EFFECT OF OVERCONSOLIDATION AND ANISOTROPY OF KAOLIN CLAY USING TRUE TRIAXIAL TESTING

摘要

A series of strain controlled undrained true triaxial tests on cubical specimens have been performed using a fully automated flexible boundary experimental setup, with real-time feedback control system to evaluate the three-dimensional mechanical behavior of kaolin clay. This paper concentrates on the comparative response of the soil elements under monotonic shear loading observed at various overconsolidation levels. A possible shape of the initial yield surface is explored based on the limit of purely elastic deformations. The discussion includes the influence of the relative magnitudes of principal stresses on the clay behavior observed at different overconsolidation ratio values. Failure conditions are shown to be governed by the onset of localizations developed within the specimens, and because of which the specimens show sudden failure response before reaching a perfectly plastic deformation conditions. A reference surface constraining the ultimate plastic yielding of clay is found to be different from the observed failure surface. Based on the experimental observations, a 3-D failure criterion is developed that grows in size as a function of pre-consolidation stress.