Abstract：The true triaxial tests to the undisturbed and the saturated remould soft clay from the city of Yingkou were carried out to study the effect of confining pressure and principal stress on the strength of soft clay. The stress ratio of soft clay under the three-dimensional stress conditions is presented according to the comprehensive structure potential theory and the relationship between the deviatoric stress and the generalized shear strain of the undisturbed soft clay with structural parameters is established. The curve of the deviatoric stress(q) vs the generalized shear strain( ) of undisturbed soft clay is related to the pre-consolidation pressures. It is strain softening when the confining pressures are smaller than the pre-consolidation pressures and the volumetric strain appears shear shrinkage. It is strain hardening when the confining pressures are larger than the pre-consolidation pressures and the volumetric strain appears shear dilation. The type of curves of q vs. of the disturbed saturated soft clay is not affected by the structural yield stress and is basically the strain hardening one. The strengths of undisturbed soft clay and saturated soft clay are increased with the increasing of the confining pressure and coefficient of the principal stress. But the structural parameters of stress ratio decreased with the increasing of the shear strain，confining pressure and coefficient of the principal stress. The structural parameters of stress ratio varies logarithmically with the generalized shear strain. The structural parameters of stress ratio was introduced into the q- curves of undisturbed soft clay and the curves were thus obtained. The relationship between the deviatoric stress and the generalized shear strain for undisturbed soft clay was established and it has a good agreement with the experimental results.
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2017, Vol. 36 
