AU657819B2 - Organic geotextile - Google Patents

Description

6578 19 P/00/011 Regulation 3.2 COMMONWEALTH OF AUSTRALIA Patents Act 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT Name of Applicant: Actual Inventor(s): Address for Service: Invention Title: S Details of Associated Provisional Application: UNITED BONDED FABRICS PTY. LTD.

trading as FELT TRADERS (ACN 000 430 124) MARK ALFRED DE FINA

AHEARNS

Patent Trade Mark Attorneys, GPO Box 185, Brisbane, 4001 "ORGANIC GEOTEXTILE" No: PL2579 filed 22 May 1992 The following statement is a full description of this invention, including the best method of performing it known to Sus t s The present invention is concerned with geotextiles and more particularly, with geotextiles for soil stabilisation.

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 run off the land causing rainfall and wash erosion. Particularly susceptible areas are river and creek banks and road cuttings.

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.

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

0It is a further object of the invention to provide an organic geotextile which suppresses growth of undesirable vegetation by providing a physical barrier to growth of the 4 vegetation and sunlight blockage, promoting water infiltration and reducing runoff and evaporation.

According to one broad aspect of the invention there is provided an organic geotextile for soil stabilisation 3 comprising a first layer of fine, intertwining tibres secured eto a woven 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 run off is reduced, deep infiltration of water into the soil is promoted and the soil is protected from rainfall erosion.

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 Sdensity of the geotextile be 300 to 400 grams/metre 2 and, more particularly, 360 grams/metre 2 Alternatively, the geotextile may further comprise a third layer of fine, intertwining fibres secured to the scrim on the other side of the scrim to said first layer.

Preferably, the first layer, the scrim and the third layer are of sufficiently high density that vegetation cannot penetrate said organic geotextile. More particularly, the organic geotextile has a density between 600g/m 2 and 700g/m 2 preferably 620g/m 2 In a particularly preferred embodiment of the invention Ssaid first layer consists of a web of teased jute fibres e-adth scrim is a jute srim. Preferably said third layer, where present, also consists of a web of teased jute fibres 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 "lapped" on .3 4 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 plan 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.

According to a further broad aspect of the invention there is provided a method of stabilising soil comprising the steps of:providing an organic geotextile comprising a first layer of fine, intertwining fibres secured to a woven scrim constituting a second layer, said organic geotextile being adapted to be applied to an area of o, soil as a mat which serves to dissipate hydraulic V -Q, impact of rain drops and absorbs water; laying said organic geotextile over the soil with said first layer in contact with soil; and _o ptonal-y, securing said organic geotextile in position; whereby run off is reduced, deep infiltration of water into the soil is promoted and the soil is protected from rainfall erosion.

According to a still further broad aspect of the invention there is provided method of stabilising an area of soil that is vulnerable to erosion and establishing desirable vegetation in said area comprising the steps of:providing an organic geotextile comprising a first lowdensity layer of fine, intertwining fibres secured to an open-weave woven scrim constituting a second layer, said organic geotextile being adapted to be applied to said area as a mat which serves to dissipate the hydraulic impact of rain drops and absorbs water; laying said organic geotextile over said area with said first layer in contact with the soil; oGpti-&alysecuring said organic geotextile in position; and allowing desirable vegetation to grow through said organic geotextile; whereby run off in said area is reduced, deep Sinfrilation of water into the soil is promoted and the soil is protected from rainfall erosion.

Prforably, -he geotextile is fixed to the ground to ensure it remains in place. Pinning the geotextile at intervals to the ground also ensures that vigorous plant r '<7x y u 6 species such a 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 fertilizer prior to covering the ground with 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.

According to yet another broad aspect of the invention there is provided method of stabilising soil and preventing growth of undesirable vegetation in the soil comprising the steps of:providing an organic geotextile comprising a first high density layer of fine, intertwining fibres secured to a high density woven scrim constituting a second layer and a third high density layer of fine, intertwining fibres secured to the other side of the scrim, 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; laying said organic geotextile over the soil with either said first layer or said third layer in contact with soil; and e!14yr, securing said organic geotextile in position; whereby run off is reduced, deep infiltration of water into the soil is promoted and the soil is protected from rainfall erosion, said organic geotextile acting as a barrier to prevent growth of undesirable vegetation.

Preferably, the geotextile is nominally 6 mm thick, has an overall density between 600g/m 2 and 700 g/m 2 more preferably, of 620 g/m 2 and is thus sufficiently dense that it provides a physical barrier to weed growth as well as preventing sunlight reaching any weeds already growing in the vicinity of the young trees. Competition for nutrients and sunlight is therefore reduced and growth of the trees is enhanced. The growth of trees on land susceptible to erosion further serves to stabilise that land but the method of enhancing the growth of young trees according to the present 8 invention is not limited to that application and is generally applicable to gardening and horticulture.

