Peat water content measurement using time domain reflectometry

1992 ◽  
Vol 22 (4) ◽  
pp. 534-540 ◽  
Author(s):  
Steeve Pepin ◽  
André P. Plamondon ◽  
Jean Stein
Keyword(s):  
Standard Deviation ◽  
Water Content ◽  
Time Domain ◽  
Empirical Relationship ◽  
High Standard ◽  
Organic Soil ◽  
Time Domain Reflectometry ◽  
Volumetric Water Content ◽  
Water Tables ◽  
Apparent Dielectric Constant

The calibration of time domain reflectometry, previously established for an organic soil of 0.422 Mg•m−3 bulk density, was established for peat blocks with bulk densities ranging from 0.06 to 0.25 Mg•m−3. An empirical relationship between the volumetric water content and the measured apparent dielectric constant was established in the laboratory. This relationship can be used to estimate volumetric water content between 0.21 and 0.95 cm3•cm−3 with a standard deviation of 0.03 cm3•cm−3. The large variations observed during the calibration were mainly attributed to the size and heterogeneousness of peat samples. When water tables in the field were high, standard deviation decreased to 0.02 cm3•cm−3, which agrees very well with other time domain reflectometry experiments.

Using time domain reflectometry in triaxial testing

2000 ◽  
Vol 37 (6) ◽  
pp. 1325-1331
Author(s):  
J LH Grozic ◽  
M E Lefebvre ◽  
P K Robertson ◽  
N R Morgenstern
Keyword(s):  
Cyclic Loading ◽  
Water Content ◽  
Time Domain ◽  
Void Ratio ◽  
Time Domain Reflectometry ◽  
Volumetric Water Content ◽  
Degree Of Saturation ◽  
Triaxial Testing ◽  
Empirical Correlations ◽  
Static And Cyclic Loading

Time domain reflectometry (TDR) can be used to determine the volumetric water content of soils. This note describes the utilization of a TDR miniprobe in triaxial testing. The TDR performance was examined with a series of tests that not only proved its reliability but also resulted in two empirical correlations. Using these correlations, the degree of saturation and volumetric water content during triaxial testing could be determined. The TDR was then put to use in a laboratory program designed to investigate the response of loose gassy sand under static and cyclic loading. Because of the TDR measurements it was possible to determine the degree of saturation and void ratio of the gassy specimens. The TDR miniprobe proved to be accurate, simple to use, and inexpensive to build.Key words: time domain reflectometry, TDR, triaxial testing, gassy, unsaturated.

The measurement of unfrozen water content by time domain reflectometry: results from laboratory tests

1981 ◽  
Vol 18 (1) ◽  
pp. 131-144 ◽  
Author(s):  
D. E. Patterson ◽  
M. W. Smith
Keyword(s):  
Dielectric Property ◽  
Water Content ◽  
Time Domain ◽  
Empirical Relationship ◽  
Time Domain Reflectometry ◽  
Unfrozen Water ◽  
Published Data ◽  
Frozen Soils ◽  
Unfrozen Water Content ◽  
Property Versus

A new technique for determining the volumetric unfrozen water content of frozen soils is reported, which uses time domain reflectometry (TDR) to measure the dielectric property. Using precise temperature control, the technique, which was developed previously by others for unfrozen soils, has been successfully applied to the measurement of unfrozen water contents of frozen soils. Curves of the dielectric property versus temperature show a close similarity to unfrozen water content curves, for a variety of soils. Results from experiments on ice–water mixtures and from combined TDR–dilatometry experiments on frozen soils suggest that an empirical relationship obtained by Topp, Davis, and Annan may be applicable to frozen media as well as unfrozen soils. Using this relationship, dielectric values were converted to unfrozen water content values, and the results agreed very closely with published data for similar soils, determined by other methods. For silt loams, agreement is typically within ± 1½% in volumetric water content, and for clays ± 3 %. Some of this difference is undoubtedly due to soil sample variations.

Unfrozen water content in saline soils: results using time-domain reflectometry

1985 ◽  
Vol 22 (1) ◽  
pp. 95-101 ◽  
Author(s):  
D. E. Patterson ◽  
M. W. Smith
Keyword(s):  
Water Content ◽  
Time Domain ◽  
Time Domain Reflectometry ◽  
Frozen Soil ◽  
Probe Design ◽  
Unfrozen Water ◽  
Use Of Time ◽  
Unfrozen Water Content ◽  
Pore Water Salinity ◽  
Apparent Dielectric Constant

The use of time-domain reflectometry (TDR) for determining the phase composition of saline permafrost from measurement of the apparent dielectric constant, Ka, is examined.Combined TDR–dilatometry experiments were performed to assess whether the TDR method could be used on frozen soil samples with high pore water salinity. In general, unfrozen water content determinations by TDR were within ±0.025 cm3∙cm−3 of those obtained by dilatometry, with no marked influence due to salinity. A novel probe design for use on saline core samples shows promise as a means for determining unfrozen water contents in the field.

