Separation and Drainage for Road and Rail Applications

Using Geofirma® nonwoven Geotextiles

Geofirma® is a proprietary nonwoven geotextile that is available in a wide range of variants for different applications. This geotextile is manufactured from the extrusion of fibres which are laid on a manufacturing ‘bed’ and then needle punched to entangle the fibres, creating a dimensionally stable product.

With the addition of thermal treatment to further improve the strength of the material, Geofirma® Geotextiles are suitable for a wide range of geotechnical applications involving drainage, filtration, protection and separation.

One of the applications that Geofirma® delivers excellent performance in is road and rail projects.

Benefits of Geofirma® Geotextiles for Road and Rail

Strong separation properties

The need for geotextiles for separation commonly occurs when high-quality fills are being imported and are to be placed over lower-quality in-situ materials. This could be for both short-term structures such as access road construction, or for longer-term applications where the embankment will form a longer-term structure such as a permanent road.

The geotextile type to be used will be largely a function of groundwater conditions, ground support conditions (CBR value) and if filtration requirements are critical or not.

Of course, like all geotextile applications, the survivability of the fabric to construction damage will be a function of the imported fill material stone size placed on the geotextile. The primary function of the geotextile is to prevent short and long-term intermixing of dissimilar materials with some secondary reinforcement benefits.

Geofirma® Geotextiles are recommended for separation applications with fill stone sizes up to 400mm in diameter. Different Geofirma® grades are suitable for filtration and drainage requirements of silt and clay soils, and can also be used in low permeability soils.

Excellent drainage characteristics

In the construction of roads, railways and similar infrastructure, good drainage is critical to the long-term success of the project.

Road projects that do not adequately take into account the necessary drainage requirements can experience significant rutting and degradation of the pavement surface. Water ingress into fine cracks can quickly cause the asphalt surface to deteriorate further, shortening the pavement’s life and creating a need for early maintenance to rectify the damage.

In many projects, trench drains are installed within and adjacent to pavements. These are used to lower the water table and drain away water within pavements or free draining layers, preventing damage to the surface.

Geofirma® nonwoven geotextiles perform an important drainage function, with most grades suitable for filtration and drainage requirements of silt and clay soils, low permeability granular soils and pervious granular soils. Geofirma® geotextiles are also suitable for many blanket drain applications such as underneath railway embankments.

In drainage and filtration applications, the designer should consider the survivability of the geotextile against damage during the installation process, the soil type that the geotextile will be in contact with (considering the maximum particle size and grading), the type of drain to be constructed, the likely flow requirements of the geotextile and in some applications, the ground conditions on which the drainage structure is to be constructed.

For advice and support on the best choice of drainage and separation geotextiles , our engineering team is here to assist. With large stock holdings held in strategically located warehouses throughout Australia, Global Synthetics can deliver in a timely manner to meet demanding construction schedules.