School of Agricultural Civil & Bio-Industrial Engineering, Kyungpook National University, Daegu 41566, Korea.
School of Civil, Environmental and Architectural Engineering, Korea University, Seoul 02841, Korea.
Sensors (Basel). 2020 Nov 29;20(23):6834. doi: 10.3390/s20236834.
The objective of this study was to develop a horizontally elongated time domain reflectometry (HETDR) system to evaluate the water content in nonuniformly wetted soils. The HETDR probe consists of three rods of stainless steel and a cuboid head: A center electrode and two outer electrodes are connected to the inner and outer conductors of a coaxial cable, respectively. An acrylic container divided into several segments was used to prepare nonuniformly wetted soils with different water contents for a series of model tests. The HETDR probe was placed horizontally at the middle height of each soil specimen, while a conventional time domain reflectometry (TDR) probe was applied vertically on the surface of the specimen. The experimental results show that as the soil water content (SWC) at a segment increases, the average amplitude decreases and the duration increases. The estimated SWC increases with the measured SWC, and especially, the difference between actual segment length and the segment length estimated from the HETDR probes is significant under dry conditions. This study demonstrates that HETDR may be a promising field-testing method for evaluating the average water content in nonuniformly wetted soils.
本研究旨在开发一种水平拉长时域反射仪（HETDR）系统，以评估非均匀润湿土壤中的含水量。HETDR 探头由三根不锈钢棒和一个长方体头组成：中心电极和两个外电极分别连接到同轴电缆的内导体和外导体。使用一个丙烯酸容器将其分成几个部分，以制备具有不同含水量的非均匀润湿土壤进行一系列模型试验。HETDR 探头水平放置在每个土壤样本的中间高度，而传统的时域反射仪（TDR）探头则垂直放置在样本表面。实验结果表明，随着土壤水分含量（SWC）在一个部分的增加，平均幅度减小，持续时间增加。估计的 SWC 随测量的 SWC 增加，特别是在干燥条件下，从 HETDR 探头测量的实际部分长度与估计的部分长度之间的差异非常显著。本研究表明，HETDR 可能是评估非均匀润湿土壤中平均含水量的一种很有前途的现场测试方法。
