A New Model for the Cross Anisotropic Nonlinear Elastic Behavior of Unbounded Soils for Road Pavements

Abstract

This study presents a new generalized small strain nonlinear anisotropic constitutive model for use in the elastic analysis of unbounded soils for road pavements. The model rests on a method to determine the cross anisotropic moduli of unbounded soils based on the classic repeated-load triaxial compression test. The model incorporates nonlinear small-strain behavior in a triaxial stress space by considering the inter-dependency of the bulk K*, shear G* and cross anisotropic modulus, J. In agreement with the laboratory test results the moduli, at a given water content, are dependent on the initial state of stress in p–q space. The model is derived by considering pure isothermal elastic behavior and by letting the net elastic work per unit volume along a closed stress path equal to zero. An approximate stress–strain curve, using solely the non linear constitutive model, is obtained using a linear analysis that simulates a typical triaxial test. Finally a non linear finite element analysis, which incorporates the non linear constitutive model, is carried out to provide a more elaborate assessment of model performance.