting of the concrete.

23. A method as claimed in claim 2, 21, or 22, wherein the liquid or additional liquid is applied to the structure after the concrete has set.

24. A method as claimed in any one of claims 21 to 23, wherein the liquid concerned is water.

25. A method as claimed in any one of claims 21 to 23, wherein the liquid concerned is a detergent.

26. A collapsible structure substantially as described herein with reference to the drawings.

27. A method of building substantially as described herein with reference to the drawings.