FIELD OBSERVATIONS ON STABILIZATION OF UNPAVED ROADS WITH GEOSYNTHETICS

The construction, instrumentation, and response to vehicle trafficking of an unpaved road on soft ground are described. The road is comprise d of an unreinforced section, three sections with different geotextile s, and a section with geogrid. The performance of the unreinforced sec tion compares reasonably well, at large rut depths, to prediction usin g the analytical approach most commonly used in current design practic e. Inclusion of a geosynthetic between tile base course layer and subg rade soil led to a significant improvement in trafficability, The impr ovement was greatest for the thinner base layer of 25 cm, acid diminis hed with increasing layer thickness. Reasonable agreement was, again, observed between the field performance and analytical predictions at l arge rut depths. The analytical approach was found to significantly ov erpredict the number of vehicle passes to develop a 5 cm rut. The lack of agreement at small to moderate rut depths is attributed to compact ion of the base course layer in response to vehicle trafficking that i s not accounted for in the analytical approach. Some implications of t he held observations for selection of a geosynthetic are discussed, wi th reference to separation and reinforcement of gravel layers over sof t soils.