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Field Investigation of Geosynthetics Used for Subgrade Stabilization

Project #: 4W2005
Start Date: 02/01/2008
End Date: 06/30/2009
Status: Completed

The use of reinforcement geosynthetics in unsurfaced roads built upon a soft subgrade is known to provide benefit through better distribution of applied loads and increased bearing capacity. This report describes a research project where field test sections were constructed to evaluate the performance of several geosynthetics commonly used for subgrade stabilization. A sandy clay soil was prepared as a weak roadbed material to a CBR strength of approximately 1.8 and a 20 cm thick aggregate layer was compacted over the geosynthetics. Trafficking was provided by a fully-loaded tandem axle dump truck. Longitudinal rut depth, along with discrete measurements of displacement and pore pressure were monitored throughout the trafficking period. Post-trafficking excavations were conducted to evaluate damage to the geosynthetic, base contamination and deformation of the layers. The construction and monitoring techniques employed during the course of this project helped establish a test bed of relatively similar conditions to facilitate more direct comparison of individual test sections to one another. An empirical analysis was used to normalize small differences between the subgrade strength after trafficking and base course thickness between test sections to facilitate a more direct comparison of performance. The results showed that the welded geogrids, woven geogrids and the stronger integrally-formed geogrid product seemed to provide the best overall performance, while the two geotextile products and the weaker integrally-formed geogrid provided significantly less stabilization benefit based on the normalized rutting performance at 50, 75 and 100 mm of longitudinal rut data, and this performance is likely directly related to the tensile strength of the materials in the cross-machine direction. Overall, this research provides additional and much needed insight regarding which properties have a significant role on performance, as well as an assessment of two design methodologies’ ability to predict rutting performance using the test section parameters as design inputs. Additional work is needed to more fully understand which geosynthetic material parameters are most relevant in these situations.


This project aims to construct test sections in the field to investigate the relative benefit of various geosynthetics available on the market to an unpaved road.


  • Eli Cuelho
    Eli Cuelho