Traffic Effects on Subgrade Layer Deformation

by Bryan Gee, P.E., on August 27, 2018

Over time, repeated traffic will cause deformation (or rutting) of pavement, base and subgrade layers. When the subgrade and base are unstabilized, this rutting often occurs much faster, causing serious maintenance issues resulting in pavement repairs. How does a designer ensure that these roads last as long as they should, or better yet, extend the life of these roads? This is where geogrids come into play.

A geogrid is a geosynthetic material used to stabilize the soil. Geogrids have openings, called apertures, which allows aggregate to strike through, providing confinement and interlock. Aggregate movement is greatly reduced and produces a stiffened layer. Integrating this stiffened layer, known as a mechanically stabilized layer (MSL), into the roadway section is what improves performance.  Pavement sections incorporating MSL’s are proven to have significantly less rutting in the asphalt, base, and subgrade layers. Take a look at the animation above for a brief demonstration.

TriAx Geogrid, from Tensar International, is the most advanced type of geogrid due to its triangular apertures and high profile ribs. The triangular shape allows loads to be spread over a wider area, lessening the impact of repeated traffic. Tensar has conducted extensive research for over three decades to study the effects of geogrid on pavement design. With more than 1,000,000 ESAL’s of research and counting, the performance of TriAx is well documented, even outperforming biaxial geogrid. 

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