NZ203178A - Method of forming drainage element having cuspated sheet core overlaid by filter fabric - Google Patents

Description

4 v 203178 Priority Date(s): ..

Complete Specification Filed: A Class: ...fS&S'Ajfo}; „ Li^wvigee Publication Date: P.O. Journal, No: .

NEW ZEALAND PATENTS ACT, 1953 No.: Date: COMPLETE SPECIFICATION A DRAINAGE DEVICE" ^VVe, NYLEX CORPORATION LIMITED, a company incorporated under the laws of the State of Victoria, of 10 Queens Road, Melbourne, in the State of Victoria, Commonwealth of Australia hereby declare the invention for which Jf'l we pray that a patent may be granted to p*€7us, and the method by which it is to be performed, to be particularly described in and by the following statement: - (followed by page -la-) 203178 ^«4KIWM!Hj£, V,v This invention relates to drainage devices.

More particularly, the invention relates to a method of makinq a drainage device which can be used for drainaqe of 5 sub-surface water or in other sites where it is necessary to drain wet or damp ground.

According to the present invention there is provided a method of making a drainage device comprising a core in strip form and water permeable geotextile filter fabric which envelops the core, said core being imperforate and having an array of protuberances and wherein said fabric spans said protuberances thereby defining interconnected spaces ; which constitute a passage between the fabric and the core whereby, in use, water can pass through the fabric and then run in said passage characterised in that said method comprises the steps of feeding the strip of core to a forming station, feeding a single strip of fabric to the forming station, folding the strip of fabric around the core such that one lateral edge of the strip of fabric overlies one face of the core, applying bonding means to the strip of fabric adjacent said one lateral edge and overlapping the other lateral edge of the strip of fabric, whereby the strip of fabric encircles the core but is not bonded thereto, and withdrawing the device in strip form from the forming station.

In a preferred embodiment of the invention, the core comprises a layer of plastics material which is formed with integral protuberances and wherein the web comprises a filter fabric which is held in engagement with the outer faces of the projections. Preferably further, the plastics layer has protuberances on both Hn 203378 %'64mnm "• r i >' sides thereof and the fibrous fabric engages the protuberances on either side of the layer.

The invention will now be further described with 5 reference to the accompanying drawings, in which: Figure 1 is a cross-section through a core used in the drainage device made by the method of the invention, Figure 2 is a plan view of the core shown in Figure 1, Figure 3 is a cross-sectional view through one form of drainage device, Figure 4 is a fragmentary side view of a sheet drainage device having the cross-section as shown in Figure 3, Figure 5 shows the use of the sheet drainage device adjacent to a retaining wall, Figure 6 shows one technique for interlocking the core with a perforated conduit, Figure 7 shows a convenient arrangement for joining adjacent sheets of drainage devices, J Figure 8 shows an embodiment of the drainage device which is in strip form, / / 20317s 26Jmine6 3 Figure 9 is a cross-section through the drainage strip shown in Figure 8, Figure 10 diagrammatically illustrates one technique for fabricating the drainage strip shown in Figures 8 and 9, Figure 11 illustrates a typical application of the drainage strip, Figures 12 and 13 illustrate techniques for forming joints of the drainage strips, Figure 14 is a cross-section through another form 15 of drainage strip made Dy the method of the invention, Figure 15 illustrates a typical application of the drainage strip illustrated in Figure 14, and Figure 16 illustrates one technique by which the strips are driven into a soil mass.

The core structure illustrated in Figure l comprises core2 of plastics material such as high impact resistance polystyrene and preferably comprises a layer of bi-cuspated/material as disclosed in aj v \LwixC Augtaral 1041 Patent No. <16 0 , 84 9-. The core 2 is formed with regular arrays of projections 4 and 6 which project from opposite sides of the layer respectively, 30 as seen in cross-section in Figure 1 (which is a ■/ ✓ 203178 r > f' ' »• r o 4 sectional view taken along the line 1-1 marked on Figure 2).

The outer extremities of the protuberances 4 and 6 are flat and lie in respective planes 8 and 10. The exact profile of the protuberances 4 and 6 is not important but it is desirable that they have flat outer faces as illustrated.

Figure 3 illustrates in cross-section one embodiment which comprises the core 2 in the form of a sheet and having a web or fabric layer 12 connected to the outer faces of the array of protuberances 4 by means of a hot melt adhesive. It will be appreciated that there will be interconnected voids 14 defined between the web 12 and the core 2. The web 12 comprises a flexible sheet of water permeable material such as a geotextile filter fabric. One form of filter fabric comprises polyester spun-bonded filter material which is sometimes used in soil stabilization applications, one suitable textile being made by I.C.I. Limited and known as "TERRAM".

