臺灣博碩士論文加值系統

摘要
由於前人的海床液化試驗研究中指出波浪作用時海床液化反應與土壤組成顆粒大小具有密切關係，且海床之不穩定現象與海床表層的懸浮漂砂活動似乎有關連。本文乃選擇一細砂質 (D50 = 0.069 mm) 土壤作為試驗海床材料於斷面水槽中進行一系列造波試驗，探討規則波浪作用下細砂質海床土壤液化反應特性與其與懸浮漂砂濃度之關連性。試驗時於近海床上架設一支光學式濃度計量取懸浮漂砂濃度，並於其下海床內部設 5 支孔隙水壓計同步量測土壤之反應。孔隙水壓試驗結果顯示，本研究所使用之細砂在波浪作用下可產生液化反應，且具有類似蘇 (1999, D50 = 0.085 mm) 之研究所定義的非液化、起始液化及連續液化三種類型，但發生液化的次數較蘇 (1999) 所使用之試驗砂頻繁且起始液化反應大多發生於每一回合之第一試次。從同步之懸浮漂砂量測結果顯示，往往在海床土壤產生液化後近底床處懸浮漂砂濃度方才明顯上升，且從同一回合連續數試次之造波作用結果發現海床上方懸浮漂砂濃度值在起始液化反應時最大，且隨著其後連續液化反應所達深度減少其最大上升值亦逐漸降低，而非液化反應發生之試次，懸浮漂砂濃度均相當微小。本文研究於相關文獻中首度初步證實波浪作用時，海床內之液化反應與近底床處之懸浮漂砂有直接關係，同時更確定砂質海床其組成顆粒越細其液化潛能也相對提高。最後，本文研究建議現有之懸浮漂砂公式應就海床反應特性進一步修正。
關鍵詞：規則波浪、細砂質土壤、海床液化、懸浮漂砂濃度

Abstract
Previous several wave flume studies on wave-induced seabed responses indicate certain relationships between seabed’s fluidization and soil’s constituent particle sizes. In addition, near bed suspended sediment activities are closely related to seabed’s instability. Thus, in this thesis, a fine sand (D50 = 0.069 mm) is used as test seabed material to investigate the links between internal soil fluidization response and the near bed suspended sediment concentrations. In the experimental tests, an optical concentration probe near above bed and 5 probe pressure transducers were applied for simultaneous measurements of both quantities. The pore pressure measurements show that the fine sandy seabed could be fluidized under wave loading. Compared with Sue’s (1999) tests with sands (D50 = 0.085 mm), it immediately illustrates that typical responses are similar to those defined by Sue as unfluidized, initially fluidized and continuously fluidized, respectively. But, there are more fluidized test runs in present fine sandy beds, especially most initially fluidized response occur in the first run. The measurements show that the values of suspended sediment concentration used to increase significantly short after seabed is fluidized. For the same test, the maximum values of suspended sediment concentration are largest in the initially fluidized runs and the values decrease in consecutive runs as shallower soil layer are fluidized. Essentially, only very low suspended sediment concentrations are detected in the unfluidized response. As a result, this study has for the first time preliminarily confirmed the direct relationship between seabed fluidization and near bed suspended sediment concentration while fine-grained sediments are more potentially fluidized. It is suggested that practical models of suspended sediment concentration should be modified by taking into account of the seabed responses.
Keywords: regular waves, fine sandy soils, seabed fluidization, suspended sediment concentration.

