橋墩為重要交通建設，長年於河道或水路中受水流沖刷，過度沖刷會造成橋墩地基破壞，因此如何保護橋墩不受沖刷破壞為橋上安全的重要問題。橋墩周圍局部沖刷主要受到向下水流、馬蹄形渦流及尾跡渦流作用影響。
本研究利用三種不同橋墩保護工，在循環水槽下模擬變量流，探討沖刷深度的變化。試驗設計兩組變量流，包括中峰型與前峰型變量流歷線，搭配三種不同保護工，分別有犧牲樁、螺紋及淹沒葉片保護工，在均勻顆粒下，針對犧牲樁數目、螺紋直徑及厚度還有淹沒葉片厚度不同參數條件，利用探針紀錄橋墩前方沖刷深度歷程及沖刷地形，分析不同橋墩保護工對於沖刷深度影響，得到最佳橋墩保護工配置模式。
研究結果顯示，在淹沒葉片及螺紋保護工下，在沖刷剛開始0~30分鐘內，其減少效率約為50%，不過30分鐘後，甚至出現比無防護橋墩下更深的深度，這兩種保護工保護效果不佳; 但在犧牲樁保護工下，發現沖刷時間30~60分鐘內，樁後有沙丘形成，可明顯降低沖刷深度，此時效率可高達50%以上，且在五根犧牲樁保護下時，出現超過100%的減少效率，而平均效率也有40%左右，是三保護工中效率最顯著保護工。

Pier scouring can cause damage of hydraulic construction, so protecting piers against scour is an important issue in bridge construction. In the study, a series of experiments were conducted under the unsteady flow conditions to evaluate the effectiveness of different countermeasures protection arrangements for protecting the pier. Both central peak and advanced peak hydrographs were adopted and uniform sediment was used. Sacrificial piles, threaded pile, and submerged vanes were adopted. This study considered various parameter, including (1)numbers of piles, (2)threaded pile diameter and thickness, and (3)vane thickness. Temporal evolutions of pier scour are recorded by using a probe. The results show that the efficiency of submerged vanes and threaded pile are less than 50% within 30 minutes; however, after 30 minutes, the scour depth with protection exceeds that without protection. The countermeasures of submerged vanes and threaded pile do not perform well, compared to sacrificial piles. The average efficiency of sacrificial piles up to 40%, and the maximum efficiency of five sacrificial piles can exceed 100%. Consequently, sacrificial piles have the most significant efficiency in the three countermeasures.

目錄
表目錄 III
圖目錄 IV
第一章 前言 1
1.1 研究動機及目的 1
1.2 本文架構 3
第二章 沖刷原理 4
2.1 沖刷類型 4
2.2 局部沖刷分類 6
2.3局部沖刷運動 7
2.4 沖刷保護技術 8
2.5 橋墩保護工 10
2.6 橋墩沖刷參數 14
第三章 試驗設備及方法 15
3.1 試驗設備 15
3.1.1試驗水槽 15
3.1.2 試驗橋墩模型 21
3.1.3試驗儀器 23
3.2 流量計算 25
3.3試驗配置及條件 27
3.3.1 覆土高度	27
3.3.2 試驗底床質 27
3.3.3 試驗水流條件 29
3.3.4試驗操作步驟 32
3.4砂丘運動 34
3.5研究方法 36
3.5.1無因次分析 36
3.5.2完全發展段 38
3.5.3沖刷深度減少效率 39
第四章 結果及討論 40
4.1無防護橋墩	41
4.2 犧牲樁保護工 43
4.3 螺紋保護工 53
4.4 淹沒葉片保護工 61
第五章 結論 69
參考文獻	71
附錄A 符號 75
附錄B 不同保護工於洪峰流量時地形剖面圖 77

表目錄
表 1 保護工幾何條件 23
表2 轉速10~50間水流條件 26
表3 底床質條件 28
表4 實驗洪峰流量時水流條件 29
表5 中峰型設計流量歷線下水流條件 30
表6 前峰型設計流量歷線下水流條件 31
表7 式(18)中的a、b值 38
表8 案例分類 40

