GB2240350A

GB2240350A - Forming foundation beams

Info

Publication number: GB2240350A
Application number: GB9020460A
Authority: GB
Inventors: Roy Dennis Willmott
Original assignee: IMER
Current assignee: IMER
Priority date: 1989-10-11
Filing date: 1990-09-19
Publication date: 1991-07-31
Also published as: GB9020460D0; GB8922865D0

Abstract

The invention relates to a method and mould members suitable for use in producing foundations, footing beams, pipe ducts or the like. The mould members comprise channel members (2) which are received on a first layer of settable material (concrete 20) in a trench (18). The channel is then filled to a required depth by a second amount of settable material to form a foundation beam (26). At least the base of the channel mould member is retained in place to form part of the foundation structure. The mould members (2) are formed from lightweight concrete, polystyrene glass-fibre reinforced resin or plastics material and are laid end-to end in the desired path. The beams may be formed in a progressive manner placing one or two mould members and filling the channels before progressing to subsequent laying of layers of concrete (20) further along the trench (18). <IMAGE>

Description

FORMING FOUNDATION BEAMS The invention is concerned with improvements in or relating to the forming of beams and the like for use as footings in the constructions of foundations for buildings.

There are several methods of forming concrete foundation beams for light building use, such as in the domestic and light industrial construction industry. A first technique involves the digging of a trench at least one metre deep and 0.9 to 1 metre wide to enable access.

However, for purposes of constructional strength it is necessary only to form a concrete strip or fillet at least about 0.6 metres wide and 0.3 metres deep along the trench. Brick walling should then be erected on the concrete strip to a level appropriate to the intended damp proof course. The trench is then infilled on each side of the brick walling.

This technique has several disadvantages.

Firstly, all the necessary excavation has to be completed before the concrete is placed and levelled and because of the delay involved, there is a considerable risk of collapse of the trench sides. Water collecting in the trench may also be a problem due to rainfall or breaching of the water table. Moreover, the width of the trench has to be such as to allow access to a bricklayer, and is much greater than that required by the construction itself. Thirdly, setting time has to be allowed firstly for the concrete and then the mortar of the brickwork.

Another technique involves the digging of a trench at least 1 metre deep and 0.6-0.7 metres wide. The entire trench is then filled with concrete at least substantially upto the level of the intended damp proof course. This is wasteful of concrete, since the full width of concrete is only required in the lower part of the trench and the upper part of the trench is thus filled with two or three times the volume of concrete required for structural support purposes.

Moreover, since such filled-trench footings form an enclosure around a given area of ground (earth), particularly where the earth is unstable clay, considerable expansion and shrinkage of the enclosed earth takes place which can result in the concrete and/or brickwork cracking and failing. In order to prevent this, compressible material is required to be inserted against all the inwardly facing surfaces of the concrete based enclosure for the full depth of the trench. The operation is thus labour-intensive and time-consuming.

A third technique involves the digging of a series of trenches (say, 0.6 metres wide and 0.6 metres deep) to accommodate so-called ground beams, each of which extends between two pre-constructed columns or blocks, in concrete or steel. Shuttering is then placed in each trench to define a strip or fillet of concrete upto damp proof course or floor level. When the concrete is set, the shuttering is removed and voids at each side of the cast beam are then in-filled with earth. This technique involves digging a wider trench than is required by the dimensions of the beam in order to accommodate the shuttering and time wastage waiting for the concrete to set. Casting the concrete is not easily achieved and the shuttering can sometimes move to an extent where the whole exercise has to be repeated.Some of these disadvantages may be relieved by the use of pre-cast ground beams but these introduce site storage problems and involve careful organisation of supply, delivery and the timing of demand in addition to introducing extra cost. Their use also increases the risk where trenches lie open for periods of time, that trench walls are more liable to collapse.

It is an object of the present invention to minimise or obviate many of the above stated disadvantages.

