Tensar® FilterGridTM (FG)
When stabilizing paved or unpaved structures it is important to not only consider the appropriate geogrid product and thickness of granular fill, but also whether adequate filtration and separation of dissimilar materials will be maintained throughout the life of the structure. While Tensar TriAx geogrid frequently provides adequate confinement of the fill to achieve both filtration and separation, there are times when specifiers recommend a geotextile in conjunction with the geogrid. FilterGrid provides the superior performance to Tensar’s patented TriAx technology along with the added assurance of a non-woven geotextile – all in a single composite product.
HOW FILTERGRID WORKS
FilterGrid stabilizes working surfaces, such as paved and unpaved roadways, airfields, crane pads and other working surfaces by providing confinement, separation and filtration. FilterGrid combines the stabilization benefits of TriAx with the separation and filtration benefits of a non-woven fabric.
TriAx’s unique structure provides a high degree of in-plane stiffness through a mechanism known as lateral restraint. Lateral restraint is the ability to confine and stabilize aggregate particles within the plane of the geogrid. As granular base courses are stress-dependent materials, the confinement offered by properly designed, stiff geogrids improves the modulus of an aggregate material, improves load distribution, and maintains that modulus over a much longer period of time than an unstabilized aggregate. This confinement improves speed of construction, reduces fill requirements, and enhances the performance and durability of these working structures over time.
The non-woven filter fabric attached at the nodes of the TriAx provides separation and filtration. Fine grained subgrades, especially those consisting of low plasticity silts and clays, present separation and possibly filtration needs. Tensar’s SP4PRO software provides tools to assess if a non-woven separator is needed. This tool is based on guidance outlined in many resource documents including those of Cadergren, Terzaghi, Peck and Mesri where piping and uniformity ratios are set based on the soil type.