彎道泥砂沖淤之試驗研究

本研究選擇加蘭彎做縱橫斷面測量，並調查其水文、地文等因子，再於室內進行水工模型試驗研究，以探討河岸冲刷及河道泥砂冲淤之情形。以修正何智武公式和梅彼穆公式做為輸砂量之估算模式，用廻歸週期25年之流量、泥砂冲淤延時分別為1日和2日進行試驗比較。並且，以修正何智武公式為主，於2日延時下，探討廻歸週期爲25年、50年和100年之流量下，泥砂之冲淤情形。經分析6組試驗共84個斷面資料後，在輸砂量估算上，不論延時爲1日或2日，實驗結果與理論計算結果之相對誤差值之絕對值，均以修正何智武公式較小，故可知修正何智武公式爲一個極富潛力之本土化推移質輸砂模式。另外，於模型試驗時，若凹岸頂冲區之冲刷已達模型邊壁，則水流有溯源冲刷之現象，故同理可知，於此處設置護岸，將導致其上游河岸之冲刷。由於河道床形之影響，加上東部河川之堆積層甚厚，故2日延時後水流之深泓線仍與原來之深泓線一致，而有異於一般深泓線必在凹岸之情形。最後，於各組試驗中得知，斷面25～28間其河岸之冲刷最爲嚴重，且斷面之冲刷面積亦最大，其原因爲此區段為彎道之頂冲區，水流直接冲擊所致。

關鍵字

彎道；泥砂冲淤；河岸冲刷

並列摘要

This study chose Chialan Bend for surveying longitudinal and cross sectional profiles, and investigating hydrologic as well as morphological factors to make hydraulic modelling indoors for exploring the mechanisms of bank erosion and sediment transport. This study adopt the modified Ho's model and the Meyer-Peter and Müller model to calculate sediment discharge, associated with the discharge of 25 return period years, and one day as well as two days' of silt-and-scour. Moreover, based on the modified Ho's model and two days' duration, this study discussed the mechanism of silt-and-scour under the conditions of return periods of 25, 50 and 100 years, respectively. After analyzing 6 sets of data which included 84 cross section, the absolute value for relative error of experimental results to calculating data on sediment discharge with one day or two days' durations had showed minimum value by modified Ho's model. Hence, Ho's model would be a potential native model for bed-load transport. And, from results of hydraulic modelling, stream flow would begin to erode upstream when it tonched unerodible outer bank. Hence, the setup of revetment here would result in erosion occurred on upstream area. Because of the influence of topography and heavy thick alluvial deposits of river bed in Eastern Taiwan, the thalweg was still located in same side of the original one. And, this phenomenon was different from the general condition which thalweg was located in area of outer bank. Moreover, from experimental results, the bank erosion and scouring area of section 25~28, which was located in top area of bend, was the biggest resulted from stream flow attacking this area directly.

並列關鍵字

River bend ； Silt-and-Scour ； Bank erosion

主題瀏覽