The invention provides in one of its aspects a method of producing a structure by deposition of mouldable, settable material in the formation of foundations, footing beams, pipe ducts and the like, comprising the steps of (a) constructing a trench or similar recess in a substrate, (b) applying to a base portion of said trench or recess a first amount of mouldable, settable material in a layer, (c) positioning upon that layer while it is still in a mouldable condition pre-formed channel means having a generally U-shaped cross-section providing a channel, (d) depositing a second amount of mouldable, settable material in said channel and (e) allowing the material to set.

In some examples of a method according to the invention, it may be found advantageous to retain at least a portion of said channel means as an integrated component of the deposited structure.

Where the foundation, footing beam or the like is to be formed entirely below ground level there may be interposed between steps (c) and (d), the step of filling in voids occurring between outer surfaces of wall portions of said channel means and walls of the trench or recess with suitable filler material.

Advantageously, the channel means may be open-ended and positioned end-to-end to form an elongate mould or shuttering means of the desired length.

Where appropriate, the channel means may be constructed from a plurality of panels for ease of transport to a site at which they may readily be assembled.

Conveniently, the panels may be L-shaped in cross-section or may comprise initially separate wall and base portions, connection being made between wall and base portions by means of dovetail or other tongue and groove joints.

In an example according to the invention, the mouldable settable material is concrete, and the viscosity of the first amount may be less than that of the second amount, if preferred. In this example, the substrate is bare earth and the filler material positioned between the walls of the channel means and the trench is earth which has been removed in the formation of said trench.

Advantageously, the base of the U-shaped channel member may be perforated or otherwise provided with suitable surfaces into which said first amount of mouldable material may key.

The invention further provides in another of its aspects mould members suitable for use as shuttering in the method described above of a deposition of mouldable settable material, comprising generally U-shaped channel means having a wall portion and a base portion or portions.

Advantageously, the channel means may be open-ended.

Preferably, end portions of side walls of the channel means may be cut back or recessed to inter-engage smoothly with complementary end portions of an adjacent channel means arranged end-to-end therewith.

Conveniently the channel means may be formed from lightweight concrete, polystyrene, glass-fibre reinforced resin or plastics material, or may comprise a rigid metal skeleton support such as wire mesh provided with cladding panels, or may be formed from any other suitable non-biodegradable material. Where necessary, ends of the member(s) of the channel means may be cut, mitred or suitably shaped at corners or wall members thereof may be cut away for example to form T-junctions in the line of the foundations being laid, if required.

There will now be described six examples of mould members for use in the method according to the invention.

It will be understood that the description, which is intended to be read with reference to the drawings, is given by way of example only and not by way of limitation.

In the drawings: Fig. 1 is a perspective view of a first mould member for use according to the invention; Fig. 2 is a plan view of the mould member of Fig. 1; Fig. 3 is a diagrammatic, sectional view through a moulding member in use as permanent shuttering; Fig. 4 is a perspective view of a second, composite, mould member for use according to the invention; Fig. 5 is an exploded, perspective view of a third mould member for use according to the invention.

Fig. 6 is a perspective view of a wall portion of a fourth mould member according to the invention; Fig. 7 is a rear view of the wall portion of Fig. 6; Fig. 8 shows an end view of a fifth mould member assembly; Fig. 9 is a side view of a wall portion of a sixth mould member assembly; and Fig. 10 is a fragmentary, perspective view of the mould member assembly of Fig. 9.

Fig. 1 shows an open-ended channel member 2, comprising a base portion 4 and two side wall portions 6.

End portions 8, 10 of the wall portions protrude lengthwise of the member beyond the base portion 4, the end portions being rebated to approximately one half the thickness of the wall portions 6 to accept corresponding rebated end portions of adjacently disposed members as shown in chain-dot lines in Fig. 2. When a run of members 2 is to be laid, the protruding portions 10 or 12 of the end members may be removed, slots 14 being provided to assist in this operation. Apertures 16 are provided in the base portion 4 of the member 2 for purposes to be described below.

