GB2106168A - Securing a body to a base of settable material - Google Patents

Abstract

An underground storage tank 10 is secured in a trench 9 by means of anchor straps 1 of fabric webbing. Each strap 1 passes around the tank 10, and is embedded in a base 11 of concrete. Each strap 1 has two loops 2 at opposite ends, which loops are joined by a tensioning strap 5, which is tightened by a ratchet tightening mechanism 6. The anchor straps 1 serve to prevent the tank 10 from floating in wet concrete, which is subsequently poured into the trench 9. <IMAGE>

Description

SPECIFICATION Securing a body to a base of settable material This invention relates to the securing of a body to a base of settable material, and is particularly although not exclusively concerned with the securing of underground storage tanks.

In the construction industry, it is often necessary to install storage tanks underground.

For example, this is necessary at most petrol stations, for the bulk storage of petrol. The conventional method of securing such an underground storage tank comprises the steps of excavating a trench to accommodate the tank, and laying a concrete base at the bottom of the trench.

The concrete base is laid around steel securing means, such as bolts or hoops, which are positioned along the sides of the trench. Once the concrete is firmly set, the tank is lowered onto the concrete base, and wire ropes secured to the securing means are passed over the tanks and tightened by means of bottle screws or other threaded metal tightening devices. Once the tank is firmly secured to the concrete base by means of the wire ropes, concrete is poured into the trench around the storage tank, until it is fully encased.

The main purpose of tying down the tank by means of the wire ropes is to prevent the tank floating off the base when the wet concrete is poured in around it. It is to be appreciated that the tank must be left empty, and various safety tests have to be performed on the tank before it is concreted in. Although the use of wire ropes is generally effective, there are several disadvantages. One disadvantage is that the concrete base needs to be appreciably wider than the tank, in order to secure the fixing points for the wire ropes. Also, the concrete base needs to be allowed to set very hard before the tank is secured in place, to ensure that the securing means for the wire ropes are firmly embedded.Further, considerable skill, expertise and time are involved in tightening down the wire ropes, and as tension is applied to the ropes, there is a tendency for them to damage the surface of the tank, which is usually provided with a protective bitumen or paint coating.

Preferred embodiments of the present invention aim to provide a method of securing an underground storage tank, which may be improved in the foregoing respects.

More generally, according to a first aspect of the present invention, there is provided a method of securing a body to a base of set material, including the steps of laying part of a length of webbing across a surface, laying settable material on said surface over said part of the webbing, allowing said material to set to form a base, disposing said body on the base, and fastening the webbing around said body.

Preferably, the settable material comprises concrete, although other settable materials may be used if desired.

Preferably, the webbing comprises fabric webbing, although any other suitable material may be used if desired.

The invention has particular application wherein said body is an underground storage tank, and said surface is at the bottom of a trench for receiving the storage tank. Then, the method may include the preliminary step of excavating said trench.

Preferably, there is provided a plurality of lengths of webbing at intervals along said surface, a respective part of each said length being covered by in said settable material, and each said length of webbing being fastened around said body.

The or each length of webbing may advantageously be provided with a loop at each of two respective ends thereof. Then, the two ends of the or each length of webbing may be secured together by a further length of webbing provided with means for tightening said further length. The or each tightening means may with advantage comprise a ratchet tightening means adapted to receive both ends of the respective said further length of webbing.

The or each length of webbing may be provided with anchor means for anchoring the respective said part of the length of webbing to said surface.

The or each said anchor means may advantageously provide a pair of angled members through which the respective webbing passes, each angled member being adapted to be secured to said surface.

Preferably, the width of said surface corresponds substantially to the width of said body.

For a better understanding of the invention and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying diagrammatic drawings, in which: Figure 1 illustrates an anchor strap for securing an underground storage tank; Figure 2 illustrates a tensioning strap for use with the anchor strap of Figure 1; Figure 3 is a sketch in perspective of a trench for accommodating an underground storage tank, with anchor straps fitted in position; and Figure 4 is a sectional view of a storage tank secured in the trench.

