Study on the influencing factors about pore pressure generated for soft clay under complex stress path

A hollow cylinder apparatus is used to carry out tests on the principal stress axis rotation for Hangzhou intact soft clay under consolidated undrained conditions, and complex stress path under axisymmetric and three-dimensional stress state is designed. The theoretical results about the impact of rotation rate of the principal stress axis, coefficient of the intermediate principal stress and the initial shear stress on the pore pressure characteristic is validated in tests. The theoretical analyses and test results reveal that the deformation of specimens and the increment of pore pressure generated in the rotation rate of the principal stress axis between 0 and 45 degrees are different from those in the rotation rate of the principal stress axis between 45 and 90 degrees during the rotation of the principal stress axis, and the rotation rate of 45 degrees is the cut-off point. When the coefficient of the intermediate principal stress changes between 0 and 1, the increment of the pore pressure generated decreases first and then increases with the increase of the coefficient of the intermediate principal stress, and the coefficient of 0.5 is the cut-off point, and the impact of the coefficient of the intermediate principal stress on the pore pressure generated is controlled by the level of shear stress in the shearing process. The higher the initial shear stress, the greater the increment of the pore pressure generated in the increasing stage of the initial shear stress and the higher the overall level of the pore pressure in the shearing process. The angle of the major principal stress direction as the control conditions will generate more increment of pore pressure than the initial shear stress as the control conditions in the initial stage of shear stress path including the rotation of the principal stress axis and the increase of the shear stress, and it has a greater impact on the pore pressure generated in the shearing process.