United States Department of Transportation
i
Development of Guideline for the Use of Geosynthetics in Different Roadway Layered System in Nebraska
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2024-01-01
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[PDF-15.65 MB]
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Edition:Final Report July 2020 – Jan 2024
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Abstract:This study evaluated the design properties of the geosynthetic reinforced soils for the roadway pavement and compared the reinforcing performance depending on different geosynthetics and soil types, particularly for a subgrade layer in Nebraska. The results obtained from a large direct shear test, pullout test, and soil chamber test with a dynamic cone penetrometer (DCP) showed that geosynthetic improves soil properties associated with the pullout and interface shear resistance, strength related parameters. The Large Scale Tracking Wheel Test also showed how the performance of biaxial geogrid reinforced pavement improved the strength/stiffness and reduced the total permanent deformation and pressure acting on the base/subgrade interface. Among the geosynthetic, three geogrids consistently showed better enhancement than geotextile, significantly improving all soils, including sand, red shale, and clay. Numerical modeling employing the input parameters obtained from the lab tests to simulate practical pavement layers for reinforced and unreinforced cases with geosynthetic application proved a significant enhancement when applying geosynthetics to reduce settlement and vertical stress. During the soil chamber test, the dynamic cone penetrometer index (DPI) successfully identified the depth of the geosynthetic installation, and the confined zone reinforced by the geosynthetic compared to the unreinforced case. Thus, in designing and analyzing geosynthetic reinforced subgrades in roadway pavements, it was found that the DCP test provides a valid and reliable method to evaluate the performance of geosynthetic reinforced soils. Furthermore, the Large-Scale Tracking Wheel test, performed for both reinforced and unreinforced cases, successfully showed improvement in strength/stiffness and total deformation reduction of a biaxial geogrid reinforced pavement. Based on these results, different percentage increases in the resilient modulus of reinforced subgrades were proposed for different soil and geosynthetic types. Finally, the relationships with DPI and other design properties, such as interface friction angle, subgrade reaction, and resilient modulus, were suggested for the geosynthetic reinforced soils.
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