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Title:
GEOTEXTILE PROTECTION MATERIAL
Document Type and Number:
WIPO Patent Application WO/2001/077436
Kind Code:
A1
Abstract:
Disclosed is a geotextile (5) comprising at least a first layer being formed at least partly from a granular material, particularly rubber crumbs (10), for lining landfill sites. The geotextile uses recycled vehicle tyre rubber and protects the membrane liners placed in landfill sites.

Inventors:
Guild, Robin (Don & Low Limited Newfordpark House Glamis Road Forfar, Angus DD8 1FR, GB)
Hoy, Gregor (Don & Low Limited Newfordpark House Glamis Road Forfar, Angus DD8 1FR, GB)
Application Number:
PCT/GB2001/001605
Publication Date:
October 18, 2001
Filing Date:
April 06, 2001
Export Citation:
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Assignee:
DON & LOW LIMITED (Newfordpark House Glamis Road Forfar Angus DD8 1FR, GB)
Guild, Robin (Don & Low Limited Newfordpark House Glamis Road Forfar, Angus DD8 1FR, GB)
Hoy, Gregor (Don & Low Limited Newfordpark House Glamis Road Forfar, Angus DD8 1FR, GB)
International Classes:
B32B27/12; D06N7/00; E02D31/00; (IPC1-7): D06N7/00; B32B27/12; E02D31/00
Foreign References:
US5544976A
DE19617317A1
EP0629746A2
EP0736633A1
EP0490529A1
EP0059625A1
EP0436928A1
Attorney, Agent or Firm:
Mccallum, William Potter (Cruikshank & Fairweather 19 Royal Exchange Square Glasgow G1 3AE, GB)
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Claims:
CLAIMS
1. A geotextile comprising at least a first layer being formed at least partly from a granular material.
2. The geotextile of claim 1 which includes a further layer, for example a substrate layer.
3. The geotextile of claim 2 wherein said substrate layer and first layer are in intimate contact, and adhered, one to the other.
4. The geotextile of claim 2 or claim 3 wherein the substrate layer is a fabric layer.
5. The geotextile of claims 1 to 4 wherein said first layer is formed substantially from said granular material.
6. The geotextile of claim 4 wherein said fabric layer is a woven or nonwoven fabric.
7. The geotextile of claim 6 wherein said fabric comprises polyethylene or polypropylene.
8. The geotextile of claim 7 comprising a woven fabric made wholly from polypropylene.
9. The geotextile according to any of claims 6 to 8 wherein said fabric comprises a plurality of threads in the form of tapes.
10. The geotextile according to any previous claim wherein at least a part of said granular material comprises an organic polymeric material.
11. The geotextile of claim 10 wherein said organic polymeric material is chosen from the group consisting of polyethylene, polypropylene, or natural or synthetic rubbers or mixtures or copolymers thereof.
12. The geotextile of claim 11 wherein said granules comprise a rubber material.
13. The geotextile of claims 11 or 12 wherein said granular material additionally comprises further materials chosen from the group consisting of carbon black, vulcanising agents, sulphur, calcium carbonate, mica, talc, clays and metals.
14. The geotextile of claim 4 at least a first layer is. adhered intimately to the substrate layer.
15. The geotextile of claim 14 wherein said granular material is adhered by use of a glue being a natural rubber latex and/or synthetic latex binder.
16. The geotextile of claim 15 wherein said first layer has a thickness in the range 3 mm10 mm.
17. The geotextile of claim 16 wherein said first layer has a thickness of 4 mm or 6 mm.
18. The geotextile of any previous claim wherein said granular material comprises rubber granules.
19. The geotextile of claim 18 wherein said rubber granules are in the form of rubber crumb obtained from disused vehicle tyres.
20. The geotextile to any previous claims wherein said granular material comprises granules in the size range 0.1 mm to 6.0 mm.
21. The geotextile of claim 20 wherein the granule size range is 0.5 mm to 2.0 mm.
22. A geotextile comprising at least a first layer being formed at least partly from a granular material fixed intimately to a substrate layer formed from a woven fabric.
23. Use of a material comprising a first layer being formed at least partly from a granular material as a landfill liner or as a contaminated land remediation liner.
24. A landfill site or brown field site including a liner comprising a geotextile comprising at least a first layer being formed at least partly from a granular material.
25. A method of lining a landfill site or contaminated land site wherein said method comprises: providing a geotextile comprising at least a first layer being formed at least partly from a granular material; and laying said geotextile within the landfill site.
26. The method according to claim 25 wherein said method includes the further step of providing a membrane next to or adjacent to said geotextile.
27. The method according to claim 26 wherein said landfill site provides a surface, and wherein said geotextile is placed on or adjacent to at least a portion of said surface.
28. The method according to claim 27 wherein there is provided a second layer being a geotextile comprising at least a first layer being formed at least partly from a granular material.
29. The method according to claim 28 wherein said first and second layers are separated by a liner or membrane.
30. The method according to claim 29 wherein there is provided on a surface of said second layer, remote from said first layer, an angular aggregate layer.
31. The method according to claim 30 wherein a layer of sand is provided on a surface of the aggregate layer.
Description:
GEOTEXTILE PROTECTION MATERIAL The present invention relates to geotextile protection materials. In particular, though not exclusively, the present invention relates to a geotextile for use as a protecting layer in landfill waste sites.

