The dielectric constant of soil is used to estimate its water content in a range of applications. Unlike the widely known effect of water content on the soil dielectric constant (consistent direct proportionality), only a limited number of studies have reported the effects of soil dry density, however, with equivocal results. This paper, therefore, investigates the effects of dry density or degree of compaction on the dielectric constant of five different soil types. The results of the experimental work for the soils ranging from sand to Bentonite clay with distinct specific surface areas were evaluated based on the use of two simple mixture models (De Loor and Birchak). The effects of dry density on the soil dielectric constant were found to be soil type dependent. This is demonstrated by the experimental data and further proven by the modified De Loor model. The behavior is shown to be defined by the changes in the free water, bound water, and solid particle volume fractions, ultimately controlled by the soil specific surface area. The dielectric constant changes from being directly proportional to dry density to inversely proportional at a threshold specific surface area of between 122 and 147 m²/g. Supported by the experimental observations, parametric analysis has revealed that the range for the dielectric constant of bound water was found to be 9–37, while the geometrical parameter α in the Birchak model was found to be 0.4–0.8.

中文翻译：

---

干密度对不同比表面积土壤水混合物介电性能影响的实验研究

土壤的介电常数用于估算其在一系列应用中的水分含量。与众所周知的水分对土壤介电常数（一致的直接比例）的影响不同，只有有限的研究报道了土壤干燥密度的影响，但结果却模棱两可。因此，本文研究了干密度或压实度对五种不同土壤类型的介电常数的影响。基于两种简单的混合模型（De Loor和Birchak），评估了从沙土到膨润土具有不同比表面积的土壤的实验结果。发现干密度对土壤介电常数的影响取决于土壤类型。实验数据证明了这一点，改进的De Loor模型进一步证明了这一点。表现出的行为是由游离水，结合水和固体颗粒体积分数的变化定义的，最终由土壤比表面积控制。介电常数从与干密度成正比变化到在122和147 m之间的阈值比表面积成反比² /克。在实验观察的支持下，参数分析显示结合水的介电常数范围为9-37，而Birchak模型中的几何参数α为0.4-0.8。