Elasto-Plastic Constitutive Equation for Geological Materials Withffabric

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There seems to be two major trends in the recent development of soil science. One trend is based on the material science in which soils are treated as assemblies of discrete particles. The spatial arrangement of particles and associated voids (called the fabric) plays an important role in the development. Another trend is motivated by the recent development of soil plasticity in which soils are treated as continuum. In this research, a tensor called the fabric tensor is introduced to express concretely the geometry made by discrete particles, and a continuum model is formulated such that the tensor is explicitly used in the framework of soil plasticity. The present interest is not to show a complete theory covering the whole range of soil behavior, but rather to exemplify a general method for combining the discrete approach with the continuum model. The conclusions are summarized as follows :The fabric tensor for three-dimensional assemblies of granular soils is introduced as an index showing the anisotropy due to the preferred orientation of constituent particles and is actually determined by using data derived from a material science approach of soils. Using the fabric tensor, a Drucker-Prager type of yield function is extended so as to take into account the anisotropic yielding behavior of granular soils. Plane strain tests on Toyoura sand are analyzed with a result that the anisotropic shear strength is well fitted by the extended Drucker-Prager yield function. Based on this, it is concluded that this study provides a step to link the material science approach of soils, in which the spatial arrangement of particles and associated voids plays an important role, to the continuum theory of plasticity/