Designing a geogrid for stabilisation

If it ain’t broke…don’t fix it. But why not improve it?

Geogrids have been around for over 40 years: there are plenty to choose from and they all work. So do we really need another? Well, they may all work, but they do not all work the same. Geogrid performance in roads and trafficked areas is a function of the geogrid structure and its properties. By improving our understanding of the relationship between structure, properties and performance we can re-design the geogrid to further enhance performance. That is what Tensar has achieved with Tensar InterAx geogrid.

In this blog, read on to learn more about: 

• Design for improved performance
• Designing for efficient interlock and confinement
• The key design aspects that influenced performancee:
  - Materials, science & coextrusion
  - A more complex geometry
  - Why is Tensar InterAx white?
• Proving the performance of Tensar InterAx
• How does an increase in performance create real value?
• Want to learn more about Tensar InterAx geogrids? 

Design for improved performance

If we are to design for improved performance, we must first define what we mean by performance. Tensar has long advocated that the only performance that really matters to engineers is the in-situ performance of the geogrid, by which we mean the performance of the stabilised layer, rather than the geogrid in isolation. This is typically measured by resistance of the layer to deformation or rutting under the action of traffic. This can be most effectively measured in trafficking rigs or accelerated pavement test (APT) facilities.

In this episode of 'Ask Andrew", Andrew  Lees tells us about designing geogrids for stabilisation.

Designing for efficient interlock and confinement

Tensar set out to re-design the geogrid with one aim, to achieve maximum performance efficiency. Based on an improved understanding of the mechanism of stabilisation - resulting from many years of laboratory and field research supported by numerical modelling - a completely new geogrid form and structure was developed. The new structure has a revolutionary geometry, and utilises new materials technology to deliver improved interlock and particle confinement.

The key design aspects that influenced performance

Materials, science and coextrusion

Tensar have combined a strong, stiff core with a more ductile outer surface. This has been achieved by bringing together two polymer streams with different characteristics, using a coextrusion manufacturing technique. The ductile outer surface can deform under pressure allowing aggregate particles to be forced deeper into the apertures during compaction and to be gripped by the geogrid, maximising confinement.

A more complex geometry

The geometric structure of the new geogrid is more complex than previous Tensar geogrids. A series of ribs in three directions create a triangular structure that provides in-plane stiffness. Within the triangular structure there are two concentric hexagons that deliver the enhanced interlock and confinement. Confinement is optimised by the high aspect ratio of the rib profile that allows a degree of in-plane flexure of the ribs increasing aggregate penetration and interlock while maintaining high rib stiffness at low strain. The inner hexagon, which is elevated above the junction nodes, also provides additional flexural capability to enhance interlock and further increase confinement.

Why is Tensar InterAx white?

All previous Tensar geogrids have been black, so why is Tensar InterAx white? Well in fact it is black and white, which becomes clear when looking at the sides of the ribs. The inner core is black, while the ductile outer core is white. Why is the new design white as well as black? Tensar is very proud of its advanced coextrusion manufacturing technique and colour is the best way of highlighting this improved technology

Proving the performance of Tensar InterAx

Tensar InterAx is the most efficient and best performing geogrid that Tensar has ever produced. Proof is evidenced from the multiple testing and research projects undertaken during and after the product’s development. Some of this research, including APT testing, has already been published - with more to follow. Many hundreds of thousands of square metres of Tensar InterAx have already been installed in multiple projects throughout the Americas, where it was first launched in 2021. Further details and case studies can be obtained from Tensar representatives

How does an increase in performance create real value?

An increase in performance translates to greater strength and stiffness of the stabilised layer. For unpaved roads and working platforms, the increase in strength of the stabilised layer can enable a reduction in layer thickness delivering reduced volume of imported aggregate with the associated cost and emissions reductions. For paved roads, the enhanced stiffness of the stabilised road foundation provides greater support to the pavement layers, increasing pavement life and reduced maintenance.

Want to learn more about Tensar InterAx geogrids?

For more information about Tensar InterAx, our best performing geogrid which provides better value and cost savings than all our previous geogrids, then visit our website here for more detail.