Granular Material Characterization for Mechanistic Pavement Design

This paper presents a procedure for characterizing granular base and subbase materials to provide the properties needed by the mechanistic methods for pavement design. It includes repetitive testing under different confining pressures and axial stresses. It is different from the resilient modulus test. Each specimen is tested at a different confining pressure for 10,000–100,000 load repetitions. Both the resilient and the permanent responses are collected. The sample compaction, the setup for measuring vertical and horizontal deformations, and the repetitive testing are described. Test results at different confining pressures and axial stresses show that (1) the material exhibits hysteretic behavior, (2) the material response is nonlinear [after a large number of load repetitions (of the order of 10,000) the material may be considered as elastic], (3) the material dilates in the resilient mode; (4) the resilient behavior can be modeled reasonably using the extended bulk modulus equation or the hypoelastic model, and (5) the variability in the material response indicates that the specimen size is, at best, marginal for the aggregate gradation used in the study.