Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/12944
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
摘要: 
卵礫石層由於顆粒大強度高,不易如一般土層採取不擾動試樣來進行室內試驗,故大都以縮小粒徑重模試體進行大型室內剪力試驗,或以現地直接剪力試驗與平鈑載重試驗來調查其強度性質,然其人力物力費用非常高,故歷來卵礫石層強度性質資料與土層相較均屬少數,在工程設計上常感不足。因此以數值模擬現有卵礫石層試驗之結果,熟悉模擬技巧以推求其他卵礫石層之強度性質乃本研究之目的。採用著重材料微觀顆粒間不連續行為之兩個研究方法之程式來進行研究:即個別元素法之二維顆粒流動程式,與微觀元素顆粒連體分析法之諧和模式程式。
本研究討論如何將此兩個顆粒材料微觀力學程式運用於卵礫石層強度之測求,首先以雙軸數值試驗進行程式參數靈敏度分析,求出影響較大之參數與其趨勢,結果為:二維顆粒流動程式為接觸勁度及摩擦係數等,諧和模式程式為基質摩擦係數及接觸基質厚度與顆粒半徑比等;並求出最佳參數,與比較兩個程式之差異性。接著進行礫石土大型室內三軸試驗求得莫爾庫倫強度參數,進行卵礫石層現地平鈑載重試驗求得極限承載力;再以程式數值模擬這些實際試驗,獲得良好之結果,印證此兩電腦程式與參數之適用性。最後以現地粒徑之卵礫石雙軸模擬試驗,推求現地卵礫石層強度。

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.
URI: http://hdl.handle.net/11455/12944
Appears in Collections:土木工程學系所

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