以分離元素法探討孔隙材料之水力－力學耦合行為

A Study of Hydro-mechanical Coupling Behavior of Porous Materials by DEM

葉孟維(Meng-Wei Yeh)

指導教授 ： 鄭富書

共同指導教授 ： 翁孟嘉(Meng-Chia Weng)

國立臺灣大學/工學院/土木工程學研究所/碩士(2012年)

https://doi.org/10.6342/NTU.2012.03188

摘要

滲流特性為大地材料中不可忽略的一環，大地工程一般採用單一的滲透係數代表整個工程區域的滲透性。然而大地材料受到外力的作用下會改變物理性質，諸如應變和孔隙率，滲透性亦隨之改變，此互制的現象稱為水力－力學耦合的行為。值得探究大地材料受到應力的作用下，材料結構與其滲流性變化。舉凡隧道開挖湧水與大壩蓄水等皆涉及大地應力的改變與滲透性之間的關係。

基於大地材料種類繁多，本研究簡化探討顆粒材料之滲流特性，應用基於顆粒力學理論基礎之分離元素法發展的PFC3D軟體為工具，分別由微觀尺度的孔隙率與流率變化與宏觀尺度的應力－應變曲線，探討之間的關係。

本研究以實驗三軸壓密排水試驗的結果作為數值模型比對基礎，求得PFC3D三軸試體的微觀參數，數值模型由試體顆粒與邊界顆粒組成，分別模擬實驗鋁珠與橡皮膜，得以觀察試體破壞型態。驗證比對後，數值模型以力學機制和實驗相同的條件下，繼而進行三軸透水試驗的模擬，探討多孔隙材料受到應力與水力的作用之下，顆粒結構的改變與滲透係數的變化。比較實驗與數值模擬的結果，探討其異同。並進一步探討在水力－力學耦合的行為下，觀察試體隨著應變的增加，顆粒的位移情況、各位置的孔隙率以及各層流率變化。結果顯示滲透係數確實會受到應力與水力作用的影響而產生變化，並非是單一定值，但實驗與模擬的滲透係數存在差異。

關鍵字

分離元素法 ； 水力－力學耦合 ； PFC

並列摘要

Seepage is one of the major concerns in geotechnical engineering. The permeability adopted in engineering design usually applies a fixed value in entire area. However, the physical properties of geotechnical material may vary due to different external loading. For example, the variations of strain and porosity induce the different permeability. This interaction phenomenon is known as hydraulic-mechanical coupling behavior. It is worth to study geotechnical materials under stress condition, how to affect the materials structure and permeability.

Based on a wide range of geotechnical materials, this study explores the hydraulic-mechanical coupling behavior of granular material. The software PFC3D based on distinct element method is used to simulate the stress-strain-flow relationship.

In order to get the micro parameters of numerical model, this model is first verified by experimental triaxial compaction drainage test. The numerical model is composed of two kinds of particles, represented the aluminum balls and membrane, respectively. Then, the triaxial permeability test is simulated to explore the variation of permeability subject to different stress conditions. The results show that the permeability will increase as the stress arise. However, some error exists between the experimental and simulated results.

並列關鍵字

DEM ； hydro-mechanics ； PFC.

參考文獻

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