Evaluation of geogrid reinforcement effects on unbound granular pavement base courses using loaded wheel tester

Loaded wheel tester (LWT) was employed in this study to investigate the effect of geogrid reinforcement on unbound granular pavement base materials. In the LWT test, the compacted base course specimen was tested under the repeated wheel loading given by the LWT to simulate the actual service situation, and the rut depths of the base specimen were measured along the loading path. Four types of geogrids with different apertures and stiffness were tested with river sand and gravel base courses. In order to verify the effectiveness of the LWT tests, commonly applied cyclic plate loading tests were also performed on the same geogrids and base materials as comparisons. Three technical indices, the Traffic Benefit Ratio (TBR), the Rutting Reduction Ratio (RRR), and the Rate of Deflection (ROD), were employed in the study for the evaluation of the potential benefits of geogrid reinforcement. It was found that the results from LWT tests were generally in agreement with those from the cyclic plate loading tests, which indicates that the LWT test was an effective method to characterize the reinforcement effects of different combinations of geogrids and base courses. The corresponding technical indices proposed in the study were also valid to evaluate the reinforcement effects of geogrids on the specimens with or without geogrid reinforcement. From both LWT and cyclic plate loading tests, the geogrid-reinforced base courses exhibited significant improvement in rutting resistance comparing to the base courses without geogrid reinforcement.