2004年

# 摘要或動機

This research is devoted to researching the influence of rain-drop impact on the rate of infiltration. Rain-drop simulators 160cm tall drip water into a transparent container (14 x 10 x 4) of three kinds of soil (quartz sandstone, loess, sand soil) Through the manipulation of factors such as rain impact (raindrop diameter, raindrop descendent height, frequency of impact) and soil property, we experiment the different possibilities of infiltration and its rate under various conditions. Through this comparison we aim to discover the relation between rain impact and infiltration rate. This research concludes the following: 1. The larger the diameter of the raindrop, the quicker the infiltration rate. 2. The greater the descendent height, the greater the speed of infiltration due to collected descending speed. 3. In the early stage of rain, the greater the frequency of rain impact, the faster the rate of infiltration. 4. Under controlled raining conditions, the larger blank sand soil allows greater infiltration speed. 5. In the later stage of rain impact, a blanket of water accumulates on the surface of the soil, reducing the impact force and thus affecting the rate of infiltration. 本研究試探究雨滴撞擊對土壤入滲速度所造成的影響，針對此問題設計下列方法，以進行探討。我們採用高160cm 的自製雨滴模擬器來滴濺長14cm，寬10cm、高4cm 的透明實驗盒裝入三種土樣（石英砂、黃土與黑砂壤），接著改變各種雨水衝擊因子（不同直徑的水滴、不同的落下高度、不同的撞擊頻率）和土壤條件（土壤性質…）等變因，讓滴濺過程產生不同的情形，滴濺過後再行滲透作用，比較各情況所造成的滲透速率快慢的差異，尋找出雨滴衝擊和土壤滲透速率的關係。本研究有以下幾點結論：1. 雨滴粒徑愈大，對於土壤的入滲速率愈快。2. 雨水落下高度愈大時，因水滴動能的增加，土壤的入滲速率也愈快。3. 在水滴撞擊的初期，當水滴滴落頻率愈大時，土壤的入滲速率也會愈快。4. 當雨滴條件相同時，平均粒度較大的黑砂壤其入滲速率較快。5. 在雨滴撞擊後期，因表層土壤產生的水膜造成雨滴撞擊能量的變化。當水膜厚度愈大時，撞擊產生的能量有減少的趨勢而影響了土壤的入滲速率。