Use of nonwoven geotextile in the construction
of a highway on critical soils
Location of work/project:
Austria – Linz/Graz – A9 Pyhrn Autobahn
Geo & Tex 2000
Road foundations of highways on critical soils can maintain their long term efficiency providing that their contamination by fine subsoil particles is prevented: the use of a properly designed nonwoven separation and filtration layer has been proven to be an efficacious solution to achieve this goal.
Pyhrn Autobahn has been conceived to link together the highways A1, A8 and the southern area of the country. The completion of A9 allowed a further direct link between northern and southern part of Austria, insuring a direct line between Germany and Slovenia, Croatia and Italy.
The complicated soil conditions in the area of Kirchdorf (semi-liquid, plastic and organic soils) evidenced the need to proceed with a soil stabilization.
According to the Austrian regulations for the use of geotextiles in road constructions, the following site parameters have been considered:
• Deformation modulus of soil Ev1 ≤ 5 MN/m2
• Traffic class I-IV according to RVS
• Angular and sharp fill material with dmax > 63 mm
In compliance with the prescriptions of specifications, the following performances have been required for the nonwoven geotextile:
• Tensile strength (EN ISO 10319) > 26 kN/m
• Elongation at break (EN ISO 10319) > 55%
• CBR static puncture resistance > 4200 N
Approximately 300.000 m2 of nonwoven geotextile type GEO PP AG 390 were installed.
Thanks to its filtration efficiency and mechanical robustness as separation layer, the nonwoven has prevented the contamination of fill material by fine soil particles, so that the road foundation has been able to maintain its original mechanical behaviour with time.
GEO PP AG 390 was installed at the base of road foundation and also it was laid down in order to wrap around the drainage gravel of the lateral drainage trench. The elongation characteristics of GEO PP AG 390 have allowed the geotextile to maintain a perfect contact with the soil of the trench, preventing the erosion of fine particles and avoiding the clogging of the nonwoven.