The drawings are to illustrate a method of securing an underground storage tank in a trench, and also to illustrate the components used in such a method.

The anchor strap 1 shown in Figure 1 comprises a length of fabric webbing made from high tenacity Nylon/Polyester, or other suitable fibres.

At each of its two ends, the strap 1 is formed with a loop 2, secured by reinforced stitching 3. The strap 1 passes through two anchoring means in the form of angled corner pieces 4, which are of rigid or semi-rigid material.

The tensioning strap 5 shown in Figure 2 is also of fabric webbing, made from high tenacity Nylon/Polyester or other suitable fibre, and is secured at one of its ends to a ratchet tightening mechanism 6. The tightening mechanism 6 is adapted to receive the other free end 7 of the tensioning strap, and by movement of a handle 8 on the mechanism 6, gradually tighten the tensioning strap 5 in use.

In Figure 3, a trench 9 has been excavated to accommodate a storage tank 10 (Figure 4). The trench 9 has a width just somewhat greater than the diameter of the tank 10. Five anchor straps 1 are each positioned in the trench 9 with a part thereof extending across the bottom surface of the trench 9. At each side of the trench 9, each anchor strap 1 is secured in position by its respective angled corner piece 4. The end loops 2 of the anchor straps 1 are temporarily held in position along the sides of the trench 9, towards the top thereof. It may be appreciated that, once the trench 9 has been excavated, the five anchor straps 1 can be positioned therein very quickly indeed. Once the straps 1 have been positioned in the trench 9, concrete is poured over the bottom surface of the trench, over the bottom parts of the anchor straps 1, and allowed to set.When set, the concrete forms a base 11, which may be seen in Figure 4.

The concrete base 11 extends over the bottom parts of the anchor straps 1, and in the illustrated example, the straps 1 pass upwardly through the concrete base 11. If desired, the arrangement may be such that the concrete base 11 tends to envelop the bottom parts of the anchor straps 1 completely.

The tank 10 is then positioned upon the concrete base 11, and the anchor straps 1 are fastened securely around the circumference of the tank 10. To this end, the loops 2 of each anchor strap 1 are linked by a respective tensioning strap 5, as illustrated in Figure 4. The tensioning strap 5 passes through the two loops 2, and the free end 7 thereof passes through the ratchet tensioning machine 6, as shown. The handle 8 of the tensioning machine 6 is then operated to gradually increase the tension on the tensioning strap 5, until the anchor strap 1 is tightly held around the tank 10. It may be appreciated that this fastening and tightening of the anchor strap 1 may be carried out very rapidly.

Once all of the anchor straps 1 have been satisfactorily tightened around the tank 10, the trench 9 is filled with wet concrete until the tank 10 is fully immersed therein. The concrete is then allowed to set, following which the tank 10 is ready for its subsequent use. The ground above the tank 10 is finished off as desired. It will be appreciated that, as the concrete in the trench 9 is setting, the straps 1 restrain the tank 10 against any tendency for flotation in the wet concrete.

It may be appreciated that the illustrated method may be carried out very simply and quickly, and may have several advantages over the conventional method of anchoring underground storage tanks by means of wire ropes.

Initially, once the trench 9 is excavated, almost negligible time is needed to place the anchor straps 1 in position. Then, once the concrete base 11 has set, the anchor straps 1 are secured very much more strongly than the previously proposed wire ropes. In this respect, it will be appreciated that the bottom part of each anchor strap 1 is embedded under the weight of the entire concrete base 11, and because of the web configuration of each strap 1, there is virtually no possibility of the strap 11 being able to cut upwardly through the concrete base 11.Due to this much enhanced securing of the anchor straps 1, it may not be necessary to allow the concrete base 11 to dry out quite so thoroughly as is required with conventional securing methods, so that the work can proceed more quickly. Finally, once the tank 10 has been lowered onto the concrete base 11, the straps 1 may be tightened-up extremely quickly, without danger of damage to any protective coating on the tank 10. Another important advantage is that the anchor straps 1 and their securing components may together be significantly cheaper than the previously used wire ropes and their fastening components.

