Large scale tests on geosynthetic reinforced unpaved roads subjected to surface maintenance

Geosynthetic can be effectively used as reinforcement in paved and unpaved roads. This paper presents a study on the use of geosynthetic to reinforce unpaved roads on poor subgrade. A large equipment was used to perform the tests under cyclic loading and a nonwoven geotextile and a geogrid were used as reinforcing layers installed at the fill-subgrade interface. Displacements along the fill surface and stresses and strains in the subgrade were measured during the tests. Three cyclic loading stages were applied in each test up to a rut depth at the fill surface of 25 mm be reached in each stage. At the end of a loading stage the fill surface was repaired for the following loading stage. Monotonic loading tests were also carried out for comparisons. The results obtained show the significant contribution of the presence of the reinforcement layer in increasing the number of load cycles for a given rut depth to be reached and in reducing the stresses and strains in the subgrade, particularly when geogrid reinforcement was used. It was also observed that monotonic loading tests underestimated the contribution from the reinforcement. A simple cost-effectiveness analysis showed that the reduction of maintenance works due to the use of geosynthetic reinforcement may yield to significant savings in this type of problem, seldom considered in the analysis of the economics of this type of application on a routine basis.