GB2255127A - Watertight enclosure. - Google Patents

Abstract

A watertight enclosure e.g. a liquid tank or a basement comprises a base slab (20) of reinforced concrete. A waterproof membrane (24) is provided on the base slab and a surrounding wall comprising a plurality of pre-cast reinforced concrete sections (26) is also provided. Each section has a foot (28) at its lower end which is placed on the waterproof membrane, and one or more passages therethrough for the reception of tensioning members by which a plurality of said sections can be compressed together to form the wall. A partition (48) and a roof (54) may be provided, and the sections are separated by compressible sealing gaskets. <IMAGE>

Description

Improvements in or Relating to Water-tight Enclosures The present invention concerns improvements in or relating to water-tight enclosures, especially but not exclusively water-tight enclosures fabricated from reinforced concrete and intended to form liquid retaining tanks, basements, subterranean enclosures for weighbridges etc.

For the construction of relatively large load bearing structures reinforced concrete is an ideal medium but in certain circumstances difficulties have been encountered in the use of this medium, especially where the concrete is cast in situ, as without constant supervision of a highly trained work force the integrity of the cast concrete is not sufficient high to ensure complete water-tightness. The disadvantages of this in a basement area is the obvious generation of damp conditions owing to ingress of water from the ground in which the basement is formed. Similarly, with water tanks, for example reservoirs for supplying large numbers of homes, factories etc., especially subterranean reservoirs, seepage of water outwards is undesirable but seepage of contaminated ground water inwards can cause polution problems.

There are other subterranean or even surface built structures where the provision of a substantially watertight enclosure, having high strength and constructed by relatively simple means to give a high quality structure is desirable. One such example is a concrete enclosure for a weighbridge.

An object of the present invention is to obviate or mitigate the disadvantages inherent in earlier reinforced concrete in situ structures of this nature and in the methods of constructing said structures.

According to a first aspect of the present invention there is provided a watertight enclosure comprising a base member of reinforced concrete, a waterproof membrane on said base member and a surrounding wall comprising a plurality of pre-cast reinforced concrete sections each having a transverse flange at its lower end placed on said water-tight membrane, said sections being pre-cast under controlled conditions to ensure that they are waterproof with one or more passages therethrough for the reception of a tensioning member in the or each passage by which a plurality of said sections can be compressed together to form the wall.

Preferably between each section there is provided a sealing gasket. The gasket is preferably compressible and tacky.

Preferably the enclosure is of a rectangular configuration and corner sections having two limbs disposed at right angles are provided. In modifications the enclosure can be circular, octagonal, triangular or any other suitable configuration.

Preferably the base member is in the form of a slab and a further reinforced concrete slab may be cast over the waterproof membrane between the ends of the flanges of the sections.

Central support columns or a centre support wall may be mounted on said further concrete slab.

Preferably a roof is supported by the tops of the sections and said central columns or wall.

Preferably tie bolts extend downwardly through said slabs and membrane to the underlying strata to anchor the enclosure on said strata.

According to a further aspect of the present invention there is provided a method of forming a watertight enclosure comprising casting a reinforced concrete base member, placing a waterproof membrane over said base member, erecting a surrounding wall on said base member from a plurality of pre-cast sections each having a transverse flange at its base and at least one passage therethrough, arranging wall fixing tensionable members through said passage(s), and applying a tension to said tensioning member(s) to compress said sections one alongside the other.

Preferably the base member is in the form of a slab and a further reinforced concrete slab may be thereafter formed on the waterproof membrane.

Preferably the enclosure is formed in a subterranean cavity which, at least during construction, is kept dry by means of a pump.

Preferably after construction the external surfaces of the wall are coated with a waterproof substance. Furthermore the enclosure may be provided with a roof.

The tensionable members may be tensioned hydraulically or manually. Preferably they are so arranged that they may be tensioned from externally of the enclosure.

Tie bolts may be inserted through the base of the enclosure to fix the enclosure to the underlying strata to resist uplift due, for example, to external hydrostatic forces.