圖1‑1 橋墩沖刷周圍水流型態示意圖(轉繪自：Idaho Transportation Department Office Manual., 2004) 2
圖2‑1 各種類型沖刷之樹狀圖(Cheremisinoff et al., 1987) 5
圖2‑2 拋石保護工(Lauchlan & Melville, 2001) 8
圖2‑3 蛇籠保護工(Yoon, 2005) 8
圖2‑4 第二類沖刷保護技術之例子示意圖：(a)淹沒葉片;(b)底床檻;(c)犧牲樁;(d)軸環;(e)螺紋;(f)橋墩槽(Tafarojnoruz et al., 2012) 9
圖3‑1 試驗水槽示意圖 16
圖3‑2 進水口水箱 17
圖3‑3 圓弧底座及擋板 17
圖3‑4 三角形擋板 18
圖3‑5 進水口水箱與試驗段水槽 19
圖3‑6 出水口水箱及尾水堰板 19
圖3‑7 蓄水槽及麻布袋 20
圖3‑8 泵浦 20
圖3‑9 橋墩配置示意圖 21
圖3‑10 犧牲樁保護工	22
圖3‑11 三根犧牲樁(a)側面、(b)俯視圖 22
圖3‑12 五根犧牲樁(a)側面、(b)俯視圖 22
圖3‑13 細螺紋保護工 22
圖3‑14 粗螺紋保護工 22
圖3‑15 螺紋(a)側面(b)俯視圖 22
圖3‑16 薄葉片保護工 22
圖3‑17 厚葉片保護工 22
圖3‑18 葉片(a)側面(b)俯視圖 22
圖3‑19 TECO變頻器 24
圖3‑20 探針 24
圖3‑21 針尺與沙面交界處 24
圖3‑22 線性迴歸圖	26
圖3‑23 粒徑分佈圖	28
圖3‑24 中峰型設計流量歷線圖 30
圖3‑25 前峰型設計流量歷線圖 31
圖3‑26 試驗歷程 33
圖3‑27 沙丘於橋墩周圍推移之五個階段(Hong et al., 2016) 34
圖3‑28 砂丘往沖刷坑推移 35
圖3‑29 沙丘落淤於沖刷坑內 35
圖3‑30 橋墩後方砂丘發展 35
圖3‑31 洪峰流量時之水面線分佈圖	39
圖4‑1 中峰型流量歷線下於洪峰流量沖刷過後無防護橋墩之沖刷地形 42
圖4‑2 前峰型流量歷線下於洪峰流量沖刷過後無防護橋墩之沖刷地形 42
圖4‑3 抵達洪峰流量時橋墩周圍沖刷地形發展	42
圖4‑4 中峰型流量歷線下於洪峰流量沖刷過後三根犧牲樁保護橋墩之沖刷地形 45
圖4‑5 中峰型流量歷線下於洪峰流量沖刷過後五根犧牲樁保護橋墩之沖刷地形 45
圖4‑6  犧牲樁保護工下橋墩周圍水流發展 46
圖4‑7 中峰型流量歷線下三根犧牲樁保護工與無防護橋墩沖刷深度時序列比較 46
圖4‑8 前峰型流量歷線下五根犧牲樁保護工與無防護橋墩沖刷深度時序列比較 46
圖4‑9 中峰型流量歷線下三根犧牲樁後之小砂丘 47
圖4‑10 中峰型流量歷線下五根犧牲樁後之小砂丘 47
圖4‑11 中峰型流量歷線下三根、五根犧牲樁保護工深度減少效率比較 47
圖4‑12 中峰型流量歷線下洪峰流量沖刷過後三根犧牲樁保護工與無防護橋墩沖刷地形比較 48
圖4‑13 中峰型流量歷線下洪峰流量沖刷過後五根犧牲樁保護工與無防護橋墩沖刷地形比較 48
圖4‑14 前峰型流量歷線下於洪峰流量沖刷過後三根犧牲樁保護工之沖刷地形	50
圖4‑15 前峰型流量歷線下於洪峰流量沖刷過後五根犧牲樁保護工之沖刷地形	50
圖4‑16 前峰型流量歷線下三根犧牲樁保護工與無防護橋墩沖刷深度時序列比較 50
