GB2077804A - Improvements in or relating to underground chambers - Google Patents

Abstract

The invention relates to an underground chamber which can be used as an inspection pit or an air raid shelter. The chamber is formed by burying a preformed container of stainless steel in a hole. Part of the space surrounding the container is first filled with a plastics foam and a layer of concrete 16 is laid over the plastics foam to make good floor surface up to the edge of the buried container. The container may be double walled with bracing struts and foamed plastics in the wall cavity. Water or fuel storage tanks may also be incorporated in the cavity. <IMAGE>

Description

SPECIFICATION Improvements in or relating to underground chambers The present invention relates to underground chambers which, depending on size, can be used as inspection pits for motor vehicles or underground nuclear shelters.

It is often advantageous to provide an underground chamber but a problem which has hitherto been found in constructing such a chamber is the tendency for water to enter the chamber, seeping in through the sides.

Furthermore, the constructional difficulties in forming such a chamber have resulted in their cost being relatively high.

With a view to mitigating the above problems,.

the invention provides according to a first aspect a preformed waterproof container which is totally buried underground and has an opening to allow human access.

The container must be made of a material which does not corrode when buried in this fashion and is therefore preferably formed of stainless steel. Alternatively, the container may be formed of other forms of steel protected against corrosion, for example by a plastics coating.

In accordance with a second aspect of the present invention, there is provided a method of forming an underground chamber which comprises excavating a cavity, inserting into the cavity a preformed waterproof container having an opening affording human access into the container, partly filling the space between the outer wall of the container and the wall of the cavity with a plastics foam and filling the remainder of the space between the container and the cavity wall with concrete.

In the case of an inspection pit, the opening allowing human access would be in the top of the container, but when such a buried container is to be used as an air raid shelter it is convenient to bury two separate containers into the ground, the first being in the form of an inspection pit and the second being a totally covered container having a trap door communicating with the inspection pit.

In this way, the inspection pit can act as an entry passageway and an air lock for the air raid shelter.

The interior of the air raid shelter container can be provided with fold-away furniture etc. as could be found in a caravan.

Because materials such as stainless steel which are resistant to corrosion are relatively expensive, the manufacturing costs become significant when the container is made of large size because of the gauge of the material and because of the additional reinforcement which are required to provide a large size container with the necessary rigidity.

Preferably, the container is double skinned, the outer skin being of a corrosion resistant material while the rigidity of the wall sections of the container is assured by webs in the space between the two skins.

By a virtue of this construction, it is seen that the outer skin is only provided for corrosion resistance and is not relied upon for providing structural rigidity so that as a result the material costs can be reduced significantly. Furthermore, the double skinned contruction offers the advantage that the space between the two skins can be used to accommodate storage tanks for the storage of water or fuel. The space between the skins can also be filled with a plastics material to provide thermal insulation.

The opening at the upper end of the container may be of the same width as the overall width of the container but alternatively the opening may be restricted.

Advantageously, when installed the container has a lip which is proud of the surface of the ground in order to prevent any liquid from pouring into the container.

If desired, the upper end of the container may be fitted with a waterproof cover when the chamber is not in use.

In order to provide access, it is convenient for the container to include steps. The steps may in a preferred embodiment be pivotably secured to parallel uprights in a manner analagous to louvres such that when the steps are raised they may close the entry to the interior of the chamber to prevent unauthorised access to the chamber when already occupied.

The invention will now be described further, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a sectioned perspective view of an inspection pit constructed in accordance with the invention; Figure 2a to 2d are horizontal sections showing alternative form of reinforcing ribs to strengthen the sides of the steel container of Figure 1; Figure 3 shows a combined inspection pit and fall-out shelter; Figure 4 is a section through an alternative embodiment of the invention; Figure 5 shows a container with a construction at its upper end, and Figure 6 shows a side view of a cover which can be folded shown to act as steps.

To form the inspection pit shown in Figure 1 a hole is first dug in the ground. The bottom of the hole is strengthened by means of a hard core base 10 and there is then inserted a preformed stainless steel container 12. A foam material such as polyurethane foam 14 is injected around the lower part of the container 12 and finally concrete 16 is laid to fill in the rest of the hole leaving an upper flange 18 of the preformed container slightly raised from the lower floor surface to form a shoulder for receiving a cover to close off the inspection pit when not in use.

The plastics foam 1 4 serves many functions which will now be explained. Firstly, the foam serves to retain the container in place during the laying of the concrete and also acts as a base for the upper concrete layer 1 6, thus reducing the amount of concrete used and therefore the setting time. This can allow the inspection pit to be installed very rapidly, in the second place, the plastics foam acts as a thermal insulation and to protect the outside of the container against corrosion.

To facilitate entry into the inspection pit brackets 20 are welded to the inner walls of the container and these are in turn welded to and support steps 22 which are preferably formed with a tread to provide improved grip.