An embodiment of the present invention will now be described by way of example only with reference to the accompanying drawings, in which: Fig. 1 shows a cross-sectional elevation through a subterranean enclosure forming a reservoir; and Fig. 2 shows a sectional plan through a corner of the enclosure.

The embodiment to be described relates to a subterranean reservoir for drinking water but, as will be described hereinafter, the enclosure could equally well be constructed on the surface or could be a domestic, commercial or industrial basement or any other enclosure.

In the first instance, a pit is excavated in which the reservoir has to be constructed. A sump 12 is formed in the pit so that water collecting therein during the construction of the reservoir can be pumped off by a surface-mounted pump 14 and riser 16. On the flat base 18 of the pit there is then formed, in situ, a base slab 20 having standard steel mesh reinforcement 22 formed therein. A waterproof membrane 24, for example of butyl is laid on the base slab 20 after the concrete thereof has set and surrounding walls forming the sides of the reservoir can then be constructed on the membrane. The walls comprise a plurality of pre-cast reinforced concrete sections 26 arranged in abutting side-by-side relationship to form a rectangle.Each section has an inwardly directed flange 28 with a step 27 at its outer end and a small outwardly directed flange 29 at its base, roof support projections 30 near its top and a plurality of spaced horizontally extending through passages 32.

Right angled corner sections 34 are specially fabricated and have dimensions corresponding to the sections 26. As all the sect ions are pre-cast in factory conditions, normally on mechanised vibratory casting machinery with controlled setting environments, they can be manufactured to the highest quality and consequently can be guaranteed to be waterproof. This is not possible with concrete poured and allowed to set in situ as with this method much depends on the skill and attention of the operative, the ambient conditions etc.

As can be seen from Fig. 2, the sections are assembled side-by-side and an elongate tensioning member, for example a stranded wire rope 36, is threaded through each passage 30 from one end of the wall thus formed to the other.

Before assembly, each section has fixed to at least one of its transverse sides a sealing gasket which is preferably of a tacky material to allow it to adhere at least temporarily to the section while a neighbouring section is placed alongside it but is certainly compressable to form a watertight seal between the sections.

The inter-section seal is enhanced when one end of each tensioning member 36 is fixed at one corner and a tensioning force is applied to its other end at the other corner thus drawing the sections together to increase the watertight seal and to provide a composite wall of the required structural strength.

The tensioning member may be tensioned by mechanical or hydraulic means and before the tensioning force is released it is fixed, in the tensioned condition, by appropriate fixing means at the free end.

After the tensioning step has been completed ground anchors or tie down bolts 45 can be fitted.

These pass through holes in the outwardly directed flange 29, the membrane 24 and the base slab 20 can penetrate into the sub-soil for a predetermined distance. They serve to locate the concrete sections 26 and pull them down against the membrane ensuring the watertightness of the seal around the periphery of the reservoir.

The next stage in the operation is to cast a further concrete slab 40 between the facing end faces 42 of the flanges 28 of the sections, the slab 40 being cast on top of the membrane 24 and including further mesh reinforcement 44.

To ensure that the finished reservoir can withstand hydrostatic lift it is preferable to anchor it to the strata by ground anchors 46, only one of which is shown in Fig. 1. These anchors can be inserted by any suitable means. It is preferable that these are fitted prior to the laying of the membrane 24. The ground anchors can take any convenient form and as they do not form part of the present invention they will not now be described in any further detail.

After the concrete slab 34 has set it is possible to construct partition walls of pillars and Fig. 1 shows a partition wall 48 having a flanged base 50 and protrusions 52 near its upper end to support a roof structure which is indicated by the chain dotted lines 54 in Fig. 1.

Before infilling the pit around the reservoir it is preferable, as a further precautionary measure, to coat the outside surfaces of each section with a waterproof sealant.

Various modifications can be made without departing from the scope of the invention. For example, it will be realised that the structure could be built above ground in which case the step of excavating the pit would not be called for. Similar structures could be used to construct the basement of a building, for example, a house, office or factory. The basement may be multi-tiered and would be constructed by successively building structures by the method described above, one on top of the other.

