SEPARATION, FILTRATION

Separation means keeping two layers of soil (with different functions) apart in order to prevent in mixing and thus deterioration of their functions in the structure. We meet such requirement most frequently in case of transportation (road and railway) constructions or under flat foundation constructions.

Long-term functionality of all structural layers is provided by preventing any intermixing. A separation element is used in most cases together with reinforcing (when it is necessary to increase load bearing capacity of subsoil) or filtration one (preventing in migration of fine particles in the protected layer by water flowing). It is possible to utilize beneficially so called strength separation for combination of separation and reinforcing function - a woven geotextile with low value of elongation and high mechanical resistance.

If top filtration properties are not required (especially in clayey soils), woven geotextiles are more suitable for this purpose than nonwoven ones.

REPLACEMENT NONWOVENS OF WOVEN PP GEOTEXTILES:

nonwoven geotextile	200-300 g/m²	300-400 g/m²	400-450 g/m²
strength	12 - 15 kN/m	15 - 19 kN/m	18 - 25 kN/m
strain	60 - 80 %	60 - 80 %	60 - 80 %
CBR	2 - 2,3 kN	3 - 4 kN	4 kN
cone test	mesh 16 - 25 mm	mesh 14 - 25 mm	mesh 8 - 20 mm
water permeability	0,035 - 0,085 m/s	0,055 m/s	0,055 m/s

can be replaced by PP geotextile	Kortex^® GTPP 14/14	Kortex^® GTPP 18/18	Kortex^® GTPP 30/30
strength	14 kN/m	18 kN/m	30 kN/m
strain	18 %	19 %	15 %
CBR	3 kN	4 kN	4 kN
cone test	mesh 17 mm	mesh 14 mm	mesh 8 mm
water permeability	0,04 m/s	0,05 m/s	0,06 m/s