圖4‑17 前峰型流量歷線下五根犧牲樁保護工與無防護橋墩沖刷深度時序列比較 51
圖4‑18 前峰型流量歷線下三根犧牲樁後之小砂丘 51
圖4‑19 前峰型流量歷線下五根犧牲樁後之小砂丘 51
圖4‑20 前峰型流量歷線下三根、五根犧牲樁保護工深度減少效率比較 52
圖4‑21 前峰型流量歷線下洪峰流量沖刷過後三根犧牲樁保護工與無防護橋墩沖刷地形比較 52
圖4‑22 前峰型流量歷線下洪峰流量沖刷過後五根犧牲樁保護工與無防護橋墩沖刷地形比較 52
圖4‑23 中峰型流量歷線下於洪峰流量沖刷過後細螺紋保護橋墩之沖刷地形 54
圖4‑24 中峰型流量歷線下於洪峰流量沖刷過後粗螺紋保護橋墩之沖刷地形 54
圖4‑25 螺紋保護工下橋墩周圍水流發展	55
圖4‑26 中峰型流量歷線下細螺紋保護工與無防護橋墩下沖刷深度時序列比較	55
圖4‑27 中峰型流量歷線下粗螺紋保護工與無防護橋墩下沖刷深度時序列比較	55
圖4‑28 中峰型流量歷線下粗、細螺紋保護工深度減少效率比較 56
圖4‑29 中峰型流量歷線下洪峰流量沖刷過後細螺紋保護工與無防護橋墩沖刷地形比較 56
圖4‑30 中峰型流量歷線下洪峰流量沖刷過後粗螺紋保護工與無防護橋墩沖刷地形比較 56
圖4‑31 前峰型流量歷線下於洪峰流量沖刷過後細螺紋保護橋墩之沖刷地形 58
圖4‑32 前峰型流量歷線下於洪峰流量沖刷過後粗螺紋保護橋墩之沖刷地形 58
圖4‑33 前峰型流量歷線下細螺紋保護工與無防護橋墩下沖刷深度時序列比較	59
圖4‑34 前峰型流量歷線下粗螺紋保護工與無防護橋墩下沖刷深度時序列比較	59
圖4‑35 前峰型流量歷線下粗、細螺紋保護工深度減少效率比較 59
圖4‑36 前峰型流量歷線下洪峰流量沖刷過後細螺紋保護工與無防護橋墩沖刷地形比較	60
圖4‑37 前峰型流量歷線下洪峰流量沖刷過後粗螺紋保護工與無防護橋墩沖刷地形比較	60
圖4‑38 中峰型流量歷線下於洪峰流量沖刷過後薄葉片保護橋墩之沖刷地形 62
圖4‑39 中峰型流量歷線下於洪峰流量沖刷過後厚葉片保護橋墩之沖刷地形 62
圖4‑40 淹沒葉片保護工下橋墩周圍水流發展	63
圖4‑41 中峰型流量歷線下薄葉片保護工與無防護橋墩下沖刷深度時序列比較	63
圖4‑42 中峰型流量歷線下厚葉片保護工與無防護橋墩下沖刷深度時序列比較	63
圖4‑43 中峰型流量歷線下厚、薄葉片保護工深度減少效率比較 64
圖4‑44 中峰型流量歷線下洪峰流量沖刷過後薄葉片保護工與無防護橋墩沖刷地形比較	64
圖4‑45 中峰型流量歷線下洪峰流量沖刷過後厚葉片保護工與無防護橋墩沖刷地形比較	64
圖4‑46 前峰型流量歷線下於洪峰流量沖刷過後薄葉片保護橋墩之沖刷地形 66
圖4‑47 前峰型流量歷線下於洪峰流量沖刷過後厚葉片保護橋墩之沖刷地形 66
圖4‑48 前峰型流量歷線下薄葉片保護工與無防護橋墩下沖刷深度時序列比較	67
圖4‑49 前峰型流量歷線下厚葉片保護工與無防護橋墩下沖刷深度時序列比較	67
圖4‑50 前峰型流量歷線下厚、薄葉片保護工下深度減少效率比較	67
圖4‑51 前峰型流量歷線下洪峰流量沖刷過後薄葉片保護工與無防護橋墩沖刷地形比較	68
圖4‑52 前峰型流量歷線下洪峰流量沖刷過後厚葉片保護工與無防護橋墩沖刷地形比較	68

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