THE PLASTIC POTENTIAL OF NORMALLY CONSOLIDATED CLAYS

This paper discusses the possibility of using the concept of plastic potential to study the stress-strain relationship of normally consolidated clays. By following that the moisture content of a normally consolidated clay depends uniquely on the stress state and is independent of the stress path, Calladine's method is proved to be valid in finding the yield surface according to the stress path of undrained triaxial compression test. Analyzing the experimental data of four different clays with this method gives the result that the yield surfaces in the plastic regime of normally consolidated state take the elliptical shapes in the coordinate system of (p, q), and may be expressed by the following equation : where p is the mean effective normal stress, q is the deviator stress. Then the only parameter which controls the hardening laws of normally consolidated clays will be the equivalent hydrostatic compression pressure p_e. It is also proposed that the data of undrained triaxial compression tests and hydrostatic compression tests with rebound curves may be used to evaluate approximately the amount of plastic strain of normally consolidated clays subjected to various stress paths.