Note: Descriptions are shown in the official language in which they were submitted.
~.x-~ WO 93~24315 ~ 13 6 f~ 2 2 PCr/AU93/00237
ORGANIC GEOTEXTILE
TECHNICAL FIELD
~ he present invention is concerned with geotextiles and
more particularly, with geotextiles for soil 6tabili~ation.
~CRGROUND ART
Erosion i8 a significant problem on unvegetated land,
particularly if it 8 lope6 6teeply, where water run6 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 bank~ and road cuttings.
It is well known that a slope which is 6ubject to ero6ion
can be stabili6ed if vegetation can be established on the 610pe,
but vegetation will not e6tablish it6elf when the top soil i6
being washed away periodically. A number of proposals to
stabili6e erosion banks using matting ba6ed on 6ugarcane
bagasse, wood, wool or coconut fibre6 and including additive6
such as binding agent6 have had limited succe66.
DISCLOSURE OF IN~ENTION ~;
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 soil,
and enhancing establishment of desirable vegetation through
favourable soil moisture and temperature.
It 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
vegetation and sunlight blockage, promoting water infiltration
and reducing runoff and evaporation.
According to one broad aspect of the invention there i6
provided 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 ~erves
to dissipate the hydraulic impact of rain drops and absorbs
water whereby run off is reduced, deep infiltration of water
into the 60il is promoted` and the 80il i5 protected from
rainfall ero6ion.
Preferably, the scrim is of sufficiently open weave and
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W093/243lS ~ PCT/AU93/00237
said first layer is of sufficiently low density that de6irable
vegetation can penetrate said organic geotextile in growing
therethrough. It is particularly preferred that the overall
den6ity of the geotextile be 300 to 400 gram~/metre2 and, more
particularly, 360 grams/metre2.
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/m2 and 700g/m2, preferably 620g/m2.
~ n a particularly preferred embodiment of the invention
said first layer consists of a web of teased jute fibres and the
scrim is a jute scrim. 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 an
"apron" and the jute 6crim (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 proces6ed through a "needle punching
machine~. ~his machine comprise6 a plurality of barbed needle6
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 6crim to the web.
This proce6s i~ known as ~felting" or needle punching. It is
preferred that no bonding agent be added. The product i~ then
trimmed to the desired width and thicknes6 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 tea~ed 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 1l 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
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- W093/2431; 21~ 6 ~12 ~ PCT/AU93/00237
is provided a method of ~tabilising 60il comprising the 6teps
of:-
(i) providing an organic geotextile comprising a first layer offine, intertwining fibres 6ecured to a woven scrim
constituting a ~econd layer, ~aid organic geotextlle being
adapted to be applied to an area of 60il as a mat which
6erves to dissipate hydraulic impact of rain drops and
absorbs water;
(ii) laying said organic geotextile over the soil with said
first layer in contact with soil; and, optionally,
(iii)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 ~till further broad a6pect 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:-
(i) providing an organic geotextile comprising a first low-
density 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 6erves to dissipate the hydraulic impact of
rain drops and ab60rbs water;
(ii) laying said organic geotextile over said area with said
~;~ first layer in contact with the 60il; optionally,
(iii)securing said organic geotextile in position; and
; (iv) allowing desirable vegetation to grow through said organic
geotextile, whereby run off in said area is reduced, deap
infiltration of water into the 60il iS promoted and the
soil is protected from rainfall erosion.
Preferably, the 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 species such as millet
do not lift~the geotextile cover as they grow thereby reducing
its effectiveness as an erosion control agent. ~ypically, pins
would be driven in every 600-700 mm on a gentle 610p and every
400 mm on a steeper slope at the joins between each roll of
geotextile u6ed or at a rate so stipulated by a site engineer or
similar. Each roll would also be pinned with one pin on a
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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
610pe 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 t~e 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 60il, desired 6eed
and fertili6er 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
6uch as millet is cho6en. Preferably, a mixture of fast growing
species such as millet and more desirable 6pecies such as couch,
acacia, eucalypt, etc. is u6ed. Tree and 6hrub specie~ may be
planted in seed form under the mat or, once the vegetation or
gra6s i6 established, by cutting holes in the cover and planting
them in those hole6.
According to yet another broad aspect of the invention
there is provided method of stabili6ing soil and preventing
growth of undesirable vegetation in the 60il comprising the
steps of:-
(ij providing an organic geotextile comprising a first highdensity 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
ecured to the other 6ide of the 6crim, said organic
geotextile being adapted to be applied to an area of soil
as a mat which serve6 to dissipate the hydraulic impact of
rain drops and ab60rb water;
(ii) laying said organic geotextile over the soil with either
said first layer or 6aid third layer in contact with soil;
and, optionally,
(iii)securing said organic geotextile in po6ition, whereby run
off is reduced, deep infiltration of water into the soil is
promoted and the 80il 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/m2 and 700g/m2, more preferably, of
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' ` W O 93/~4315 ~ 1 ~ 642~ PCT/AU93/00237
620g/m2 and is thus 6ufficiently dense that it provides a
physical barrier to weed growth a6 well as preventing ~unlight
reaching any weeds already growing in the vicinity of the young
tree~. Competition fo, nutrient6 and ~unlight is therefore
reduced and growth of the trees is enhanced. The growth of
trees on land susceptible to erosion further ~erves to stabilise
that land but the method of enhancing the growth of young trees
according to the present invention is not limited to that
application and is generally applicable to gardening and
horticulture.
