Field Observations on Stabilization of Unpaved Roads with Geosynthetics

Abstract

The construction, instrumentation, and response to vehicle trafficking of an unpaved road on soft ground are described. The road is comprised of an unreinforced section, three sections with different geotextiles, and a section with geogrid. The performance of the unreinforced section compares reasonably well, at large rut depths, to prediction using the analytical approach most commonly used in current design practice. Inclusion of a geosynthetic between the base course layer and subgrade soil led to a significant improvement in trafficability. The improvement was greatest for the thinner base layer of 25 cm, and diminished with increasing layer thickness. Reasonable agreement was, again, observed between the field performance and analytical predictions at large rut depths. The analytical approach was found to significantly overpredict the number of vehicle passes to develop a 5 cm rut. The lack of agreement at small to moderate rut depths is attributed to compaction of the base course layer in response to vehicle trafficking that is not accounted for in the analytical approach. Some implications of the field observations for selection of a geosynthetic are discussed, with reference to separation and reinforcement of gravel layers over soft soils.