In order to more fully describe the invention reference will now be made to the accompanying drawings in which:- Figure 1 is a schematic diagram of one illustrative example of a geotextile in accordance with invention suitable for soil stabilisation and establishment of desirable vegetation, and Figure 2 is a schematic diagram providing a partially exploded view of one illustrative example of a geotextile in accordance with the present invention suitable for use as a weed barrier.

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 layer 11 of jute scrim. The jute scrim used herein is a very open weave of jute fibres. The product is nominally 3 mm thick, has a density of 360 g/m 2 and is to be referred to through the specification as"JUTEMASTER FM".

Figure 2 illustrates a geotextile 20 having a top layer 23 and a bottom layer 22 of teased jute fibre. Each of the layers is attached to the middle layer 21 which is a jute scrim, although layer 23 is shown spaced fro the scrim so that the location of the scrim can be seen. The product is nominally 6 mm thick, has a density of 620 g/m 2 and is to be referred to throughout the specification as "JUTEMASTER

TM".

I

Example ExamplExample 1 Example 1

MATERIALS

Jutemaster FM and Jutemaster TM were subject to a rainfall simulator evaluation using a soil which has been shown to be highly erodible. It is hard setting sand loam about deep, overlying a dense clay which becomes increasingly sodic with depth. It has the following physical and chemical characteristics.

Soil type: sodic red brown earth Clay content: 26% Silt content: 14% Sand content: pH: 7.1 Cation Exchange Capacity (CEC): 16 meg/100g Rainfall: Simulated rainfall using a rotating disc rainfall simulator was applied for 30 minutes at 65 mm/h and minutes at 130mm/h. The high intensities were chosen to highlight the effectiveness of the geotextile against typical short, heavy storm in northern Australia. The occurrence of minutes of rain at 65 mm/h would be an annual event in most parts of Queensland. The 130 mm/h rain represents exceptional but not unusual storms in the tropics.

The total rainfall for the low and high intensities were 16.3 and 32.5 mm respectively.

Slope gradient: three gradients were tested: 3:1, 4:1 and 10:1. These gradients cover the range of slopes often F- .1 requiring geotextile materials for stabilisation.

Sample preparation: After removing large rocks and fore.Ign materials, the soil was firmly packed 'nto galvanised steel boxes (250 mm wide, 450 mm long and 75 mm deep). The soil surface was covered completely by either Ju',emaster FM or TM.

The boxes were filled with special spouts to collect runoff water and were tilted to the required gradients on a stand. For each simulator run, two boxes were used.

Replication: Each treatment (geotextile grade X gradient) was replicated twice.

Data Collection For Each run the following data were collected: Runoff Rate Total runoff Total soil movement Depth of wetting at 30 cm from the collecting spout From these results, water infiltration rate, total infiltration and rainfall before runoff were calculated.

Results on water runoff and soil moisture tests.

Surface runoff: Following rain the amount of water that cannot be absorbed by the soil will run off, the runoff quantity depends greatly on the surface cover, soil roughness and land slopes. Results from Table 1 clearly show that both Jutemaster FM and TM reduce runoff greatly, particularly under high rainfall intensity.

Under low rainfall intensity conditions, where minimum t i

M

!ii 11 runoff would be expected on bare soil surface, runoff was reduced by more than 50% under Jutemaster FM and up to under Jutemaster TM on all slope gradients.

The effectiveness of both grades was best demonstrated under high rainfall conditions. The average reduction of runoff was up to 90%. These results clearly demonstrate the suitability of Jutemaster FM for steep slope stabilisation.

The uniformity of the results between replications indicates that the variation in mat density is minimal and quality control is satisfactory.

Table 1: Runoff as a percentage of total rain.

SLOPE GRADIENTS RAINFALL SURFACE SO G I INTENSITY COVER 10:1 4:1 3:1 3are 33 23 Lowv mm,'h) FM 10 13 TM 7 5 3 Sare 52 2 39 Hich (130 mm/h) FM A 3 TM 3 2 Water Infiltration: SWater infiltration into the soil depends greatly on the soil surface cover which protects the roughness of soil surface (soil surface structure) and also to slow down the movement of water thus enhancing the water entry/absorption to the soil Results shown in Table 2 demonstrate the effectiveness of both Jutemaster FM and TM in improving water infiltration to the soil. Almost total absorption were recorded under both low and high rainfall intensities and at all three gradients for both grades. This can be explained by the fact that surface soil structure under Jutemaster remained almost intact after 30 minutes of rain while the bare soil surface structure was completely destroyed.

