Drainage and separation in highway tunnels

Geodren® PPSEX 500 for highway tunnels in Algeria

Geodren® PPSEX 500: nonwoven geotextile used as a drainage and separation layer in tunnel construction.

Problem

The East-West highway is one of the largest infrastructure projects in Algeria’s history: it connects the border with Morocco in the west to the Tunisian border in the east. The project comprises three sections: the eastern, central and western lots. Along the highway route, a wide variety of soils forms the foundation and surroundings of the project.

In particular, the stretch from Constantine to the Tunisian border features mountainous terrain and landslide-prone slopes that required major infrastructure work. In lot 4 alone, contractors built 3 rockfall tunnels of varying length. The goal was to secure a section of the highway running between two steep slopes.

Solution

Engineers chose to use Geodren® PPSEX 500, a 500 g/m² needle-punched polypropylene geotextile. The material acts as a drainage layer for rainwater and as a separation layer between the covering soil and the tunnel vault. In terms of drainage, the geotextile carries rainwater within its own plane.

Thanks to the use of high linear-density fibers and the absence of heat treatment on the finished product, the drainage capacity of Geodren® PPSEX 500 meets the project requirements. In addition, the additives used during raw material production increase resistance to weathering and to the chemical attacks typical of alkaline environments. This gives the product high durability characteristics.