Evaluation of the performance of TDR and capacitance techniques for soil moisture measurement

Susha S. U Lekshmi , D. N. Singh, Alessandro Tarantino, M. Shojaei Baghini

Research output: Contribution to journalArticle

Abstract

Though researchers have employed various techniques (gravimetric, electromagnetic, neutron scattering, heat pulse, micro-wave and optical remote sensing techniques) for soil moisture measurement, dielectric based techniques (Time Domain Reflectometry, TDR, and capacitance technique, CT) have gained much more popularity, mainly due to revolutionary developments in the field of electronics and data communication systems. However, suitability and relative performance of these techniques for moisture measurement of soils is a point of debate. Hence, in order to address this issue, extensive studies were conducted on the soils of entirely different characteristics, compacted at various compaction states (dry density and water content) by employing TDR and capacitance probes. Subsequently, the dielectric constant of the soil and its bulk electrical conductivity were obtained using these probes and compared against each other and that computed from Topp’s equation, which is a well-established relationship between the dielectric constant of the soil and its volumetric moisture content. An attempt was also made to correlate Ka values obtained from the dielectric techniques and Topp’s equation with that of Time Propagation (TP) mixing model, which incorporates in it the properties of the soil matrix as well. It has been observed that Ka-TDR matches well with the Ka-Topp and Ka-TP, while the best match has been observed between Ka-TDR and Ka- Topp as compared to the Ka-CT. As such, the study demonstrates, clearly, that Topp’s equation, which ignores the soil specific parameters, is capable of determining the soil moisture content appropriately . This study proposes an empirical equation which relates dielectric constants obtained from Topp's equation to those obtained from the TDR, capacitance technique and TP mixing model. Such a relationship can be further utilized for estimating the volumetric soil moisture content.
LanguageEnglish
JournalGeotechnical Testing Journal
Publication statusAccepted/In press - 24 Jul 2017

Fingerprint

time domain reflectometry
Soil moisture
Capacitance
soil moisture
Soils
Moisture
moisture content
Permittivity
soil
probe
neutron scattering
dry density
Neutron scattering
Data communication systems
Water content
electrical conductivity
evaluation
Remote sensing
compaction
Compaction

Keywords

  • soils
  • dielectric constant
  • volumetric moisture content
  • time domain reflectometry
  • capacitance probe
  • electrical conductivity

Cite this

@article{e357a8c165c647369329901a0f3016af,
title = "Evaluation of the performance of TDR and capacitance techniques for soil moisture measurement",
abstract = "Though researchers have employed various techniques (gravimetric, electromagnetic, neutron scattering, heat pulse, micro-wave and optical remote sensing techniques) for soil moisture measurement, dielectric based techniques (Time Domain Reflectometry, TDR, and capacitance technique, CT) have gained much more popularity, mainly due to revolutionary developments in the field of electronics and data communication systems. However, suitability and relative performance of these techniques for moisture measurement of soils is a point of debate. Hence, in order to address this issue, extensive studies were conducted on the soils of entirely different characteristics, compacted at various compaction states (dry density and water content) by employing TDR and capacitance probes. Subsequently, the dielectric constant of the soil and its bulk electrical conductivity were obtained using these probes and compared against each other and that computed from Topp’s equation, which is a well-established relationship between the dielectric constant of the soil and its volumetric moisture content. An attempt was also made to correlate Ka values obtained from the dielectric techniques and Topp’s equation with that of Time Propagation (TP) mixing model, which incorporates in it the properties of the soil matrix as well. It has been observed that Ka-TDR matches well with the Ka-Topp and Ka-TP, while the best match has been observed between Ka-TDR and Ka- Topp as compared to the Ka-CT. As such, the study demonstrates, clearly, that Topp’s equation, which ignores the soil specific parameters, is capable of determining the soil moisture content appropriately . This study proposes an empirical equation which relates dielectric constants obtained from Topp's equation to those obtained from the TDR, capacitance technique and TP mixing model. Such a relationship can be further utilized for estimating the volumetric soil moisture content.",
keywords = "soils, dielectric constant, volumetric moisture content, time domain reflectometry, capacitance probe, electrical conductivity",
author = "Lekshmi, {Susha S. U} and Singh, {D. N.} and Alessandro Tarantino and Baghini, {M. Shojaei}",
note = "This is an accepted author manuscript of an article accepted for publication in Geotechnical Testing Journal Copyright @ 2017, ASTM International, West Conshohocken, PA, https://doi.org/10.1520/GTJ20160240",
year = "2017",
month = "7",
day = "24",
language = "English",
journal = "Geotechnical Testing Journal",
issn = "0149-6115",

}

Evaluation of the performance of TDR and capacitance techniques for soil moisture measurement. / Lekshmi , Susha S. U; Singh, D. N.; Tarantino, Alessandro; Baghini, M. Shojaei .

