A New Generation of Resilient Modulus Characterization of Unbound Materials

Pavement damage is heavily influenced by seasonal variations in the environmental regime and by externally applied loads. The state of the art methodology currently evaluated by pavement engineers focuses upon coupling the effects on pavement performance of moisture content/matric suction properties of unbound materials with the external stresses. The literature review showed that several equations have been proposed to incorporate moisture variation effects on resilient modulus; however, the limited models available lack fundamental principles or have not been properly validated. A feasibility study on cohesionless granular base material is presented, whereas matric suction was controlled during drained and measured during undrained resilient modulus tests. It is apparent that certain modifications in the recommended stress state conditions of the NCHRP 1-28A protocol may be necessary when measuring matric suction due to the axis-translation needed during the test. Difficulties associated with the test include the current confinement fluid, which allows for air diffusion during the suction equilibration stage. Preliminary results show that the k₁-k₂-k₃ parameters used in the approved AASHTO Mechanistic Empirical Pavement Design Guide (ME-PDG) may be functions of the suction applied to the specimen during the test protocol.