STUDY OF INFLUENCE OF PARAMETERS OF INTERMEDIATE PRINCIPAL STRESS AND PRINCIPAL STRESS DIRECTION ON ANISOTROPY OF INTACT CLAY

There was lack of knowledge about the anisotropy of soft intact clay since most studies were performed on cohesionless soils. A hollow cylinder apparatus(HCA) is used to study the anisotropy of typical Hangzhou intact clay to investigate the influence of the parameters of intermediate principal stress and the principal stress direction on anisotropy. It is revealed that the anisotropy of intact clay is greatly affected by the value of the parameters of intermediate principal stress b,and is hardly affected by the principal stress direction. The intact clay is transversely isotropic along the depositional plane when b equals zero. When b equals 0.5,the characteristic of anisotropy is different. Regardless of the direction of the principal stress,the radial strain and the tangential strain of the sample always equal in magnitude and opposite in direction. Meanwhile the volumetric strain of intact clay is equal to the value of the second principal strain. Apparent dilatancy and strain softening are observed when samples fail at small rotation angle. Shrinking is significantly noticed in the beginning of failure with the increase of the rotation angle,while strain softening gradually vanishes. All these phenomena are not observed in b equaling tests. Test results also present that the intact clays have the lowest compressibility along the direction of deposition and the highest compressibility along the direction of rotation angle 50°.