Development of a Novel Settlement Monitoring System Using Fiber-Optic Liquid-Level Transducers With Automatic Temperature Compensation

A novel monitoring system using innovative fiber-optical liquid-level transducers is proposed for continuously monitoring the settlement of geotechnical infrastructures. Each fiber-optical liquid-level transducer has two fiber Bragg gratings (FBGs) embedded in an elongated cantilever beam such that the temperature effect of the FBGs is automatically compensated and the Bragg’s wavelength shift indicates a liquid-level change. The operating principles of an individual transducer and a settlement monitoring system consisting of multiple transducers are described in detail. Four fiber-optical liquid-level transducers were fabricated in the laboratory. The measurement range was ±75.61 mm, and the designed sensitivity was $0.089~\mu \varepsilon $ /mm and was then updated through a calibration test. A settlement monitoring system was formed by connecting the four transducers with a water tank as an automatic level controller. A demonstration test of the system showed that its relative measurement error is within 4%, confirming the feasibility of the system for in situ applications.

[1]  Stephen P. Timoshenko,et al.  History of strength of materials : with a brief account of the history of theory of elasticity and theory of structures , 1983 .

[2]  N. Bidin,et al.  Liquid refractometer based mirrorless fiber optic displacement sensor , 2016 .

[3]  Herbert H. Einstein,et al.  Describing settlement troughs over twin tunnels using a superposition technique , 2007 .

[4]  Qida Zhao,et al.  Temperature-insensitive fiber Bragg grating liquid-level sensor based on bending cantilever beam , 2005, IEEE Photonics Technology Letters.

[6]  Nigel Hancock,et al.  Liquid level sensors using thin walled cylinders vibrating in circumferential modes , 1995 .

[7]  Kyung-Rak Sohn,et al.  Liquid-level monitoring sensor systems using fiber Bragg grating embedded in cantilever , 2009 .

[8]  L. Bruce Wilner.  Variable Capacitance Liquid Level Sensors , 1960 .

[9]  Jing Yang,et al.  A new method for measuring subgrade settlement in high-speed railway by using a linear CCD , 2013 .

[10]  P. Phukpattaranont,et al.  A self-calibration water level measurement using an interdigital capacitive sensor , 2014 .

[11]  Aaas News,et al.  Book Reviews , 1893, Buffalo Medical and Surgical Journal.

[12]  Romeo Bernini,et al.  Optical fiber fuel level sensor for aeronautical applications , 2017 .

[13]  Frédéric Bourquin,et al.  A magnet-based vibrating wire sensor: design and simulation , 2005 .

[14]  Dong-Sheng Xu,et al.  A New Measurement Approach for Small Deformations of Soil Specimens Using Fiber Bragg Grating Sensors , 2017, Sensors.

[15]  C. Ou,et al.  Building response and ground movements induced by a deep excavation , 2000 .

[16]  Jianhua Yin,et al.  A new measurement approach for deflection monitoring of large-scale bored piles using distributed fiber sensing technology , 2018 .