On the concept of characteristic states of cohesionless soil and constitutive modeling

The concepts of two characteristic states and their representation as characteristic state lines in the stress space are introduced to describe volumetric behavior of cohesionless soil during shearing. The first characteristic state line represents the state of cohesionless soil at failure while the second characteristic line represents the state at which the rate of volumetric strain momentarily vanishes as the soil passes from the compressive mode of deformation to the dilative mode of deformation during shearing. Explicit forms of the two characteristic state lines in the stress space are proposed and used to develop a constitutive model based on the framework of plasticity theory. The general forms of the characteristic state lines are verified using drained shear test data for a fine sand. Stress-strain and volumetric-axial strain responses are predicted using the proposed model.