A Constitutive Model for Soils Evaluating Principal Stress Rotation and Its Application to Some Deformation Problems

Abstract

A constitutive model for soils by which the strain increments ( dɛ x , dɛ y and dγ xy ) are directly related to the stress increments (dσ x , dσ y and dτ xy ) is proposed. The stress-strain matrix between the strain increments and the stress increments is expressed in xy -coordinates fixed arbitrarily. In order to evaluate the influence of rotation of the principal stress axes on strains, “principal stress rotation tests” with several rotation times, in which the stress path circles several times along the circumference of a Mohr’s stress circle, are carried out by a “two-dimensional arbitrary stress apparatus” using a stack of aluminium rods. The “arbitrary” stress path dependency of strains is also examined by the same apparatus, and analyzed by the proposed model. The finite element analysis of soil foundation under a uniform strip load is performed using the proposed model, and the influence of rotation of the principal stress axes on settlements and lateral displacements is checked by comparing the computed results under different contribution factors (5% to 100%) of strains due to rotation of the principal stress axes. It is seen from the computed results that the settlements and lateral displacements are influenced significantly by the principal stress rotation.