The relationship between electrical capacitance-based dielectric constant and soil water content |
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Authors: | Shi Yan Wu Qi You Zhou Gang Wang Lei Yang Cheng Peng Ling |
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Institution: | (1) Department of Hydrosciences, School of Earth Sciences and Engineering, Nanjing University, #22 Han Kou Road, Nanjing, 210093, China |
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Abstract: | Based on batch experiments conducted on soil samples in the laboratory, the relationship between dielectric constant and water
content based on electrical capacitance measurement was investigated. Factors that may affect the relationship, such as measurement
frequency, electrode array methods, and soil particle sizes, were analyzed. A model fitting the relationship between dielectric
constant and water content was proposed. The results clearly indicate that even with the use of rod-like sensors, the measured
electrical capacitance with 1 kHz frequency can be used to construct a good relationship between dielectric constant and water
content. Although the electrode array methods (parallel or non-parallel electrode pair) and soil particle sizes do affect
the obtained absolute values of dielectric constant to some extent, the relationship between dielectric constant and water
content remains unchanged. A clear characteristic is the increase reduction in the dielectric constant at near saturation
condition, and the low increase speed when water content is small. The proposed modified VG model incorporated this characteristic
into it and fitted the data better than the reported models. These results suggest that the electrical capacitance-based dielectric
constant measurement can be extensively used and would be useful, especially in the situations where parallel sensor requirement
is difficult to satisfy. |
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