冻融过程对FDR测量土壤体积含水量的影响

Effect of freezing and thawing process on FDR's measuring volumetric water content of soil

为研究冻融过程对FDR测量土壤体积含水量的影响,采用基于FDR技术的土壤水分传感器TDR-3,通过室内温度实验箱控制环境温度范围为-20～20℃,对冻融过程中黏性土样体积含水量进行了测试分析.结果表明:采用FDR测量黏性土样体积含水量,在土样未进行冻融前,温度在0℃以上时,FDR的测量值随温度呈线性变化,随着温度的升高而增大,随着温度的降低而减小;黏性土样冻融过程中,在冻结过程中,FDR的测量值随着温度的降低逐渐减小;在融化过程中,随着温度的升高,FDR的测量值逐渐增大;相同温度条件下,黏性土冻结过程中FDR的测量值明显大于黏性土融化过程中FDR的测量值,0℃时两者差值最大,该差值受土壤初始体积含水量和冻融温度的影响.研究成果对于提高FDR测量冻融过程中土壤体积含水量的可靠性具有重要意义.

In order to study the effect of freezing and thawing process on FDR（frequency domain reflectometry）′s measuring volumetric water content of soil,the TDR-3 soil moisture sensor,based on FDR,was used to measure volumetric water content of soil at different temperatures ranged between-20-20 ℃,controlled by the temperature box in laboratory.The results show that,before freezing process above 0℃,during thawing process,the volumetric water content of soil measured by FDR increases or decreases as the temperature increases or decreases;the volumetric water content of soil,measured by FDR,decreases as temperature decreases during freezing process;and increases as temperature increases during thawing process.At the same temperature,the volumetric water content of soil measured during freezing process is higher than that measured during thawing process;at 0 ℃,the difference between them is maximal,which is significantly affected by the initial volumetric water content of soil and temperature.The results are valuable for improving the reliability of measuring the vo-lumetric water content of soil by applying FDR in freezing and thawing process.