Filtration cross-plane permeability

From the above description of the basic geo-filtration mechanism, it becomes evident that the performance of geotextiles as filter media depends largely on two properties the material s cross-plane permeability and pore-size characteristics. 

Filtration can be defined as a soil—geotextile system in equilibrium that allows for adequate liquid flow with hmited soil loss across the plane of the geotextile over a lifetime of service compatible with the application under consideration (Koerner, 2005). Therefore, the filter function refers to geotextile pore size distribution (PSD) or filtration opening size and to the geotextile cross-plane permeability (or permittivity). 

If theoretical equations (Giroud, 1996) are used to evaluate the cross-plane permeability and filtration opening size of a nonwoven geotextile, the porosity and thickness must be known (see the section on cross-plane permeability). 

Thus for separation, filtration, and drainage applications the cross-plane and in-plane permeability values obtained by index testing would be moderated according to ... 

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