A large portion of the road network in Canada is unpaved. It is desirable to minimize construction cost and maintenance cost of these road systems. One way to minimize the maintenance cost of these roads is to reduce their rate of deterioration, therefore extending their period of acceptable service. This can be achieved by reinforcement of the road base or subbase. A high strength polyethylene grid (geogrid) has been selected as the reinforcing material in this research.
A comprehensive testing program was designed with its main objective to investigate the effectiveness of using grid reinforcement in unpaved road systems. The different variables in the major experimental program included : base thickness, absence or presence of reinforcement and grid location. Instrumentation was installed to measure dynamic and static strains induced in the reinforcement grid, static rebound, permanent deformation, deflection conditions at the base-subgrade interface and at the base surface.
The analysis of the experimental results has proven that the use of grid reinforcement is effective in reducing damage to unpaved roads. The experimental results also showed that the inclusion of grid reinforcement can enable an unpaved structure to carry fifty percent more load applications than without reinforcement. It was found that the best location of the geogrid is at the bottom of the base layer. Inclusion of the reinforcing grid helped to distribute the applied load over a wider area on the surface of the subgrade with reduced stress levels (25% stress reduction). Such findings have led to the important conclusion that grid reinforcement can be used to extend the service life of unpaved roads and to minimize their maintenance cost substantially.