Overall, therefore, the illustrated method may enable a storage tank to be installed underground much more quickly and safely than has been possible in the past, with important consequential savings in labour costs adding to the savings in materials mentioned above. Apart from the straight forward savings of costs, the illustrated method also affords important safety advantages in that the trench need be left open for less time (with consequential reduced risk of collapse), and in that there is no need for workers to go down into the trench, between the tank 10 and the walls of the trench 9, once the anchor straps 1 have been put into place.

As the illustrated anchor straps 1 may each have an individual breaking strength of 1 6 tons, it will be appreciated that the five anchor straps 1 give a total securing strength of 1 60 tons (each strap providing a total strength of 32 tons). As an alternative to providing the loops 2 at the ends of each anchor strap 1 by means of the reinforcing stitching 3, each anchor strap 1 may be provided as a continuous loop in an elongate configuration corresponding substantially to that shown in Figure 1. The respective tensioning strap 5 then passes through the two ends of the elongated loop.In such an alternative arrangement, it will be appreciated that the overall strength of each anchor strap is effectively doubled, in that each anchor strap affords four sections of webbing extending around the tank 1 0. Thus, in a method as illustrated, the overall strength of the arrangement may be increased to 320 tons, or alternatively, the straps may be made of webbing of one half the original thickness, for the same overall strength.

Another possible advantage of the illustrated method is that, should it be desired to remove the tank 10 from the ground at a later date, then the anchor straps 1 may be used to hoist the tank, complete in its concrete shell. In this respect, the strength of the straps, as discussed above, may be quite sufficient to support the combined weight of storage tank 10 and its concrete jacket, and the anchor straps 1 may be made of a material which retains its strength over a long period of time. If desired, the anchor straps 1 may be provided with extensions which project upwardly out of the concrete jacket, for possible future use in hoisting the storage tank 10 out of the ground.

Claims (14)

1. A method of securing a body to a base of set material, including the steps of laying part of a length of webbing across a surface, laying settable material on said surface over said part of the webbing, allowing said material to set to form a base, disposing said body on the base, and fastening the webbing around said body.

2. A method according to Claim 1, wherein the settable material comprises concrete.

3. A method according to Claim 1 or 2, wherein the webbing comprises fabric webbing.

4. A method according to Claim 1 , 2 or 3, wherein said body is an underground storage tank, and said surface is at the bottom of a trench for receiving the storage tank.

5. A method according to Claim 4, including the preliminary step of excavating said trench.

6. A method according to any preceding claim, wherein there is provided a plurality of lengths of webbing at intervals along said surface, a respective part of each said length being covered by said settable material, and each said length of webbing being fastened around said body.

7. A method according to any preceding claim, wherein the or each length of webbing is provided with a loop at each of two respective ends thereof.

8. A method according to Claim 7, wherein the two ends of the or each length of webbing are secured together by a further length of webbing provided with means for tightening said further length.

9. A method according to Claim 8, wherein the or each tightening means comprises a ratchet tightening means adapted to receive both ends of the respective said further length of webbing.

10. A method according to any preceding claim, wherein the or each length of webbing is provided with anchor means for anchoring the respective said part of the length of webbing to said surface.

1 A method according to Claim 10, wherein the or each said anchor means comprises a pair of angled members through which the respective webbing passes, each angled member being adapted to be secured to said surface.

12. A method according to any preceding claim, wherein the width of said surface corresponds substantially to the width of said body.

13. A method of securing a body to a base of set material, the method being substantially as hereinbefore described with reference to the accompanying drawings.

14. A body which has been secured to a base of set material by a method according to any preceding claim.