Understanding geotextiles and gravel stabilisation methods

What are Geotextiles?

Geotextiles are permeable fabrics or materials associated with landscaping and soil. Geotextiles are used to: separate, filter, reinforce, protect, or drain soils.Typically, geotextiles are made from polypropylene or polyester.

When it comes to gravel stabilisation products (made from geotextiles) the porous membrane is typically made from polyesters and using a process called thermal wielding is connected to the honeycomb-like structure constructed out of polypropylene.

Weight versus design - the truth about geotextiles

It is important to remember weight does NOT equal quality when it comes to geotextiles. There is a false perception that the heavier the geotextile the better the quality. A fabric clocking in at a 100g/m2 is not superior to 40g/m2. In fact, when it comes to green roof applications - the lighter the building material the better for the civil engineer. The heavier the geotextile is the greater the risk of the porous membrane being blocked by sediment.

How the hexagonal frame distributes weight

Gravel stabilisation products are designed to withstand the weight of a car and other heavy objects.

BERA Gravel Fix Pro is not your common garden variety. The Gravel Fix Pro sheets are designed to evenly distribute the weight from of a vehicle driving over it. The walling of the BERA Gravel Fix Pro are tapered – meaning it is thicker at the bottom and thinner at the top – increasing the strength from 120 tonnes per m2 without gravel inside. Thinner walls at the top allow for increased flexibility to prevent the structure from breaking.

The gravel stones move away from thicker walls which is aesthetically displeasing. It is essential when using BERA Gravel Fix Pro to keep one to two centimetres of gravel within the structure as the gravel stones act as 'rolling-element bearing' when weight is being applied This means the gravel stones are able to absorb heavy weights of cranes and trucks. The gravel also decrease the amount of direct sunlight the polypropylene walls are exposed to.

Thicker polypropylene walls generally do not last as long because they are unable to bend and therefore break. Denser walls also mean an increased surface area is exposed to harmful UV rays that weaken the product overtime. BERA Gravel Fix Pro has been designed in such a way that minimises exposure to UV Light whilst maintaining the product's strength and flexibility.


Polypropylene versus Polyester geotextiles

Geotextiles made from polypropylene are better resistant to humidity than Polyester textiles. The water permeability is extremely high and guaranteed 180 l/sm2. The geotextile connected to the base of the hexagonal frame also prevents gravel loss into the subbase and weeds from taking root.

While most geotextiles are made from polyesters, BERA Gravel Fix Pro is made from Polypropylene geotextile connected to Polypropylene honeycomb structure. BERA Gravel Fix Pro is made from Typar, a porous geotextile filter of exceptionally high-quality developed by DuPont factory in Luxemburg. DuPont is the leading factory for civil engineering products and construction. Most of their products have a lifespan of 100 years.

The Polypropylene geotextile found in BERA Gravel Fix Pro is a non-woven textile. Instead, made from countless individual fibres joined together through extreme adhesion. The adhesion process means the product is more porous and less likely to clog.


Connecting the geotextile to the Polypropylene honeycomb grid

When using a polypropylene textile cautionary measures have to be taken during the thermal wielding process not to overheat the geotextile before the honeycomb walls melt. Should the geotextile over heat this will reduce its water permeability.

BERA Gravel Fix Pro is made from unique patented ultrasound technology invented by Mr Slavoj Cegan. Cegan is able to connect the geotextile to the Polypropylene honeycomb frame without glue. The ultrasound waves to create minuscule grooves where both materials are to be connected without compromising the strength the permeability of the structure. 

Lighter, better more efficient green roofs