UNDRAINED PLASTIC MODULUS FROM ORIGINAL CAM CLAY

One aspect of the original Cam-clay model is that the derived undraine d stress-strain curve can be expressed in closed form and used to dete rmine a finite value of stiffness at epsilon = 0 that is equivalent to an undrained plastic modulus (or E(u)) for normally consolidated clay s. With respect to soil behavior, this predicted modulus in no way rep resents the initial modulus E(max) that is fundamental and obtained fr om resonant column tests at small-strain levels (epsilon < 10(-5)), bu t interestingly corresponds to the apparent initial undrained stiffnes s obtained from a hyperbolic fit of isotropically consolidated undrain ed triaxial stress-strain data over the range of intermediate to large strains (0.001 < epsilon < 0.10). A review of triaxial and consolidat ion data from 17 clays supports this observation.