STRESS-DEFORMATION AND STRENGTH CHARACTERISTICS OF SOIL UNDER THREE DIFFERENT PRINCIPAL STRESSES

The concept that the deformation of soil is governed by the shear-normal stress ratio on the mobilized plane of soil particles has already been discussed on the basis of the microscopic analysis of the behaviors of soil particles under shear. 5 This discussion originates in an idea that soil is one of the materials to which the frictional law in its broad sense of word applies. In the present paper, the authors expand the formerly proposed concept2),4 of three mobilized planes (compounded mobilized planes) among the three principal stress axes into a new postulate that a stress plane called "spatial mobilized plane" occurs in the three-dimensional stress space. Then, they propsse to verify, with various test data, the fact that stress-strain relationships of soil under three different principal stresses can uniquely be expressed by interpreting the relationships with respect to this plane. They also propose a new yield condition (failure criterion) of soil that soil yields when the shear-normal stress ratio on this plane has reached a fixed value.