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To study the behaviour of geotextiles used as filters under the critical circumstance of soils in suspension this research was carried out in cooperation with the University of Grenoble.
A global study with geotextile-wrapped drainage pipes under different soil conditions was carried out. In a first test the fine soil was slightly compacted around the pipe, in a second test the same fine soil was built in by stacking compacted soil blocks. This second system showed a 15 times higher long-term permeability compared with the first one.
A local study with a perll!eameter for suspension filtration with different geotextiles and different slurries has also been realised to analyse clogging and piping mechanisms.
The result showed e.g. that geotexties with an opening size 3 times larger than particle size held back 50 % of the soil after 8 min. ( concentration 3 g/1). Also the better soil retention capability of nonwoven geotextiles against monofilament woven geotextiles and a very fast clogging of slit film wovens and heat bonded geotextiles is obvious.
In addition to that an optimum range for the number of filaments is given. That should lead to a good path size distribution of nonwoven geotextiles.