SIMULATION OF SHEAR AND ONE-DIMENSIONAL COMPRESSION BEHAVIOR OF NATURALLY DEPOSITED CLAYS BY SUPER/SUBLOADING YIELD SURFACE CAM-CLAY MODEL

摘要

Naturally deposited clays exhibit complicated mechanical behavior that differs from that of remolded clays. For example, clay in a normally consolidated state commonly exhibits softening in undrained shear tests or "rewinding" in a heavily overconsolidated state. The Super/subloading Yield Surface Cam-clay model (Asaoka et al., 1998, 2000, 2002) was proposed in ah attempt to clarify the complicated mechanical behavior in naturally deposited clays. In this constitutive model, the concepts of "structure," overconsolidation, anisotropy, and their evolution laws, are introduced into the modified Cam-clay model. In the present study, undrained triaxial compression tests and oedometer tests were carried out on two types of naturally deposited undisturbed clay, Pleistocene clay and Holocene clay, and the behavior was then simulated using the Super/subloading Yield Surface Cam-clay model. The findings of the present study are as follows: 1) For the two types of undisturbed clay, the Super/subloading Yield Surface Cam-clay model can simulate undrained triaxial compression behavior ranging from the normally consolidated state to the overconsolidated state, corresponding to various isotropic pressures using a single set of material constants. 2) In addition, the model can simulate one-dimensional compression behavior using the same material constants as those used for the simulation of the undrained triaxial compression behavior. 3) Through the simulation, the mechanical behavior of Pleistocene clay and Holocene clay, which have different loading histories and have undergone different aging effects, can be described by the different evolution parameters, as well as the elasto-plastic parameters.