Accurate Determination of Equivalent Modulus of Nonlinear Anisotropic Granular Base Layer
A variety of mechanistic models have been proposed to characterize the resilient behavior of unbound granular materials as a function of applied stress states including confinement and shear effects. However, significant computation effort is needed to implement the nonlinear stress-dependent modulus in the pavement structure response analysis. In this study, an equivalent modulus of granular base layer was developed to represent the nonlinear anisotropic behavior of aggregate base layer using three-dimensional finite element modeling analysis. The analysis results indicate that the equivalent modulus is not a constant value but changes with temperature, vehicle speed, and load. The equivalent modulus increases as the temperature increases but decreases as the vehicle speed increases due to the viscoelastic nature of asphalt surface layer. The equivalent modulus results in comparable results in the prediction of critical pavement responses, compared to the responses predicted using the real nonlinear anisotropic model for the granular base. The developed equivalent modulus can be used as an alternative approach when the sophisticated model is not available or the analysis needs to be conducted in a quick manner.