AU686053B2 - Organic geotextile - Google Patents

Description

S F Ref: 351717 FORM COMMONWEALTH OF AUSTRALIA PATENTS ACT 1990 COMPLETE SPECIFICATION

(ORIGINAL)

S

Name and Address of Applicant: United Bonded Fabrics Pty Ltd t/as Felt Traders Araluen Street Kedron Queensland 4031

AUSTRALIA

Inventor(s): Address for Service: Spruson Ferguson, Patent Attorneys, Level 33 St Martins Tower, 31 Market Street, Sydney, New South Wales, 2000, Australia Complete Specification for the invention entitled: Organic Geotextile The following statement is a full description of this invention, including the best method of performing it known to me/us 5846 Organic Geotextile Technical Field The present invention is concerned with geotextiles and more particularly, with geotextiles for erosion control through soil stabilisation.

Background Art Erosion is a significant problem on unvegetated land, particularly if it slopes steeply, where water runs over that land. Any significant rainfall is likely to runoff the land causing rainfall and wash erosion. Particularly susceptible areas are river and creek banks and road cuttings.

1o It is well known that a slope which is subject to erosion can be stabilised if vegetation can be established on the slope, but vegetation will not establish itself when the top soil is being washed away periodically. A number of proposals to stabilise erosion banks using matting based on sugarcane bagasse, wood, wool or coconut fibres and including additives such as binding agents have had limited success.

Described in Australian Patent Application No. 40531/93 is an organic geotextile. Particularly disclosed in this earlier application is a geotextile having a density of between 300 g/m 2 and 400 g/m 2 and more particularly a geotextile having a density of 360 g/m 2 The present invention is an improvement in or modification of the invention disclosed in this earlier application. It has been found that a geotextile of lower density provides unexpected advantages in areas having a relatively low intensity rainfall. Furthermore, whilst a geotextile of the type described in Australian patent Application No. 40531/93 having a density of 360 g/m 2 has proved to be very effective in steep slope stabilisation, and erosion and sediment control and also to promote both primary and secondary grass covers, field experience has indicated a lighter grade of 25 geotextile is needed for different seasons and regions of Australia, in particular, a geotextile suitable for land stabilisation and rehabilitation in locations and seasons where erosive forces are not excessive.

Object of the Invention It is therefore an object of the invention to provide an organic geotextile which promotes soil stabilisation by substantially protecting the soil surface from rainfall erosion, reducing surface runoff and promoting water infiltration into the soil, and enhancing establishment of desirable vegetation through favourable soil moisture and temperature.

Disclosure of the Invention According to the invention there is provided an organic geotextile for soil stabilisation comprising a first layer of fine, intertwining fibres secured to a woven jute -t [N:\LLBT100990:hrw scrim constituting a second layer, said organic geotextile being adapted to be applied to an area of soil as a mat which serves to dissipate the hydraulic impact of rain drops and absorbs water whereby runoff is reduced, deep infiltration of water into the soil is promoted and the soil is substantially protected from rainfall erosion, said organic geotextile having a density between 180 g/m 2 and 300 g/m 2 Preferably, the scrim is of sufficiently open weave and said first layer is of sufficiently low density that desirable vegetation can penetrate said organic geotextile in growing therethrough. It is particularly preferred that the overall density of the geotextile be 200 g/m 2 for areas with very low intensity rainfall such as semi-arid or alpine areas, or 280 g/m 2 for temperate areas.

In a particularly preferred embodiment of the invention said first layer consists of a web of teased jute, flax, hemp, kenaf, ramie, coir, hennequin, sisal, cotton, or kapok fibres in isolation or combination.

In the geotextile industry, the term "density" is referred to in relation to an area rather than a volume. Thus, the person skilled in the field of geotextiles would consider the term "mass or weight per unit area" to be synonymous with the term "density" when referring to geotextiles and would use the units "g/m 2 The organic geotextile embodying the invention has a number of advantages.

In particular it provides a method of soil erosion control through a surface cover mat which increases water filtration, reduces surface run-off and minimises soil movement.

The promotion of vegetation establishment is preferably achieved by modifying the microclimate of the soil surface through partial shading, moderating the surface temperature, reducing water evaporation, improving the soil organic content and protecting the seedlings in the soil underneath from wind blast.

