Drained torsional shear tests were performed on hollow cylindrical intact soft clay specimens to investigate the anisotropic deformation, strength, and noncoaxial behavior in general stress states involving variations in both the magnitude and direction of the principal stresses. Tests were conducted by maintaining a fixed principal stress direction α relative to the vertical direction while keeping the intermediate principal stress coefficient b constant. It was found that the magnitudes of the radial strain ε_r were dependent on the b value, and the magnitudes of circumferential strain ε_θ were dependent on the α angle. The influence of b and α on the relationship between volumetric strain and shear stress was less significant. The stress paths for all α angles at b = 0.5 were determined under various stress levels. Furthermore, the experimental results showed that the noncoincidence between the directions of strain increment and stress existed in clay, and the noncoaxiality was influenced by both intermediate principal stress and principal stress direction.

The deformation behavior and shear strength of soft marine clays subjected to wave or traffic loads are different from that in triaxial loading due to the changes of major principal stress direction β and intermediate principal stress coefficient b. To investigate the anisotropy affected by β and b in natural soft marine clay, a series of drained tests were conducted by hollow cylinder apparatus. The principal stress direction relative to vertical direction were maintained constant under an increasing shear stress, with fixed intermediate principal stress coefficient b. The influence of the b and β on anisotropy of typically Wenzhou intact clay is discussed. It was found that octahedral stress–strain relationships expressed anisotropy with different b and β. The friction angle and deviator stress ratio with different b and β were presented to provide guidance for engineering projects in the coastal zone.