It will be readily apparent that it is not necessary to restrict the plan of the structure constructed to a rectangular form. It could, by use of arcuate sections be circular or by use of alternative corner sections be of any multi-sided form.

The tie bolts 45 extending downwardly through the outwardly projecting flange 29 of the wall sections may be replaced by bolts cast into the base 20 and passing through said flanges nuts being attached on said bolts and tightened down to tighten the wall sections against the resilient membrane thereby increasing the waterproof seal therebetween.

A further use of the structure could be the provision for a pit for a weighbridge. In this instance, as the weighbridge is normally no wider than three metres and its depth is probably less than a metre, it is possible to cast an entire end wall rather than fabricate the end wall from two corner units and plurality of sections. The pre-fabricated end section would effectively have two corner sections formed intergrally with a continuous centre section. In this way, it would not be necessary to provide tensioning means through the end sections.

Claims (20)

Claims:

1. A watertight enclosure comprising a base member of reinforced concrete, a waterproof membrane on said base member and a surrounding wall comprising a plurality of pre-cast reinforced concrete sections each having a transverse flange at its lower end placed on said waterproof membrane, said sections being pre-cast under controlled conditions to ensure that they are water-tight with one or more passages therethrough for the reception of a tensioning member in the or each passage by which a plurality of said sections can be compressed together to form the wall.

2. An enclosure according to Claim 1, wherein between each section there is provided a sealing gasket.

3. An enclosure according to Claim 2, wherein the gasket is compressible and tacky.

4. An enclosure according to any preceding Claim which is of a rectangular configuration and has corner sections having two limbs disposed substantially at right angles.

5. An enclosure according to any preceding Claim, wherein a reinforced concrete slab is cast over the waterproof membrane between the ends of the flanges of the sections.

6. An enclosure according to Claim 5, wherein central support columns or a centre support wall are mounted on said concrete slab.

7. An enclosure according to Claim 6, wherein a roof is supported by the tops of the sections and said central columns or wall.

8. An enclosure according to any of Claims 5 to 7, wherein tie bolts extend downwardly through said slab and membrane to the underlying strata to anchor the enclosure on said strata.

9. An enclosure according to any of Claims 1 to 8, wherein tie bolts extend downwardly through the slab membrane and wall section to hold said sections against said membrane.

10. A method of forming a watertight enclosure comprising casting a reinforced concrete base member, placing a waterproof membrane over said base member, erecting a surrounding wall on said base member from a plurality of pre-cast sections each having a transverse flange at its base and at least one passage therethrough, arranging wall fixing tensionable members through the or each passage, and applying a tension to the or each tensioning member to compress said sections one alongside the other.

11. A method according to Claim 10, wherein a reinforced concrete slab is thereafter formed on the waterproof membrane.

12. A method according to Claim 10 or 11, wherein the enclosure is formed in a subterranean cavity which, at least during construction, is kept dry by means of a pump.

13. A method according to any of Claims 10 to 12, wherein after construction the external surfaces of the wall are coated with a waterproof substance.

14. A method according to any of Claims 10 to 13, wherein the enclosure is provided with a roof.

15. A method according to any of Claims 10 to 14, wherein the, or each, tensionable members is tensioned hydraulically or manually. Preferably they are so arranged that they may be tensioned from externally of the enclosure.

16. A method according to any of Claims 10 to 15, wherein tie bolts are inserted through the base of the enclosure to fix the enclosure to the underlying strata to resist uplift.

17. A method according to any of Claims 10 to 16, wherein tie bolts are inserted through the base of the wall sections, the membrane and the base to hold the sections against the membrane.

18. A watertight enclosure substantially as herein described with reference to and as shown in the accompanying drawings.

19. A method of forming a watertight enclosure substantially as herein described with reference to the accompanying drawings.

20. Any novel subject matter or combination including novel subject matter disclosed in the foregoing specification or claims and/or shown in the drawings, whether or not within the scope of or relating to the same invention as any of the preceding claims.