scholarly journals Measurement of Volumetric Water Content by Gravimetric and Time Domain Reflectometry Methods at Field Experiment with Biochar and N Fertilizer

2019 ◽  
Vol 22 (2) ◽  
pp. 61-64 ◽  
Author(s):  
Lucia Toková ◽  
Dušan Igaz ◽  
Elena Aydin
Keyword(s):  
Field Experiment ◽  
Water Content ◽  
Time Domain ◽  
Soil Property ◽  
Time Domain Reflectometry ◽  
Soil Samples ◽  
Volumetric Water Content ◽  
N Fertilizer ◽  
High Concentration ◽  
Indirect Methods

Abstract There are many methods used for soil water content measurement which we can divide into direct gravimetric methods from using soil samples or indirect methods that are based on the measurement of another soil property which is dependent on soil moisture. The paper presents the findings of volumetric water content measurements with gravimetric and time domain reflectometry (TDR) methods. We focused on four variants in the field experiment in Dolná Malanta (Slovakia): control variant (B0+N0), variant with biochar at dose 20 t.ha−1 without N fertilizer (B20+N0), variant with biochar 20 t.ha−1 and N fertilizer 160 kg.ha−1 (B20+N160) and variant with biochar 20 t.ha−1 and N fertilizer 240 kg.ha−1 (B20+N240). TDR is nowadays a well-established dielectric technique to measure volumetric water content; however, its accuracy is influenced by high concentration of salts in soil. In this paper, we evaluated the effect of added N fertilizer on the measuring accuracy of HydroSense II device that is operating under the TDR principle.

Time domain reflectometry for water content and density of soils: study of soil-dependent calibration constants

2005 ◽  
Vol 42 (4) ◽  
pp. 1053-1065 ◽  
Author(s):  
V P Drnevich ◽  
A K Ashmawy ◽  
X Yu ◽  
A M Sallam
Keyword(s):  
Dielectric Constant ◽  
Water Content ◽  
Time Domain ◽  
Field Experiments ◽  
Engineering Application ◽  
Time Domain Reflectometry ◽  
Sensitivity Analyses ◽  
Dry Density ◽  
Theoretical Predictions ◽  
Apparent Dielectric Constant

The paper studies the soil-dependent calibration constants used for determining water content and density of soil using time domain reflectometry (TDR), specifically, to establish the typical soil calibration values and study the extent of the uncertainty in calibration factors on measurement accuracy. The TDR method described here makes use of a calibration equation normalized by soil dry density, which involves two soil-dependent constants, a and b. Both a and b have physical significance, with the value of a related to the apparent dielectric constant of the dry density – normalized dry soil solids and the value of b related to the apparent dielectric constant of the pore fluid. From theoretical predictions, typical values of a are around 1.0, and typical values of b are around 9. Practically, the constants a and b are obtained through calibration tests performed in conjunction with standard compaction tests. Experimental study shows that calibration constants fall within the ranges from theoretical predictions. Tests on five soil mixtures provided average values of a = 0.945 and b = 8.76, while 11 clean sands resulted in average values of a = 1.0 and b = 8.5. The study also shows that there are no significant effects of compaction energy on the measured values of a and b. Sensitivity analyses indicate that variations in a and b both cause variations in TDR-determined water content and density, but the variations are typically within acceptable limits for engineering application purpose. Results from TDR tests on simulated field experiments are consistent with the sensitivity analyses.Key words: time domain reflectometry, TDR, calibration constants, water content, dry density, sensitivity.

Time-domain reflectometry measurements and soil-water characteristic curves of coarse granular materials used in road pavements

2007 ◽  
Vol 44 (7) ◽  
pp. 858-872 ◽  
Author(s):  
Jonas Ekblad ◽  
Ulf Isacsson
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Granular Materials ◽  
Time Domain ◽  
Characteristic Curve ◽  
Road Construction ◽  
Time Domain Reflectometry ◽  
Volumetric Water Content ◽  
Characteristic Curves ◽  
Soil Water Characteristic Curves

Coarse granular materials are used extensively in road construction. Bearing capacity can be affected by the water content in the layers of these materials. The ability to estimate water content and to infer water movements is therefore important. The purpose of the work described herein was to determine soil-water characteristic curves and the relationship between relative apparent permittivity and volumetric water content for coarse (maximum particle size 90 mm) granular materials having various gradations. The relative apparent permittivity was measured with the aid of time-domain reflectometry (TDR), and the concurrent matric suction was measured with a tensiometer. Samples were prepared in a steel box and were heavily compacted, and TDR probes and a tensiometer cup were buried within the matrix. The variation in volumetric water content with apparent relative permittivity was found to deviate from the Topp et al. relationship. Soil-water characteristic curves were described using the Brooks–Corey and van Genuchten models. A pronounced hysteresis between wetting and drying paths was observed. For the low water retention coarse materials, measurements of water content might, in general, require correction because of the nonlinear distribution of water in the sample.Key words: pavement, time-domain reflectometry, soil-water characteristic curve, granular material.

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