Figure 4 illustrates the preferred form in which the sheets of material are formed. In this arrangement it will be seen that the web 12 is wider than the core 2 and is arranged to overhang the core on either side thereof so as to form an upper flap 20 and a lower flap 22 of the geotextile material. For a core width of say 1.2 metres the upper flap 20 is say 10cm in width whereas the lower flap 22 is 35cm. The 1 1 2C>3i78^26J®tB» •"«••• material in this form can be formed in convenient lengths say 25 metres and transported in the form of a roll. The material in this form can be used most advantageously to form a sub-surface drain adjacent to 5 a retaining wall, embankment or other structure which is at least partially covered by soil.

Figure 5 schematically illustrates the use of the device of Figure 4 in draining a retaining wall 24. 10 The retaining wall has an inner face 26 against which the device is laid such that the projections 6 engage the face 26. A.-slotted conduit 28 is located adjacent to the foot 30 of the wall and the lower flap 22 of the device is wrapped about the conduit so as to 15 prevent soil entering the slotted conduit 28. The backfill material 32 may be then placed behind the wall such that it bears directly against the fabric layer 12, as shown. Moisture in the backfill 32 can seep through the layer 12 into the voids 14 so that it 20 will thereafter flow under gravity to the conduit 2 8 where it can be drained away, as required. The device is preferably fixed to the face 26 to avoid inadvertent displacement during backfilling.

Figure 7 shows one convenient technique for forming a joint between sheet drainage material of the type shown in Figure 4. It will be seen that the cores of the two sheets are overlapped in a manner which at least partially interlocks them and the flap 30 20 is made to overlie the fabric layer of the other device. A strip 3 3 of adhesive tape may be then t t ™ »***^. 203178 2 £ * / ' applied to cover any gap between the edge of the flap 20 and the underlying fabric layer 12.

Figure 6 illustrates a preferred way of 5 connecting the sheet material to the slotted conduit 28. In this arrangement, the conduit 28 is formed with an opening 3 4 which is large enough so that the lower edge of the core 2 can be inserted at least f"N partially into the core of the conduit. The arrangement is such that the opening 34 forms a mechanical interlock with the protuberances 4 and 6 of the core so as to retain the conduit 28 in position. The flap 22 is then passed about the conduit 28 as >. \ illustrated.

Figures 8 and 9 illustrate another form ofidevice made by the method of the invention in which the device is in the form of a drainage strip 35 which is more suited to drainage of water from damp ground, hillsides or highway 20 shoulders. The core 2 is preferably of the same construction as that described in Figures 1, 2 and 3 except however that it is usually say 4cm thick i.e. the spacing between the planes 8 and 10 is 4cm. The strips 35 can be made in standard widths say 20cm, 25 30cm, 60cm and 90cm and supplied in roll form in lengths of say 50 metres. In this arrangement, the layer 12 is wrapped about the strip of core material ^ so as to enclose the core. In the preferred V". ¥ construction the width of the fabric 12 is somewhat 30 greater than the periphery of the core in transverse section so that an edge region of the fabric forms an / 203178 overlapping flap 3 6 which is adhered to the underlying region of the fabric 12 by means of a line 38 of hot melt adhesive. One convenient arrangement for fabricating the drainage strips is diagrammatically 5 illustrated in Figure 10. In this arrangement, the core material 2 is supplied from a roll 40 thereof to an enveloping station 42. The layer 12 is supplied from a roll 44 thereof to the station 42 where it is wrapped about the strip of core. Within the station 10 42, the line 3 8 of adhesive is applied to the fabric layer just prior to the flap 36 being pressed into engagement with the underlying layer. In this arrangement there is no need for the core 2 to be bonded to the fabric layer 12 since it is snuggly 15 enveloped within the fabric layer.

Figure 11 illustrates a typical application of the drainage strips 35 shown in Figures 8 and 9. In this arrangement the strips are used for draining land 20 which is prone to become sodden. The first step is to dig a trench 46 which can be as narrow as say 10cm and to an appropriate depth. The strip is then inserted and the trench is backfilled with soil 48 to complete the subterranean drain. In most applications, the 25 depth of the trench can be kept constant and yet the drained water will still flow within the drainage strip, thus simplifying the trench digging.

