Geogrid-Reinforced Pavement: Full Scale Testing

Tensar International Corporation, Inc. has released a paper presenting the results of full-scale testing on geogrid-reinforced roadways performed by the United States Army Corps of Engineers. Specifically, Tensar is trying to provide performance data for their new triaxial geogrid product. For those who don't know, the new triaxial geogrid (also known as the TriAx geogrid) not only provides strength in the latitudinal and longitudinal directions, but also in the radial direction. This, theoretically, provides much more stiffness to the pavement system.

We have known by now that geogrids do provide reduced pavement/base thickness, increases stiffness, decreased rutting, etc. when used properly. What's rare to see is the performance of full-scale testing showing the positive value of adding a geogrid at the base-subgrade interface under a thin pavement section in order to greatly reduce rutting for a pavement underlain with poor subsurface materials.

Based on the data contained in the report, the Traffic Benefit Ratio (TBR), which is an index that presents the benefit of using a geosynthetic relative to an unreinforced pavement section, of a geogrid-reinforced roadway was over 5 times relative to the control (unreinforced) pavement section.

The authors of the paper do (and rightfully so) suggest that the recommendation for the use of a geogrid for a particular project should be dictated by performance-based factors (i.e. test sections) as opposed to the providing minimum property values provided by the manufacturer. Even though I completely agree with this approach, it's often hard to convince a client (in this case typically being a government agency since they own most of the roads in the country) to perform field testing which can be quite expensive. Many engineers who are not familiar with this technology tend to recommend geogrids with the highest tensile strength thinking that this will suffice. Little do they know that this is NOT how geosynthetics function. The performance-based recommendation will do away with a lot of these false beliefs that many engineers have regarding the behavior of geogrids in pavement systems.

It seems like these days geosynthetics are getting very popular. In the coming years we'll see more people educated with this technology since more Universities are offering courses covering geosynthetics, more research is being conducted, and better quality products are being produced. Let's see what the future holds for the implementation of geogrids in pavement sections.

Article: Tensar Corporation, Inc.

Posted by: Reinaldo Villa