Yield and Failure of a Clay under Triaxial Stresses

A study is made of the three-dimensional stress-deformation behavior of a normally consolidated saturated remolded clay. It is demonstrated that unless certain requirements of analytical models (e.g., isotropy and volume change) are reconciled with the observed physical performance of the clay in yield, serious errors and misinterpretations would arise in the use of classical plasticity techniques for analysis. The true triaxial test results permit the measurement of associated deformations, and allow for the development of modifications to the classical theory. The adaptation of plasticity theory proposed in this study affords a suitable analytical model for the description of response behavior of the clay over a considerable range of applied stress levels. Beyond this range the changes in material properties accompanying shear deformation can no longer be compatible with the requirements of isotropic plasticity theory. In the ultimate stage of yielding, the clay performance tended to that of an internally frictional material.