Landfill sites produce environmentally damaging leachates and methane gas due to decomposition of the waste materials contained in them. The leachates must therefore be contained. The methane gas should also be contained and dispersed in a controlled and safe manner since it is flammable and also a"green house"gas.

Containment is presently achieved by using thick impermeable plastic sheeting, typically polypropylene or polyethylene, to line the landfill cavity before filling with waste material. However, although the plastic liner is relatively thick and robust, some form of protection is needed to prevent damage or puncture to the liner.

Typically protection is achieved by using a thick non- woven fleece type geotextile. This is more advantageous than eg. thick blankets of fine soil or sand or a layer of discarded automobile tyres, since these latter methods do not guarantee a constant level of protection, are difficult to manage, and also take up valuable tipping volume because they form thick layers within the landfill site cavity.

Although non-woven fleece material is currently preferred, this has the disadvantage that a preferred standard of protection is achieved by using relatively high quality"virgin"polymer eg. Polypropylene rather than recycled polymer, and hence the price can be relatively high which can change dramatically in relation varying

global polymer prices. Use of virgin polymer also has environmentally unfriendly implications.

An object of the present invention is to obviate or mitigate the above mentioned disadvantages.

According to a first aspect of the present invention there is provided a geotextile comprising at least a first layer being formed at least partly from a granular material.

A geotextile is a textile material used for example in civil engineering.

Preferably the geotextile is adapted to be used as a landfill liner or as a contaminated land remediation liner.

Preferably the geotextile includes a further layer, for example a substrate layer.

Preferably the substrate layer and first layer are in intimate contact, and are preferably adhered, one to the other.

Preferably the substrate layer is a fabric layer.

Preferably also the first layer is formed substantially from the granular material.

Preferably also at least a part of said granular material comprises an organic polymeric material.

The fabric layer may be for example a woven or non- woven fabric. Said fabric may be wholly or partially made, from, for example, a polyolefin such as polyethylene or polypropylene. A woven fabric made wholly from polypropylene may be preferred. Threads of said fabric layer may be of any suitable shape for weaving. Preferably the threads are in the form of tapes, wherein said tapes preferably possess a high elasticity. A woven fabric layer comprising such tapes may be woven on a loom, and the

resultant fabric preferably possesses a high tensile strength such as about 24-25kN/m (measured according to BS EN 150 10319) in both the warp and weft directions. Such a fabric typically also has an elongation to break being about 15% as determined using BS EN 150 10319 method. Such a fabric should also ideally be puncture resistant, preferably to a high degree; typical push through resistance is 3000N as determined using BS EN 150 12236, and cone drop penetration of 13mm as measured using the method according to BS EN 918.

A typical fabric width is 4 metres, however, smaller or larger widths are possible. Fabrics of a width which is larger than that produced on a typical single loom may be produced by joining fabrics of smaller width by bonding or sewing the long edges thereof.

The granular material may comprise any suitable organic polymer. The size of the granules is typically in the range 0. lmm to 6. Omm, preferably 0. 5mm to 2. Omm.

Generally, the granular material will comprise granules wherein the size thereof is distributed between the ranges given above. The granules may be of any desirable shape; generally spherical being preferred. The surface of the granules may be generally smooth, but more preferably and typically rough and/or uneven.

Suitable organic polymers of which the granules are comprised may be chosen from the group consisting of polyethylene, polypropylene, or natural or synthetic rubbers or mixtures or copolymers thereof.

All of the granules of the granular material may -comprise one type of organic polymer chosen from the group listed above. Alternatively some granules of the granular

material may comprise one type of organic polymer chosen from the list above and other granules another type of organic polymer chosen from the list above. The granular material may therefore comprise one or more than one type of granule as defined by the polymer from which it is comprised. Furthermore, some or all of the granules may be comprised from at least two types of organic polymer.

Each granule, whether comprised of one or more types of organic polymer, may additionally comprise further materials, for example carbon black, vulcanising agents, sulphur and fillers such as calcium carbonate, mica, talc, clays and metals.

Preferably the granules comprise a rubber material.

A convenient source of such granules is"rubber crumb" manufactured from disused vehicle tyres, such as automobile tyres.

