ABSTRACT
Performance of rigid pavements depends primarily upon uniformity in the slab support condition and a composite response of unbound aggregate layers and subgrade. Several pavement design and analysis methods (e.g., AASHTO, PCA) consider modulus of subgrade reaction (k-value) as one of the key parameters representing pavement foundation strength. The k-value is represented by the reaction pressure required for per unit settlement and is directly influenced by the characteristics of unbound pavement layers and subgrade strength. AASHTO T222 provides guidance for measuring k-value in the field for ensuring that the compacted aggregate layers have achieved the target stiffness. However, such a method of measuring in-situ k-value is not common in practice. As an alternative, some empirical approaches are available for estimating “theoretical” k-value that include back-calculating FWD deflection data or correlating with material stiffness parameters. This paper presents k-value test results from static plate load testing on geogrid stabilized and unstabilized roadways at two sites. Two types of multi-axial geogrid were selected for constructing two separate stabilized aggregate layers over the existing subgrade. An Automated Plate Load Testing (APLT) system was used for conducting the static plate load tests to measure k-value, by following the AASHTO T222 protocol. At the first site, the aggregate base course (ABC) thicknesses of the stabilized and unstabilized sections were 125 mm and 287 mm, respectively. Similarly, the ABC thicknesses of the stabilized and unstabilized sections were 118 mm and 212 mm at the second site. Despite this reduction in thickness, the geogrid stabilized sections exhibited higher k-values in comparison to the unstabilized sections.