Table 2: Water infiltration as a percentage of rainfall.

SLOPE GRADIENTS RAINFALL SURFACE

L

INTENSITY COVER 10:1 4:1 3:1 Bare 67 77 Lcw mm/h) FM 90 87 cO TM 93 94 92 Eare i8 58 51 Hich mm/n) FM 96 97 15 TM 97 98 Time before runoff occurred: The results presented above can be best seen in terms of the time elapsed before runoff occurred. Table 3 shows that S 20 under low intensity rainfall (65mm/h) runoff occurred [Bproximately 13 minutes after rain on bare soil on all slope gradients. Under high rainfall intensity (130mm/h) runoff occurred only 7 minutes after rain.

However, when soils surface was protected by either Jutemaster FM or TM, no runoff occurred at the end of the experimental periods (30 for low intensity and 15 minutes for high intensity rainfall). Both soil erosion and soil moisture levels are inversely related to runoff quantity and .3 13 rate. These results further indicate the suitability of both grades of Jutemaster in soil erosion control.

Table 3: Time (minutes) before runoff occurred.

SLOPE GRADIENTS RAINFALL SURFACE INTENSITY COVER 10:1 4:1 3:1 Bare 10 16 12 Low mm/h) FM 30+ 30- TM 30+ 30+ Bare 7 8 7 High S(130 mm/h) FM 15-+ 5+ TM 15- 15+ and 30+ indicating no runoff occurred at the end of experimental periods of 15 and 30 minutes respectively.

Depth of wetting: Soil protected by both Jutemaster FM and TM were almost completely saturated with water under both rainfall intensities and all three gradients. These are in sharp contrast with the bare soil where only up to two thirds of the soil profile were wet (Table 4).

Table 4: Wetting depth 30 cm from the collection spouts.

I SLOPE GRADIENTS RAINFALL

SURFACE

INTENSITY COVER 10:1 4:1 3:1 Sare 50 50 Low mm/h) FM 75 73 73 TMM /0 :15 .20 High (130 mm/h) caETV 7F; -'0 .5 o Completely saturated.

Results on soil loss: Results on Table 5 clearly show that both Jutemaster FM and TM were highly effective against soil erosion. When soil surface was bare, soil losses increased as slope gradient increased particularly under high rainfall intensity. When the surface was protected by either FM or TM grades, soil losses was virtually stopped even under high rainfall intensity.

These results indicate that for general slope stabilisation Jutemaster FM is an extremely effective geotextile in soil erosion control Table 5: Soil concentration in runoff water SLOPE GRADIENTS 15 RAINFALL SURFACE S:NTENSITY COVER 10:1 4:1 3:1 Sara 12.5 51.1 60.8 L Dw rm/h) FM 0 0 0 TM 0 0 0 Sara 154.6 i 236.3 253.

H!cn (130 mm/h) FM 1.0 1.5 I TM 0 0 0 Example 2 A heavily eroded creek bank was rehabilitated using Jutemaster FM in the following manner.

i 1I~- I~ 1~ -~I1 -PCI SLOPE PREPARATION 4.1 Day One (i) (ii) .e (iii) All protruding edges along the bank were smoothed by the Case 350 Drott.

An impervious barrier of heavy black plastic (concrete liner) was pinned up against the embankment 0.5 1 metre above the existing bed level and approximately 2 metres on the gully bed. It was pinned against the embankment to help potential piping.

72 tonnes (6 truck loads) of various sizes of quarry face spoor were brought in and were spread on the gully bed to give protection from gully flow. The optimum size for the bed rocks is 200-400 mm.

The embankment was graded by the Drott and major depressions were filled.

Agricultural gypsum was spread manually at a rate of 0.5 1 kg per square metre.

4.2 Day Two (i) -4.

(ii) (iii) 4.2 Day Three (i)

INSTALLATION

(i) 16 Top soil, was spread on the embankment to a depth of 20-30 cm and compacted to 10 cm.

The embankment was lightly raked and then seeded with a mixture of Green Couch and Giant Bermuda Couch. Native seed of Tallowwood, Matt Rush and Black Wattle were broadcast separately.

Fertiliser was broadcast over the side.

The Jutemaster FM was rolled from the top of the slope to the bottom with each roll overlapping cm, and leaving an extra metre at the toe. It was laid loosely enough to conform to contours and firmly enough to prevent soil movement and bagging.

A trench approximately 10 15 cm was dug at the top of the slope with the Jutemaster being pinned in the trench and then the trench backfilled. This ensures that Jutemaster is well secured, as when wet it becomes very heavy.

'ii) F_ i

I

17 (iii) Anchor pins were driven in along the joins. Each roll was then pinned in the centre. The Jutemaster was folded under the toe of the slope and placed under rocks where possible or pinned.

