Abstract
Geogrids are commonly used in paved and unpaved roadways for unbound aggregate stabilization, which restrains the lateral movement of granular materials by means of geogrid-aggregate interaction. The effectiveness of geogrid stabilization highly depends on the relationship between geogrid aperture geometry and aggregate particle size and shape properties. The direct measurement and quantification of aggregate particle interlocking within the vicinity of the geogrid is the key to evaluating the effectiveness of geogrid stabilization. This paper presents an experimental study recently conducted to investigate multi-axial geogrid stabilized dense-graded aggregates through permanent deformation behavior and shear wave measurement. Repeated loading tests in a triaxial setup were conducted to characterize the permanent deformation behavior while shear wave transducers, also known as bender element (BE) sensors, were used to measure the shear wave velocity propagated through aggregates. The improved modulus of unbound aggregates within the vicinity of the geogrid was successfully quantified using BE sensors. The collective experimental results showed that the ratio of geogrid aperture size (S) and median aggregate size (D50) serves as a good indicator of the effectiveness of geogrid stabilization for well-graded aggregate gradations. An optimum range between 2 to 3 for S/D50 ratio is recommended to achieve the maximum interlock and therefore most effectively stabilize dense-graded pavement base/subbase layers using geogrids.