The Development of Consitutive Equation under General Stress Condition for Sands Anisotropic Deformation-Failure Behaviors due to Initial Structure and Stress History

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The results of the research during two years are sunmmarized as follows :1. The constitutive model for three-dimensional deformation-failure behaviors of sands was developed. The model is named 'Multi-Directional Slinding Model'.(a) The basic soncept of the model is that granular materials such as sands are essentially descrete and have innumerable potential sliding planes in all locations and in all directions, and its deformation characteristics are governed by the slidin13EA\ : g mechanisma on each sliding plane.(b) Theree types of deformation mechanisms are considered on each sliding plane : compression, shear deformation and dilatancy.(c) The values of model parameters can be determined from the deformation behabiors observed in conventional triaxial tests.2. The model was applied to various stress conditions, and was verified by the observed deformation-failure behaviors.(a) The model is applicable to the general stress conditions including the rotation of stress axs, and can take the effects of confining pressure and overconsolidation into account.(b) The model can siulate the inherent and induced anisotropies in sands deformation-failure behaviors : the former is due to the anisotropic initial structures formed by sand grains and the latter is due to the shear stress history.3. The model was incorporated to the finite element method for boundary value problem. The calculation method is applied to the bearing capacity probles of shallow footing.(a) It was found that the model can predict the load-displacement behaviors and deformation properties of graound with initial anisotropic structures.(b) The scale effect of footing width on bearing capacity was predicted propwerly by the calculation method, becouse the effect of confining pressure on shear strength of sand element is taken into account by the model.