孔隙材料應力-水力偶合行為之研究

A Study of Stress-Flow Coupling Behavior of Porous materials

李宛瑾(Wan-Chin Lee)

指導教授 ： 黃燦輝

共同指導教授 ： 翁孟嘉

國立臺灣大學/工學院/土木工程學研究所/碩士(2011年)

https://doi.org/10.6342/NTU.2011.03097

摘要

大地材料的滲透特性與水力偶合作用是重要的課題。無論是隧道開挖湧水、核廢料貯置場、油氣開採與儲存槽或大壩蓄水等工程或近來興起的碳封存技術，皆涉及大材料應力、滲透特性的問題。材料結構影響滲流特性發展，而結構的條件又受到應力作用而產生變化；因此，滲透性被視為孔隙材料應力狀態函數。
為了釐清應力對於材料之結構與其滲流性變化，本研究在分析方法上，採用以分離元素法為理論基礎所發展之顆粒流分析軟體（particle flow code，簡稱PFC）為分析工具，並針對孔隙材料進行一系列三軸排水試驗與三軸透水試驗，最後根據實驗結果及現象調整出合理的模型，以利觀察結構微觀的行為發展。
本研究所使用之模擬孔隙材料為(1)鋁球顆粒、(2)鋁球混和高嶺土製作之三軸圓柱試體，並於受剪過程中進行三軸透水試驗。實驗結果顯示：添加高嶺土之試體，強度參數明顯比純鋁球試體高，且在受剪過程中皆為體積膨脹的行為。兩種試體之滲透性隨著有效圍壓上升而下降，但卻不隨體積膨脹而上升。另外，試體滲透性在受壓剪過程中並非定值，顯示滲透率受應力作用而改變，但僅由鋁球顆粒組成之試體其滲透性變化不大，而添加高嶺土之試體在應力降伏點附近之滲透率有突然上升的現象。
由於三軸實驗試體受壓變形僅能透過肉眼來，而其內部顆粒的運動與變型之狀態無法切實掌握，因此藉以數值模擬分析以利觀察顆粒材料在三軸應力狀態下之微觀行為。其結果說明試體受壓時，顆粒會發生旋轉的現象，低應力皆段顆粒運動無特定方向，趨近破壞時才會逐漸沿特定的方向移動，即出現滑動面。發生滑動面處之顆粒運動方向有相反情形，附近顆粒運動較不規則及混亂，並且發現其剪應變為最大；對於設有鍵結之顆粒模型，亦可觀察到滑動面上之鍵結斷裂情形較其他部分嚴重。最後利用PFC所提供之流力模組進行上述試體之滲流率分析，但模擬結果與實驗值存在一差異。

關鍵字

分離變數法 ； 滲透性 ； 應力作用

並列摘要

The permeability of earth materials and hydro-mechanic coupling behavior are important issue, the disastrous fluid in-rush into excavations, nuclear waste disposal, mining and petroleum industries, the seepage estimate of dam and the technology of carbon storage are involving the relation between stress and permeability of earth materials in civil engineering projects.
In this research, the effects of stress on the structure and permeability of earth materials are investigated through experimental characterizations and numerical simulations which is based on the discrete element method conducted with PFC2D using micro-mechanical parameters derived from physical testing to select appropriate micro-mechanical models and parameters. The first part of the paper summarizes the previous studies in this area, outlines such experimental method and depicts the steps of triaxial drained test and permeability test for the preparation of cemented granular. The following part discusses the results of physical tests and numerical compression.
The physical samples were prepared with aluminum particles and using kaolinite as cement. The results of experiment showed that the higher confine pressure, samples dilated more obviously during shearing, and the strength of sample of particles bonded with kaolinite is stronger than the one of only particles. In the complete stress-strain process, it was found the change of permeability was not constant, and it rised obviously around yielding. For the sample composed of only particles, the change of permeability was invariable. However, the numerical simulations and physical tests showed good correspondence in macroscopic behavior i.e. peak strength. But it has difference between the fluid analysis and the permeability of physical samples.

並列關鍵字

distinct element method ； permeability ； hydro-mechanic coupling behavior

參考文獻

1.李宏輝(2004)，砂岩力學行為之微觀機制-以個別元素法探討，國立台灣大學土木工程博士論文。

2.陳建勛(2004)，剪力作用下岩石節理面粗糙特性對其導水性之影響探討，國立台灣大學土木工程學研究碩士論文。

4.Brace, W. F. (1968), A Note on Permeability Changes in Geologic Material.

5.Brace, W. F., Walsh, J. B., and Frangos, W. T.(1978), Permeability of Granite Under High Pressure, J. Geophys. Res. Vol.73, No.6, pp.2225-2236.

6.Li, Shiping, Li, Yushou et al.(1994), Permeability-Strain Equations Corresponding to the Complete Stress-Strain Path of Yinzhuang Sandstone , Int. J. Rock Mech. Min. Sci. & Geomech. Abstr., Vol.31,No.4, pp.383-391.