DESCRIPTION OF INHERENT/INDUCED ANISOTROPY OF SOILS:
ROTATIONAL HARDENING RULE WITH OBJECTIVITY

Koichi Hashiguchi

ABSTRACT : The inherent/induced anisotropy of soils could be described concisely by the concept of the rotation of yield surface around the origin of stress space, called the rotational hardening by Hashiguchi (1977), whilst the description of the inherent anisotropy of natural grounds by the rotation of yield surface was advocated by Sekiguchi and Ohta (1977). In this article the interpretation of the evolution rule for the rotation of yield surface, i. e. the rotational hardening rule for soils is given on the pertinent physical background, revealing the similarity to the nonlinear kinematic hardening rule for metals. The rotational hardening variable is the second-order tensor and thus the material-time derivative does not obey the ordinary transformation of second-order tensor losing the objectivity. Some comments for its pertinent integration are given in brief.

Key words: anisotropy, constitutive equation of soil, (corotational rate), (objectivity), plasticity, (rotational hardening) (IGC : D6/ E2)