Fiber Bragg Grating Sensors for Pile Jacking Monitoring in Clay Soil

Abstract

The small deformation of the model pile in a pile jacking test makes its accurate measurement very difficult. Based on the installation method of clamping at both ends, a sensitized miniature fiber Bragg grating (FBG) strain sensor was developed to measure the pile strain of small-size model piles. This study investigated the working principle of the sensitized miniature FBG sensor and analyzed the strain transfer characteristics of the sensor by calibration test. The lateral resistance and the earth plug resistance of the model pile were measured accurately by the grooves embedded in the outer tube of the double-wall opening model pile and the sensors directly pasted on the surface of the inner tube. The results of this study show that the sensitized miniature FBG strain sensor has the advantages of high sensitivity, strong interference resistance, and high test accuracy. The FBG strain sensor was completely fixed on the pile by clamping supports at both ends, and the strain measured using the FBG strain sensor was found to be consistent with the pile deformation.

Cylindrical Bidirectional Strain Sensors Based on Fiber Bragg Grating

“…However, a fiber Bragg grating is relatively fragile; a bare fiber Bragg grating, as a strain sensor, which is directly adhered to the surface of a structure to be tested or buried inside the structure, is very easy to damage in harsh working conditions. Therefore, it needs to be packaged before using [ 21 , 22 , 23 , 24 ]; it has mostly been pasted on the surface of the measured object [ 25 ] through metal tube packaging [ 26 ], capillary steel tube packaging [ 27 ], and substrate packaging [ 28 ], etc. A fiber Bragg grating sensor has been shown to be suitable for underground coal mine sensing because of its anti-electromagnetic interference, high-temperature resistance, long-term stability, and high radiation resistance [ 29 , 30 ].…”

Large deflection deformation detection method of steel strip based on ultra-weak fiber bragg grating

“…Traditional metal structure deformation measurement mostly uses resistance strain gauge, digital camera, laser displacement sensor, 3D scanner, and remote automatic total station [5][6][7][8]. These technologies are mostly limited to small-scale fixed-point measurement, and the instruments used are large in volume and have complex installation, so that large-scale real-time detection is difficult to realize [9,10]. Fiber Bragg grating (FBG) sensor can sense the change in strain by writing Bragg grating in the fiber core, and it can be applied to structural deformation detection given its advantages of small volume, high sensitivity, good anti-interference, and real-time detection [11][12][13].…”