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A newly developed wick drain, formed from a jute sleeve packed with
coir, showed how combinations of geotextile types provide benefits greater
than the sum of each. Professor Bob Sarsby of Bolton Institute reported on
full-scale trials of soil walls incorporating jute rope reinforcement.
This work graphically demonstrated the strength of jute in supporting
walls of 4m or more. He went on to describe the use jute in road
construction especially over areas of poor ground. Not enough attention
has yet been paid to this potentially extensive application.
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The micro-climate surrounding jute geotextiles has been explored by
Yves Henri Faure of Grenoble University who has tested the efficiency of
jute sheets in preventing loss of soil in shallow and steep slopes. Earth
works were built on a test-bed capable of being rotated to various
inclinations and subjected to simulated rainfall, varying from light to
heavy tropical downpours. The amount of soil lost to erosion was measured.
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The faces were then protected by various geotextiles and the soil erosion
again measured. The tests simulated wash out of vegetated soil slopes and
provided data of use in landscaping projects. Over the whole range of
rainfall intensities and slope angles jute geotextiles outshone the other
materials. A jute of approximately 500g per m2 appeared to be
cost effective. |
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Using jute to protect large areas from erosion, including
high-altitude ski-slopes with significant precipitation, has been trialed
by Francoise Dinger of CEMAGREF. The ability of jute to absorb five times
its own weight of water ( 3kg per m2 of slope ) was
demonstrated. The retained water firstly attenuates the run-off into the
drainage system and is then released gradually to soak into the adjacent
soil to nourish the vegetation from severe frosts, so aiding
growth.
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Mike Hyder of Hy-Tex Ltd. commented that prevention of soil erosion
was better and more cost effective than remedial works. The most
vulnerable sites were over steepened slopes, exposed highly erodible
sub-soil, and disturbed or badly compacted ground.
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Consequences of soil erosion were: poor growing conditions,
additional costs for remedial works, blocked drains and flooding,
pollution of waterways and increased maintenance. Many applications of
jute made by his company were illustrated by ‘before and after’
photographs showing the dramatic improvement in vegetation growth and
erosion control.
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Barbara Lois of SIRAS Company described the extensive environmental
works undertaken in France using jute geotextiles, including
rehabilitating mine dumps, restoring the Rhone river banks and the
vegetating high altitude steep slopes at the Winter Olympic ski jump in
Savoie. Landscaping of slopes alongside the TGV rail line and along
highway cuttings and embankments showed the effectiveness of the
geotextiles.
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Dr. Finn Terkelsen from Denmark felt that the partners in this
field are playing a waiting game. The jute mills are waiting for the
engineers to tell them what to do, whilst the engineers are waiting for
the jute mills to show them what is available. Much research has been
carried out by several institutes in jute producing countries as well as
in Europe. Interesting results were seen but wider use did not materialise. It will be important to address this issue and to use past
experiences as stepping stone for future work. There is currently a very
wide gap. Erosion control, foundations, sound barriers, filters, and
reinforcement and drainage were suggested as the most appropriate target
uses of jute geotextiles. |