In a preferred embodiment, a woven fabric is used, to which is bonded granules formed from the rubber of automobile tyres. It will be appreciated by the skilled person that the granules and woven fabric may be bonded together by any suitable method. Preferably a glue is used which is typically a natural rubber latex and/or synthetic rubber latex binder.

Typically the thickness of the rubber crumb layer may be in the range 3mm-10mm, with around 4mm or 6mm being preferred.

The geotextile is generally comprised of one woven fabric layer and one rubber crumb layer bonded thereto.

However other configurations may be envisaged such as rubber crumb applied to both sides of the woven fabric, without departing from the scope of the invention disclosed

herein.

According to a second aspect of the present invention there is provided use of a material comprising a first layer being formed at least partly from a granular material as a landfill liner or as a contaminated land remediation liner.

According to a third aspect of the present invention there is provided a landfill site or brown field site including a liner comprising a geotextile according to the first aspect.

According to a fourth aspect of the present invention there is provided a method of lining a landfill site or contaminated land site wherein said method comprises : providing a geotextile according to the first aspect of the present invention; and laying said geotextile within the landfill site.

Preferably the method according to the fourth aspect includes the further step of providing a membrane next to or adjacent to said geotextile.

Preferably the landfill site provides a surface, the geotextile being placed on or adjacent to at least a portion of the surface.

Preferably there is provided a second layer according to the first aspect of the present invention.

Preferably the two layers according to the first aspect are separated by a liner or membrane.

Preferably there is provided on a surface of the second layer, remote from the first layer, an angular aggregate layer.

Preferably on a surface of the aggregate layer there is provided a layer of sand or the like.

It will be understood by the skilled person that the geotextile of the present invention may be used in conventional land fill sites in any manner suitable for lining such sites. For example one or more layers of the said geotextile may be used.

It will be understood that further embodiments of the present invention may be envisaged, without departing from the scope of the invention described herein, for example a geotextile may be provided integrally with a membrane for use in landfill sites directly. Furthermore the geotextile described herein may be used in other civil engineering applications, for example where protection of a membrane or other material may be required.

Typically a geotextile is or comprises a strong fabric used for example in road making and for the stabilization of embankments and other civil engineering applications.

The present invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a schematic cross sectional view of a geotextile in accordance with an embodiment of the first aspect of the present invention.

Figure la shows an enlarged portion of Figure 1.

Figure 2 is a schematic cross sectional view of a landfill site according to an embodiment of the third aspect of the present invention, which includes a geotextile in accordance with an embodiment of the first aspect of the present invention.

Figure 2a shows an enlarged portion of Figure 2.

Figure 3 is a schematic cross-sectional view of a cylinder test rig for determining the protective effectiveness of a geotextile.

The geotextile 5 according to an embodiment of the first aspect of the present invention as shown in Figure 1 comprises a rubber crumb layer 10 bonded to a substrate layer 15, this being a woven fabric.

Figure la shows the rubber crumb granules 20 are bonded to each other and to the fabric layer 15 by means of an adhesive/glue 25.

The fabric layer in this embodiment is a woven fabric and can be obtained from Don & Low Limited Wovens, under the trade'name"Lotrak 25/25". Typical properties of Lotrak 25/25 are represented in Table 1 below.

TABLE 1 The figures quoted are the mean of several tests. Tensile strength (kN/m) Warp 25 BS EN ISO 10319 Weft 24 Elongation at break (%) Warp 15 BS EN ISO 10319 Weft 15 CBR Push through resistance (N) 3000 BS EN ISO 12236 Cone Drop Penetration (mm) 13 BS EN 918 Pore Size 90% finer than (microns) 150 BS 6906 Part 2 Water flow normal to plane 15 (1/m2/sec) BS 6906 Part 3 Effect of uV Light The polypropylene used contains a W inhibitor Weight (g/m2) 120 BS EN 965: 1995 Fabric thickness under 2kN/m2 (mm) 0.5 BS EN 964-1 : 1995 Minimum Overlap (mm) 400 LOTRAK 25/25 incorporates an overlap marker set at the above minimum. Over areas of soft soil this overlap may require to be increased. RollSizes Standard Widths (m) 5. Om Longer lengths are available Standard Lengths (m) 100m

Figures 2 and 2a show a cross sectional view of a typical landfill site 30 and an enlarged portion thereof respectively. The site incorporates two layers of the geotextile 5 separated by a high density polyethylene liner 35 disposed between the layers 5.

The three layer construct: geotextile 5, liner 35, geotextile 5 is further protected by a layer of granular material for example angular aggregate 40 and a layer of sand 45. The geotextile on either side of the liner 35 helps protect the liner 35 from damage and punctures, thereby maintaining its effectiveness in seeking to prevent escape of leachates into the surrounding ground.

