Tensar invented, developed and commercialized the uniaxial, biaxial and triaxial forms (i.e. Tensar TriAx®) of “extruded, punched and drawn” (“Tensar Process”) geogrids. The uniaxial (strength in one direction) and biaxial forms were introduced in the early 1980s as the first forms of Tensar Process geogrids and over time became trusted and proven products for a variety of civil and geotechnical applications. The triaxial form was developed and introduced in the late 2000s as an improvement to the biaxial form, particularly for civil and geotechnical engineering applications where the applied loads are not limited to one or two directions (for example, pavements, haul roads, working platforms and general soft soil stabilization). Since its introduction TriAx has undergone significant testing and evaluations and has become the preferred form of geogrid for all roadbed and stabilization applications.
Biaxial and triaxial geogrids are unique and distinct engineering materials, each with their own in-application performance capabilities. The presence of ribs in three directions, rather than two, is an obvious, definitive and meaningful distinction between biaxial and triaxial geogrids. Just as a uniaxial geogrid cannot be equivalent to a biaxial geogrid, a biaxial geogrid cannot be equivalent to a triaxial geogrid. As such, one should not be substituted for the other without fully redesigning the application. Further, the mechanisms that create aggregate confinement in roadbed applications are very complex, and no two geogrids are the same. While biaxial and triaxial geogrids can both be used in many applications there are impacts on the other materials (i.e., aggregate, asphalt) involved in the application. For example, a haul road over soft ground can be designed with either biaxial or triaxial geogrids (provided both products have undergone appropriate performance and validation testing) – however, if the same level of performance is necessary, there will be different thicknesses of aggregate material required for each product.
Thus substituting one geogrid for another should only be considered if (1) a full design review is conducted, (2) the alternative product has undergone the appropriate performance and validation testing, and (3) it is acceptable to either have a different level of performance, or a different design (e.g., a thicker or thinner aggregate layer).
Even products that appear to be very similar and have “equal” strength may not perform the same. Tensar has performed rolling wheel traffic testing on a Tensar biaxial geogrid and another non-Tensar biaxial geogrid of equal tensile strength: this testing showed the two products do not perform the same. As a result, each product must stand on its own data. Attempts to apply property data from one product to other ‘similar’ products introduces the risk of non-performance. Further, and despite much research and effort, there are no proven correlations between physical properties of geogrids and performance in roadbed and stabilization applications. To assure performance of biaxial or triaxial geogrids in these applications, designs must be based on performance and validation data of the specific geogrid product in consideration.