首页|Examination of the Dry Density Importances in TDR Use and of the ASTM D6780 Standard Based on a New Calibration Procedure
Examination of the Dry Density Importances in TDR Use and of the ASTM D6780 Standard Based on a New Calibration Procedure
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NETL
NSTL
Amer Soc Testing Materials
The use of time domain reflectometry (TDR) to monitor soil water content at either field orlaboratory scales is highly common. Regarding the soil dry density, ρd, effect on the TDR application,three main approaches are found in the literature: (1) Ignore the density issue and usecalibration to evaluate the water content regardless of the density. This approach is basic, yetcommon. (2) Include soil density in the calibration equation and use calibration for the watercontent as a function of both the TDR output and soil density. In this approach, the soil densityshould be provided from an independent source. (3) Determined ρd from the TDR waveform. Inthis case both water content and ρd are set from the TDR analysis. In cases where the ρd is notavailable, in order to use TDR for water content measurement, a decision has to be madewhether to address the density issue although it requires resources, or to neglect it. This articlereviews this issue and validates the density effect using an efficient TDR calibration methodology.A calibration scheme that controls ρd of the specimen has been developed and applied.The methodology creates continuous calibration curves over a range of volumetric water contentfrom a single test specimen. Based on the results, it has been demonstrated that the soildensity has a major effect on the TDR output and it cannot be ignored. In addition, this articlepresents a unique examination of ASTM D6780, Standard Test Methods for Water Content andDensity of Soil In Situ by Time Domain Reflectometry (TDR). The ASTM dry density estimationwas found to provide reliable results; however, the gravimetric water contents estimation givesunsatisfactory results, especially for low densities.
time domain reflectometrydry densitystandards and codes of practice
Shay Nachum
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Department of Civil Engineering,Braude College of Engineering,Snunit 51 St., Karmiel 2161002,Israel
NETL
NSTL
Amer Soc Testing Materials
