Research on the Influence of the Rotation of Principle Axis of Stress to the Constitutive Relation Soil

The rotation of principal axis of stress is a mechanical problem that must be considered in geotechnical engineering. In light of matrix theory, the characteristic of stress increment that causes the rotation of principal axis of stress is obtained and the arbitrary stress increment is decomposed into the coaxial part and rotary part. A general mode for stress-strain behaviors involving the rotation of the principal axis of stress is presented. Based on the generalization from the increment of stress invariant to the invariant of stress increment, the expression system of elastoplastic theory for complete stress increment is presented. The plastic deformation caused by the rotation of the principal axis of stress can be computed strictly, and it indicates that the influences can be attributed to the shearing deformation and dilatancy caused by the generalized shear of the stress increment.