~RIEF ~ESCRIPTION OF DFU~WINGS
In order to more fully describe the invention reference
will now be made to the accompanying drawings in which:-
Figure 1 i6 a schematic diagram of one illu6trative
example of a geotextile in accordance with the invention
suitable for 60il stabilisation and establishment of
desirable vegetation, and
Figure 2 is a 6chematic diagram providing a partially
exploded view of one illustrative example of a geotextilein accordance with the present invention suitable for use
a6 a weed barrier.
EST MODE FOR CARRYING OUT THE INVENTION
Figure 1 show6 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
o$ jute scrim. The jute scrim used herein is a very open weave
of jute fibres. The product is nominally 3mm thick, has a
density of 360g/m2 and is to be referred to through the
specification as "Jutemaster FM".
Figure 2 illustrate6 a geotextile 20 having a top layer 23
and a bottom layer 22 of tea6ed jute fibre. Each of the layers
is attached to the middle layer 21 which is a jute scrim,
although layer 23 is shown spaced from the scrim so that the
location of the scrim can be seen. The product is nominally 6
mm thick, has a density of 620g/m2 and is to be referred to
throughout the specification as "Jutemaster TM".
~x~m~les
~1
(a) ~erials
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W093~24315 4~ PCT/AU93/00237
Jutemaster FM and Jutema6ter TM were subject to a rainfall
6imulator evaluation using a ~oil which has been shown to be
highly erodible. It is hard 6etting sand loam about lOcm deep,
ovèrlying a dense clay which becomes increasingly sodic with
depth. It has the following physical and ~chemical
characteristics.
Soil type: ~odic red brown earth
Clay content: 26%
Silt content: 14%
Sand content: 60%
pH: 7.1
Cation Exchange Capacity (CEC): 16 meg/lOOg
(b) Rainfall
Simulated rainfall using a rotating disc rainfall simulator
was applied for 30 minutes at 65 mm/h and 15 minutes at 130
mm/h. The high intensities were chosen to highlight the
effectiveness of the geot~xtile against typical short, heavy
storm in northern Australia. The occurrence of 30 minutes of
rain at 65 mm/h would be an annual event in most parts of
Queensland. The 130 mm/h rain represent6 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.
(c) Slope Gradient
Three~ gradients were tested: 3:1, 4:1 and 10:1. These
gradients cover ~he range of slopes often requiring geotextile
materials for stabilisation.
(d) Sample Preparation
After removing large rocks and foreign materials, the soil
:,
was firmly packed into galvani~ed steel boxes (250 mm wide, 450
mm long and 75 mm deep). The soil surface was covered
completely by either Jutema6ter 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 simulat~r run, two boxes were used.
(e) Replication
Each treatment (geotextile grade X gradient) was replicated
twice.
~f) Data Collection
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For each run the following data were collected:
Runoff rate
Total runoff
Total ~oil movement
Depth of wetting at 30 cm from the collecting spou~
From these results, water infiltration rate, total
infiltration and rainfall before runoff were calculated.
(g) Results on water runoff and soil moistu~e tests
(i) 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, ~oil roughnes~ and
land slopes. Results from Table l clearly show that both
Jutemaster FM and TM reduce runoff greatly, particularly
under high rainfall inten6ity.
Under low rainfall intensity conditions, where
minimum runoff would be expected on bare 60il 6urface,
runoff was reduced by more than 50~ under Jutemaster FM and
up to 80% under Jutemaster TM on all slope gradients.
The effectivene6s of both grade6 wa6 be6t
~ .
demonstrated under high rainfall condition6. The average
reduction of runoff was up to 90%. These results clearly
demonstrate the suitability of Jutemaster FM for steep
slope stabili6ation.
The uniformity of the results between replications
~-~ indicates that the variation in mat density i~ minimal and
quality control is sati6factory.
Table l: Runoff a~ a porcontage of total rain.
~ . . ,_ .. , ,~ .
S~OPE G~ADIENTS
RAINFALLSURFACE l
¦ INTENSIT~COVER 10:1 4:1 3:1
Low Bare 33 23 20
~65 mm/h) FM 10 163 10
. I
High Bare 52 42 39
(130 mm/h) FM 43 32 5
~____
.`
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W093/2431~ PCT/AU93/00237 5
(ii) Water Infiltration:
water infiltration into the ~oil depends greatly on
the soil surface cover which protects the roughnes6 of soil
6urface (soil ~urface ~tructure) and also to 510w down the
movement of water thus enhancing the water entry/a~60rption
to the 80il.
Results hown in Table 2 demonstrate the
effectiveness of both Jutemaster FM and TM in improving
water infiltration to the 60il. Almo6t total absorption
was recorded under both low and high rainfall intensities
and at all three ~radients for both grades. This can be
explained by the fact that surface 60il 6tructure under
Jutemaster remained almost intact after 30 minutes of rain
while the bare soil surface structure wa6 completely
destroyed.
