Experimental Determination of TDR Calibration Relationship for Pyroclastic Ashes of Campania (Italy)
Time domain reflectometry (TDR) is one of the most widely used techniques for indirect determination of soil volumetric water content (<i>θ</i>). TDR measures the relative dielectric constant (<i>ε<sub>r</sub></i>) which, in a three-phase system...
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| Format: | Article |
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MDPI AG
2018-11-01
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| Series: | Sensors |
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| Online Access: | https://www.mdpi.com/1424-8220/18/11/3727 |
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| author | Giovanna Capparelli Gennaro Spolverino Roberto Greco |
| author_facet | Giovanna Capparelli Gennaro Spolverino Roberto Greco |
| author_sort | Giovanna Capparelli |
| collection | DOAJ |
| description | Time domain reflectometry (TDR) is one of the most widely used techniques for indirect determination of soil volumetric water content (<i>θ</i>). TDR measures the relative dielectric constant (<i>ε<sub>r</sub></i>) which, in a three-phase system like the soil, depends on water, air, and solid matrix dielectric constants. Since dielectric constant of water is much larger than the other two, <i>ε<sub>r</sub></i> of bulk soil mainly depends on water content. In many cases, the application of TDR requires a specific calibration of the relationship <i>θ</i>(<i>ε<sub>r</sub></i>) to get quantitatively accurate estimates of soil water content. In fact, the relationship <i>θ</i>(<i>ε<sub>r</sub></i>) is influenced by various soil properties, such as clay content, organic matter content, bulk density, and aggregation. Numerous studies have shown that pyroclastic soils often exhibit a peculiar dielectric behavior. In Campania (Southern Italy) wide mountainous areas are covered by layered pyroclastic deposits of ashes (loamy sands) and pumices (sandy gravels), often involved in the triggering of landslides induced by rainwater infiltration. Reliable field measurements of water content of such soils are therefore important for the assessment of landslide risk. Hence, in this paper, the <i>θ</i>(<i>ε<sub>r</sub></i>) relationship has been experimentally determined on samples of typical pyroclastic soil of Campania, collected around Sarno, reconstituted with different porosities. The aim of the study is to identify specific calibration relationships for such soils based not only on empirical approaches. In this respect, a three-phase dielectric mixing model with a variable exponent is introduced, and the variable value of the exponent is related to the different dielectric properties of bond and free water within the soil pores. |
| first_indexed | 2024-04-11T11:53:10Z |
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| id | doaj.art-8835bb01359844fabb9e1a1c0da07440 |
| institution | Directory Open Access Journal |
| issn | 1424-8220 |
| language | English |
| last_indexed | 2024-04-11T11:53:10Z |
| publishDate | 2018-11-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Sensors |
| spelling | doaj.art-8835bb01359844fabb9e1a1c0da074402022-12-22T04:25:15ZengMDPI AGSensors1424-82202018-11-011811372710.3390/s18113727s18113727Experimental Determination of TDR Calibration Relationship for Pyroclastic Ashes of Campania (Italy)Giovanna Capparelli0Gennaro Spolverino1Roberto Greco2Dipartimento di Ingegneria Informatica, Modellistica, Elettronica e Sistemistica, Università della Calabria, 87036 Rende, ItalyDipartimento di Ingegneria Informatica, Modellistica, Elettronica e Sistemistica, Università della Calabria, 87036 Rende, ItalyDipartimento di Ingegneria, Università della Campania ‘L. Vanvitelli’, 81031 Aversa, ItalyTime domain reflectometry (TDR) is one of the most widely used techniques for indirect determination of soil volumetric water content (<i>θ</i>). TDR measures the relative dielectric constant (<i>ε<sub>r</sub></i>) which, in a three-phase system like the soil, depends on water, air, and solid matrix dielectric constants. Since dielectric constant of water is much larger than the other two, <i>ε<sub>r</sub></i> of bulk soil mainly depends on water content. In many cases, the application of TDR requires a specific calibration of the relationship <i>θ</i>(<i>ε<sub>r</sub></i>) to get quantitatively accurate estimates of soil water content. In fact, the relationship <i>θ</i>(<i>ε<sub>r</sub></i>) is influenced by various soil properties, such as clay content, organic matter content, bulk density, and aggregation. Numerous studies have shown that pyroclastic soils often exhibit a peculiar dielectric behavior. In Campania (Southern Italy) wide mountainous areas are covered by layered pyroclastic deposits of ashes (loamy sands) and pumices (sandy gravels), often involved in the triggering of landslides induced by rainwater infiltration. Reliable field measurements of water content of such soils are therefore important for the assessment of landslide risk. Hence, in this paper, the <i>θ</i>(<i>ε<sub>r</sub></i>) relationship has been experimentally determined on samples of typical pyroclastic soil of Campania, collected around Sarno, reconstituted with different porosities. The aim of the study is to identify specific calibration relationships for such soils based not only on empirical approaches. In this respect, a three-phase dielectric mixing model with a variable exponent is introduced, and the variable value of the exponent is related to the different dielectric properties of bond and free water within the soil pores.https://www.mdpi.com/1424-8220/18/11/3727TDR calibration relationshippyroclastic soildielectric constantsoil bulk density |
| spellingShingle | Giovanna Capparelli Gennaro Spolverino Roberto Greco Experimental Determination of TDR Calibration Relationship for Pyroclastic Ashes of Campania (Italy) Sensors TDR calibration relationship pyroclastic soil dielectric constant soil bulk density |
| title | Experimental Determination of TDR Calibration Relationship for Pyroclastic Ashes of Campania (Italy) |
| title_full | Experimental Determination of TDR Calibration Relationship for Pyroclastic Ashes of Campania (Italy) |
| title_fullStr | Experimental Determination of TDR Calibration Relationship for Pyroclastic Ashes of Campania (Italy) |
| title_full_unstemmed | Experimental Determination of TDR Calibration Relationship for Pyroclastic Ashes of Campania (Italy) |
| title_short | Experimental Determination of TDR Calibration Relationship for Pyroclastic Ashes of Campania (Italy) |
| title_sort | experimental determination of tdr calibration relationship for pyroclastic ashes of campania italy |
| topic | TDR calibration relationship pyroclastic soil dielectric constant soil bulk density |
| url | https://www.mdpi.com/1424-8220/18/11/3727 |
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