DEVELOPMENT OF VEGETATIVE COVER 6.1 Day Four The entire slope was thoroughly watered, making sure the moisture penetrated the top 20mm of soil. Follow-up sprinkling was required. Within one week the millet appeared through the Jutemaster.

6.2 Progress of Vegetative Cover.

The couch grass did not appear to be germinating evenly, so the millet was cut to a height of 40 mm and then lightly raked to allow for greater light penetration.

By 6 weeks the millet had been brushcut twice, but seed heads started appearing. These were completely removed by brushcutting.

The Acacia seed started germinating after 7 weeks.

Holes were cut in the Jutemaster and local tree and shrub species were planted. By this time the grasses were sufficiently established to hold the Jutemaster in place, stabilising the bank.

Variations and modifications apparent to those skilled in the art may be made without departing from the broad ambit and scope of the invention as defined in the appended claims.

Claims (15)

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 absorbs water whereby run off is reduced, deep infiltration of water into the soil is promoted and the soil is protected from rainfall erosion.

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 Claim 2 having a density between 300g/m 2 and 400g/m 2

4. An organic geotextile as claimed in Claim 2 having a o density of 360g/m 2 o 5. An organic geotextile as claimed in Claim 1 further 0° comprising a third layer of fine, intertwining fibres secured to the scrim on the other side of the scrim to said first C layer.

6. An organic geotextile as claimed in Claim 5 wherein the scrim, said first layer and said third layer are of sufficiently high density that vegetation cannot penetrate said organic geotextile.

7. An organic geotextile as claimed in Claim 6 having a density between 600g/m 2 and 700g/m 2

8. An organic geotextile as claimed in Claim 7 having a density of 620g/m 2 -7 -19-

9. An organic geotextile as claimed in Claim 1 wherein said first layer consists of a web of teased jute fibres. An organic geotextile as claimed in Claim 5 wherein said third layer consists of a web of teased jute fibres.

11. An organic geotextile as claimed in Claim 1 wherein said first layer is secured to the scrim by re-orienting certain of the fibres from an orientation entirely within the first layer to an orientation extending into the scrim.

12. An organic geotextile as claimed in Claim 5 wherein said third layer is secured to the scrim by re-orienting certain of the fibres from an orientation entirely within the respective layers to an orientation extending from the respective layers into the scrim.

13. An organic geotextile as claimed in Claim 11 or Claim 12 wherein the fibres are re-orientated in a needle punching operation.

14. A method of stabilising soil comprising the 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; laying said organic geotextile over the soil with said first layer in contact with soil; and securing said organic geotextile in posi-ion; whereby run off is reduced, deep infiltration of water into the soil is promoted and the soil is protected from rainfall erosion. s A method of stabilising an area of soil that is vulnerable to erosion and establishing desirable vegetation in said area comprising the steps of:- providing an organic geotextile comprising a first low-density layer of fine, intertwining fibres secured to an open-weave woven jute scrim constituting a second layer, said organic geotextile being adapted to be applied to said area as a mat which serves to dissipate the hydraulic impact of rain drops and absorbs water; laying said organic geotextile over said area with said first layer in contact with the soil; securing said organic geotextile in position; and allowing desirable vegetation to grow through said organic geotextile; whereby run off in said area is reduced, deep infiltration of water into the soil is promoted and the soil is protected from rainfall erosion.

16. A method as claimed in Claim 15 wherein said area is a sloping area of unvegetated land such as a river or creek bank, erosion gully or road cutting.

17. A method of stabilising soil and preventing growth of undesirable vegetation in the soil comprising the steps of:- providing an organic geotextile comprising a first high density layer of fine, intertwining fibres secured to a high density woven jute scrim constituting a second layer and a third high density layer of fine, intertwining fibres secured to the *other side of the scrim, said organic geotextile t I -21- 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; laying said organic geotextile over the soil with either said first layer or said third layer in contact with soil; and securing said organic geotextile in position; whereby run off is reduced, deep infiltration of water into the soil is promoted and the soil is protected from rainfall erosion, said organic geotextile acting as a barrier to prevent growth of undesirable vegetation.

18. A method as claimed in Claim 17 wherein said organic geotextile is laid around desirable vegetation such as young trees to prevent weed growth. Dated this 22nd day of December, 1994 UNITED BONDED FABRICS PTY. LTD. trading as FELT TRADERS By its Patent Attorneys AHEARNS o I p. ABSTRACT An organic geotextile for soil stabilisation comprising a first layer of fine, intertwining fibres secured to a woven 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 run off is reduced, deep infiltration of water into the soil is promoted and the soil is protected from rainfall erosion.