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標題: 以顆粒材料力學探討卵礫石層強度性質之研究
A Study of the Strength of Gravelly Cobble Deposit Based on Mechanics of Granular Materials
作者: 楊麗文
Yang, Li-Wen
關鍵字: gravelly cobble deposits;卵礫石層;mechanics of granular material;Distinct Element Method;Micro-structural continuum Method;numerical simulation;顆粒材料力學;個別元素法;微觀元素顆粒連體分析法;數值模擬
出版社: 土木工程學系

The geologic formation of the gravelly cobble deposits makes it very difficult to obtain their large undisturbed samples for laboratory testing. Besides, it needs to scale down the grain size and then remold the samples with dimension at least 30 cm for laboratory testing. And, the in situ direct shear test or plate-load test needs to be conducted to evaluate the strength of this material. As the scale of these tests is quite large, and its expense is high, the cumulative data of the strength character of the gravelly cobble deposit is so limited, as compared with that of soil layers, it is insufficient for engineering design. Thus, this study aims to numerically simulate the existing test results of the gravelly cobble deposit, which is a kind of granular material, to become familiar with the skill of simulation, and then to evaluate the strength character of other gravelly cobble deposits by means of two computer programs, both emphasizing on the discrete behavior of microstructure of granular materials, including the Particle Flow Code in 2 Dimensions of the Distinct Element Method(DEM) and the Compatibility Model Code of the Micro-structural continuum Method(MCM).
This study also aims to discuss how to apply the two computer programs to evaluating the strength character of the gravelly cobble deposit, beginning with parameters sensitivity study of the two programs to find the more influential parameters and the trends. The results reveal that contact stiffness and friction coefficient are for the Particle Flow Code in 2 Dimensions; whereas friction coefficient and the ratio of contact matrix thickness to particle radius are for the Compatibility Model Code. It is then to choose the adequate parameters and to compare the differences of the two computer codes. The laboratory triaxial tests of gravelly soil were proceeded to find the Mohr-Coulomb strength parameters, and the in situ plate-load tests of gravelly cobble deposit were conducted to find the ultimate bearing capacity. The computer codes were then adopted to simulate these tests with reasonable results to prove whether the two computer codes and their parameters are suitable. A numerical biaxial test of large particles with dimension the same as the in situ gravelly cobble deposit was used to simulate the real triaxial tests to evaluate the Mohr-Coulomb strength parameters of in situ materials.
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