Stress-Strain Relationship of Soils as Anisotropic Bodies Under Three Different Principal Stresses

Abstract

The author has shown in his previous paper (Yoshida, 1978) that a set of mean normal stress and deviatoric stress (which is not identical to principal stress difference) can be adopted reasonably to describe the stress-strain relationship for soils ; furthermore, the author’s new idea that dilatancy is defined as the volumetric strain induced by deviatoric stress led to the conclusion that dilatancy is a phenomenon caused by anisotropy in deformation. These were verified by the results of the triaxial tests by Matsuoka (1974) under radial isotropy. The stress-strain relationship in a more general case with three different principal stresses under orthogonal anisotropy is developed in this paper, and is verified by the empirical results obtained by Ko and Scott (1967, 1968). Herein, two types of coefficients of deformation, D and G , are introduced for ‘shear’ and they are assumed to be expressed by the parameters of mean normal stress and principal stress ratios. Five constants n, ( a, α ) and ( b , β ) are used to define these coefficients of deformation and were determined directly from the results of conventional triaxial compression tests.