25 The interlocking fibrous layer of the organic geotextile embodying the invention contacts the soil in use and is of such a density that the spaces formed in between the weave of the jute scrim are preferably substantially covered by the S•interlocking fibres. The first layer of fine intertwining fibres attached to the woven jute scrim of the present invention absorbs the water droplets and conducts the water to the soil thereby feeding the soil underneath.

The organic geotextile of the present invention provides a high percentage surface cover (preferably 100% cover) to protect the soil surface from erosive rainfall and to intercept splashed soil particles. The composite geotextile embodying the invention is of such a density that light penetration is permitted therethrough and seedlings may grow through the geotextile. When wet, the geotextile swells up, producing a spongy cover which is very effective in reducing run-off but at the same time does not hinder seedling emergence.

In order to prepare the preferred geotextile described above, jute fibre is teased through a web forming machine such as a "Garnet" or a "Card". The web is then [N:\LIBT-]00990:hrw "lapped" on an "apron" and the jute scrim (which is woven in a separate operation) is laid on the web of jute fibre. The web with the scrim laid on top is then processed through a "needle punching machine". This machine comprises a plurality of barbed needles which move up and down through the web of jute fibre and have the effect of re-orientating certain individual jute fibres from the horizontal plane to the vertical plane thereby mechanically bonding the fibres together and joining the scrim to the web. This process is known as "felting" or needle punching. It is preferred that no bonding agent be added. The product is then trimmed to the desired width and thickness and cut into the desired length. Conveniently, the geotextile is sold in a roll 25-30 metres long by 1.83 metres wide and 3.0 millimetres thick, by way of example.

The jute used to form the teased jute fibre can come from a variety of sources such as new or recycled hessian fabric or bagging, compressed bales of jute fibre known as "caddies" or jute hessian off cuts known as "gunny cuttings". Any of these may be used individually or in combination.

S 15 A method using the geotextile embodying the present invention comprises the S.steps of: providing an organic geotextile comprising a first layer of fine, intertwining fibres secured to a woven jute scrim constituting a second layer, said organic geotextile being adapted to be applied to an area of soil as a mat which serves to dissipate hydraulic impact of rain drops and absorbs water, said organic geotextile having a density between 180 g/m 2 and 300 g/m 2 and (ii) laying said organic geotextile over the soil with said first layer in contact with soil.

~Preferably, said organic geotextile is secured in position, whereby runoff is reduced, deep infiltration of water into the soil is promoted and the soil is protected from rainfall erosion.

Preferably, the geotextile is fixed to the ground to ensure it remains in place.

oV 0* Pinning the geotextile at intervals to the ground also ensures that vigorous plant species such as millet do not lift the geotextile cover as they grow thereby reducing its effectiveness as an erosion control agent. Typically, pins would be driven in every 600-700 mm on a gentle slope and every 400 mm on a steeper slope at the joins between each roll of geotextile used or at a rate so stipulated by a site engineer or similar. Each roll would also be pinned with one pin on a gentle slope and two pins on a steeper slope in the centre of the roll at the same intervals as at the joins. At the top of a slope to be stabilised the cover may be pinned in a trench which is then filled in to hold the cover more securely. At the bottom of the slope the cover should be folded under the toe of the slope and secured under rocks where possible or pinned.

The ground may be pretreated by grading, filling and associated earthworks, then provided with top soil, desired seed and fertiliser prior to covering the ground with [N:\LIBT]00990:hrw the geotextile cover. It would then be expected that vegetation will appear through the cover within one to two weeks if a vigorous species such as millet is chosen.

Preferably, a mixture of fast growing species such as millet and more desirable species such as couch, acacia, eucalypt, etc. is used. Tree and shrub species may be planted in seed form under the mat or, once the vegetation or grass is established, by cutting holes in the cover and planting them in those holes.

Brief Description of the Drawings In order to more fully describe the invention reference will now be made to the accompanying drawings in which: 1o Figure 1 is a schematic diagram of one illustrative example of a geotextile in accordance with the invention suitable for soil stabilisation and establishment of desirable vegetation Figure 2 is a graph showing the emergence of Japanese millet seedlings through an organic geotextile embodying the invention; and S. 15 Figure 3 is a graph showing the emergence of green couch seedlings through an organic geotextile embodying the invention.

