An Experimental Study on Fiber Bragg Grating-Point Heat Source Integration System for Seepage Monitoring

Abstract

Monitoring results of the linear heat source (LHS) method are generally affected by infiltration angle. In order to solve this problem, a novel point heat source (PHS) seepage integration system was designed in this study based on the spherical symmetry of PHS. Each sensing-heating element consisting of a fiber Bragg grating (FBG) temperature sensor, and a ceramic heating tube was enclosed in a copper tube. Several sensing-heating elements that were arranged in series in a monitoring tube, a regulated power supply, and a FBG demodulator constituted the PHS seepage monitoring system. Calibration tests were carried out under different magnitudes and directions of seepage velocity. The proposed PHS seepage monitoring system effectively eliminated the influences of infiltration angle. The magnitude of the seepage identification index (ξ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">v</sub> ) maintained a certain correlation with seepage velocity. Finally, a scheme for improving the sensitivity of the proposed monitoring system was discussed.