Experimental Study on Triaxial Geogrid-Reinforced Bases over Weak Subgrade under Cyclic Loading

Geogrids have been successfully used to improve soft subgrade and reinforce weak base course by providing lateral confinement. However, uniaxial and biaxial geogrids cannot provide uniform resistance in all directions. A new product termed "Triaxial geogrid" was developed to overcome this limitation. The triaxial geogrid is expected to have a more stable grid structure to provide uniform resistance in all directions as compared with uniaxial and biaxial geogrids. However, the effects of the triaxial geogrids on the performance of reinforced bases have not been well evaluated. In this study, unreinforced and triaxial geogrid-reinforced bases over a weak subgrade were constructed in a large geotechnical testing box (2m x 2.2m x 2m high) at the University of Kansas and tested under cyclic loading. During the tests, the surface deformations and the vertical stresses at the interface between the base and the subgrade were monitored. The test results showed that triaxial geogrids increased percentage of resilient displacement and reduced permanent displacement and vertical stresses at the interface as compared with the unreinforced base.