Anisotropy in Heavily Overconsolidated Kaolin

Triaxial tests have been carried out on laboratory prepared Kaolin specimens at overconsolidation ratios from about l0 to 200 and at low stress level. Both isotropically and anisotropically consolidated specimens were tested in compression and extension and under drained and undrained conditions. It was found that anisotropy had little influence on e-log p' consolidation - swelling curves and on effective stress failure envelopes. It had an important effect on pore pressure development, undrained shear strength, secant modulus values, recoverable shear strain, and volumetric strains. The effective stress envelopes, although not influenced by anisotropy, were stress path dependent. In most cases, the envelopes tended to extrapolate through the origin.