Evaluating nonlinear elastic models for unbound granular materials in accelerated testing facility

The characterization of unbound granular materials is particularly important in thin-surfaced pavements where most of the bearing capacity is provided by the granular layers. For an accurate modeling of the elastic response of these materials, several important models described in the literature have been considered in a study. Three of the most-used nonlinear elastic models for unbound granular materials used by researchers and practitioners in the pavement engineering field are evaluated. The nonlinear elastic models of the materials were especially implemented in ABAQUS, a general purpose, three-dimensional finite element code (3D-FEM) that uses user-defined material subroutines. The 3D-FEM solutions were validated through a set of data collected in the full-scale Canterbury Accelerated Pavement Testing Indoor Facility (CAPTIF). Vertical, transverse, and longitudinal strains were measured at CAPTIF through an array of strain gauges buried at different depths in the pavement sections. The vertical stresses were measured by load pressure cells at different locations in the pavement sections. In general, the results obtained from the nonlinear models are considered good for the materials and structures studied in the research. Little difference in the accuracy of the nonlinear models was found.