Application of PI-FBG sensor for humidity measurement in unsaturated soils

•The PI-FBG humidity sensor suitable for use in unsaturated soils was developed.•The encapsulated PI-FBG sensor performed well in ten different sand-kaolin mixtures.•The function between water content and humidity in unsaturated soils was established.•The influence of kaolin content on pore gas rela...

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Published inMeasurement : journal of the International Measurement Confederation Vol. 188; p. 110415
Main Authors Guo, Jun-Yi, Shi, Bin, Sun, Meng-Ya, Cheng, Wei, Zhang, Cheng-Cheng, Wei, Guang-Qing, Wang, Xing
Format Journal Article
LanguageEnglish
Published London Elsevier Ltd 01.01.2022
Elsevier Science Ltd
Subjects
Bragg gratings
Coated fibers
Fiber Bragg grating
Humidity
Humidity measurement
Kaolin
Kaolin content
Laboratory tests
Measurement techniques
Moisture content
Polyimide
Pore gas relative humidity
Quadratic equations
Relative humidity
Sensor
Sensors
Soil testing
Soils
Unsaturated soil
Unsaturated soils
Polyimide
Fiber Bragg grating
Kaolin content
Unsaturated soil
Pore gas relative humidity
Sensor
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Summary:•The PI-FBG humidity sensor suitable for use in unsaturated soils was developed.•The encapsulated PI-FBG sensor performed well in ten different sand-kaolin mixtures.•The function between water content and humidity in unsaturated soils was established.•The influence of kaolin content on pore gas relative humidity was discussed. In this paper, the polyimide-coated fiber Bragg grating (PI-FBG) humidity sensor suitable for use in unsaturated soils was developed. Through a series of laboratory tests, the pore gas relative humidity in different sand-kaolin mixtures were measured and analyzed to verify the feasibility of the sensor in unsaturated soils. The results shows that the pore gas relative humidity in unsaturated soils first increases rapidly and then tends to be stable with the increase of water content. The relationship between them can be fitted by quadratic function when the pore gas relative humidity is less than 100%. In addition, the critical water content (w100%RH) of mixed soils increases linearly with the increase of kaolin content; when the water contents of mixed soils are same, higher kaolin content induces higher pore gas relative humidity.
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ISSN:0263-2241
1873-412X
DOI:10.1016/j.measurement.2021.110415