Biaxial or Triaxial geogrid? Does it really matter?

“I am really confused and tired… Every supplier says something different… Which one finally performs better?”… Are you confused as well?

Biaxial geogrids have a long history in the reinforcement of pavements and ballast and/or capping layers in road and railway projects. Some years ago, a new concept of triangular aperture was introduced to the world as a better way to reinforce the soil. Not long after, various independent laboratory and field trials, including the full-scale trial by Montana State University and US Department of Transportation (DOT) in 2014, and the full-scale trial by Technical University Clausthal in Germany in 2016 demonstrated that the biaxial product perform better. The test sections reinforced by triaxial geogrid were actually one of the sections with the weakest performance in these trials.

This is not surprising. The main mechanism for geogrid reinforced pavements (especially flexible pavements) is lateral confinement of the granular material. This is mainly provided by interlocking of granular particles into geogrid apertures. The triangular geogrid has more ribs which leads to reduction of tensile forces in each rib.. Good for the geogrid, but what is the benefit for the granular layer? There are sufficient independent laboratory and field tests around the world that verify interlocking and lateral confinement is not necessarily related to the aperture shape.

Let’s think rationally and design as an engineer…

Wait for a second… Have you thought of the installation damage resistance of narrow ribs in a geogrid?