A NEW MODEL FOR UNSATURATED SOIL USING SKELETON STRESS AND DEGREE OF SATURATION AS STATE VARIABLES

摘要

A new constitutive model using skeleton stress and degree of saturation as independent state variables is proposed for unsaturated soil, which can properly describe the influence of the degree of saturation. In the model, a very simple moisture characteristics curve considering moisture hysteresis of unsaturated soil is also proposed. Not only can the moisture characteristics curve be applied to secondary drying process but also to primary drying process originated from slurry soil. The constitutive model is able to describe the behaviors of both unsaturated soil and saturated soil since the skeleton stress can smoothly shift to effective stress if the saturation changes from the unsaturated condition to the saturated condition. Meanwhile, overconsolidation, one of the main features of soils discussed in the models for saturated soils, is also considered together with the degree of saturation. Other mechanical features, such as the structure of soil and stress-induced anisotropy, can be easily incorporated into the proposed model within the framework of the present research. Results from the simulation have shown that the main features of unsaturated soil in the isotropic consolidation test and triaxial compression test under both the drained and exhausted condition with different confining stress and suction can be qualitatively described.