本研究主要係透過渠槽試驗，探討順直河道於設置傳統式固床工及沉箱式固床工前後對河川橋樑基礎保護之成效。透過不同配置條件(坡度、間距、埋設深度)之固床工試驗，以瞭解固床工設置前後河床之沖淤變化機制，藉由河道沖淤變化程度及沖刷體積減緩率等指標判定河床之穩定性，據以提出安全之固床工配置模式，以供日後相關工程人員之參考。
研究結果發現，由河道沖淤變化及沖刷體積減緩率等指標可知，設置任何型式固床工均較未設置時能有效保護橋墩基礎，其中又以坡度為1/30時設置固床工有較明顯之保護效果。就墩前沖刷深度及沖刷體積減緩率而言，當坡度為1/50情況下，沉箱式固床工優於傳統式固床工，在坡度為1/30時，兩種固床工型式之沖刷深度減緩效果差異不大；在設置固床工間距方面，坡度為1/50時以緊鄰墩後設置固床工時有較佳之沖刷體積減緩效果，當坡度為1/30時則兩者差異不大；固床工設置排數方面，不論何種坡度之沖刷體積皆隨固床工排數之增加而有減少之趨勢。
此外，就沉箱式固床工之回填粒料而言，當坡度為1/50時回填較大填石有較佳之減緩沖刷體積效果，而當坡度為1/30時，填石大小對減緩沖刷體積效果不甚顯著。整體而言，當渠道坡度為1/50時，於墩後下游一倍墩徑距離處設置與河床面齊平之沉箱式固床工，並填充原河床質粒徑，其沖刷深度減緩率可達90%，顯示沉箱式固床工對橋墩基礎具有良好的保護效果。

The main purpose of this study is to discover the protection effects of pier foundation before and after the installations of the traditional and box caisson consolidation works for the straight channel by hydraulic experiments. This study is to increase our understanding of the mechanism of scour and deposition under different arrangement conditions including the type, slope, interval and elevation of consolidation works. The variation of riverbed and the retardation rate of riverbed scour are indexes used to determine the stability of river. It can be served as a reference of design for relevant engineers in future.
The results showed that certain degree of protection were obtained after any type of consolidation works were set downstream of the pier through the indices of river variation, retardation rate of riverbed scour, and riverbed transverse stability, especially for a slope of 1/30. For the scour depth in front of pier and retardation rate of riverbed, the scour of box caisson consolidation work is better than the traditional consolidation work for a slope of 1/50, and the types of consolidation works have no difference while the slope is 1/30. In terms of interval between pier with consolidation work, the better retardation rate of riverbed scour was observed for consolidation work installed immediately downstream of the pier under the slope 1/50, and the types of consolidation works have no difference while the slope is 1/30. The scour volume for all kinds of consolidation works decrease with an increase of rows of consolidation works in any slope.
In addition, better protection effect was observed while bigger stuffing stones were used for the box caisson consolidation work under the condition of 1/50, and the stuffing stone size of box caisson consolidation work has no effect for the slope of 1/30. In general, the best protection effect was obtained for box caisson consolidation works with an interval of pier width
downstream of the pier, stuffing original riverbed sediment. The resulting retardation rate of riverbed scour is about 90%. Therefore, box caisson consolidation work gives good protection effects for pier foundation.

謝誌----------------------------------------------I
摘要----------------------------------------------II
Abstract------------------------------------------III
目錄----------------------------------------------V
圖目錄-----------------------------------------VIII
表目錄-------------------------------------------XI
照片目錄----------------------------------------XII
符號表-----------------------------------------XIII
頁次
第一章前言·················································································1
1.1研究動機·······························································································1
1.2研究目的·······························································································1
1.3研究架構·······························································································2
1.4研究流程·······························································································3
第二章文獻回顧·········································································4
2.1沖刷起因與分類···················································································4
2.2橋墩周圍水流之流況···········································································6
2.3橋墩沖刷之保護工法···········································································7
2.4固床工種類···························································································8
2.4.1混凝土鋪石固床工············································································8
2.4.2拱型排砌塊石固床工········································································9
2.4.3階梯式固床工··················································································10
2.4.4傳統固床工······················································································11
2.5固床工理論·························································································12
第三章渠槽試驗·······································································17
3.1試驗設備·····························································································17
3.1.1試驗渠槽··························································································17
3.1.2試驗河床質······················································································19
3.1.3定量供水系統··················································································19
3.2試驗流況·····························································································20
3.3固床工模型·························································································21
3.4試驗假設·····························································································22
3.5試驗方法·····························································································22
3.5.1量測方法··························································································23
3.5.2試驗配置··························································································24
3.5.3試驗流程··························································································24
第四章 結果分析與討論···························································27
4.1試驗組編碼·························································································27
4.2沖刷深度·····························································································29
4.2.1橋墩前最大沖刷深··········································································29
4.2.2固床工下游最大沖刷深··································································30
4.3固床工設置位置·················································································34
4.4固床工型式·························································································38
4.5沖刷體積·····························································································43
第五章 結論與建議···································································50
5.1結論·····································································································50
5.2建議·····································································································51
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