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

Drnevich, VP; Ashmawy, Alaa K.; Yu, Xiong; Sallam, Amr

doi:10.1139/t05-047

Cited by 47 publications

(31 citation statements)

References 5 publications

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“…Electromagnetic (EM) techniques have been widely used for measuring (Robinson et al 2008). Among these, time domain reflectometry (TDR) is a well-established method that has been used to measure and electrical parameters at point locations in the field based on the measurement of the apparent dielectric permittivity, K a (Herkelrath et al 1991;Robinson et al 2003a;Delin and Herkelrath 2005;Curioni et al 2017).…”

Section: Introductionmentioning

confidence: 99%

Time domain reflectometry (TDR) potential for soil condition monitoring of geotechnical assets

et al. 2019

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The performance of geotechnical assets is influenced by various external factors including time and changing loading and environmental conditions. These changes could reduce the asset’s ability to maintain its function, potentially resulting in failure, which could be extremely disruptive and expensive to remediate; thus, the ability to monitor the long-term condition of the ground is clearly desirable as this could function as an early-warning system, permitting intervention prior to failure. This study demonstrates, for the first time, the potential of using time domain reflectometry (TDR) for long-term monitoring of the relative health of an asset (via water content and dry density) in a field trial where a clayey sandy silt was exposed to leaking water from a pipe. TDR sensors were able to provide detailed information on the variation in the soil conditions and detect abrupt changes that would relay a prompt for asset inspections or interventions. It is proposed that TDR could be used alone or together with other shallow geophysical techniques for long-term condition monitoring of critical geotechnical assets. Early-warning systems could be based on thresholds defined from the values or the relative change of the measured parameters.

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Section: Introductionmentioning

confidence: 99%

Time domain reflectometry (TDR) potential for soil condition monitoring of geotechnical assets

et al. 2019

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“…The success of such methods is caused by the dipolar character of the water molecules resulting in a high permittivity in comparison to other phases such as solid particles or gas voids. However, evidence suggests that the frequency-dependent dielectric permittivity contains far more information than water content only: structure [12], density [13], mineralogy, cohesion forces on the pore solution [14] and even material strength may leave distinct signatures that could potentially be quantified. Nevertheless, despite its great success, HF-EM methods are still confronted with theoretical challenges.…”

Section: Introductionmentioning

confidence: 99%

Dielectric properties of the pore solution in cement-based materials

Honório

Boré

Benboudjema

et al. 2020

Journal of Molecular Liquids

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Dielectric properties are intimately related to the content and composition of the liquid phase present in micro-and mesoporous materials. The presence of ions is recognized to affect the dielectric response of electrolytes in a complex way that depends on the ion-water and ion-ion interactions and respective concentrations. Pore solutions in cement-based materials are complex and age-dependent exhibiting different ion pair states, which make them an interesting candidate for the study of the complex pore solution found in geomaterials in general. Here, we study the dielectric properties of bulk aqueous solutions representative of the pore solution found in cement-based materials using molecular dynamics simulations. Broadband dielectric spectra and frequency-dependent conductivities are provided. A mean field upscaling strategy is deployed to compute the dielectric response at cement-paste scale. In cement-based materials, the measurement of dielectric properties can be used for non-destructive monitoring of concrete structures conditions and to unravel details of the hierarchical pore structure of the material, notably at early-age when the microstructure of the material changes significantly. Our results can be used in the interpretation of high frequency electromagnetic methods, such as ground-penetrating radar, enhancing the quality of interpretation and improving the confidence in the corresponding results.

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“…Extensive research was undertaken in early studies focusing on empirical determination of material-specific calibration equations [15,194,195,196]. With advancing studies on dielectric soil properties, it has been found that relative permittivity is not a function of soil water content, but is also influenced by the porous structure of a soil [20,21,22,197,198,199]. In order to consider this, semi-empirical material-specific calibration equations have been developed to consider the dry density of soils.…”

Section: Dielectric Mixture Approachesmentioning

confidence: 99%

“…Equation 4.21 can be rewritten in terms of the volumetric water content, θ , using the relationship defined in Equation 2.10, which leads to [22]:…”

Section: Material-specific Empirical Calibration Equationsmentioning

confidence: 99%

“…These responses not only originate from pore water but also from the soil composition, structure, and mineralogy, as well as many other important soil characteristics [18,19]. With continuing research, the dielectric soil property at around 1 GHz is found to be not only a function of water content, but also of porosity and saturation [20,21,22]. Recent studies have focused on the broadband electromagnetic behaviour of soil as a porous multiple-phase material.…”

Section: Introductionmentioning

confidence: 99%

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Mechanical, hydraulic, and dielectric characterisation of fine-grained soils during densification

Schwing¹

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Soil characterisation is of primary interest for several disciplines, including geotechnical and geo-environmental engineering, soil science, and agriculture. An upcoming and promising method for soil characterisation relies on the high-frequency electromagnetic measurement technique which provides the potential to explore and investigate soils. However, successful application of this technique requires a profound understanding of the multi-physical processes arising from interactions between soil as a porous medium and the propagation of electromagnetic waves. This thesis focuses on a coupled experimental investigation of the mechanical, hydraulic, and dielectric characterisation of fine-grained soil during densification.In the framework of this thesis, the following steps have been completed and novel findings have been made:1. Probe designs have been developed, modified and improved to measure the dielectric soil properties in a frequency range from 1 MHz to 3 GHz during shrinkage and compaction. A low-cost in-house-manufactured probe was introduced, which was specifically designed for standardised geotechnical soil shrinkage test. During preliminary investigations, the calibration procedure and performance of these sensors were experimentally and numerically tested. The results showed agreement in the targeted frequency window.2. Compaction and shrinkage tests on fine-grained soils were conducted in combination with dielectric and soil suction measurements. The shrinkage curve and soil water characteristic curve (SWCC) was established and successfully parameterised with physical based models. The complex permittivity was determined in a frequency range from 1 MHz to 3 GHz. The dielectric properties measured during the shrinkage test showed a sudden drop of complex permittivity which could be located in the residual shrinkage zone.3. A theoretical electromagnetic mixture approach was used to model the measured frequency dependent dielectric properties of soils during shrinkage and compaction based on the parameterised shrinkage curve and SWCC. The theoretical results were compared to the dielectric measurements on different fine-grained soils. The comparison ii showed that the real part of permittivity could be well predicted whereas the imaginary part suffered inaccuracies.4. A sensitivity analysis was performed with the theoretical electromagnetic mixture approach in consideration of the shrinkage behaviour and SWCC in order to investigate the influence of soil suction and dry density on the frequency dependent permittivity.The sensitivity analysis showed that the real part of the permittivity near 1 GHz was insensitive to changes in the soil suction and dry density. In the MHz range, the real part of the permittivity was more sensitive to changes in soil suction than it was to dry density. The imaginary part of the permittivity was generally observed to be more sensitive to soil suction over the entire frequency range.

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

Cited by 47 publications

References 5 publications

Time domain reflectometry (TDR) potential for soil condition monitoring of geotechnical assets

Time domain reflectometry (TDR) potential for soil condition monitoring of geotechnical assets

Dielectric properties of the pore solution in cement-based materials

Mechanical, hydraulic, and dielectric characterisation of fine-grained soils during densification

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