Figure 12 illustrates a simple technique for 30 forming a joint between ends of two adjacent drainage strips. First of all, the fabric layers 12 at the KJ 11 FtBi933 'b 2031726'"tt"986 8 J ends of the drainage strips are peeled back so as to expose say 3 or 4 rows of protuberances. These rows of protuberances are interlocked as shown in Figure 12. Thereafter the fabric layer of one of the drainage strips is replaced and subsequently the end portion 50 of the fabric layer of the other drainage strip is then located so that it overlies the fabric layer of the other strip. A band 52 of adhesive tape completes the junction.

Figure 13 illustrates a technique whereby a T-joint can be conveniently made by a jointing technique analagous to that shown in Figure 12.

Briefly, part of the fabric layer 12 of each of the strips to be joined is partially removed to expose core portions. The exposed core end portion is then bent laterally and interlocked with the exposed portion of the core of the continuous strip. The adjacent fabric layers are folded to overlie one another, as illustrated.

Bands 52 of adhesive tape are then placed about the exposed edges of the fabric layers.

Buried ends of the strips can be covered by removal of part (say 7.5cm) of the core at the end of the strip and folding the free portions of the layer about the exposed end of the core. The folded layer can be retained in position by means of adhesive tape.

Figure 14 illustrates another form of drainage device in the form of a thin strip 53. In this 20317S arrangement the core 2 is made from plastic sheet material say 0.5mm thickness. The protuberances 4 and 6 are such that the overall thickness of the core is in the range 3-5mm and the spacing between the 5 protuberances 4 being say 25mm (as for the spacing between the protuberances 6). The width is preferably in the range 7.5 to 12.5cm and is supplied in rolls say 120m in length.

The drainage strips 53 are particularly suitable for deep de-watering of swampy land where construction or dry-fill is to be located.

Figure 15 illustrates a typical application of 15 the strips. As will be seen, the strips are disposed vertically and in a generally uniform array in the soil mass 54 to be drained. In a typical application, the strips 53 are located at 1.2 metre centres. The strips 53 extend to an appropriate depth usually in 20 the range of say 5 to 30 metres. A porous layer 56 say of sand is then formed at approximately ground level and the ends of the strips 53 extend into the layer 56. A layer 58 of backfill or soil is then placed on the layer 56 so as to increase the pressure 25 in the mass 54 to be drained. The arrangement is such that water will flow into the strips 53 and then will flow upwardly to the porous layer 56 where it is then ^ free to drain laterally. In this manner, the mass 54 can be effectively drained. i v ItfXfVY .11 FEB:r33 203178 Figure 16 schematically illustrates one arrangement for placement of the strips 53. In this arrangement, the strips 5 3 are located within a hollow driving member 60 which is arranged to be driven into the soil mass 54 by means of a pile-driver (not shown). A head piece 62 having the profile as illustrated can be located over the lower end of the member 60 so as to prevent entry of soil to its interior. The member 60 is then driven to the desired depth in the mass 54 and thereafter the member 60 withdrawn. The head piece 62 and strip 5 3 will be retained in the soil mass 54 by virtue of the lateral pressure of the soil. &Z.PA7"?;— 11 FEB 1933

Claims (4)

- 11 - 2 t WHAT HE CLAIM IS:

1. A method of making a drainage device comprising a core in strip form and water permeable geotextile filter fabric which envelops the core, said core being imperforate and having an array of protuber-5. ances and wherein said fabric spans said protuberances thereby defining interconnected spaces .i . which constitute a passage between the fabric .. and the core whereby, in use, water can pass through the fabric 'and then run in said 10. passage characterised in that said method comprises the steps of feeding the strip of core to a forming station, feeding a single strip of fabric to the forming station, folding the strip of fabric around the core such that one lateral edge of the strip of fabric 15. overlies one face of the core, applying bonding means to the strip of fabric adjacent said one lateral edge and overlapping the other lateral edge of the strip of fabric, whereby the strip of fabric encircles the core but is not bonded thereto, and withdrawing the 20. device in strip form from the forming station.

2. A method as claimed in Claim 1 wherein the bonding means comprises a hot melt adhesive and the method includes the step of pressing said overlapping edges together for sufficient time for said edges 25. to be bonded together.

3. A method as claimed in Claim 1 or 2 wherein the completed product is cut into predetermined lengths for rolling or folding in readiness for packaging.

4. A method of making a drainage device substantially as hereinbefore described with reference to the accompanying drawings. 7 W'helr .uchor|S«f A£Mt, A '■ WKrf SON 1 ' Mr'