變量流流況下非同心圓枉型橋墩局部沖刷之研究

Local Scour around Eccentric Circular Piers under Unsteady Flows

王傅益(Chuan-Yi Wang) ； 鄭人豪(Jen-Hao Cheng) ； 施漢鵬(Han-Peng Shih) ； 黃奕超(Yi-Chao Huang) ； 除浩寧(Hao-Ning Chen)

《水保技術》 3卷3期 (2008/06) Pp. 118-130

https://doi.org/10.30040/JSWCT.200806.0002

摘要

本研究主要利用水工試驗，模擬近似天然流況之變量歷線（前峰型、中峰型及後峰型）作用下，非同心圓枉型橋墩墩徑比(D/D(上標 *)=0.4~0.7)於不同的覆土高度時。橋墩局部沖刷深度及歴程之變化。結果顯示，於不同型式變量流屋線作用下，沖刷深度會隨相封水流強度(V/Vc)的增加而加大，同時最大沖刷深度於變量流歴線之上升段完成。中峰型歴線及後峰型歴線之沖刷歴程類似，其最大沖刷深度相當且均高於前峰型，兩者僅有時間稽延之差巽。在不同墩徑比時，以D/D(上標 *)=0.4時，其沖刷坑體積減緩效果最佳；又非同心圓枉型橋墩封樸減緩橋墩局部沖刷較同心圓枉型橋墩有效。在考量橋墩水理安全之情況下，D/D(上標 *)=0.4爲較理想之非同心圓枉型橋墩型式。

關鍵字

變量流屋線 ； 非同心圓枉型橋墩 ； 局部沖刷深度

並列摘要

This study uses hydraulic models to measure the variation of local scour depth with time for eccentric circular pier diameter ratios D/D(superscript *) of 0.4~0.7, and different initial bed level relative to the foundation top elevation under unsteady flows with advanced, central and delayed peaks. The results show that the scour depth increases with increasing relative flow intensity (V/Vc) under different types of unsteady flow hydrographs. The scour depth reaches a maximum value within the rising phase of the unsteady flow. The scour variation for the central peak hydrograph is similar to that for the delayed peak hydrograph. Both scour depths are greater than that for the advanced peak hydrograph. The only discrepancy for the first two curves is the time lag. With regard to the effect of eccentric circular pier diameter ratios (D/D(superscript *)), the most effective scour hole volume retardation occurs when D/D(superscript *) equals 0.4. The retardation of local scour by the eccentric circular pier is more effective than the centric circular pier. Considering the safety of bridge structure, a eccentric circular pier with D/D(superscript *) equals to 0.4 is an ideal pier style.

並列關鍵字

Unsteady flow hydrographs ； Eccentric circular pier ； Local scour depth