A Thermo–TDR Sensor for Simultaneous Measurement of Unfrozen Water Content and Thermal Conductivity of Frozen Soil
Due to increasing human engineering activities in cold regions, the precise measurement of frozen soil’s physical property parameters has become particularly important. Traditional measurements of thermal conductivity and unfrozen water content of frozen soil are usually tested separately, leading t...
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MDPI AG
2025-03-01
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| author | Panting Liu Simao Fan Qingyi Mu Qifan Zhang Linlin Tang Jine Liu Fuqing Cui Zhiyun Liu Xuna Wang |
| author_facet | Panting Liu Simao Fan Qingyi Mu Qifan Zhang Linlin Tang Jine Liu Fuqing Cui Zhiyun Liu Xuna Wang |
| author_sort | Panting Liu |
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| description | Due to increasing human engineering activities in cold regions, the precise measurement of frozen soil’s physical property parameters has become particularly important. Traditional measurements of thermal conductivity and unfrozen water content of frozen soil are usually tested separately, leading to errors in accurately understanding the dynamic variation law of permafrost’s hydrothermal parameters in the near-phase transition zone. To address this, a multi-sensor fusion technology–thermo time domain reflectometry (thermo-TDR) sensor was designed and optimized for measuring the unfrozen water content and thermal conductivity of frozen soil. Three-dimensional thermal and electromagnetic numerical models were developed to analyze and validate the design parameters of the proposed sensor. Furthermore, a corresponding validation experiment was carried out to confirm the usability and accuracy of the designed sensor. The results show that (1) under the optimized probe parameters, the deviation between the theoretical thermal conductivity and the numerical preset value is 2.94%, verifying the accuracy of the sensor in thermal physical testing. (2) With a 10 mm probe spacing design, the test area of the thermo-TDR significantly increased, and the skin effect coefficient reached 25.54%, satisfying the electromagnetic design requirements of the TDR method. (3) The designed thermo-TDR sensor realizes the simultaneous measurement of unfrozen water and thermal conductivity of frozen soil, and the experimental results present a good consistency with that of the nuclear magnetic resonance (NMR) and transient planar heat source methods. (4) Additionally, due to the drastic changes in the soil’s physical properties due to the probe’s heating process, testing errors of the thermo-TDR sensor will significantly increase in the near-phase transition range, especially in the range of −2~−1 °C. |
| format | Article |
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| institution | OA Journals |
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| publishDate | 2025-03-01 |
| publisher | MDPI AG |
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| spelling | doaj-art-96fc243fd8f44d90a8b12044dea37b932025-08-20T02:09:17ZengMDPI AGSensors1424-82202025-03-01257215510.3390/s25072155A Thermo–TDR Sensor for Simultaneous Measurement of Unfrozen Water Content and Thermal Conductivity of Frozen SoilPanting Liu0Simao Fan1Qingyi Mu2Qifan Zhang3Linlin Tang4Jine Liu5Fuqing Cui6Zhiyun Liu7Xuna Wang8College of Geology Engineering and Geomatics, Chang’an University, Xi’an 710054, ChinaCollege of Geology Engineering and Geomatics, Chang’an University, Xi’an 710054, ChinaCollege of Geology Engineering and Geomatics, Chang’an University, Xi’an 710054, ChinaCollege of Geology Engineering and Geomatics, Chang’an University, Xi’an 710054, ChinaCollege of Geology Engineering and Geomatics, Chang’an University, Xi’an 710054, ChinaCollege of Geology Engineering and Geomatics, Chang’an University, Xi’an 710054, ChinaCollege of Geology Engineering and Geomatics, Chang’an University, Xi’an 710054, ChinaCollege of Geology Engineering and Geomatics, Chang’an University, Xi’an 710054, ChinaCollege of Geology Engineering and Geomatics, Chang’an University, Xi’an 710054, ChinaDue to increasing human engineering activities in cold regions, the precise measurement of frozen soil’s physical property parameters has become particularly important. Traditional measurements of thermal conductivity and unfrozen water content of frozen soil are usually tested separately, leading to errors in accurately understanding the dynamic variation law of permafrost’s hydrothermal parameters in the near-phase transition zone. To address this, a multi-sensor fusion technology–thermo time domain reflectometry (thermo-TDR) sensor was designed and optimized for measuring the unfrozen water content and thermal conductivity of frozen soil. Three-dimensional thermal and electromagnetic numerical models were developed to analyze and validate the design parameters of the proposed sensor. Furthermore, a corresponding validation experiment was carried out to confirm the usability and accuracy of the designed sensor. The results show that (1) under the optimized probe parameters, the deviation between the theoretical thermal conductivity and the numerical preset value is 2.94%, verifying the accuracy of the sensor in thermal physical testing. (2) With a 10 mm probe spacing design, the test area of the thermo-TDR significantly increased, and the skin effect coefficient reached 25.54%, satisfying the electromagnetic design requirements of the TDR method. (3) The designed thermo-TDR sensor realizes the simultaneous measurement of unfrozen water and thermal conductivity of frozen soil, and the experimental results present a good consistency with that of the nuclear magnetic resonance (NMR) and transient planar heat source methods. (4) Additionally, due to the drastic changes in the soil’s physical properties due to the probe’s heating process, testing errors of the thermo-TDR sensor will significantly increase in the near-phase transition range, especially in the range of −2~−1 °C.https://www.mdpi.com/1424-8220/25/7/2155multi-sensor fusionthermo-TDR probefrozen soilunfrozen water contentthermal conductivity |
| spellingShingle | Panting Liu Simao Fan Qingyi Mu Qifan Zhang Linlin Tang Jine Liu Fuqing Cui Zhiyun Liu Xuna Wang A Thermo–TDR Sensor for Simultaneous Measurement of Unfrozen Water Content and Thermal Conductivity of Frozen Soil Sensors multi-sensor fusion thermo-TDR probe frozen soil unfrozen water content thermal conductivity |
| title | A Thermo–TDR Sensor for Simultaneous Measurement of Unfrozen Water Content and Thermal Conductivity of Frozen Soil |
| title_full | A Thermo–TDR Sensor for Simultaneous Measurement of Unfrozen Water Content and Thermal Conductivity of Frozen Soil |
| title_fullStr | A Thermo–TDR Sensor for Simultaneous Measurement of Unfrozen Water Content and Thermal Conductivity of Frozen Soil |
| title_full_unstemmed | A Thermo–TDR Sensor for Simultaneous Measurement of Unfrozen Water Content and Thermal Conductivity of Frozen Soil |
| title_short | A Thermo–TDR Sensor for Simultaneous Measurement of Unfrozen Water Content and Thermal Conductivity of Frozen Soil |
| title_sort | thermo tdr sensor for simultaneous measurement of unfrozen water content and thermal conductivity of frozen soil |
| topic | multi-sensor fusion thermo-TDR probe frozen soil unfrozen water content thermal conductivity |
| url | https://www.mdpi.com/1424-8220/25/7/2155 |
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