A trench 18 (Fig. 3) is dug along the desired line of a foundation footing to a depth of, in the present example, 1.0 metres. The trench is 0.66 metres wide.

A first amount of settable, mouldable material in the form of a shallow layer 20 of workable concrete of the desired mix and having a slump of 50 mm, is laid along a portion of the length of the trench. A member 2 is placed upon the layer 20 and manually manoeuvred into the exact position required, aligned and levelled. The concrete in the layer 20 is thus able to enter the apertures 16 in the base portion 4 of the member 2 and also to protrude into the space 22 (Fig. 2) between adjacent members 2.

The operation is repeated until the desired length of trench is provided with channel members 2. It will be appreciated that only sufficient concrete is laid in the layer 20 for the immediate placing of one or two members 2 at any one time, so that there is no time lag between the spreading of the layer 20 and the placing of the member 2. The risk of premature setting is thus reduced.

Voids formed between the sides of the trench 18 and the outside surfaces of the walls 6 of the member 2 are then in-filled, or back-filled,with material 24 removed from the trench when it was cut, care being taken to preserve the desired position of the line of the members 2.

A second, principal, amount of lean-mix concrete is now laid along the channel formed by the line of channel members 2 to form a foundation beam 26. If desired, reinforcement in the form of steel allow rods 28 may be embedded in the concrete of the beam as it is laid. It will be appreciated that if the beam 26 is to be exposed or partially exposed, the trench 18 will be shallow so as to accommodate the layer of concrete 20. Little or no infill or back-filling of material at 24 will be necessary.

Fig. 4 shows a second, composite, mould member for use in the method according to the invention. A member 30 comprises walls 32 and a base portion 34 both of steel alloy wire mesh and is in the form of a U-shaped channel.

The channel members are aligned in a trench, as above, the floor of which has been covered by a layer of concrete 36. Expanded polystyrene bricks 38 are selected in the present example to be placed against the walls 32 to provide thickness to these walls, being especially useful where the ground is of a clayey nature and therefore liable to expansion/contraction. Moreover the presence of the polystyrene blocks may also assist in minimising chemical attack on the concrete by acid soil. Wire mesh members may conveniently be used in trenches excavated to a depth of 0.6 metres. In this example also, steel rod or mesh reinforcement may be included when the concrete beam is formed.

If desired, the U-shaped channel members required to be placed in the trench may be assembled on site, and to this end, Fig. 5 shows an exploded view of a channel member 40. This member 40 comprises two wall members 42 each rebated at end portions 44 in a manner similar to that of the first example shown in Fig. 1. Two bores 46 are provided in each wall member 42 through which pass bolts (not shown) which are received in appropriate bores 48 of two concrete cross members 50. The manner of use of the assembled U-shaped channel member is according to the methods described above.

Figures 6 to 8 show a fourth mould member according to the invention which comprises a wall portion 52 which is initially separate from a base member 54 (Figure 8) but is connected thereto by the inter-engagement of a rib or bead 56 formed on the base portion 54 received in a groove 58 on the wall portion in the manner of a dovetail joint. In the present example, the rib or bead is formed on the base member 54, but it could alternatively be formed on the wall portion and received in a groove on the base portion. However, for reasons which will be explained, the arrangement at present illustrated is preferred.

On a rear surface of the wall portion 52 remote from the groove 58 there is provided a laterally extending flange 60 adapted to enhance the stability of the assembly of member portions by providing a greater dimension across the base of the trench than that of the distance between the walls of the channel means. Recesses or pockets 62 are provided in the flange 60 to receive in-fill material added to the trench as referred to above.

When the wall portions 52 are laid end to end, ribs 62 formed on one edge face of each portion are received in confronting grooves 64 formed on the opposite edge face of the adjacent wall portion. As illustrated in Figure 8, the base member 54 may be comprised of two portions, each having a rib 56 receivable in the groove of the adjacent wall portion 52. Base member portions may be in varying widths d, d11 so that the width of the U-shaped channel can be selected as required.

