Research conducted in Virginia and Montana highlights the growing use of geosynthetics for stabilization of subgrades beneath roadways. The Virginia Transportation Research Council, a partnership between the Virginia Department of Transportation (VDOT) and the University of Virginia, released a report that explores the potential benefits of using a geotextile as a separator in low-volume roadways such as secondary and subdivision streets. Researchers concluded that “the use of geotextile materials appears to have great potential to extend the service life of pavement on the secondary road system, offering significant cost savings to VDOT.” The report is available at www.virginiadot.org/vtrc/main/online_reports/pdf/10-r1.pdf

Four NAUE Secugrid geogrid-reinforced stone columns support a 4,800-pound vehicle.

The Montana Department of Transportation and NAUE GmbH & Co. KG sponsored research by the Western Transportation Institute at Montana State University-Bozeman that examined the use of several geosynthetics in unsurfaced roads to provide subgrade stabilization. Researchers concluded that, in the roadway tested, welded geogrids, woven geogrids, and integrally formed geogrids provided the best performance. The report is available at www.mdt.mt.gov/research/docs/research_proj/subgrade/final_report.pdf

In a public demonstration of the capabilities of its Secugrid geogrid, NAUE recently created geogrid-reinforced stone columns to support a 4,800-pound vehicle. The four columns, each 16 by 16 by 16 inches, were constructed from crushed gravel with Secugrid 40/40 Q1 geogrid inserted every 4 inches to create three layers of reinforcement.

Secugrid geogrids are manufactured from high tensile strength extruded monolithic flat polymer bars with high-strength welded junctions.

Another geogrid product, Tensar International’s TriAx Geogrid uses multi-directional properties of triangular geometry to increase in-plane, radial stiffness. According to the company, its square-edged rib shape and deeper rib profile confines aggregate to form a stabilized composite layer that optimizes the component thicknesses of aggregate and asphalt for paved applications and granular fill for unpaved applications. Tensar said that TriAx Geogrid can reduce asphalt quantities by 15 percent to 30 percent and aggregate base/subbase requirements by 25 percent to 50 percent, as well as extend maintenance and rehabilitation intervals and increase the service life of flexible pavements.

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