Bulletin of Computational Science Research Center, Hosei University

異方性降伏関数

材料パラメータ

非線形計画法

材料試験

岩盤

Plasticity

anisotropic yield function

material parameter

nonlinear optimization programming

Rock

A new anisotropic yield function was proposed for the hydrostatic stress dependent materials. This function consists of an idea that each independent components of a stress tensor is multiplied by the arbitrary coefficient corresponding to each anisotropic principal axis. Both of a meridian of this yield surface and a shape of the deviatoric stress plane are dependent upon hydrostatic pressure. It was shown that a number of classical yield functions are derived from the proposed yield function as special cases. The material parameters included in the proposed yield function ware evaluated by using a nonlinear optimization programming method with certain constraint conditions. This method can evaluate the material parameters only by conventional uniaxial and triaxial compression tests, and do not require any difficult tests as simple shear tests or uniaxial tention tests for rock like materials. To prove the usefulness of the proposed yield function and material parameter evaluation method, the numerical analysis results for various anisotropic rock materials were compared with the experimental results. The conclusions are as follows; ・ the numerical results of yield strength have good agreement to the experimental results for various anisotropic rock materials, ・ the minimum yield stress occurs at an orientation angle within 30 and 45 degree to a principal axis of anisotropy, ・ an orientation angle that the minimum yield stress occurs increases according to hydrostatic pressure, ・ the ratio of anisotropy decreases acoording to hydrostatic pressure. By this results, it was shown that the proposed yield function has good expression for the mechanical characteristics of anisotropic materials.

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