3D and 2D Formulations of Incremental Stress-Strain Relations for Granular Soils

3D formulation of incremental relations, describing pre-failure deformations of granular soils, is presented. The starting point are respective equations formulated previously for the axi-symmetrical configuration, as that in the tri-axial apparatus. These relations, proposed for particular configuration, are generalized in the form of tensor equations for the strain increments. Similarly, the loading/unloading criterion and the instability line have been generalized for 3D conditions. A kind of cross-isotropy of granular soil is taken into account. Then, the incremental stress-strain relations for the plane strain state are re-derived from general equations, as such conditions are most often used for simulations of practically important problems. The procedure proposed in this paper is practically oriented, as the soil parameters can be determined just from the tri-axial tests.