TDR水分计标定试验分析

Analysis on calibration tests for TDR moisture meter

土体含水量是控制非饱和土特性不可或缺的状态变量,快捷、准确地测量该变量成为推动非饱和土研究的重要环节。TDR水分计测定含水量具有方便、快速、经济的优点。围绕TDR测量原理,开展了探测体积、测量误差的标定试验,并在操作中总结出了TDR水分计的安装经验,结果表明:两针型TDR水分计探测范围集中在1.7倍探针间距的圆柱体内;针对砂土和黄土,TDR测量值比烘干含水量稍大,两者间可采用三次多项式拟合修正。为确保TDR水分计为实际应用提供准确可靠的水分数据,未来室内试验和室外监测使用前需预先进行标定。

Soil water content （SWC） is an indispensable state variable which controls the characteristics of unsaturated soil. The fast and accurate measurement of this variable is an important part promoting the study of unsaturated soil. Using TDR soil moisture meter measuring SWC is with the convenient, fast and economic characteristics. The calibration tests to detect the volumes and to measure the errors are carried out based on the TDR measurement principle, and the installation experience of the meters is summed in the operation. The results show that the detection volume of the two-pin type TDR moisture meter is concentrated in a cylinder with the radius of 1.7 times of the probe spacing. When measuring the SWC of sand and loess, the TDR values are of the large difference with that from oven-drying, but the cubic polynomial can be used to fit them. So in order to provide the practical application with accurate and reliable moisture data, the TDR moisture meter should be calibrated in advance before the indoor tests and the field inspection.