Volume 2, Issue 1 (January 2005)
Density Compensation of TDR Calibration for Geotechnical Applications
Time Domain Reflectometry (TDR) technology has been widely used in areas such as agricultural science, soil science, and water resources for measuring soil volumetric water content and is beginning to be used in geotechnical engineering. Calibration relationships, which generally relate the soil volumetric water content to TDR measured dielectric constant, are critical for the accuracy of TDR measurements. For TDR technology to be useful for geotechnical engineering practice, the calibration relationship needs to be expressed in terms of gravimetric water content. Besides, geotechnical engineering deals with more compacted earth materials, where the effects of soil density on TDR calibration are significant. This paper introduces an improved TDR calibration relation that accounts for the density of soil skeleton while at the same time is simple in format. Application of this calibration relationship shows that it significantly reduces data scatter and achieves more accurate results than other existing calibration relationships.