Abstract:Subjected to complex loads, such as wave, earthquake and traffic loads, the corresponding stress states of the foundation soil are complicated. The simultaneous variations of the deviatoric stress and principal stress direction occur in practical engineering. However, there are few studies on properties of natural soft clay under combined principal stress rotation, which means that when the principal stress axis rotates, the deviatoric stress increases continuously, and the average principal stress and the medium principal stress coefficient remain unchanged. In order to study the deformation characteristics of saturated natural soft clay under combined principal stress rotation, the torsional shear tests of natural soft clay were carried out based on the hollow cylinder apparatus (HCA). The influence of different inclined consolidation and intermediate principal stress on the deformation and pore pressure of natural soft clay under combined principal stress rotation were discussed. The results showed that the deformation behavior and pore water pressure accumulation of tested samples were significantly influenced by the intermediate principal stress coefficient b. The compressive deformation was dominated in the axial direction when b equaled to 0 or 0.5, and extensive deformation was dominated under b equaled to 1.0. The generation of axial, circumferential and torsional deformation was different obviously, while the radial deformation was almost the same, the value of radial stain was approximate 0 when b equaled to 0.5. The corresponding major principal stress angles to the maximum value of pore water pressure were different under different inclined consolidation conditions. The change of stress and strain was not synchronous with the increase of the azimuth of deviator stress and principal stress, i.e., there was an obvious non-coaxial behavior.