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  • 學位論文

裂隙岩體之滲透係數張量建立研究

Developing on Permeability Tensor for Fractured Rocks

指導教授 : 黃燦輝

摘要


綜觀各樣地下工程皆需要對材料岩體行為建構適當的描述模式,以對潛在工程問題進行預測及分析,便於設計暨選擇施工工法。而一般在評估岩體行為時大多會依照該工程之特性進行評估,分為應力場、溫度場、滲流場抑或是化學場個別描述。然而,各外在因素並不僅是單獨對岩體之行為影響,彼此之間也都互有影響。在大部分隧道工程案例中,滲流場以及應力場主導岩體之工程行為,進而成為主導工程穩定之關鍵,因此岩體之滲流─應力─應變相互關係的水力─力學耦合行為是確保隧道工程安全之重要課題。 本研究採用江誌偉(2008)設計之離散裂隙網絡進行裂隙岩體之描述,並設計求取裂隙岩體之滲透係數張量方法,基於離散裂隙網絡之結果獲得滲透係數張量。研究中建立旋轉取域方法,用以獲得裂隙岩體滲透係數張量,從而觀察滲透係數之方向性。在旋轉取域方法之下,考量代表性體積元素之適當性再發展出二階段選域法,此方法可在研究區域一樣具有代表性特徵的前提下顯著改善取域效率,將以往取樣花費之時間由數小時不等縮減至約半小時。 本研究最後透過模型進行一系列探討,先對於建立之方法的結果討論,而後參數分析概括下列兩種:連續模式之裂隙岩體進行不同隙寬以及不同夾角之參數分析,比較其相對數值,且觀察裂隙正交情形之下其kxy、kyx是否為零;離散模式之裂隙岩體則進行應力分析,觀察不同應力路徑之下滲透係數張量之改變。在數個驗證下都顯示本研究設計之旋轉取域法應用在離散裂隙網絡中的結果相當理想。

並列摘要


Before underground excavation, engineers have to build a suitable model describing the behavior of rock masses to predict and analyze all sorts of possible engineering problems. Generally speaking, the behavior of rock masses should be described specifically in accordance with the characteristic of the engineering project such as mechanical field, thermal field, flow field or chemical field. However, every field not only affect the corresponding behavior for rock masses, but also influence each other. For tunnel excavation projects, flow field and mechanical field control the engineering stability in most cases. Therefore, appropriate prediction on the coupled hydraulic-mechanical behavior related to permeability, stress and strain relationships of fractured rock masses become an important issue to ensure the safety of tunnel engineering. This study utilize the Discrete Fractured Network (DFN) model of Chiang (2008) to describe fractured rock mass, and propose an approach to obtain its permeability tensor. In order to obtain a reasonable permeability tensor, a rotary sampling method is constructed to observe the directionality of permeability. To improve the efficiency of rotary sampling method, a 2-steps sampling method is also proposed, which reduces the sampling time from several hours to thirty minutes only. Finally, this study proceeds a parameter study base on the discussion of the results mentioned above. The continuum model is used to figure out the change in permeability tensor under different apertures and dip angles. Theoretically, the kxy and kyx of models with two sets of orthogonal fractures should be zero. In the other hand, the discrete model is utilized to observe the change of permeability tensor in different stress paths. All series of tests indicate that the rotary sampling method provides great approximation on computing permeability tensor of discrete fractured networks.

參考文獻


2. 江誌偉(2008),“裂隙岩體滲流離散模式之研究”,國立臺灣大學土木工程研究所碩士論文,台北。
10. 鄭允嘉(2006),“節理岩體滲透係數之滲透異向性與應力引致異向性”,國立中央大學應用地質研究所碩士論文,桃園。
7. 黃永鈴(2003),“規則節理岩體滲透模式之研究”,國立台灣大學土木工程學研究所碩士論文,台北。
11. A. Baghbanan(2006), “Hydraulic Properties of Fractured Rock Masses with Correlated Fracture Length and Aperture” International Journal of Rock Mechanics & mining Science 44(2007) 704-719.
12. A.C. Liakopoulos(1965), “Darcy’s Coefficient of Permeability as Symmetric Tensor of Second Rank.”, International Association of Scientific Hydrology. Bulletin Volume 10, Issue 3.

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歐福全(2005)。凹槽平板之動態反應〔碩士論文,國立臺灣大學〕。華藝線上圖書館。https://doi.org/10.6342%2fNTU.2005.00136
林俊彥(2004)。T矩陣法運用於具孔洞平板之動態應力分析〔碩士論文,國立臺灣大學〕。華藝線上圖書館。https://doi.org/10.6342%2fNTU.2004.02220

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