Impact of Reduced Permanent Deformation in Pavement Foundations Using Geogrid Stabilization

In this paper, the impacts of loss of support beneath a concrete pavement due to permanent deformations within the supporting foundation layer are studied using 2D finite-element (FE) modeling of a rigid slab resting on a `solid' foundation system. Field testing using cyclic plate load tests were conducted on two side-by-side sections with similar subgrade involving a control section (no geogrid) aggregate base course (ABC) layer (thickness = 203.2 mm) and a geogrid stabilized ABC section ( thickness = 101.6 mm). Automated cyclic plate load tests were used to determine permanent deformation (delta(p)) and composite in situ resilient moduli (M-r) values of the foundation system. Field testing showed statistically significant differences between the two sections with lower dp in the geogrid stabilized section compared to the control section. The dp values measured for the two sections were used to model a void beneath the slab over a defined area (i.e. loss of support, LOS). FE analysis was performed on a jointed square pavement slab with loading applied near the joint corner for different LOS conditions beneath the slab corner. The principal stresses in the pavement layer were calculated for standard 80 kN single axle highway loading and SWL50 aircraft loading cases for different pavement thicknesses. Using the principal stresses and the stress ratio (SR), the number of load repetitions for fatigue failure were calculated. FE analysis results showed that the magnitude and the void size have significant impacts on the SR and the resulting fatigue life of the pavement layer.