| Summary: | 碩士 === 國立臺灣大學 === 土木工程學研究所 === 93 === The numberic method of finite element is mostly based on the applicable simplification and hypotheses as to proceeding the simulation analysis. Generally speaking, the present finite element method adopts the isotropic-linear model, assisted by the plastic model of Drucker-Prager or Mohr-Columb to simulate the deformation of rock materials, and also applies them to describe the deformation behaviors of western foothill sandstones. However, this kind of model is hard to represent the realistic deformed characters of western foothill sandstones, such as (1) the nonlinear elastic deformation and plastic strain closure condition under volumetric stress effect, (2) the coupling behavior between shear stress and elastic volumetric strain under shear stress effect, and (3) the existence of elliptical plastic potential surface.
It would be inaccurate to estimate the rock deformation when ignoring the shear dilation effect, thus this research utilizes the advanced Green nonlinear elastic component model to describe the characters of shear dilation. To apply it to finite element method of ABAQUS program, the tangent stiffness matrix was deduced based on certain model, ensuing by its verification and coding the subroutine belonging to ABAQUS to proceed the further analysis.
Before analyzing the engineering construction cases, single element was applied to triaxial test to verify the accuracy of the subroutine, and to inspect if the material model is proper to describe the elastic component model of western foothill sandstone. According to the result comparisons of single element analysis and testing data, this model presents its appropriateness for represent the elastic deformation behavior of western foothill sandstone. Besides, this model is also applied to analyze the tunnel, foundation or slope cases to testify its application. Moreover, the results are compared with the ones of linear elastic method, which reveals a more reasonable condition.
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