In order to allow long-term drainage performance of the percolation layer, filter geotextiles are deployed to transmit shear stress on the percolation layer. Mechanically bonded nonwovens (see filtration) are especially suitable for filtration functions. Randomly entangled mesh matrices are especially suitable as drainage layers since they have a stable three-dimensional static structure. Shearing stresses can be transferred without damage, and thus the long-term hydraulic performance is maintained.


Drainage is the collection of precipitation, groundwater and other liquids or gases which have to be discharged. Drainage systems are supplied as single elements or composites consisting of at least one filtering layer and one percolation layer. The latter takes up the liquid and discharges it with a minimum loss of pressure. Surface drainage systems are frequently combined with sealing systems, e. g. in landfills, and waterproofing applications, like underground car parks or tunnels. Geosynthetic drainage systems substitute expensive mineral drainage layers.