Measurement of unfrozen water content and relative permittivity of frozen unsaturated soil using NMR and TDR
Measurement of unfrozen water content and relative permittivity of frozen unsaturated soil using NMR and TDR
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DOI：
10.1016/j.coldregions.2009.05.011
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发表时间：
2009-10
影响因子：
4.1
通讯作者：
Kunio Watanabe;Tomomi Wake
中科院分区：
文献类型：
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作者：
Kunio Watanabe;Tomomi Wake
土壤的冻结特性，即未冻水含量与温度的关系，与冻结多孔介质中的任何传质过程有关。为了确定土壤冻结特性，我们同时测量液态水含量和相对介电常数的各种非饱和土壤在零度以上和零度以下的温度下，通过使用脉冲核磁共振（NMR）和时域反射仪（TDR）。冻土的介电常数随着温度的降低而降低，这是伴随着液态（未冻）水含量的减少。总含水量不同的冻土在-1 °C以下有相同量的未冻水;然而，冻土的介电常数取决于总含水量。一个没有考虑由于表面力和冰的形成而降低的介电常数的介电混合模型只能描述桑迪的数据。我们扩展了混合模型，包括减少介电常数由于表面力和冰的形成。液态水含量的估计，使用扩展混合模型与NMR测量值在任何土壤类型，总含水量，冰含量，和温度一致。
The soil-freezing characteristic, the relationship between unfrozen water content and temperature, is relevant for any mass transfer processes in frozen porous media. To determine the soil-freezing characteristic, we simultaneously measured liquid water content and relative permittivity of various unsaturated soils at above-zero and subzero temperatures by using pulsed nuclear magnetic resonance (NMR) and time-domain reflectometry (TDR). The dielectric permittivity of frozen soil decreased with a decrease in temperature, which was accompanied by a decrease in liquid (unfrozen) water content. Frozen soils with different total water content had the same amount of unfrozen water at below −1 °C; however, the permittivity of frozen soil depended on the total water content. A dielectric mixing model without considering reduced dielectric permittivity due to surface forces and ice formation could only describe the data for sandy soils. We expanded the mixing model by including reduced dielectric permittivity due to surface forces and ice formation. The estimations of liquid water content using the expanded mixing model were in agreement with the values measured by NMR at any soil type, total water content, ice content, and temperature.