基于TDR技术的水分测量系统量测膨胀土含水量偏差分析

Analysis on Water Content Deviation of Expansive Soil Measured by Moisture Measurement System Based on TDR

针对某基于TDR技术的水分测量系统量测膨胀土路堑边坡体积含水量偏离真值这一现象,对岩土的电磁特性、TDR技术量测原理和膨胀土的结构特征进行了研究。通过介电常数与多种类型土的含水量间的对应关系,可以得到介电常数与土体含水量之间有直接的密切关系,进而测量介电常数可以表征土体含水量。结果表明:相对于普通粘土而言,膨胀土粘粒含量和密度的增加引起电磁波传播过程中介电常数的变化,从而引起体积含水量增大;某基于TDR技术的水分测量系统在出厂前标定时采用的是石英砂材料,与膨胀土的颗粒粒径相差很大,产生量测偏差。

Since the data from a TDR moisture measurement system are deviated from the true values in measuring the slope of expansive soils on road-cutting, the geotechnical electromagnetic property, the principle of TDR moisture measurement system and the texture characteristics of expansive soils were studied.Through the correspondence relationship of dielectric constant with kinds of soil＇ s water content, the direct intimate connection between dielectric constant and water-content of soil was found out, and the dielectric constant which represents water content of soil was measured. The result indicates that （ 1 ） the increment of clay particle and bulk density generates the change of dielectric constant between the expansive soils and the clays which results in increase of bulk water content; （2） because the TDR moisture measurement system was calibrated by arenaceous quartz before sale and the grain size of expansive soils is much smaller than that of arenaceous quartz, the deviation was produced.