.9.9 S°Best Mode for Carrying out the Invention Figure 1 shows schematically a geotextile 10 having a bottom layer 12 which contacts the soil to be stabilised consisting of low density teased jute fibre and a top S 20 layer 11 of jute scrim. The jute scrim used herein is a very open weave of jute fibres.

S"The product is nominally 3mm thick, and has a density of between 180 g/m 2 and 300 g/m 2 Emergence Test The seeds used in this test were Japanese millet and green couch, which have S 25 different growth characteristics from each other and different seed sizes, and represent grasses commonly used for land stabilisation and rehabilitation.

Seeds of Japanese millet (0.3g) and green couch (0.2g) were sown into 250 x 400 mm plastic trays which were filled with garden soil to a depth of 100 mm. After sowing, the soil surface of respective trays was covered with one or other of an organic geotextile according to the present invention having a density of 200 g/m 2 an organic geotextile according to the present invention having a density of 280 g/m 2 or an organic geotextile comprising a woven jute scrim to which is attached a fibrous layer, the composite having a density of 360g/m 2 as described in Australian Patent Application No. 40531/93. One tray was left with a bare soil surface to act as a control. Clothes pegs and metal pins were used to ensure good soil contact.

[N:\LIBT'100990:hrw The test was conducted in a glasshouse over a period of four weeks. Watering was carried out at least twice a week and seedling emergence was recorded daily over the test period.

Results Very good emergence was recorded for both species of seedlings in all three grades of organic geotextile after twenty two days. Due to the smaller seed size and therefore smaller seedlings, emergence of green couch was recorded best on the lighter 200 g/m 2 grade of geotextile. There was little difference in emergence of millet seedlings through the three grades of geotextile.

Figure 2 shows that 85 of Japanese millet seedlings emerged from all three grades of geotextile after five days, whereas green couch seedlings only reached an 88% emergence rate after eleven days, the latter only with respect to the geotextile having a density of 200 g/m 2 However 71% to 79% emergence of green couch seedlings was reached after twenty two days on all three grades of geotextile tested, as 15 shown in Figure 3.

The data presented in Figures 2 and 3 indicates that for larger seeds such as millet there was little difference in the emergence rate between the three grades.

However, with smaller seeds such as green couch, much higher and earlier emergence was recorded for the organic geotextile embodying the invention and having a density 20 of 200 g/m 2 In terms of ground surface protection against erosive forces, generally the heavier the grade of geotextile, the more effective it is. Therefore the organic geotextiles having a density of 360 g/m 2 or 280 g/m 2 are more effective in erosion and sediment control than the geotextiles having the lower 200 g/m 2 density. However, organic geotextiles having a density of 360 g/m 2 have much slower and lower rates of emergence for small seeded species than the organic geotextiles embodying the present invention having densities of 200 g/m 2 and 280 g/m 2 [N:\LIBTI]0099:hrw

Claims (6)

1. An organic geotextile for soil stabilisation comprising a first layer of fine, intertwining fibres secured to a woven jute scrim constituting a second layer, said organic geotextile being adapted to be applied to an area of soil as a mat which serves to dissipate the hydraulic impact of rain drops and absorb water whereby water runoff is reduced, deep infiltration of water into the soil is promoted and the soil is substantially protected from rainfall erosion, said geotextile having a density between 180 g/m 2 and 300 g/m 2

2. An organic geotextile as claimed in claim 1 wherein the scrim is of sufficiently open weave and said first layer is of sufficiently low density that desirable vegetation can penetrate said organic geotextile in growing therethrough.

3. An organic geotextile as claimed in any one of the preceding claims, having a density of 200 g/m 2

4. An organic geotextile as claimed in any one of claims 1 or 2, having a S 15 density of 280 g/m 2

5. An organic geotextile as claimed in any one of the preceding claims wherein said first layer comprises a web of teased jute, flax, hemp, kenaf, ramie, coir, hennequin, sisal, cotton or kapok fibres, either alone or any combination thereof.

6. An organic geotextile substantially as hereinbefore described with reference to Figure 1 of the accompanying drawings. Dated 13 September, 1996 United Bonded Fabrics Pty Ltd Patent Attorneys for the Applicant/Nominated Person SPRUSON FERGUSON j [N:\LIBTT]00990:hrw