Geogrid stabilization effectiveness – Comprehensive assessment through multiscale experiments with bender element sensor technology

Geogrids are commonly used in pavement structures to mechanically stabilize unbound aggregate layers to improve structural performance and extend lifespan. Geogrids stabilize aggregate particles by restraining their lateral movements through mechanisms such as interlocking and friction. This paper presents a multiscale experimental study conducted on extruded and welded geogrids, having different aperture shapes and properties, for their stabilization effectiveness through quantifying modulus enhancement using the bender element (BE) sensor technology. The study examines geogrid-stabilized aggregates both in a large-scale testbed with three embedded BE field sensors and in a repeated load triaxial device with geogrid coupons installed at midheight and embedded BE sensor pairs above geogrids. The large-scale testbed allowed lateral pressure measurements under a series of loading and unloading stages. Small strain moduli from the shear wave measurements determined from both experiments quantified geogrid stiffened zones when tested with the same dense-graded aggregates. All four geogrids showed modulus enhancements in both test setups when compared to control test results. The geogrid mechanical stabilization influence zone was observed to be as large as 6 in. (15 cm) above one extruded geogrid. Such quantified modulus enhancements and influence zones are essential for incorporating geogrid into mechanistic-empirical (M-E) pavement design framework.