Optimum location of geogrid reinforcement in unpaved road

This study evaluated the optimum location of a reinforcement layer to maximize the efficiency of the reinforcement inclusion in an unpaved road section. The analyses are used to investigate the optimum location of the reinforcement layer within the aggregate base course (ABC) layer, and provide a possible reason for the improvement in performance. A series of three-dimensional finite element method analyses was performed, and the strain and stress response of a reinforced unpaved road section with two different ABC thicknesses was evaluated. The analyses were conducted under cyclic loading with three different radii of the circular loaded area. The embedded depth of reinforcement was varied within the ABC layer. Results indicate that regardless of ABC layer thickness, the surface deformation is minimized when the reinforcement is embedded at a depth equal to half of the radius of the loaded area (D = 0.5r). A higher tension force is mobilized in the reinforcement element when it is placed at D = 0.5r. It is also shown that the required thickness of ABC is reduced when the reinforcement layer is implemented at the depth at which the maximum vertical strain occurs. Depending on the thickness of the ABC layer, the finite element analysis results indicate that the reinforcement layer could be ineffectual if it is placed at the interface between the ABC and the subgrade layer as is traditionally the case.