Analysis of Seepage in a Laboratory Scaled Model Using Passive Optical Fiber Distributed Temperature Sensor

Ghafoori, Yaser; Maček, Matej; Vidmar, Andrej; Říha, Jaromír; Kryžanowski, Andrej

doi:10.3390/w12020367

Cited by 20 publications

(14 citation statements)

References 28 publications

(31 reference statements)

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“…At the same time, any defects or breakdowns of the heating power source will influence the seepage monitoring system. With the recent advances in the optical fiber DTS and increasing temperature resolution, the passive measurement has been proven experimentally as a reliable method for seepage detection even in the presence of a low-temperature gradient between the seepage water and the soil [ 80 ].…”

Section: Discussionmentioning

confidence: 99%

A Review of Measurement Calibration and Interpretation for Seepage Monitoring by Optical Fiber Distributed Temperature Sensors

Ghafoori

Vidmar

Říha

et al. 2020

Sensors

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Seepage flow through embankment dams and their sub-base is a crucial safety concern that can initiate internal erosion of the structure. The thermometric method of seepage monitoring employs the study of heat transfer characteristics in the soils, as the temperature distribution in earth-filled structures can be influenced by the presence of seepage. Thus, continuous temperature measurements can allow detection of seepage flows. With the recent advances in optical fiber temperature sensor technology, accurate and fast temperature measurements, with relatively high spatial resolution, have been made possible using optical fiber distributed temperature sensors (DTSs). As with any sensor system, to obtain a precise temperature, the DTS measurements need to be calibrated. DTS systems automatically calibrate the measurements using an internal thermometer and reference section. Additionally, manual calibration techniques have been developed which are discussed in this paper. The temperature data do not provide any direct information about the seepage, and this requires further processing and analysis. Several methods have been developed to interpret the temperature data for the localization of the seepage and in some cases to estimate the seepage quantity. An efficient DTS application in seepage monitoring strongly depends on the following factors: installation approach, calibration technique, along with temperature data interpretation and post-processing. This paper reviews the different techniques for calibration of DTS measurements as well as the methods of interpretation of the temperature data.

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Section: Discussionmentioning

confidence: 99%

A Review of Measurement Calibration and Interpretation for Seepage Monitoring by Optical Fiber Distributed Temperature Sensors

Ghafoori

Vidmar

Říha

et al. 2020

Sensors

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“…This is beyond the objective of the present work, which mainly focused on the comparison of ERT and fiber optic technologies as early warning systems for seepages. An exhaustive modeling would require the knowledge or the measurements of a number of thermal, geotechnical, and hydrogeological parameters needed to constrain the simulations [42].…”

Section: Data Processing and Resultsmentioning

confidence: 99%

Laboratory Studies Using Electrical Resistivity Tomography and Fiber Optic Techniques to Detect Seepage Zones in River Embankments

et al. 2021

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We present the results of laboratory experiments on a down-scaled river levee constructed with clayey material collected from a river embankment where a permanent resistivity instrument has operated since 2015. To create potential seepages through the levee, two zones (5 × 4 cm and 10 × 2 cm) were filled with sand during the levee construction. Electrical resistivity tomography (ERT) technique and Fiber Bragg Grating (FBG) technology were used to study time-lapse variations due to seepage. The ERT profile was spread on the levee crest and the Wenner array with unit electrode spacing a = 3 cm was used. Six organic modified ceramics (ORMOCER) coated 250 μm-diameter fibers were deployed in different parts of the levee. Time-lapse measurements were performed for both techniques from the beginning of each experiment when water was added to the river side until the water was continuously exiting from the seepage zones. The results showed that ERT images could detect seepages from the early stages. Although with a short delay compared to ERT, fiber optic sensors also showed their ability to detect water infiltrations by measuring temperature changes. Both technologies being successful, a discussion about respective peculiarities and pros and cons is proposed to suggest some criteria in choosing the proper technique according to the specific needs.

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“…The response times for both the temperature sensors and the optical fiber were considered in the calibration process. The response time of the DTS system was determined as 60 s by a laboratory measurement [ 22 ], while the response time of temperature sensors was 5 min [ 21 ]. The real-time clocks of the DTS system and temperature sensors were precisely synchronized before the preparation of the model.…”

Section: Methodsmentioning

confidence: 99%

A Dynamic Calibration of Optical Fiber DTS Measurements Using PEST and Reference Thermometers

Ghafoori

Vidmar

Kryžanowski

2022

Sensors

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Temperature measurements are widely used in structural health monitoring. Optical fiber distributed temperature sensors (DTS) are developed, based on Raman spectroscopy, to measure temperature with relatively high accuracy and short temporal and spatial resolutions. DTS systems provide an extensive number of temperature measurements along the entire length of an optical fiber that can be extended to tens of kilometers. The efficiency of the temperature measurement strongly depends on the calibration of the DTS data. Although DTS systems internally calibrate the data, manual calibration techniques were developed to achieve more accurate results. Manual calibration employs reference sections or points with known temperatures and the DTS scattering data to estimate the calibration parameters and calculate temperature along the optical fiber. In some applications, manual calibration is subjected to some shortages, based on the proposed fiber installation configuration and continuity of calibration. In this article, the manual calibration approach was developed using the model-independent Parameters Estimation (PEST), together with the external temperature sensors as references for the DTS system. The proposed method improved manual calibration in terms of installation configuration, continuity of dynamic calibration, and estimation of the calibration parameters.

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Analysis of Seepage in a Laboratory Scaled Model Using Passive Optical Fiber Distributed Temperature Sensor

Cited by 20 publications

References 28 publications

A Review of Measurement Calibration and Interpretation for Seepage Monitoring by Optical Fiber Distributed Temperature Sensors

A Review of Measurement Calibration and Interpretation for Seepage Monitoring by Optical Fiber Distributed Temperature Sensors

Laboratory Studies Using Electrical Resistivity Tomography and Fiber Optic Techniques to Detect Seepage Zones in River Embankments

A Dynamic Calibration of Optical Fiber DTS Measurements Using PEST and Reference Thermometers

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