Experimental Study on Resilient Behavior of Triaxial Geogrid-Stabilized Unpaved Roads

Triaxial geogrid provides more uniform tensile resistance in all directions compared to biaxialgeogrid. Therefore, it more efficiently provides lateral restraint to aggregate during traffic loading. The performance of geogrid-stabilized unbound aggregate courses over weak subgrade has been studied over the years by many researchers. Previous studies show that the permanent deformation and vertical stress are reduced with the inclusion of geogrid. However, not many research studies have evaluated the influence of geogrid in resilient deformation and horizontal stress of base and subgrade. In this study, cyclic plate loading tests were performed in a geotechnical testing box (2 m × 2.2 m × 2 m) on unstabilized and triaxialgeogrid-stabilized sections at the University of Kansas. A 0.23-m-thick Kansas type AB aggregate was placed on soft subgrade. Cyclic plate loading was applied through a 0.3-m-diameter plate. To investigate the effect of load intensity, the plate load was increased from 5 to 45 kN in this study. Both permanent and resilient deformations were monitored by transducers placed at varying distances from the center of the loading plate at subgrade and surface. Vertical and horizontal stresses within base and top of the subgradelayer were also monitored by pressure cells. Test results indicate that the inclusion of a triaxial geogrid reduced surface and subgrade permanent deformations of the test sections. The resilient deformation did not change much during the loading at lower intensities, but increased significantly at higher loading intensities. The geogrid-stabilized base had higher horizontal stresses than the unstabilized base, indicating stiffness increase in the base course due to the lateral restraint of the geogrid. The test results also show that the horizontal pressures within the subgrade were significantly reduced by using a geogrid.