Strain-Stress Relations and Failure of Anisotropic Clays

Different degrees of anisotropy were induced in two kaolinitic clays and one illitic clay by one-dimensional consolidation of thin hollow circular cylinders in a specially designed cell. For each degree of anisotropy, a pneumatic analog computer was used to subject the clay specimens to 16 different stress paths corresponding to a wide range of inclinations of the principal stresses on the axis of symmetry of the material. The computer was programmed to maintain this inclination constant for the duration of each test. The results show that the incremental strain-stress relations which are presented are valid for the three clays at their various degrees of anisotropy. The failure criterion of Goldenblat and Kopnov which takes into account anisotropy as well as the difference in behavior between extension and compression, is found to be extremely satisfactory in the range of stresses covered.