沙體含水率與飛沙量之關係試驗

Test on the Relationships Between Sand Moisture and its Erodibility by Wind

林信輝(Shin-Hwei Lin) ； 江永哲(Yung-Cheh Chiang)

《中華水土保持學報》 10卷2期 (1979/12) Pp. 173-193

https://doi.org/10.29417/JCSWC.197912_10(2).0014

摘要

本試驗以後龍沙爲材料，在風洞內進行不同含水率時之飛沙量試驗，並依理想土壤（Ideal Soil）之假設及水體之力學理論，推估不同含水率時之飛沙量值，且闡明其實用性及與實驗值之相關性，玆摘要如下：1.試驗結果：在含水率少於1.2％時，飛沙量近似相同。介於1.2％與2.1％之間時，飛沙量急遽減少，若含水率大於2.1％以上，則飛沙量甚少，亦卽風蝕極難發生。2.理論假設與估算結果：（1）以相同孔隙率而言，後龍沙體與開放型疊置（Open Packing）之排列方式相同。（2）引用乾沙之飛沙量公式及飛沙表面上之摩擦速度V與拖曳力τ爲常數之基本假設，導出不同含水率之飛沙量公式（5.8）如下：方程式略（3）開放型疊置，含水率在6.26％時，水體開始融合爲一體，此融合之發生預測是抑止飛沙移動的主因。如圖十二。3.實驗值與推估值之關係：（1）由於風乾沙亦含有少量之水分，故應將理論計算之含水率增加0.5％左右。（2）以後龍沙爲例，其含水率在小於1.2％時，理論水體之力量及飛沙量之推估應屬無誤。但含水量大於1.2％以上時，則不適用。（3）理想土壤之假設與實體沙粒之差異，有待進一步之試驗與研究。

並列摘要

Sand samples taken from Houlong were tested the rate of their movement at different moisture contents in the wind tunnel. An estimation was also made on the theoretical value according to the hypothesis of ideal samples and the calculation of the force of water cuffs between two send particles. The results were summarized as follows: (1) The rate of sand movement was almost identical as the moisture content was less than 1.2% but decreased rapidly when the moisture content went between 1.2% and 2.1%, If the moisture content was beyond this range, there was only small amount of sands to be moved by wind. (2) Sand movement was not affected by air humidity since it made a change in sand moisture content by 0.5% only. (3) As comparing the porosities, the arrangement of Houlong sand was more likely to be open packing. (4) From the formula for the movement of air-dried sands by wind and the basic hypothesis of constant shear stress velocity, V, or drag force, τ, on the surface of the sand, we derived the following formula for sand movement including moisture variation: (The equation is abbreviated) (5) since air-dried sands contained some water, the theoretical calculation of moisture content should be added 0.5% to the calculated value for matching the real conditions of sand samples. (6) For example of Houlong sand, the theorectical force of water cuff and estimated value of sand movement should be corrected when its moisture content was less than 1.2%.