What is Geotextile?

Geotextile definitions. Typically a geotextile has a primary function of separation (preventing aggregate from mixing with subgrade), reinforcement, filtration and drainage or a combination thereof. Geotextiles are selected based upon physical properties required to fulfill those functions. Different manufacturing styles are based upon those functions. Permanent geotextiles are manufactured in polymers such as polypropylene and polyester and short term geotextiles (18 months to 5 years) are manufactured in natural products such as coir.

Description of the manufacturing processes of geotextiles:

Nonwoven geotextiles

Polypropylene geotextiles are made from needle punched polypropylene. Polyester geotextiles are made from needle punched continuous filament polyester. Polyester geotextiles have a higher melting point than polypropylene and are often selected for use in asphalt overlay applications.

The advantages of nonwoven geotextiles include their ability to retain a large range of soil particles while functioning as drainage, soil separation and earth reinforcement. Nonwoven geotextile is directly against the soil where drainage rock, perforated drainage coil, etc may be placed. Nonwoven geotextiles also have the ability to allow water to transverse horizontally through the fabric thus providing superior drainage functions when used under roads or on slopes.

Woven geotextiles

Woven geotextiles are manufactured in polypropylene which is extruded in a film and slit into individual yarns that are then woven to form a geotextile.

Woven geotextiles are used in a variety of applications from soil separation to filtration (high strength geotextile dewatering tubes). Especially suited for ground reinforcement because they offer an economical high strength solution. Especially on unpaved roads where the soil has a CBR of greater or equal to 8% the selection of woven geotextile would normally be 100 to 250 gsm. For weak subgrades (CBR less than 3%) a high strength geotextile or a combination of geotextile and geogrid needs to be considered. Silt fences are typically woven geotextile ranging from 80gsm and heavier and are designed to retain soil and filter water.

Monofilament Geotextiles

Used for filtration including baffle curtains and are available in various grades.

Geotextile applications:

Drainage such as french or trench drains will use nonwoven in grades from 135gsm to 150gsm. Slopes and under paved roads will also typically use nonwoven in grades from 150gsm to 280gsm (or heavier in some cases). Geomembrane underlay will typically be anywhere from 280gsm up to 600gsm. In either polyester or polyproylene. Polyester geotextiles are manufactured in Australia under the brand Bidem.

Horse arenas will mostly use a 280gsm nonwoven covered with sand. This will allow good drainage and support.

Dirt roads (unpaved roads), farm gateways, forestry roads, mining, etc may elect to use a woven geotextile from 100gsm and upwards.