In: Geotechnical Testing Journal, 24.07.2017.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Evaluation of the performance of TDR and capacitance techniques for soil moisture measurement

AU - Lekshmi , Susha S. U

AU - Singh, D. N.

AU - Tarantino, Alessandro

AU - Baghini, M. Shojaei

N1 - This is an accepted author manuscript of an article accepted for publication in Geotechnical Testing Journal Copyright @ 2017, ASTM International, West Conshohocken, PA, https://doi.org/10.1520/GTJ20160240

PY - 2017/7/24

Y1 - 2017/7/24

N2 - Though researchers have employed various techniques (gravimetric, electromagnetic, neutron scattering, heat pulse, micro-wave and optical remote sensing techniques) for soil moisture measurement, dielectric based techniques (Time Domain Reflectometry, TDR, and capacitance technique, CT) have gained much more popularity, mainly due to revolutionary developments in the field of electronics and data communication systems. However, suitability and relative performance of these techniques for moisture measurement of soils is a point of debate. Hence, in order to address this issue, extensive studies were conducted on the soils of entirely different characteristics, compacted at various compaction states (dry density and water content) by employing TDR and capacitance probes. Subsequently, the dielectric constant of the soil and its bulk electrical conductivity were obtained using these probes and compared against each other and that computed from Topp’s equation, which is a well-established relationship between the dielectric constant of the soil and its volumetric moisture content. An attempt was also made to correlate Ka values obtained from the dielectric techniques and Topp’s equation with that of Time Propagation (TP) mixing model, which incorporates in it the properties of the soil matrix as well. It has been observed that Ka-TDR matches well with the Ka-Topp and Ka-TP, while the best match has been observed between Ka-TDR and Ka- Topp as compared to the Ka-CT. As such, the study demonstrates, clearly, that Topp’s equation, which ignores the soil specific parameters, is capable of determining the soil moisture content appropriately . This study proposes an empirical equation which relates dielectric constants obtained from Topp's equation to those obtained from the TDR, capacitance technique and TP mixing model. Such a relationship can be further utilized for estimating the volumetric soil moisture content.

AB - Though researchers have employed various techniques (gravimetric, electromagnetic, neutron scattering, heat pulse, micro-wave and optical remote sensing techniques) for soil moisture measurement, dielectric based techniques (Time Domain Reflectometry, TDR, and capacitance technique, CT) have gained much more popularity, mainly due to revolutionary developments in the field of electronics and data communication systems. However, suitability and relative performance of these techniques for moisture measurement of soils is a point of debate. Hence, in order to address this issue, extensive studies were conducted on the soils of entirely different characteristics, compacted at various compaction states (dry density and water content) by employing TDR and capacitance probes. Subsequently, the dielectric constant of the soil and its bulk electrical conductivity were obtained using these probes and compared against each other and that computed from Topp’s equation, which is a well-established relationship between the dielectric constant of the soil and its volumetric moisture content. An attempt was also made to correlate Ka values obtained from the dielectric techniques and Topp’s equation with that of Time Propagation (TP) mixing model, which incorporates in it the properties of the soil matrix as well. It has been observed that Ka-TDR matches well with the Ka-Topp and Ka-TP, while the best match has been observed between Ka-TDR and Ka- Topp as compared to the Ka-CT. As such, the study demonstrates, clearly, that Topp’s equation, which ignores the soil specific parameters, is capable of determining the soil moisture content appropriately . This study proposes an empirical equation which relates dielectric constants obtained from Topp's equation to those obtained from the TDR, capacitance technique and TP mixing model. Such a relationship can be further utilized for estimating the volumetric soil moisture content.

KW - soils

KW - dielectric constant

KW - volumetric moisture content

KW - time domain reflectometry

KW - capacitance probe

KW - electrical conductivity

UR - https://compass.astm.org/journals/gtj/index.html

M3 - Article

JO - Geotechnical Testing Journal

T2 - Geotechnical Testing Journal

JF - Geotechnical Testing Journal

SN - 0149-6115

ER -