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題 名 | 孔隙介質板阻力對於非飽和導水係數測定的影響 |
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作 者 | 張文亮; | 書刊名 | 農業工程學報 |
卷 期 | 40:2 1994.06[民83.06] |
頁 次 | 頁48-57 |
分類號 | 434.222 |
關鍵詞 | 孔隙介質板; 導水係數; Porous plate; Hydraulic conductivity; |
語 文 | 中文(Chinese) |
中文摘要 | 孔隙介質板是測定非飽和土壤水所必需的實驗裝置,無論是壓力盒、張力計皆用孔隙介質板維持負壓下水分的移動,不受負壓產生氣泡中斷水分移動的影響。孔隙介質板有標準型,並且有標準步驟測定導水係數,也有標準公式可以計算結果。 本文的目的是提出一般標準公式,如Gardner's公式或Bruce and Klute公式,基本的假設是不考慮孔隙介質板的阻力,視為零阻力,這與真實狀況不符合。因此本文假設孔隙介質板的阻力有影響,而重新推導公式,計算阻力的影響多少。再以實驗配合,證明孔隙介質板阻力影響的顯著。 實驗係採屏東台拓的壤質沙土,與永安的坋質黏壤土,二種不同質地的土壤,實驗用負壓跌水頭的方法,結果發現在壤質沙土,於小於-200 cm的負壓下,介質板阻力減少導水係數19%,在-300 cm以下才3%,方可忽略之。另外在坋質黏壤土,則小於-30 cm負壓下有20%的影響,在-200 cm負壓下有2.5%的影響,方可忽略之。因此阻力的影響依土壤質地與所施負壓的不同而異。在粗質土壤與低負壓的情況下,孔隙介質板的阻力不可以忽略之。 |
英文摘要 | In order to prevent air bubbles moving into the soil, porous plate becomes a must to measure unsaturated soil water movement under the negative pressure condition. Thus, a standard instrument, such as using the pressure cell to measure unsaturated and tensionmeter always contains a porous plate to maintain water passing through soil column. The Soil Analysis Handbook always specify the standard size of porous plate, procedures of measurement, and equations to calculate experimental result. The purpose of this paper is to point out the traditional equations, such as Gardner, Bruce and Klute, have neglected the resistance of the porous plate and treated it as zero. Which is not true in the measurement. Therefore, equations were derived and experiments were conducted to prove that resistance of prous plate existed in the unsaturated flow. Two types of soil were used in this study. One was loamy sand of Tai-Tou, another was silty loamy clay of Yung-An. Constant falling head method was found the resistance of the porous plate reduced 19% of the hydraulic conductivity during -200cm pressure, but only contributed 3% of reduction at -300cm pressure for loamy sand soil. It also contributed 20% of reduction during -30cm pressure, but only 2.5% at -200cm pressure. Therefore, resistance effect of porous plate is dependent on type of soil and the degree of negative pressure. It become more significant in coarse material and cannot be neglected under low negative pressure condition. |
本系統中英文摘要資訊取自各篇刊載內容。