Table 2: Water infiltration as a percentage of rainfall.
l _ - I '`.
SLOPE GRADIENTS ¦
RAINFA~L SURFACE _
INTENSITY COVER lO:l 4:1 3:1
I ,
Low Bare 67 77 80 ¦
(65 mm/h) FM 90 87 90
TM 93 94 92
_
High Bare 48 58 6l
(l30 mm/h) FM 96 97 95
TM 97 98 95
I , .
(iii) Time before runoff occurred:
The results presented above can be best seen in term6
of the time elapsed before runoff occurred. Table 3 shows
that under low intensity rainfall (65 mm/h) runoff occurred
approximately 13 minutes after rain on bare 80il on all
slope gradients. Under high rainfall intensity (130 mm/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 ero6ion and soil
moisture levels are inversely related to runoff quantity
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. . ~ .
and rate. These results further indicate the suitability
of bot~ grades of Jutemaster in soil ero~ion control.
Table 3: Ti~e (minutes) before runoff occurred.
~ ':'
SLOPE GRADIENTS
RAINFALLSURFA OE .
INTENSITY COVER 10:1 4:1 3.1
Bare 10 16 12
Low
(65 mm/h) FM 30+ 30~ 30+
TM 30+ 30+ 30+
I .
Bare 7 8 7 s
High
(130 mm/h) FM 15+ 15+ 15+
TM 15+ 15+ 15+ `
: . . . .-
5+ and 30 lndlcatlng no runoff ccurred at the end of
experimental periods of 15 and 30 minutes respectively.
~iv) 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
~i contrast with the bare soil where only up to two thirds of
the soil profile were wet (Table 4).
Table 4: Wetting depth (cm), 30 cm from the collection
spouts.
:: ~ -._
S W PE GRADIENTS
RAINFAIL SURFACE
INTENSITY COVER 10:1 4:1 3:1
Low Bare 50 50 50
(65 mm/h) FM 75+ 73 73
TM 75+ 75+ 75+
l . . l
High Bare 40 45 50
(130 mm/h) FM 75+ 67 70
TM 75+ 75+ 75+
, . , " ., . ." _ .
+ Complete y saturate~.
(h) ~gsults 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
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W093/2431~ ~ PCT/AU93/00237 ~-`
~36~ o
increased particularly under high rainfall inten6ity. When the
surface wa6 protected by either FM or TM grade~, soil 106~e6
were virtually stopped even under high rainfall intensity.
The~e results indicate that for general 610pe stabili~ation
Jutemaster FM is an extremely effective geotextile in ~oil
erosion control.
Tsble 5: Soil concentration in runoff water (g~l).
.
SLOPE GRADIENTS :
RAINFAI.L SURFACE , .
IllTENSIT~r COVER 10 :1 ~ :1 3 :1
Low Bare 12.5 51.1 60.8 ,
(65 mm/h) FN 0 0 0
TM O O O
I
High Bare 154.6 236.3 253.5¦ FM ¦ 1.0 1 1.5 ¦ 1.5 ~ j
~xam~le 2
A heavily eroded creek bank wa6 rehabilitated using
Jutemaster FM in the following manner.
~ .
S~OPE PREPARATION
- 4.I Day One
(i) All protruding edge6 along the bank
were smoothed by the Case 350 Drott.
(ii) 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.
(iii) 72 tonnes (6 truck loads) of variou6
~izes of quarry face 6poor 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.
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,''t"~ , W093~24315 ll 2 1 ~ 6 ~ 2 2 PCT/AU93/00237
4.2 Day Two
(i) The embankment was graded by the
Drott and major depres6ion6 were
filled.
(ii) Agricultural gypsum was~ 6pread
manually at a rate of 0.5 - l kg per
square metre.
(iii) Top soil, was spread on the
; embankment to a depth of 20-30 cm
and compacted to l0 cm.
4.2~ Day Three
(i) The embankment was lightly raked and
then seeded with a mixture of Green
Couch and Giant Bermuda Couch.
Native seed of Tallowwood, Matt Ru6h
- ~ and Black Wattle were broadcast
separately. Fertiliser was
broadcast over the side.
5.0 INSTALLATION
he Jutemaster FM was rolled from
the top of the slope to the bottom
with each roll overlapping l0 cm,
and leaving an extra metre at the
` toe. It was laid loosely enough to
conform to contours and firmly
enough to prevent 50il movement and
bagging.
iij A trench approximately l0 - 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.
(iii) I 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
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W093/24315 ~36 4~ ~ 12 PCT/AU93/00237 ~
possible or pinned.
6.0 DEVELOPMENT OF VEGETATIVE COVER
6.1 Day Four
The entire slope was th~roughly watered, making sure the
moisture penetrated the top 20mm of soil. Follow-up s~rinkling l~
was required. Within one week the millet appeared through the F"
-Jutemaster.
6.2 Progre6s of Vegetative Cover. ;
The couch gras6 did not appear to be germinating evenly, 60
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.
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