環圈柱保護工於橋墩沖刷防治之研究

Abstract

近年來，台灣地區夏季由於滯留鋒與颱風的影響時常造成豪雨，氣候異常使得氣候型態更趨於極端，如2009年莫拉克颱風在台灣創造大雨紀錄，對台灣所造成的重大災害更是前所未見。豪雨所形成之高流量沖刷橋墩周圍河床，造成橋墩基礎裸露進而危及橋梁安全。因此，如何避免橋墩遭沖刷破壞遂成為當前之重要課題。本研究基於保護橋基安全，因此研發新型之環圈柱橋墩保護工，並進行相關水工模型之試驗研究，提出較理想之保護工配置，期能減緩橋墩沖刷，以供相關單位工程設計之參考。 本研究主要利用水工模型試驗模擬於定量流( =0.95)作用下，首先針對六種環圈堆設置距離（ =1、2、3、4、5、6）對橋墩的保護效果進行討論，並選出最佳保護效果的環圈柱設置距離，接著以最佳環圈柱設置距離分析不同直徑（ = 0.8、0.9、1）之環圈堆結構物；四種環圈堆設置高度（ =1.08、1.6、2.4、3）對橋墩保護的影響，探討環圈堆結構物遮蔽橋墩上游縱向、橫向水流對減少橋墩沖刷深度的影響，並進行比較分析。 研究結果顯示，當環圈堆直徑與橋墩直徑相同時(D=b)，能分散橋墩上游橫向水流，另外環圈堆結構物設置高度應大於試驗水深 (H/b > 2.4)與試驗進行中環圈堆下降之高度總和，可避免水流由環圈堆結構物頂端溢流，穩定橋墩上游水流使水流由橋墩兩側導流避免水流集中現象，而環圈堆結構物設置距離採用5倍橋墩直徑（L=5b）可量測得到橋墩最大沖刷深度最小值與較佳保護效果。

Abstract Heavy rainfall frequently occurs in the summer in Taiwan due to the effects of the stationary fronts and typhoons. In recent years, the climatic anomalies tend to induce more extreme weather.For example, record-breaking heavy rainfall induced by Typhoon Morakot (2009) caused an unprecedented disaster in Taiwan. High flow caused scouring of the river bed around the piers, resulting in the exposure of the pier foundation and threatening the safety of bridge. To protect the bridge foundation,theuse of Ring column groups as a pier scour countermeasure is reported. In this study, hydraulic model experiments with Ring column groups are carried out to search for the ideal arrangements to reduce the bridge scour. It can be served as a reference of design for relevant engineers in future. A series of experiment was conducted with uniform sediments under the steady flow (V/Vc =0.95) First for six kinds of distance(L/b=1、2、3、4、5、6)Conducted to discuss the protective effect of pier and elect the best protective effect of distance,and then use the best distance analys is four different diameters(D/b=0.8、0.9、1）three different heights(H/b=1.08、1.6、2.4、3）to the impact of the bridge pier protection .Investigate the The ring columns consisting of cylindrical rubber rings Obscured the vertical and horizontal flow of the bridge pier upstream to reduce the impact of the bridge pier scour depth. Based on experimental results, when the diameter of the ring columns is equal to the pier diameter(D=b), the ring columns could disperse the transverse flow when the Ring column groups settings at a distance of 5 times the pier diameter, the height of the ring column is higher than the water surface(H/b>2.4). to avoid the overflow of water from the top of the ring columns, stabilize the pier upstream flow so that water from the pier two side diversion to avoid the water concentration, when the Ring column groups settings at a distance of 6 times the pier diameter（L=5b）, Can be measured to a minimum scour depth, which is the best set type among the experimental conditions.