土石流導致底床變動邊界之研究

Abstract

本研究在室內渠道內，上游於傾倒式檔板後方堆置一三角形土壩(壩長105cm、 高30cm)，下方設有一方形動床坑(長185cm，深12cm)，探討於坡度15 度，流量 1693ml/s 下，底床顆粒與上游土石壩材料粒徑皆相同情況下，模擬由土壩形成之 土石流流經動床時，其影響動床中砂石顆粒的現象。分析過程中以影像處理方式 加上人工判斷進行顆粒定位，繪出砂石顆粒流場速度分佈，並根據流場之流速分 佈描繪出受土石流影響之變動邊界隨時間的變化。 由實驗結果可知，土石流初期在土石流前方尚未到達的位置，底床亦會受到 土石流影響。以最大值誤差過濾流場所繪製底床變動邊界，因有較多流速值較小 被忽略，其邊界包含的範圍小於由平均值誤差、方均根誤差過濾後流場繪製之底 床變動邊界。

In this study, we observe the grain articles in movable bed influence induced by debris flow through laboratory experiment. The materials in debris flow are the same with in movable bed. In the analysis, we get the successive particle image by a video camera. Through image processing, we get the enhanced images, and then we locate these particles positions by artificial method. After got the flow field velocity, we ignored the velocities which were less than value of the other error type. With the different error type, we plot the boundary between the moving particles and static particles in different time. The results showed that even the area near the debris flow snout were not covered by debris flow, some particles still moved with the neighborhood particles. And the range from the flow field which is processed with maximum-error is less than the other error type.