Measurement-Error Analysis of Fiber Bragg Grating Flexible Sensor for Displacement-Field Monitoring of Geotechnical Engineering

Abstract

Monitoring geotechnical structures and providing real-time early warning is a key measure to mitigate the impacts of disasters (slope slip, subsidence, dam deformation, bridge settlement, etc.). The fiber Bragg grating (FBG) flexible sensor, developed by the combination of flexible material and an FBG sensor, is widely used in geotechnical engineering health monitoring due to its excellent performance. The flexible sensor can perform regional and quasi-distributed measurements of the displacement field of the measured structure, and accurately reflect the operating state of the engineering structure. However, in practical engineering applications, factors such as the strain-transfer rate between the flexible substrate and sensing points, the displacement reconstruction algorithm, and the arrangement interval of the sensing points can cause measurement error, which, in turn, leads to a decrease in the displacement-measurement accuracy. In this paper, the following analysis is performed by means of theoretical derivation and model establishment. The influence of the length, width, and thickness of the cemented layer, the shear modulus of the flexible substrate, and the radius of the groove on the strain-transfer rate were analyzed, and the referential parameters were determined. The displacement reconstruction algorithm is essentially a recursive algorithm, which inevitably introduces cumulative error; the relationship between the layout interval of the sensing points and the measurement error is discussed. Considering the fabrication cost of the sensor and the allowable range of error, a sensing-point-layout interval of 100 mm was chosen. The feasibility and effectiveness of the simulation theory were verified by carrying out deformation-sensing experiments on the developed FBG flexible sensor. The research results can theoretically guide the packaging and fabrication of the FBG flexible sensor, thereby improving the measurement accuracy of the flexible sensor for the measured structure.

Construction and Application of On-Line Roof Separation Monitoring System Based on High-Precision FBG Indicator

“…FBG is a periodic perturbation of the refractive index along the fiber length, which is formed by exposure of the core to an intense optical interference pattern [5,12,15,16]. The structure and reflection characteristics of the fiber grating are shown in Figure 1.…”

Design and performance study of real-time, reliable, and highly accurate carbon fiber reinforced polymer-fiber Bragg grating sensors for wind turbine blade strain monitoring

“…On the packaging and protection of FBG sensors, Wang et al 14 developed a metal-encapsulated FBG sensor for strain measurement at low temperatures, the durability, and reliability of the sensor were verified by tensile and fatigue loading. Tian et al 15 developed a flexible materialencapsulated FBG sensor for geotechnical health monitoring. The effects of the length, width, and thickness of the cemented layer, the shear modulus of the flexible substrate, and the radius of the trench on the strain transfer rate are analyzed through theoretical derivation and modeling, and reference parameters are identified.…”

“…developed a metal-encapsulated FBG sensor for strain measurement at low temperatures, the durability, and reliability of the sensor were verified by tensile and fatigue loading. Tian et al 15 . developed a flexible material-encapsulated FBG sensor for geotechnical health monitoring.…”