目錄
中文摘要……………….…………………………………..…………… Ⅰ
Abstract …...…….………………………………………………..… Ⅱ
誌謝 …………………………………………………………………..… Ⅲ
目錄 ………….……………………………………..…..…………… Ⅳ
圖目錄 …………………………………………………..……….…... Ⅵ
表目錄 …….………………………………………………..…………. Ⅸ符號說明 …….……………………………………………………….. Ⅹ
第一章 緒論 …..……………………..…………………………….. 1
1-1 研究動機 ……….……………..…………...…...……..... 1
1-2 研究目的與方法 ………………..………...…..…….…..… 2
1-3 本文組織 ……….….……………...…..…….…………..… 2
第二章 相關背景 ………………….………..……...…..………… 4
2-1 海床反應特性 ………………………..…….….………..… 4
2-2 液化反應 …………………………………….…...….….… 4
2-3 懸浮漂砂 …………….…………………...…...….…..… 9
第三章 試驗設備與步驟 ….……………………………….….…… 13
3-1 試驗佈置與設備 ……………………….……………...…. 13
3-2 試驗步驟 ………………….……………...…..…….…… 14
3-3 儀器率定 ………………….……………...…..…….…… 21
3-4 試驗條件 ……………………….………...…..…….…… 24
第四章 試驗結果 ………….………………………….……….…… 25
4-1 孔隙水壓變化與液化反應 …………….……………..…… 25
4-2 懸浮漂砂與孔隙水壓 ………….………...…..…….…… 35
第五章 分析與討論 ……….…………………………….……….… 48
5-1 細顆粒非凝聚性海床反應類型比較 .……………………… 48
5-2 細砂質海床液化反應特性 ………….………….…………. 51
5-3 懸浮漂砂濃度之探討 ………….………...…..…….…… 61
第六章 結論與建議 ……….…………………………….…….…… 65
6-1 結論 ………………….……………...…..………….…… 65
6-2 建議 ………………….……………...…..…………….… 66
參考文獻 ………………………………………………………….….. 67
圖目錄
圖2.1 液化機制示意圖 (a)非液化土壤結構 (b)液化後土壤結構 (Huang, 1996) ....…………………………...…..…..…. 5
圖2.2 凝聚性土壤液化示意圖 (van Kessel ,1997) …........ 6
圖2.3 凝聚性土壤液化後流動現象 (van Kessel ,1997).……... 6
圖2.4 孔隙水壓歷時圖 (van Kessel ,1997) ……………...... 6
圖2.5 代表性海床土壤反應類型：[a] Tzang (1992) 沈泥質(d=-20cm), a1:非破壞 a2:共振式液化a3:非共振式液化反應；[b] 蘇(1999) 砂質(d=-30cm),b1:非液化 b2:起始液化 b3:連續液化 …………. 8
圖2.6 黃等人 (1996) 於台中港外海試驗所得濃度歷時圖 ... 10
圖2.7 Havinga (1992) 試驗所得濃度水深剖面圖 ..……..… 10
圖2.8 Dohmen (1999) 試驗所得濃度水深剖面圖...…..….… 10
圖2.9 van Kessel 和 Kranenburg (1998) 於Caland-Beer的試驗水槽 …....................................................... 12
圖2.10 van Kessel 和 Kranenburg (1998) 試驗所得濃度歷時圖 …...…….......................................... 12
圖3.1 造波水槽與儀器配置圖 …………..........……..…. 15
圖3.2 儀器配置之細部放大圖 ……………………………..…. 16
圖3.3 波高計及其增幅器示意圖 ………………………………. 16
圖3.4 孔隙水壓計及其增幅器示意圖 …………………………. 17
圖3.5 FOSLIM懸浮漂砂量測系統 …………………………..…. 17
圖3.6 試驗土壤粒徑分佈圖 ……………………………………. 18
圖3.7 試驗流程 ……………………………………………..…. 20
圖3.8 漂砂濃度計率定設備佈置圖 ………………………..…. 22
圖3.9 漂砂濃度計率定曲線 ………………………………..…. 22
圖3.10 波高計率定曲線 ……………………………………..…. 23
圖3.11 孔隙水壓計率定曲線 ………………………………..…. 23
圖4.1 典型非液化反應孔隙水壓歷時深度分佈代表性量測結果 …….…................................................. 27
圖4.2 典型起始液化反應孔隙水壓歷時深度分佈代表性量測結果 ….…................................................... 28
圖4.3 典型連續液化反應孔隙水壓歷時深度分佈代表性量測結果 …..................................................….. 29
圖4.4 D回合試驗之典型起始液化、連續液化、非液化反應孔隙水壓歷時圖...........………………………………………………...… 31
圖4.5 D回合下不同試次之孔隙水壓歷時圖 (d=30cm).………. 33
圖4.6 A-2試次下不同深度之孔隙水壓歷時圖 …….…….….. 34
圖4.7 A回合試驗之孔隙水壓及濃度歷時圖 ………………….. 36
圖4.8 B回合試驗之孔隙水壓及濃度歷時圖 ………………….. 37
圖4.9 C回合試驗之孔隙水壓及濃度歷時圖 ………………….. 38
圖4.10 D回合試驗之孔隙水壓及濃度歷時圖 ………...….….. 39
圖4.11 A回合試驗量測懸浮質濃度歷時圖(濃度計放於底床上5cm) ….…. .................................................. 41
圖4.12 C回合試驗量測懸浮質濃度歷時圖(濃度計放於底床上1cm) …..….................................................. 42
圖4.13 B-5試次之試驗前、中、後濃度影像圖 …………….…. 43
圖4.14 C-2試次之試驗前、中、後濃度影像圖 …………….... 44
圖4.15 B-1試次之試驗前、中、後濃度影像圖 ……………..… 45
圖4.16 D-1試次之試驗前、中、後濃度影像圖 ………………… 46
圖5.1 C-1試次前半段非液化時之孔彈性理論 ………………… 49
圖5.2 D-1試次之實際值與平均值比較 ………………………… 49
圖5.3 定深度下之B回合平均孔隙水壓歷時圖 ……………….. 52
圖5.4 定深度下之C回合平均孔隙水壓歷時圖 ……………….. 53
圖5.5 定深度下之D回合平均孔隙水壓歷時圖 ……………….. 54
圖5.6 B回合平均孔隙水壓歷時曲線深度分佈圖 …….………. 56
圖5.7 C回合平均孔隙水壓歷時曲線深度分佈圖 …….….….. 57
圖5.8 D回合平均孔隙水壓歷時曲線深度分佈圖 …….….….. 58
圖5.9 A、B回合之懸浮質平均濃度歷時圖 …….…..……….. 63
圖5.10 C、D回合之懸浮質平均濃度歷時圖 …….….……….. 64
表目錄
表2.1 各土深之理論靜土壓 …………………….………………. 5
表2.2 試驗土壤粒徑比較 ……………………………………….. 9
表2.3 van Kessel和Kranenburg (1998) 液化試驗之波浪條件. . 12
表3.1 試驗用海床土壤特性 …………….…………………….… 14
表3.2 試驗條件 ……………………….…………………………. 24
表4.1 試驗反應模式 ………………….…………………………. 26
表4.2 孔隙水壓及漂砂濃度抬升時間 …………………….……. 40
表5.1 各深度最大平均孔隙水壓與理論靜土壓之關係 ……..… 59
表5.2 試驗土壤粒徑與液化反應之比較結果 …………….……. 60
符號說明
C ： 漂砂濃度
d ： 土層深度
D50 ： 土壤中值粒徑
G ： 剪力模數
g ： 重力加速度
H ： 有義波高
h ： 水深
k ： 滲透係數
n ： 孔隙率
P ： 孔隙水壓
Ps ： 理論靜土壓
ΔP ： 孔隙水壓抬升值
T ： 有義週期
t ： 時間
V ： 伏特
ρs ： 土壤顆粒單位比重
ρw ： 水單位比重
ν ： 柏松比

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