While it is frequently convenient to allow the mould members to remain in place as an integrated component of the deposited foundation structure, it is, under certain circumstances, preferable to remove wall portions thereof. Figures 9 and 10 illustrate an arrangement particularly suitable to facilitate this. Wall portions 66 are therefore provided with groove 68, corresponding with grooves 58 of Figures 6 and 8, and with rib and grooves 70,72 corresponding to rib and grooves 62,64. No flange portion is however provided which would correspond to the flange portion 60. Thus when a rib 74 of a base member 76 (corresponding to member 54) is received in the groove 68, the wall portion 66 may be removed by inserting a tool down between a surface 78 of the wall portion 66 an the concrete beam formed according to the invention so as to cut through the rib 74 at its narrowest width. The wall portion may then be lifted out. To facilitate this operation still further the thickness of the wall portion 66 is shown in Figure 9 as being greater at the upper end thereof than at the foot.

Various modifications may be made within the scope of the invention as defined by the following claims.

Claims

1. A method of producing a structure by deposition of mouldable, settable material in the formation of foundations, footing beams, pipe ducts and the like, comprising the steps of (a) constructing a trench or similar recess in a substrate, (b) applying to a base portion of said trench or recess a first amount of mouldable, settable material in a layer, (c) positioning upon that layer while it is still in a mouldable condition pre-formed channel means having a generally U-shaped cross-section providing a channel, (d) depositing a second amount of mouldable, settable material in said channel and (e) allowing the material to set.

2. A method as claimed in claim 1, wherein the viscosity of said first amount of mouldable settable material has a lower viscosity than that of the second amount of mouldable settable material.

3. A method as claimed in either one of claims 1 and 2, wherein there is an additional step carried out between steps (c) and (d), said additional step comprising filling in voids occurring between outer surfaces of wall portions of said channel means and walls of the trench or recess with suitable filler material.

4. A method as claimed in any one of the preceding claims, wherein a plurality of channel means are positioned end-to-end to form an elongate mould.

5. A method as claimed in claim 4, wherein said plurality of channel means are positioned singly or in successive groups, said steps of claim 1 being carried out in a progressive manner on each channel means or group thereof.

6. A method as claimed in any one of the preceding claims wherein at least a portion of said channel means is retained in place as an integrated component of the deposited structure.

7. A method as claimed in claim 6, wherein the portion retained comprises the base portion, said wall portion being severable from the base portion at a junction therewith.

8. A mould member for use in the method according to claim 1, comprising U-shaped cross-section channel means having a wall portion and a base portion or portions.

9. A member as claimed in claim 8, wherein said base portion is apertured.

10. A member as claimed in claim 8, wherein-said channel means include an outwardly extending stabilising flange provided at a junction of said wall portion and said base portion.

11. A member as claimed in claim 10, wherein said flange is provided with upwardly facing recesses which in use receive in-fill material.

12. A member as claimed in claim 9, wherein the wall portions are tapered in cross-section, having a greater thickness at a top region thereof than at a lower region.

13. A member as claimed in any one of claims 9 to 12, wherein said base portion is adapted to be secured to one of said wall portions by a tongue and groove arrangement.

14. A member as claimed in claim 13, wherein the tongue comprises a rib provided on the base portion receivable in a groove in the wall portion.

15. A member as claimed in claim 14, wherein the rib of the base portion is severable to release the wall portion, said wall portion being removable when the method steps of claim 1 are completed.

15. A method of producing a structure by deposition of mouldable settable material in the form of foundations, footing beams, pipe ducts and the like, substantially as hereinbefore described with reference to the drawings.

16. A mould member for use in a method or producing a structure by deposition of mouldable settable material in the form of foundations, footing beams, pipe ducts and the like, constructed and arranged substantially as hereinbefore described with reference to and as shown in a) Figure 1, 2 and 3 b) Figure 4 c) Figure 5 d) Figure 6, 7 and 8 e) Figure 9 and 10 of the drawings.