Influence of Intermediate Principal Stress and Principal Stress Direction on Drained Behavior of Natural Soft Clay

Abstract

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 εr were dependent on the b value, and the magnitudes of circumferential strain εθ 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.