The sides of the container are strengthened by reinforcing ribs 24 which can take away any of the forms shown in Figures 2a to 2d. In Figure 2a the reinforcing ribs are T-shaped in cross section, in Figure 2b they are L-Shaped, in Figure 2c they are box shaped and in Figure 2d they are of triangular cross section. Any of these forms of rib may be welded to the exterior surface of the container to improve the rigidity of the walls.

In Figure 3, there is shown an inspection pit having the same general form as that shown in Figure 1 and communicating by means of a trapdoor 30 with the space in a second buried container 32. The container 32 is of iarger dimensions and is fitted internally with sleeping bunks, food storage areas and other necessities for enabling one or more people to survive for a period of time in the event of a nuclear attack.

Suitable ventilation is required within the air raid shelter and this can be provided by a manually operable pump fitted with suitable filters.

The inspection pit offers several advantages as a means of access into the air raid shelter. The pit can itself be covered by the family car to prevent debris blocking the exit from the shelter.

Furthermore, as well as providing access the inspection pit offers a second secure chamber isolated from the main living area which could, for example, contain a chemical closet.

It will be appreciated that in an inspection pit alone can act as a useful air raid shelter but in combination with a larger buried chamber it can provide a cheap and simple fall-out shelter in the event of a nuclear attack.

The construction of the fall-out shelter differs from the inspection pit in that a roof is formed as part of the container which is overlaid with concrete. In other respects, the construction and installation are similar to the inspection pit previously described by reference to Figure 1.

The advantage of a preformed container resides in the simplicity of assembly and the security against water seeping into the inspection pit or shelter.

In the embodiment of Figure 4, the walls of the container are seen to be double skinned with the outer skin 110 made of a light gauge stainless steel which renders the container watertight and corrosion-resistant. The walls of the container have an inner skin 112 which can be made of mild steel, aluminium or other suitable material, the two skins being interconnected by means of reinforcing webs 1 14 which can also be made of a relatively cheap material such as mild steel. The chambers defined by the webs are filled with a plastics foam 1 6 to provide improved thermal insulation.

One end wall 11 8 of the container is curved and accommodates in the space between the inner and outer skins storage tanks 1 20 and these can be used to store water or fuel. The tanks act instead of the webs to interconnect the two skins and provide the necessary structural rigidity. Such space as is not occupied by the tanks 120 in the wall section 1 8 is once again filled with a thermally insulating plastics material.

The embodiment shown in Figure 5 differs frown those in the previous drawings in that the access opening 210 is narrower than the full width of the underground chamber. For example, the chamber may have a width of 1 60 cm while the width of the access opening is only 60 cm. As concrete is laid over the shoulder 212 when the container is installed, triangular reinforcing webs 214 are welded on the extirior of the container to provide the required strength.

When the underground chamber is arranged out of doors, it may be provided with a waterproof cover.

Figure 6 shows an alternative form of cover which serves the dual purpose of steps permitting access to the interior of the underground chamber.

The cover is formed of individual slats 310 each pivoted at each end to two uprights 312 and 314 defining a series of louvre like paralellagrams.

When lowered, the slats 310 act as steps and when raised they form a continuous surface closing off access to the underground chamber.

The steps need only form part of the entire cover to the chamber and the remaining section can be closed off by loose boards. A latch mechanism may be incorporated to keep the cover in position, that is to say to close off the container when the underground chamber is already occupied.

Claims (11)

1. A preformed waterproof container which iS totally buried underground and has an opening to allow human access.

2. A container as claimed in Claim 1 wherein at least the outer surfaces of the container are formed of stainless steel or the like corrosion resistant material.

3. A container as claimed in Claim 1 or Claim 2, wherein the walls of the container are double skinned the outer skin being of a corrosion resistant material and the rigidity of the walls being assured by webs in the space between the two skins.

4. A container as claimed in Claim 3, wherein storage tanks are accommodated in the space between the two skins of the container.

5. A container as claimed in any preceding Claim wherein the width of the access opening is less than the overall width of the container.

6. A container as claimed in any preceding Claim, wherein the upper lip of the container remains proud of the ground surface in order to prevent liquid from pouring into the container.

7. A container as claimed in any preceding Claim, provided with a removable waterproof cover overlying the access opening.

8. A container as claimed in any of Claims 1 to 7, in which fold away steps are provided to allow access to the interior of the container, the steps in the folded away position constituting a cover closing the access opening.

9. A method of forming an underground chamber which comprises excavating a cavity, inserting into the cavity a preformed waterproof container having an opening affording human access into the container, partly filling the space between the outer wall of the container and the wall of the cavity with a plastics foam and filling the remainder of the space between the container and the cavity wall with concrete.

10. An underground shelter comprising two interconnected preformed waterproof containers of which the first is provided with an access opening above ground level and the second is closed from above, access being gained through a door interconnecting the first and second containers.

11. An underground shelter or pit constructed substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.