The protective effectiveness of the geotextile 5 was determined using the apparatus shown schematically in Figure 3. The test used the method in the UK Environment Agency document"A methodology for cylinder testing of protectors for geomembranes. A performance test for determining the protection afforded to a geomembrane by a geotextile or other protective material in specific site conditions". Thus protection afforded by the geotextile 5 to a high density polyethylene liner can be determined using this method.

The test was conducted by assembling the test rig as shown under the conditions of standard atmosphere this being 65 2% relative humidity and 202°C. The geotextile 5 was also pre-conditioned under these atmospheric conditions and temperature for at least 24 hours prior to commencement of the test. The following materials were loaded into a steel cylinder 60 having a diameter of 300mm as shown : Loading plate 65 having a diameter of 4mm smaller than

cylinder 60 ( 1mm).

Sand 70 conforming to type medium in BS 882; the depth of sand layer is 50mm.

Separator geotextile 75,300mm diameter, to prevent the sand 70 from mixing with the aggregate 80.

Aggregate 80 having-a nominal diameter of 20mm, being an angular aggregate.

Geotextile 5 being a composite of Lotrak 25/25 and rubber tyre crumb.

Liner 35 being a 2mm thick, smooth, high density polyethylene liner.

Lead impression plate 85 being 1. 3mm thick and conforming to grade 3 of BS 1178. The diameter of the lead plate 85 being 4mm smaller than cylinder 60 ( 1mm). The deformation characteristics and flatness of the plate 85 were as specified in the Environment Agency method quoted above.

Dense rubber pad 90 being 25mm thick and having a diameter 4mm smaller than cylinder 60 (+ lmm). The Shore Hardness of the rubber pad 90 should be 50A 5% according to ISO 7619.

Lower support plate 95 having a thickness of 20mm and a diameter of 4mm smaller than cylinder 60 ( 1mm).

Three calibrated load cells 100 are positioned at the base of the cylinder 60.

A load pressure of 500 kPa measured by the load cells 100 was then applied to the assembly using a pneumatic ram 50. This pressure was maintained for 100 hours. Values of pressure were observed at intervals as specified in the Environment Agency document and a continuous record of the pressure was made using a data logging system.

The settlement of the loading plate 65 was also recorded using the displacement gauge 55. i After maintaining the load pressure for 100 hours the assembly was dismantled carefully to remove the geotextile 5, liner 35, and lead plate 85.

Indentations made in, or deformation of, the lead plate 85 are a measure of the effectiveness of the protector geotextile 5. The lead plate 85 was examined for any indentations, and three indentations which appeared to have the greatest deformation were selected. Indentations at 25mm or less from the edge of the lead plate 85 were not considered in the measurements.

For each of the three selected indentations, two axes at right angles to each other were marked. The axes were in the plane of the lead plate. Starting at one edge of one of the indentations, the depth (ie. the vertical displacement) of the indentation in the lead plate was measured (to the nearest O. 01mm). This was repeated at 3mm intervals along one of the axes, until the other edge of the indentation was reached. The edge of the indentation was defined as a point where two consecutive readings 3mm apart had a vertical height difference of less than or equal to 0.06mm. The vertical height measurements were repeated in the same way as described above along the other axis of the same indentation.

The above procedure was then repeated for the remaining two chosen indentations each with two axes.

The local and incremental strains for each of the six axes were then calculated. The incremental strain values (in o) are shown in table 2.

TABLE 2

Indentation Axis Designation designation North-South (NS) East-West (EW) Mean Value (NS+ EW)/2) 1 0.10849 0.1089 0. 109 2 0.0760 0.1194 6.098 3 0. 09175 0. 1522 0. 122 The overall mean strain value was calculated to be 0. 1090. A mean strain value of less than 0. 25% is considered acceptable for a geotextile for use as a protection geotextile.

The geotextile 5 was visually examined, and it showed very little sign of any permanent deformation and nor. was it torn or punctured. The liner 35 was not permanently deformed, torn or punctured either.

The above described test shows that the geotextile 5 is able to absorb stresses applied to it without extending or deforming. This is important because if deformation was to occur, stresses may be applied to the liner 35 causing it to weaken or even burst or puncture. However advantageously, the geotextile 5 is not too stiff, which thus allows it to conform to the shape of the liner 35 by "following it"should settlement occur in a landfill site such as 30. If the geotextile 5 did not deform in this way due to it being too stiff, its protecting effect could be impaired. These properties of the geotextile 5 are due in part to the woven fabric 15 of which it is comprised. This fabric has strain characteristics which enable it to develop a large proportion of its tensile strength at very

low levels of extension, while allowing the geotextile 5 to conform to the shape of the liner 35 in the landfill site in the event of settlement.

The test also shows that the geotextile 5 has a good resistance to puncturing since no punctures were observed following the test.

For the avoidance of doubt the foregoing examples should not be taken to limit the scope of the invention as described herein in any way.