CALIBRATION OF JOINTED TUBE MODEL FOR THE GAS-DIFFUSION COEFFICIENT IN SOILS
CALIBRATION OF JOINTED TUBE MODEL FOR THE GAS-DIFFUSION COEFFICIENT IN SOILS
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DOI：
10.2136/sssaj1994.03615995005800040010x
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发表时间：
1994-07-01
影响因子：
2.9
通讯作者：
FREIJER, JI
中科院分区：
文献类型：
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作者：
FREIJER, JI
土壤中气体和水蒸气运移的模拟需要知道相对气体扩散系数。基于两根不同半径的曲管串联而成的孔洞模型，确定了相对扩散系数作为充气孔隙率的函数。该模型适用于9种土壤类型的原状土样在较大含水率范围内的相对扩散系数的测定。结果表明，模型参数随研究土壤类型的不同而不同。通过对土壤持水曲线、充气孔隙率和相对扩散系数的联合测量，评价土壤孔隙中水分分布对相对扩散系数的影响。水饱和后，残余充气孔隙度在0.051~0.167 m3m-3之间，相对扩散系数几乎为零，这是由于土壤水对孔隙的堵塞。在与水保持函数中的进气值相对应的压力水头处，充气孔隙度在0.095到0.256立方米米-3之间，相对扩散系数在0.002到0.013之间。从这一点来看，随着充气孔隙率的增加，相对扩散系数迅速增加，在零含水率下从0.165到0.383。得出的结论是，进气值是一个重要的参数，它先验地指示了孔隙堵塞的含水率。
Modeling of gas and vapor transport in soils requires knowledge of the relative gas diffusion coefficient. The relative diffusion coefficient was determined as a function of air-filled porosity, using a pore model based on two tortuous tubes of different radii joined in series. This model was fitted to measured relative diffusion coefficients on undisturbed samples of nine soil types at a wide range of water contents. It was found that model parameters vary with the soil types studied. Combined measurements of the water retention curve, air-filled porosity, and relative diffusion coefficient were made to evaluate the effects of water distribution in the soil pores on the relative diffusion coefficient. After the samples were saturated with water, the residual air-filled porosity ranged from 0.051 to 0.167 m3 m-3 and the relative diffusion coefficient was practically zero, which is due to pore blocking by soil water. At pressure heads corresponding to the air-entry value in the water retention function, air-filled porosity ranged from 0.095 to 0.256 m3 m-3 and the relative diffusion coefficient ranged from 0.002 to 0.013. From this point, with increasing air-filled porosity, the relative diffusion coefficient increased rapidly to values ranging from 0.165 to 0.383 at zero water content. It was concluded that the air-entry value is an important parameter, which indicates a priori the water content at which pore blocking becomes relevant.