Performance Properties of Geogrids - Reinforced Soil Engineering: Advances in Research and Practice - page 20

The strength of the geogrids varies between 20 and 250 kN/m, and they are used
in both road constructions and reinforced slopes.
At that time, the strong PET fabrics that were used commercially for basal
embankment reinforcement were, in fact, too strong for slope reinforcement,
which typically requires strengths of

100 kN/m. The only other materials then
available were various types of nonwovens and lightweight wovens. Due to the
unique structure of the geogrid, and the strength range in which it was available, it
was highly suitable for use in slope reinforcement applications and for bearing
capacity improvement applications in roads. The success of the product since its
introduction proved its usefulness.
As with all products developed for specific applications, other
competitive and new products came on the market as the market matured.
Today we can choose from a variety of stiff geogrid products and flexible
geogrid products.
The history of flexible geogrids differs from that of the stiff types, because
polyester fibers had already been used for quite some time in soil reinforcement
applications, mainly for basal reinforcement of embankments. The first
commercial application of these reinforcing fabrics goes back to 1977, when a
highway embankment was built near Muiden in The Netherlands. This
reinforcing fabric, type Stabilenka, was used in large projects, especially in Asia,
for basal reinforcement applications in land reclamation projects and road
constructions. The reason for this start in Asia was that a technical need existed
for the use of basal reinforcement, as the soil conditions in those projects were
very bad and infrastructural works had to be constructed there. For slope
reinforcement applications,

,

the reinforcing mat was simply too strong and

therefore too expensive.
It was technically impossible to make a reinforcing fabric with a strength
less than 150 kN/m in the traditional fabric form. A leap forward was made in
1985, when an open-fabric mesh, coated with PVC, was developed. Now it was
possible to use PET yarns with their superior properties to make a grid-type
structure with the required lower strength. Further, the PVC coating provided an
excellent protection against mechanical damage, which made the product even
more attractive. So, at the end of the 1990s, more geogrids appeared on the
market, which increased competition between the products.
Geogrids can be divided into two groups:

1. Stiff geogrids, mostly HDPE with a monolithic mesh structure
2. Flexible geogrids, mostly PET with PVC or acrylic coating with
mechanically connected longitudinal and transverse elements

Over the past years many advantages and disadvantages have been claimed
for the various products. It is the intention of this paper to make an updated
generic comparison between the two groups of products on the basis of specific