Pore Pressure Behavior of Ko‐Consolidated Clays

It is a common belief that negative incremental pore pressures occur during undrained triaxial compression loading of clays with overconsolidation ratios greater than approximately 4. While this behavior is characteristic of isotropically consolidated clays, a review of data from anisotropically consolidated tests on natural clays suggests that incremental pore pressures actually either remain positive or become only slightly negative at very high overconsolidation ratios. This phenomenon may be attributed in part to the location of the yield surface, which extends above the normally consolidated effective stress failure envelope, which is reflected by a Mohr-Coulomb cohesion intercept on the order of 4 ± 2% of the maximum preconsolidation pressure.