Eight-Year Field Performance of Secondary Road Incorporating Geosynthetics at Subgrade-Base Interface

In June 1994 an instrumented 150-m-long secondary road pavement section was built in Bedford County, Virginia. This pavement section was composed of nine individual segments each 15 m long. The nine sections include three groups with aggregate base layer thicknesses of 100, 150, and 200 mm. Three sections from each group were stabilized with geotextiles and three were stabilized with geogrids at the base-subgrade interface. The remaining three sections were kept as control sections. As part of the structural analysis, deflection data parameters such as the base damage index and surface curvature index calculated from falling weight deflectometer (FWD) data were analyzed after being corrected for temperature variations from the time of construction until October 2001. Performance criteria such as rutting measurements were also collected over the whole period. A nonlinear exponential model was used to describe the development of rutting versus cumulative equivalent single-axle loads for the 100-mm base course. A linear elastic program incorporating constitutive material properties was used to calculate vertical compressive stresses, which were used with FWD deflections to predict rutting rates with a mechanistic equation. The rutting rate results confirmed the separation function of geosynthetics that prevented the migration of fines from the subgrade to the base course layer and the penetration of the aggregate base layer into the subgrade. Rutting results, deflection data, and service life analysis showed that geosynthetically stabilized sections significantly improved the performance of the 100-mm base course sections.